1,720,970 research outputs found
Molecular and biochemical characterisation of rust and Fusarium head blight resistant wheat lines
No full textEnglish:
Wheat is one of the most important food crops and consumption in the past year was higher than production worldwide, which indicates improved wheat cultivars need to be developed to maintain the demand for wheat. One of the biggest threats of wheat is ever-evolving pathogens that overcome resistance. To overcome threatening diseases, breeders need to incorporate new resistant genes/QTL into improved cultivars. Incorporating different resistant genes/QTL into a single line using gene-pyramiding and MAS can enhance the breeding process. However, pyramiding of genes for resistance can lead to a decrease in baking quality characteristics, which are important for the milling and baking industry as well as for consumers. To overcome this problem, lines should also be tested for bread-making quality characteristics such as HMW-GS and the LUPP% which are directly linked to protein quality. The aim of the study was to identify rust and FHB resistant lines with good protein content. Rust and FHB resistant wheat lines were developed during previous studies. The best rust and FHB resistant lines were planted and self-pollinated. Lines were evaluated for the presence of five rust resistant genes/QTL (Lr19, Lr34/Yr18/Sr57, QYr.sgi.2B-1, Sr2 and Sr26) and four FHB resistant genes/QTL (Fhb1, Qfhs.ifa-5A-1, Qfhs.ifa-5A-2 and Fhb2) for two consecutive years. These selected rust and FHB resistant lines were also subjected to three biochemical tests namely SDS-PAGE, SEHPLC and RP-HPLC. PCR-based markers linked to HMW-GS alleles and the IBL.1RS translocation, associated with weak dough strength, were also tested. Since the breeding programme was still in an early stage, only few seeds per line were available and therefore biochemical tests that can be performed using single seeds were selected. Results from SDS-PAGE and molecular markers linked to HMW-GS were similar and therefore lines were further evaluated using only molecular markers. No correlations were detected for the RP-HPLC data of lines therefore it was excluded during further analysis. The rust and FHB resistant genes/QTL co-segregated based on their related parental lines. An additional round of self-pollination either led to higher levels of homozygosity for the selected traits or to the loss of traits due to recombination. MAS enabled the selection and enhancement of homozygous lines. Only a few offspring of one of the rust resistant lines contained the Sr26 gene, while the Lr34/Yr18/Sr57 gene was present in all tested lines. None of the rust resistant lines contained the Sr2 gene which is a major gene for resistance against stem rust and especially effective against the threatening Ug99 race. The top ten rust resistant lines all had the same rust resistant gene/QTL present (Lr19, Lr34/Yr18/Sr57 and QYr.sgi.2B-1) as well as the same protein quality alleles (Ax2*, Bx7+By8 and Dx5+Dy10). The LUPP% of these lines showed high levels of variation and was optimal (40% to 50%) for only one line. High levels of variation were detected for the FHB resistant markers in the FHB resistant populations. The top ten lines contained all six markers although the level of homozygosity varied. Four of these lines expressed both the Bx7+By8 and Bx17+By18 alleles and only one line did not express the Bx7OE allele. None of these lines expressed the 1BL.1RS translocation. Two of these lines showed a desirable LUPP%. Results indicated the preference towards rust or FHB resistance selection followed by selection for protein quality alleles and lastly the LUPP%. The top ten rust and FHB lines can serve as resistance sources in further breeding programmes.Afrikaans:
Koring is een van die belangrikste voedselgewasse en die afgelope jaar was die verbruik
van koring wêreldwyd hoër as produksie wat daarop dui dat verbeterde koring kultivars
ontwikkel moet word om aan die behoefte vir koringte kan voorsien. Een van die grootste
bedreigings vir koring is patogene wat steeds bly verander om weerstand te kan oorkom.
Ten einde hierdie bedreiging te kan oorkom moet planttelers nuwe weerstandsgene en
kwantitatiewe eienskap lokusse (QTL) in verbeterde kultivars inbou. Die teelproses kan
aansienlik versterk word deur van geenstapeling en merker-ondersteunde seleksie
gebruik te maak om verskillende weerstandsgene en QTL in ‘n enkele lyn in te bou. Die
stapeling van gene kan egter tot ‘n afname in bakkwaliteitseienskappe, wat belangrik vir
die meulenaars en die bakindustrie asook verbruikers is, lei. Om hierdie probleem te
oorkom behoort lyne ook vir broodkwaliteits-eienskappe soos hoë molekulêre gewig
gluten sub-eenhede (HMW-GS) en groot onekstraheerbare polimeriese proteïen
persentasie (LUPP%) wat direk aan proteïenkwaliteit gekoppel is, getoets te word.
Die doel van die studie was om roes en fusariumaarskroei (FHB) weerstandbiedende
lyne met goeie proteïeninhoud te identifiseer. Roes en FHB weerstandbiedende lyne is
gedurende vorige studies ontwikkel. Die beste roes en FHB weerstandbiedende lyne is
geplant en selfbestuif. Lyne is vir die teenwoordigheid van vyf roesweerstandsgene of
QTL (Lr19, Lr34/Yr18/Sr57, QYr.sgi.2B-1, Sr2 en Sr26) en vier FHB weerstandsgene of
QTL (Fhb1, Qfhs.ifa-5A-1, Qfhs.ifa-5A-2 en Fhb2) gedurende twee opeenvolgende jare,
geëvalueer. Hierdie geselekteerde roes en FHB weerstandbiedende lyne was ook aan
drie biochemiese toetse, naamlik natrium dodesielsulfaatpoliakrielamiedgelelektroforese
(SDS-PAGE), grootte uitsluitings-hoë prestasie vloeistof chromatografie (SE-HPLC) en
omgekeerde-fase-hoë prestasie vloeistof chromatografie (RP-HPLC) onderwerp.
Polimerase kettingreaksie (PCR) gebaseerde merkers gekoppel aan HMW-GS allele en
die 1BL.1RS translokasie, wat met swak deegsterkte geassosieer is, is ook getoets.
Aangesien die teelprogram nog in ‘n vroeë stadium van ontwikkeling was, was slegs ‘n
klein aantal saad van elke lyn beskikbaar en daarom is biochemiese toetse wat op enkel
sade gedoen kan word, geselekteer. Dieselfde resultate is verkry deur van SDS-PAGE
en molekulêre merkers gekoppel aan die HMW-GS gebruik te maak en daarom is die res
van die lyne slegs getoets deur van die molekulêre merkers gebruik te maak. Geen
korrelasies is vir die RP-HPLC data van die verskillende lyne verkry nie en daarom is die
tegniek nie verder gebruik nie. Die roes en FHB weerstandsgene of QTL het ko-segregasie getoon gebaseer op hul
onderskeie ouers. ‘n Addisionele rondte van selfbestuiwing het tot of hoër vlakke
homosigositeit van die geselekteerdeeienskappe, of tot ‘n verlies van van die eienskappe
weens rekombinasie gelei. MAS het die seleksie en verhoging van homosigotiese lyne
moontlik gemaak.
Slegs ‘n klein aantal lyne afkomstig van een van die roesweerstandbiedende lyne het die
Sr26 geen bevatterwyl die Lr34/Yr18/Sr57 geen in al die getoetste lyne teenwoordig
was. Geen van die roesweerstandbiedende lyne het die Sr2 geen wat ‘n belangrike
weerstandsgeen teen stamroes en veral die Ug99 patogeen is, bevat nie. Die top 10
roesweerstandbiedende lyne het almal dieselfde roesweerstandsgene of QTL (Lr19,
Lr34/Yr18/Sr57 en QYr.sgi.2B-1) asook dieselfde proteïen kwaliteitsallele(Ax2*, Bx7+By8
en Dx5+Dy10) bevat. Die LUPP% van hierdie lyne het hoë vlakke van variasie getoon en
was slegs optimaal (40% tot 50%) in een van die lyne.
Hoë vlakke van variasie is vir die FHB weerstandsmerkers in die FHB
weerstandbiedende populasies opgespoor. Die top tien lyne het almal ses merkers bevat
alhoewel die vlak van homosigositeit gevarieer het. Vier van hierdie lyne het beide die
Bx7+By8 en Bx17+By18 allele uitgedruk en slegs een van hierdie lyne het nie die Bx7OE
alleel bevat nie. Geen een van hierdie lyne het die 1BL.1RS translokasie uitgedruk nie.
Twee van die lyne het aanvaarbare LUPP% gehad.
Resultate het aangetoon dat daar tydens seleksie voorkeur verleen is aan roes en FHB
weerstand gevolg deur seleksie vir proteïenkwaliteitallele en laastens vir LUPP%. Die
top tien roes en FHB lyne kan in die toekoms as weerstandbronne in ander
teelprogramme gebruik word.National Research Foundation (NRF)UFS Strategic Academic ClusterTechnology and Human Resources for Industry program (THRIP)Winter Cereal Trus
Developing a breeding strategy for butternut squash (Cucurbita moschata) in South Africa
No full textKnowledge about inheritance mechanisms of economically important traits and the influence of environmental factors on their expression are crucial for the formulation of an appropriate breeding strategy in any crop. Currently limited information is available on this subject in butternut and even more so with regard to internal fruit quality characteristics. The aim of this study was to design an effective breeding approach to improve butternut internal fruit quality, without sacrificing yield. The aim was extended with the objectives to quantify phenotypic and genotypic variability in 42 genotypes for characteristics across environments and confirm stability in high-performing individuals, and to identify characteristics showing the greatest potential for improvement through estimating the genetic parameters and interrelations between these characteristics. From heterosis studies, it could be confirmed which characteristics should be improved through hybridisation. From the combined analysis of variance on 15 morpho-agronomic and internal fruit quality characteristics over three locations and two seasons, highly significant differences (p≤0.001) were observed between genotypes for all traits including leaf chlorophyll content (CHL), green-red (Leaf a*) and yellow-blue colour contribution in the leaf canopy (Leaf b*), leaf width (LW), petiole length (PL), average fruit mass (AFM), dry matter yield (DMY), fruit number (FN), uniformity, yield, total soluble solids (TSS), dry matter content (DMC), green-red colour contribution in the fruit mesocarp (Fruit a*), internal fruit breakdown (IBD) and penetrometer readings as an indication of mesocarp firmness (PEN). With the exception of CHL and LW, all characteristics displayed significant mean square differences for genotype x location x season interactions, suggesting differential ranking of genotypes across environments. Phenotypic variability attributed to genetic variation ranged from 14% to 33% in plant morphological characteristics, 16% to 62% in yield and yield-dependent traits and 50% to 67% in fruit quality characteristics, supporting the existence of immense inherent variability within the population. The additive main effect and multiplicative interaction analyses across six environments indicated internal fruit quality characteristics to be more stable across environments than AFM, FN and yield. None of the genotypes was stable for all characteristics. Based on stability and performance, G11 and G13 were identified as the most desirable genotypes for the processing and small-fruited market segments respectively. Similarly, both G16 and G17 were most desirable for the fresh market segment. Based on the genetic components estimated using 27 F1 genotypes, AFM, FN, TSS, DMC, Fruit a* and PEN were observed to be under additive genetic control, implying selection in early generations would be effective for their improvement. In contrast, heterosis breeding could be more effective for the improvement of Leaf a*, DMY, uniformity and yield. Moderately high broad-sense heritability with lower genetic gain as a percentage of the mean was recorded for CHL, Leaf b*, LW, PL and IBD, suggesting additive genetic control although the environment plays a larger role in the expression of the phenotypes. A strong negative association was observed between AFM and FN as well as a strong positive correlation between DMC and TSS. CHL had moderate correlations with AFM and FN. Weak negative correlations were also estimated between yield and internal fruit quality characteristics and more specifically TSS, DMC and Fruit a*. Findings from the line x tester analysis, involving four lines and four testers, showed none of the parents to be consistently good general combiners for all characteristics. Leaf a*, Leaf b*, FN, TSS, DMC and PEN revealed nonsignificant line x tester interaction mean squares. LW, PL, AFM, Fruit a* and IBD were found to be predominantly under additive genetic control. CHL, DMY, uniformity and yield were demonstrated to be mostly under non-additive genetic control. Significant mid-parent heterosis was estimated for all characteristics with heterosis percentages above 45% for AFM, DMY, FN and yield. Using the current germplasm collection, the most feasible strategy for the improvement of butternut genotypes would be through selection in early segregating generations. For yield, uniformity and DMY more desirable results will be achieved through heterosis breeding. Focussing on yield, FN and AFM, in combination with DMC and TSS, will be the most effective approach to develop high-performing, stable and desirable hybrids
Genetic diversity in yield traits and kernel composition of selected Ethiopian sorghum landraces
No full textThesis (Ph.D.(Plant Breeding))--University of the Free State, 2023Climate-resilient and high-yielding sorghum cultivars must be developed for sustainable food systems and improved livelihoods in sub-Saharan Africa. Low grain protein, Fe and Zn concentrations are a frequent problem in food crops and they affect the crop's nutritional value, particularly in cereals. In this study, a total of 361 Ethiopian sorghum landraces with four commercial checks were grown under well-watered, wet intermediate and natural drought conditions for two consecutive seasons. The purpose of this research was to assess the genetic diversity and drought tolerance of this Ethiopian sorghum landrace collection using agronomic and grain quality traits and to select promising lines for production and/or breeding. The specific objectives were to (i) assess the level and pattern of genetic variation and drought adaptation in a sorghum landrace collection using phenotypic traits, (ii) evaluate chemical composition, genotype by environment interaction, drought effects and environmental influence and determine performance and stability of sorghum landraces, (iii) identify genomic regions associated with grain quality to determine the genetic basis for starch, protein and mineral concentrations of Ethiopian sorghum landraces. In stress environments, yield and yield components as well as grain quality traits had low means, range, genetic variance (σ²g) and heritability values.
In terms of grain yield performance under different water regimes, Melkassa (irrigated) had a 54.5% higher mean grain yield than Miesso (drought stress) in 2020 and Melkassa (irrigated) had a 26.9% higher mean grain yield than Miesso (drought stress) in 2021. Therefor drought stress reduced mean grain yield by 44.6% and grain weight by 14%. In all environments, ten genotypes (G189, G210, G125, G324, G325, G353, G319, G219, G187 and G229) had the highest stress tolerance index (STI), geometric mean productivity (GMP), mean productivity (MP) and yield in non-stress conditions (Yp) and stress conditions (Ys). In stress environments, starch content decreased by 5%, while protein content increased by 21% when compared to wet intermediate conditions. The Zn content was 60% and 55% higher in wet intermediate environments than in irrigated and stress environments, respectively. The Fe content was 21% and 13% higher in wet intermediate environments than in irrigated and stress environments, respectively. A genome-wide association study (GWAS) on 365 diverse Ethiopian sorghum landraces identified 209,572 single nucleotide polymorphisms (SNPs) (HB ≤ 0.05). Several candidate genes were identified that were significantly associated with grain Zn, Fe, starch, protein and ash concentrations, such as LEA, CHI, bZIP, ARF12 and WOX6.
The Late Embryogenesis Abundant (LEA) and basic leucine zipper (bZIP) family of proteins are involved in various stress responses in plants. The ABC transporter and sugar carrier proteins, Auxin Response Factors 12 (ARF12), Alpha-glucan phosphorylase and Zinc finger CCHC gene, are known for starch synthesis and storage in growing seeds. The WUSCHEL-related homeobox 6 (WOX6) and TatD family of hydrolases genes, acts as a transcription factor and is known to regulate stem cell maintenance and differentiation. Chitinase (CHI), flavonoid glycosides, architecture1 (tga1) and Class III peroxidase 70 and 69 precursors are all engaged in biological processes including plant defence against pathogens. The Zinc finger proteins (ZNFs) family is involved in Zn and Fe ion uptake and transport. These genes are involved in various biological processes such as stress response, starch synthesis, plant development and defence. The identification of loci associated with grain quality provides new insight into the genetic control of the traits, while sorghum landraces with nutritious grains can serve as sources of genes for breeding for good nutritional value.
___________________________________________________________________Abstract in other languages
,Klimaatbestande en hoë-opbrengs sorghumkultivars moet ontwikkel word vir volhoubare voedselstelsels en verbeterde lewensbestaan in Afrika suid van die Sahara. Lae graanproteïen-, Fe- en Zn-konsentrasies is ’n gereelde probleem in voedselgewasse en dit beïnvloed die gewas se voedingswaarde, veral in graan. In hierdie studie is ’n totaal van 361 Ethiopiese sorghum landrasse met vier kommersiële ondersoeke gekweek onder goed natgemaakte, nat intermediêre en natuurlike droogtetoestande vir twee opeenvolgende seisoene. Die doel van hierdie navorsing was om die genetiese diversiteit en droogtetoleransie van hierdie Ethiopiese sorghum landrasversameling te bepaal deur gebruik te maak van agronomiese en graankwaliteit eienskappe en om belowende lyne vir produksie en/of plantteling te kies.
Die spesifieke doelstellings was om (i) die vlak en patroon van genetiese variasie en droogte-aanpassing in ’n sorghumlandrasversameling te evalueer deur fenotipiese eienskappe te gebruik, (ii) chemiese samestelling, genotipe volgens omgewingsinteraksie, droogte-effekte en omgewingsinvloed te evalueer en prestasie en stabiliteit van sorghumlandrasse te bepaal, (iii) en genomiese streke te identifiseer wat met graankwaliteit geassosieer word om die genetiese basis vir stysel-, proteïen- en mineraalkonsentrasies van Ethiopiese sorghumlandrasse te bepaal. In stresomgewings het opbrengs- en opbrengskomponente sowel as graankwaliteit-eienskappe lae gemiddeldes, omvang, genetiese variansie (σ²g) en oorerflikheidswaardes gehad. Wat graanopbrengsprestasie onder verskillende waterregimes betref, het Melkassa (besproei) ’n 54,5% hoër gemiddelde graanopbrengs as Miesso (droogtestres) in 2020 gehad en Melkassa (besproei) het ’n 26,9% hoër gemiddelde graanopbrengs as Miesso (droogtestres) in 2021 gehad. Daarom het droogtestres die gemiddelde graanopbrengs met 44,6% en graangewig met 14% verminder. In alle omgewings het tien genotipes (G189, G210, G125, G324, G325, G353, G319, G219, G187 en G229) die hoogste strestoleransie-indeks (STI), geometriese gemiddelde produktiwiteit (GMP), gemiddelde produktiwiteit (MP) en opbrengs in nie-strestoestande (Yp) en strestoestande (Ys) gehad. In stresomgewings het styselinhoud met 5% afgeneem, terwyl proteïeninhoud met 21% toegeneem het in vergelyking met nat intermediêre toestande. Die Zn-inhoud was onderskeidelik 60% en 55% hoër in nat intermediêre omgewings as in besproeiings- en stres-omgewings. Die Fe-inhoud was onderskeidelik 21% en 13% hoër in nat intermediêre omgewings as in besproeiings- en stres-omgewings.
’n Genoomwye assosiasiestudie (GWAS) op 365 diverse Ethiopiese sorghum landrasse het 209 572 enkelnukleotied polimorfismes (SNPs) (HB ≤ 0,05) geïdentifiseer. Verskeie kandidaatgene is geïdentifiseer wat betekenisvol geassosieer is met graan Zn, Fe, stysel, proteïen en as konsentrasies, soos LEA, CHI, bZIP, ARF12 en WOX6. Die Late Embryogenesis Abundant (LEA) en basiese leucine zipper (bZIP) families van proteïene is betrokke by verskeie stresreaksies in plante. Die ABC-vervoerder en suikerdraerproteïene, Auxin Response Factors 12 (ARF12), Alfa-glukaanfosforilase en Sinkvinger CCHC-geen, is bekend vir styselsintese en berging in groeiende sade. Die WUSCHEL-verwante homeobox 6 (WOX6) en TatD familie van hidrolase gene, dien as ’n transkripsie faktor en is bekend om stamsel-instandhouding en -differensiasie te reguleer. Chitinase (CHI), flavonoïedglikosiede, argitektuur1 (tga1) en Klas III peroksidase 70 en 69 voorlopers is almal betrokke by biologiese prosesse, insluitend plantverdediging teen patogene. Die sinkvingerproteïene-familie (ZNF) is betrokke by Zn- en Fe-ioonopname en -vervoer. Hierdie gene is betrokke by verskeie biologiese prosesse soos stresreaksie, styselsintese, plantontwikkeling en verdediging. Die identifisering van lokusse wat met graankwaliteit geassosieer word, verskaf nuwe insig in die genetiese beheer van die eienskappe, terwyl sorghumlandrasse met voedsame grane as bronne van gene vir plantteling vir goeie voedingswaarde kan dien.
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Genetic variability of carotenoids and polypoid induction towards vitamin A biofortification in plantain (Musa spp.)
No full textVitamin A deficiency (VAD) is one of the most prevalent nutrient deficiencies affecting the health of resource-poor populations in developing countries. Plantains (Musa spp. AAB) are a specific group of bananas, which serve as a staple for millions of people in the humid lowlands of West-Central Africa and high provitamin A carotenoid (pVAC) plantain varieties, could have significant impact on VAD in these regions. In this regard, the International Institute of Tropical Agriculture (IITA) based in Nigeria, is developing a breeding pipeline aiming to generate and deploy plantain hybrids combining high pVAC content with other consumer-preferred traits. The overall objective of this study was therefore to assess the variability of fruit pVAC content in banana cultivars and hybrids present in the collection of IITA, Nigeria, and investigate the potential of induced polyploidization as a breeding approach towards plantain biofortification.
A wide collection of 204 genotypes of bananas (AAB-plantains, M. acuminata cultivars and bred hybrids) was screened to determine variability in fruit pVAC content using high- performance liquid chromatography (HPLC) and spectrophotometry. Mean total carotenoids (TC) measured by spectrophotometry ranged from 1.28 to 32.03 with a mean of 8.88 μg g-1 fresh weight (FW) indicating a high variability of carotenoids in bananas. There was a strong correlation between TC measured by spectrophotometry and that estimated from HPLC, confirming the potential of spectrophotometry as a useful, inexpensive method for rapid screening for pVACs in banana. Predominant carotenoids isolated were α-carotene (38.67%), trans β-carotene (22.08%), lutein (22.08%), 13-cis-β- carotene (14.45%) and 9-cis β-carotene (2.92%), demonstrating that about 78% of the carotenoids in bananas are pVACs. Provitamin A content estimated in terms of β-carotene equivalents (BCE) ranged from 0.24 to 21.06 μg g-1 FW with a mean value of 4.42 μg g-1 FW across all genotypes. Importantly, 10 plantain cultivars, three M. acuminata diploids and four hybrids with relatively high pVAC contents were selected for integration in banana biofortification efforts to tackle VAD.
To assess the effect of ripening on pVACs in plantain fruits, nine cultivars across the three main plantain types (French, False Horn and Horn) were screened at the unripe, ripe and overripe stage. Mean TC measured by spectrophotometry for plantain cultivars at the unripe, ripe and overripe stage was 16.94, 11.98 and 10.11 μg g-1 FW while mean BCE was 13.65, 6.95 and 5.05 μg g-1 FW, respectively. Notably over 80% of carotenoids in plantain cultivars were pVACs α-carotene and β-carotene across all ripening stages. French plantains had slightly higher BCE contents than False Horn and Horn types but this difference was only significant (P<0.05) at the unripe stage. Overall, ripening led to a decrease in pVACs content from the unripe to the ripe to the overripe stages accompanied by a corresponding increase in lutein content indicating that unripe fruits could yield more provitamin A than ripe and overripe fruits.
To explore the application of induced polyploidization as a breeding strategy for pVAC enhancement in plantains, 10 induced tetraploids derived from six diploid cultivars were evaluated for their agronomic attributes, carotenoid content and fertility. Tetraploids had distinct plant morphology but generally displayed inferior vegetative and yield traits from their corresponding diploids. Similarly, a 50% decrease in pVACs accompanied by a corresponding increase in lutein was recorded in induced tetraploids in comparison to their original diploids. Nevertheless, preliminary fertility assessments indicated over 70% pollen viability for induced tetraploids from four diploid cultivars. These findings demonstrated the use of induced polyploidization to generate useful genetic material that could be incorporated in hybridization programmes aiming to produce high pVAC triploids.International Institute of Tropical Agriculture (IITA)HarvestPlus Programm
Genetic variability and inheritance studies for low pH tolerance in tropical and sub-tropical maize germplasm
No full textEnglish: In Malawi maize is grown even in marginal lands, on steep slopes, wet lands, rocky areas
and low pH soils due to the high human population which excert pressure on the land. The
objectives of this study were to investigate genetically diverse maize genotypes for
tolerance to low pH soil conditions. In the hydroponic experiment genotypes
IWDC3SYNF2-B, VPO52, and LPHpop 4 had relatively higher nett seminal root length
and were considered tolerant, and DT-YSTR SYNTHETIC-B, TZE-WPOPDTC2STR-B,
TZE-YDTSTRC4-B, LPHpop3, LPHpop13, and LPHpop14 were sensitive or susceptible
to Al toxicity. Under field conditions, genotypes LPHpop16, LPHpop3, VPO739,
VPO5173 and LOW N POOL C3-B were identified to be relatively tolerant to low pH soil
conditions. SYNDTE–STY-W-B ranked first in terms of root tolerant index (RTi) with a
good NSRL in the glasshouse hydroponic experiment and this was followed by VPO717
which also had a relatively a better root tolerance index and nett seminal root length.
Phenotypic traits associated with grain yield, such as plant vigour, seed size (100 seed
weight), shelling percentage, number of ears per plant, ear height and plant height can be
used alongside grain yield when selecting germplasm for tolerance to low pH stress. In
general, the effects of low pH soil conditions contributed to reduction in grain yields and
yield components. The combined mean yield reduction due to low pH soil in this study
was 69.9%. From AMMI and GGE analysis, genotypes LPHpop21, VPO52, VPO72,
VPO744 and VPO96 were identified as the most stable. VPO097 was identified as an
unstable genotype. Chitala low-land optimal site was identified as the most discriminating
environment in terms of genotypes while Chitedze mid-altitude optimal environment was
identified as a stable environment.
The diallel study revealed that additive and non-additive gene actions were at play in the
expression of some of the traits like grain yield, number ears per plant, shelling percentage,
100 seed weight and plant vigour, while non-additive gene action was predominant in the
inheritance of characteristics such as anthesis-silking interval, plant and ear height, grain
texture, stem and root lodging and gray leaf spot disease. Positive and highly significant
GCA effects for grain yield were observed for inbred line CZL999601 across low pH and
optimal conditions. While negative and significant GCA effects for grain yield were observed for inbred line CML161 across low pH and optimal conditions. SCA results
indicated that single-cross hybrids CML999601/CML144, CML144/CML202,
CML481/CML288 and CML161/CM172 were best for grain yield across low pH and
optimal conditions. At a cut-off point of 1.0 with a cophenetic correlation of rcop = 0.87, the
UPGMA clustered the inbred lines based on GCA for grain yield into two main clusters
through use of Euclidean distance and standard deviation as type of scale. The pattern
mostly followed the origin of the maize inbred lines such that six out of seven inbred lines
from CIMMYT-Colombia (tropical) were grouped in the second cluster. The open
pollinated inbred line varieties and specific combinations (single-crosses generated)
identified in this study will be used in the National Maize Breeding Programme for
development of genotypes tolerant to low pH and diseases for yield improvement and
subsequent food security in the country.Afrikaans: In Malawi word mielies selfs in marginale grond, op steil hellings, vleilande, klipperige gebiede en in lae pH grond verbou, weens die hoë bevolking wat druk op die land plaas. Die doelwitte van hierdie studie was om geneties diverse mielie genotipes vir
verdraagsaamheid vir lae pH grondtoestande te ondersoek. In die hidroponiese eksperiment het genotipes IWDC3SYNF2-B, VPO52 en LPHpop4 relatiewe hoër netto seminale wortel lengtes gehad en word as verdraagsaam beskou en DT-YSTR SYNTHETIC-B, TZEWPOPDTC2STR-B, TZE-YDTSTRC4-B, LPHpop 3, LPHpop13, en LPHpop14 was sensitief of vatbaar vir Al toksisiteit. Onder veldtoestande, is genotipes LPHpop16, LPHpop3, VPO739, VPO5173 en LOW N POOL C3-B as relatief verdraagsaam vir lae pH grondtoestande geïdentifiseer. In die glashuis hidroponiese eksperiment was SYNDTESTY-W-B eerste in terme van wortel tolerante indeks met 'n netto seminale wortel lengte van 2.5 cm en is gevolg deur VPO717 met ʼn wortel tolerante indeks van 1.0 en netto seminale wortel lengte van 1.7 cm.
Fenotipiese eienskappe wat geassosieer word met graanopbrengs, soos groeikrag,
saadgrootte (100 saad gewig), saad persentasie, die aantal koppe per plant, kop hoogte en plant hoogte kan gebruik word saam met graanopbrengs wanneer kiemplasma geselekteer word vir verdraagsaamheid vir lae pH stres. In die algemeen dra die effek van lae pH grondtoestande by tot die verlaging in graanopbrengste en opbrengs komponente. Die gekombineerde gemiddelde opbrengs verlaging as gevolg van lae pH grond in hierdie
studie was 69.9%. Deur die AMMI en GGE analise is LPHpop21, VPO52, VPO72 is
VPO744 en VPO96 geïdentifiseer as die mees stabiele genotipes. VPO097 is geïdentifiseer as 'n onstabiele genotipe. Chitala lae-ligging optimale omgewing is geïdentifiseer as die mees onstabiele omgewing in terme van genotipes terwyl Chitedze middel-ligging optimale omgewing geïdentifiseer is as 'n stabiele omgewing.
Die dialleel studie het getoon dat beide additiewe en nie-additiewe geenaksie ʼn rol gespeel
het by die uitdrukking van die eienskappe soos graanopbrengs, aantal koppe per plant, saad persentasie, 100 saad gewig en groeikrag, terwyl nie-additiewe geenaksie oorheersend was in die oorerwing van eienskappe soos antese-baard interval, plant en kop hoogte, graantekstuur, stam en wortel omval en blaarvlek siekte. Positiewe en hoogs betekenisvolle algemene kombineervermoë (GCA) vir graanopbrengs is in die lae pH en optimale
omgewings, vir ingeteelde lyn CZL999601 waargeneem, terwyl negatief en betekenisvolle
GCA effekte vir graanopbrengs waargeneem is vir ingeteelde lyn CML161 vir lae pH en
optimale toestande. Resultate vir spesifieke kombineervermoë (SCA) het aangedui dat
enkelkruisbasters CML99601/CML144, CML144/CML202, CML481/ CML288 en
CML161/CM172 die beste graanopbrengs oor lae pH en optimale toestande gelewer het.
By 'n afsny punt van 1.0 met 'n ko-fenetiese korrelasie van rcop = 0.87, het die UPGMA
kluster, deur die gebruik van Euklidiese afstand en standaardafwyking as skaal tipe, die
ingeteelde lyne gebaseer op GCA vir graanopbrengs in twee hoof groepe verdeel. Die
groepering het die oorsprong van die ingeteeldelyne gevolg, sodanig dat ses uit sewe
ingeteelde lyne van CIMMYT-Kolombië (tropiese) in die tweede kluster groepeer. Die
OPVs, ingeteelde lyne en spesifieke kombinasie enkelkruisings wat geïdentifiseer is in
hierdie studie sal gebruik word in die Nasionale Mielie Teelprogram vir die ontwikkeling
van genotipes tolerant vir lae pH en siektes en om opbrengs te verbeter sodat
voedselsekuriteit in die land verseker kan word.Ministry of Agricultur
Genetic improvement of beta carotene in cassava (Manihot esculenta Crantz) landraces
No full textThe aim of this study was to identify farmers’ adoption challenges, perceptions and preferences of yellow-flesh cassava. Combining ability and stability of these genotypes were also determined. Total carotenoid content (TCC), proximate values and hydrogen cyanide (HCN) of the yellow-flesh cassava were measured and the retention of carotenoids in boiled biofortified cassava was determined. This information will help breeders to identify genotypes with the best nutritional quality across the tested locations for planting and promotion in Ghana also could provide a basis for implementing a recurrent selection scheme for developing cassava varieties with high levels of carotenoids and dry matter. In all the locations visited, farmers’ knowledge on the improved cassava varieties (white flesh) and the yellow-flesh cassava were generally poor among the men and women interviewed, due to their inability to access planting materials, which could be improved by strengthening the cassava seed system for awareness, and increased availability of the varieties to farmers. Very few men and women cultivated improved varieties and yellow-flesh cassava. The young adults, who are the future of the agricultural sector, lacked access to improved varieties and they must be given extra attention to understand the activities of cassava breeding programmes, to empower them to make use of these materials. The general combining ability (GCA) was larger than specific combining ability (SCA) for cassava mosaic disease (CMD), harvest index (HI) and TCC, with predictability ratios (0.98, 0.88 and 0.92 respectively) close to one. Hence, there is a possibility for improvement of the characteristics by selection. Positive significant correlation between pulp colour and TCC (r=0.59) and pulp colour and cortex colour (r=0.58) were observed. Negative significant correlation were seen between CGM and HI (r=-0.50), CMD and RTN (r=-0.45), and HI and RTN (r=-0.51). It implies that these key traits could be effectively combined in a breeding program. In particular, breeders can rapidly screen for high TCC by visually assessing the pulp colour in addition selection for CMD symptoms (in a high disease pressure zone). The selected individuals for pulp colour at early stage screening can then be quantified for carotenoids at later stages, to save cost. Some of the yellow-fleshed genotypes (progenies) displayed comparable dry matter content (DMC) values as their white-flesh elite parents and were selected for multilocational trial testing towards commercial release in Ghana. Findings of this study demonstrated that it is possible to simultaneously select for yield and quality traits, such as DMC, at seedling stage. It was shown that the yellow flesh cassava varieties could be used in a hybridization scheme with local material to combine both TCC and DMC traits with high yield in a CMD resistance background. Carotenoid-rich varieties also showed variation for important characteristics, which are key drivers of variety adoption in Ghana. In view of this, some cassava varieties, such as IBA090151 and IBA083774, are proposed for release in Ghana. The HCN content of the cultivars varied from location to location and the values observed were below 50 µg g-1 and hence can be classified as sweet cultivars (low HCN). The cultivars that were sweet were, however, above the range of the maximum acceptable HCN limit recommended by the World Health Organisation (WHO) and for that reason need to be processed before consumption (for example as fufu, konkonte, gari). Finally, it is recommended that cassava breeders review their breeding objectives to reflect the preferred traits of end-users, and pay attention to stakeholders’ perceptions of the yellow flesh cassava to develop demand driven varieties that will serve the need of end-users. Education to create awareness on the potential advantages and diverse uses of the improved biofortified cassava is also needed
The influence of abiotic stress on CIMMYT provitamin A elite maize germplasm
No full textMicronutrient malnutrition, including vitamin A deficiency, affects more than half of the world population, having a major effect on children less than five years old, pregnant and lactating women. The problem is significant in sub-Saharan Africa (SSA) where people subsist mostly on white maize which lacks vitamin A. Vitamin A deficiency is responsible for a number of health disorders that include poor vision and reproduction, and supressed growth and immunity. Biofortification of staple food crops such as maize with β-carotene can be a sustainable approach to address dietary vitamin A deficiency. Orange maize contains high levels of β-carotene, making it an important crop for combating vitamin A deficiency. The SSA region is also prone to various abiotic stresses that impact negatively on maize productivity. To ensure food security in the region, there is a need to breed highly nutritious maize cultivars adapted to the major abiotic stresses experienced in the region. To breed increased provitamin A hybrids, it is important to understand the mode of gene action affecting grain yield and β-carotene expression, and the heritability of β-carotene concentration under the prevailing stresses. There is also a need to determine the stability of provitamin A germplasm for grain yield and nutritional traits such as β-carotene under these stress conditions. In this study, 22 elite provitamin A inbred lines and five yellow drought tolerant inbred testers were crossed following a line × tester crossing design. Thirty hybrids had sufficient seed for replicated trials out of a potential of 110. The 30 hybrids and five checks were evaluated in Zimbabwe under optimum conditions, random drought stress, managed drought stress, combined drought and heat stress, low N stress and low P stress in 2014 and again in 2015. There was significant variation between hybrids for grain yield for all environments, except grain yield under low nitrogen stress. There was a significant interaction between year, environment and genotype for grain yield but no interaction was observed for grain texture. Inbred lines were highly heterotic for grain yield, especially under stress conditions. Narrow sense heritability for grain yield was more than 50% under optimal conditions, managed drought stress, combined and drought and heat stress and low P stress. AMMI and GGE analyses showed that genotype by environment interaction (GEI) was a very important source of maize grain yield variability. The environments were grouped into one mega-environment. The highly significant correlations between the environments suggest that testing can be done in only one environment. Hybrid environment, year and GEI effects for β-carotene were highly significant. Beta-carotene concentration was higher under optimum than under stress conditions and was highly significantly correlated with grain yield. Heritability for β-carotene was very high; 97% and 90% under optimum and 70% and 94% under managed drought stress in 2014 and 2015 respectively. General combining ability for β-carotene was significant and specific combining ability was not, emphasising the importance of additive gene action in the expression of the trait. Provitamin A hybrids had β-carotene concentration in the expected range (5-12 μg g-1) for first generation medium to high provitamin A maize genotypes. Lines 6, 7 and 8 can be used for breeding hybrids suitable for all environments except for managed stress conditions. Testers 1 and 2 were ideal for breeding for optimum conditions, managed drought stress, tester 2 for random drought stress and tester 3 for low P stress. Line 8 contributed consistently positively to grain yield, line 3 was favourable under managed drought stress and combined drought and heat stress, lines 6, 7, 8 and 9 were desirable under low N, 6, 7 and 8 under optimum conditions, 4, 6, 7, 8, and 10 under random drought stress, and 3, 8 and 10 under managed drought. The best performing and most stable genotypes for both grain yield and β-carotene can be distributed to SSA farmers for production. These hybrids will go a long way to alleviate vitamin A malnutrition among resource poor households in the region
Yield linkage drag in quality protein maize inbred lines and hybrids
No full textThe development of high yielding and stable quality protein maize (QPM) hybrids is important for increasing grain yield output per unit area, to support the fight against hunger and malnutrition in sub-Saharan Africa (SSA), as well as for feed supplement formulation for the animal and poultry industries. Despite the development of QPM genotypes with increased lysine and tryptophan content, important information is lacking on the yield potential of QPM genotypes compared to non-QPM (normal) genotypes. The main objective of this study was to quantify grain yield reduction (if any) due to the QPM trait. The specific objectives were to: (i) compare QPM and non-QPM inbred lines for yield and yield related traits, as well as quality traits, and determine stability for grain yield, (ii) compare QPM and non-QPM hybrids for yield and yield stability, (iii) estimate the combining ability for grain yield and quality traits of QPM and non-QPM inbred lines (iv) estimate the heritability, variance components, principal components, correlation coefficients, and do path analysis of grain yield, and agronomic and quality traits. In this study, 130 single cross hybrids were developed from 33 QPM and non-QPM inbred lines and four testers (two QPM and two non-QPM). Five hybrid checks (two QPM and three non-QPM, all single cross hybrids) were included, obtained from the International Maize and Wheat Improvement Center, Zimbabwe. The 135 hybrids together with the 40 inbred lines were evaluated in South Africa and Zimbabwe during the 2017/2018 and 2018/2019 cropping seasons. The inbred lines were evaluated at seven locations using a 5 x 16 alpha lattice design, while the hybrids were evaluated at 13 locations using a 5 x 27 alpha lattice design with two replications. In the field experiments, two plants per plot were selfpollinated for the determination of zein, tryptophan, amylose and starch, protein, oil, moisture and fibre contents. In the inbred line trials, the top six performing lines outyielded the best yielding check by 15%. Although the top two inbred lines were non-QPM, three of the six top yielding inbred lines were QPM. The QPM inbred line average yield was 0.29 ton ha-1 higher than for non-QPM inbreds. Inbred lines 39, 27 and 10 had protein content above 9%, while lines 2, 5 and 16 had tryptophan concentrations above 0.09%. The best performing hybrids were a QPM cross of line 11 x CZL15049 (entry 41) followed by a non-QPM hybrid involving line 28 x CZL15049 (entry 108). The best QPM hybrid outperformed the best non-QPM hybrid by 8.81%. In addition, the best QPM hybrid, genotype 41, outperformed the best non-QPM check (Pioneer) and best QPM check (CBI) by 50.45 and 52.24%, respectively. Despite this, QPM hybrids yielded 13.90% lower than non-QPM genotypes on average. The additive main effects and multiplicative interaction (AMMI) and genotype main effect plus genotype by environment interaction (GGE) biplots identified genotypes 108 and 12 as the most stable and high yielding hybrids. QPM hybrid 41 and non-QPM hybrids 108 and 12 were the highest yielding genotypes. Both additive and non-additive genetic effects were important in the expression of measured traits, with non-additive gene action controlling the inheritance of grain yield. Inbred lines 11, 14 and 28 and non-QPM tester CML444 showed desirable general combining ability effects for grain yield. Based on the specific combining ability values, crosses 41, 85, 99, 105, 105 and 121 were identified as the best hybrids across the 13 locations for grain yield. Hybrids 45, 69 and 6 had a high quality index, while hybrids 45 and 57 had high tryptophan content. Hybrids 51 and 37 had high values for starch and oil contents, respectively. Additive genetic effects were predominant in the control of the quality traits. Broad sense heritability estimates were higher than 80% for the traits measured. Most of the hybrids displayed heterosis for grain yield, with some having very high values. In conclusion, QPM inbred lines yielded higher than non-QPM lines, but QPM hybrids yielded 13.9% less than
non-QPM hybrids. So it would seem that there is yield drag associated with increased protein quality in hybrids in this specific set of material. There were, however, specific QPM hybrids that had excellent and stable yield, which can be considered for commercial release
Proteomic analysis of proteins responsive to drought and low temperature stress in a hard red spring wheat cultivar
Get PDFDrought stress is becoming more prevalent with global warming, and has been shown to have large effects on gluten proteins linked to wheat bread making quality. Likewise, low temperature stress can detrimentally affect proteins in wheat. This study was done to determine the differential expression of high molecular weight (HMW) gluten proteins in a drought and low temperature stressed high quality hard red spring wheat cultivar (PAN3478), against a control. The three treatments were applied in the greenhouse when the main tillers of each pot were at the soft dough stage, on 15 pots per replication, three replications and three plants per pot for each treatment. Seed of main tillers were bulked and randomly sampled. Removal of gliadins was done with 50% (v/v) 1-propanol. The HMW proteins were then extracted and separated by 2-dimensional gel electrophoresis. Gels were analyzed with SameSpots Progenesis (version 4.6.1.218). The protein spots that had p values lower than 0.05 and fold value equal to or greater than 1.2 were considered significantly differentially expressed. Spots were excised from the gel, digested with trypsin and analysed by mass spectrometry. The proteins were identified by matching the spectra to theoretical data from the Swissprot protein database. There was a 1.3 to 1.8 fold change in 19 protein spots due to the cold treatment. The drought treatment caused 1.3 to 3.8 fold change in 20 spots that were significantly differentially expressed. Two spots, one with matching peptide sequences to HMW glutenin proteins DX5, DY10 and PC256, and one to HMW glutenin protein PW212, were differentially expressed under both drought and cold stress. Other proteins differentially expressed under cold stress included proteins with similar peptides to alpha/beta-gliadin A-IV, fructan 1- exohydrolase w3, a number of HMW-GS P212 and HMW-GS DY12 proteins and HMW-GS DY10, chloroplastic Nad(P)H-quinone oxidoreductase subunit 2 A, alpha/beta-gliadin and low molecular weight-GS PTDUCD1. Under drought stress ATPase, HMW-GS PW212, HMW/GS (HMW subunit 12) and DY10, Ubiquitin and Eukaryotic translation initiation factor isoform 4G-2 were differentially expressed. The HMW glutenins are known to have a large effect on baking quality, and clearly protein spots with similar peptide sequences with especially HMW-GS DY12, PW212, PC256, HMWGS DX5 and DY10 were responsive to cold and drought stress, and could directly influence baking quality
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