CREA Journals (Consiglio per la ricerca in agricoltura e l’analisi dell’economia agraria)
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Characterization of the genetic structure and diversity of maize (Zea mays L) landrace populations from Mexico
Get PDFMaize (Zea mays L) is a globally important crop. In Mexico, its center of origin and diversity, it forms part of the culture and staple diet of present-day towns. This condition has allowed the development of a large number of maize landraces. In southern Mexico, in the states of Yucatán, Quintana Roo, Campeche and Chiapas, little attention has been given to the diversity potential that landraces represent in order to make best use of them. This work therefore characterized the genetic structure and diversity of 16 maize landrace populations from the southern region of Mexico using ISSR markers. A total of 69 loci were generated with 100% polymorphism. The analysis revealed the formation of two groups with geographical and genetic origins in the Yucatán Peninsula and the state of Chiapas. Wide genetic diversity was found for the entire sample of assessed populations (He = 0.40 and I =
0.54), as well as in the groups formed (He = 0.36, I = 0.52 and He = 0.35, I = 0.50 respectively). At the population level within each group, the populations that formed the Yucatán Peninsula group had greater mean diversity values than in the Chiapas group (He = 0.33, I = 0.36 and He = 0.32, I = 0.35 respectively). Based on this information, it is recommended to develop in-situ conservation programs and to increase the existing ex-situ collections in the region that allow us to enhance the germplasm of the maize landraces of Mexico in breeding programs
Genotypic and morphological diversity analysis in high altitude maize (Zea mays L.) inbreds under Himalayan temperate ecologies
Get PDFThe present investigation was carried out to generate information on genetic divergence of maize (Zea mays L.) inbreds and to identify elite lines to develop potential hybrids for high altitude ecologies. Data were recorded for thirteen (13) quantitative traits viz. germination (%), root depth, shoot length, days to 50 % pollen shed, days to 50% silking, plant height, ear height, ear length, ear girth, number of kernels per row, 100 seed weight, grain yield per plant. The tested genotypes expressed significant variability with high estimates of heritability (broad sense) for all the traits revealing that these traits are amenable to genetic improvement. Grain yield per plant exhibited positive and significant correlation with plant height, ear height, ear width, number of kernels per row, number of kernel rows and 100 seed weight at both the levels which exhibit a strong possibility for improvement of grain yield per plant by selection for these traits. Genetic divergence based on thirteen quantitative traits grouped thirty maize inbred lines into four clusters as per Mahalanobis D2 analysis employing Tocher’s method which revealed wide diversity in elite genotypes owing to the involvement of diverse parental lines in the hybridization programme. Grain yield per hectare was the main factor contributing to total divergence (41.16%) which needs to be considered for highlighting clusters to be chosen for the purpose of further selection
Variance components and heritability of traits related to Striga asiatica resistance and compatibility to Fusarium oxysporum F.Sp. Strigae in maize
Get PDFGenetic gain in breeding maize for yield and yield components and Striga resistance is dependent on the magni-tude of genetic variation and heritability. The objective of this study was to determine variance components and heritability of yield and yield-related traits and Striga asiatica (L.) Kuntze resistance in maize involving a bio-control agent Fusarium oxysporum f.sp. strigae (FOS). Eighteen selected and genetically diverse maize populations were evaluated across nine testing environments in three sites under three levels of FOS treatment during the 2016/2107 growing season using an alpha lattice design with two replications. Variance components, heritability estimates and correlations among S. asiatica traits, grain yield and yield components of maize were calculated to provide a selec-tion guide. Significantdifferences (P0.5) were recorded for ear aspect (0.58), cob length (0.60), grain yield t ha-1 (0.61), grain yield plant-1 (0.65), cob diameter (0.83), 100 kernel weight (0.91); Striga counts (0.71) and Striga damage rating (0.75). Grain yield t ha -1 and its components were negatively corre-lated with Striga parameters under FOS treatments. Yield-related traits such as cob length, cob diameter, and 100 kernel weight were important in indirect selection for FOS compatible and Striga resistant maize genotypes. FOS could serve as an effective bio-control agent against S. asiatica in maize production using compatible genotype
Combining meta-QTL with RNA-seq data to identify candidate genes of kernel row number trait in maize
Get PDFKernel row number is an important component of grain yield in maize. With development of classical quantitative trait loci (QTL) mapping and modern RNA-seq, numerous QTL and tissue-specific gene expression data were accumulated in previous studies. In this paper, a total of initial 373 QTL for grain yield (GY) and kernel row number (KRN) were collected based on 29 previous literatures. Fifty-four meta-QTL (MQTL) were detected via the meta-analysis method with IBM2 2008 Neighbors as a reference map, including 19 for GY and 35 for KRN. These MQTL were unevenly distributed on all 10 chromosomes. Chromosome 1 harbored the most initial QTL and MQTL, and chromosome 7 contained the least. Three MQTL for KRN have been overlapped with MQTL for GY on chromosomes 1 and 3. A total of 1,588 (46.07%) out of 3,447 genes located in the KRN MQTL regions were identified by gene expression data, and categorized into 101 significant GO terms. Meanwhile, six candidate genes were identified from MQTL regions, which are homologous to three functionally characterized genes found to participate in plant inflorescence development. The identified MQTL could be applied to marker-assisted selection (MAS) to facilitate yield architecture, QTL fine mapping and gene cloning in the maize community. Furthermore, the identified candidate genes could enhance the selection efficiency by MAS directly, and could illuminate molecular mechanisms of grain yield in maize
Comparison between transgenic maize with exotic betaine aldehyde dehydrogenase (BADH) gene and its untransformed counterpart
Get PDFWe investigated the performance of a transgenic maize (Zea mays L) line with an exotic betaine aldehyde dehydrogenase (BADH) gene and its untransformed counterpart under drought and normal water conditions. Membrane permeability, osmoprotectant contents, and antioxidant enzyme activities of the maize lines as well as plant height and biomass were compared. The results showed that, under drought stress, compared with the untransgenic line, the contents of glycine betaine (GB), soluble sugars, soluble proteins and proline of the trans- genic line were significantly higher, so was the peroxidase (POD) activity; the contents of superoxide anion free radical, malondialdehyde (MDA) and the electrical conductivity of the transgenic line were lower; plant height and the biomass of the transgenic line were significantly higher. Under normal water conditions, the contents of soluble protein and MDA content of the transgenic line were significantly lower; but it was not the case for the content of superoxide anion free radical, electrical conductivity and superoxide dismutase (SOD) activity. No significant difference was observed in GB content and, the plant height and the biomass between the 2 lines. We conclude that the transgenic maize with exotic BADH gene was superior over its untransformed counterpart under drought stress and they performed similarly under normal water conditions
Low cost poplar inventory in the plain of Piemonte (Italy)
Get PDFThe forest inventory is an important tool to know the current and to estimate the future wood availability for industry. Generally it request high economic and time costs if based on direct sampling on the areas or on classification of aerial photo or satellite images. The paper shows a methodology based on open source software (QGIS®) and images free available on the web (trough ‘Google EarthTM’ software) to carry out a forest inventory particularly regarding poplar stands surface. This cultivation in Italy is characterized by short rotation, about ten years, and the wood is a row material very important for the industry, particularly for plywood. The results of an experimental survey located in the plain of Piemonte Region (north-west Italy) are presented in order to evaluate the timing of completion and the efficiency of the methodology. Data of land cover, divided by poplars, other forest plantations, and natural forests are showed and compared with old inventories, carried out with traditional methods. The evidence of reduction of costs in term of man involved, time, and materials is counterbalanced by some problems due to different age of the web images; however, this alternative methodology, applied by an experienced operator can ensure a good level of precision for the purposes required, with very low costs
Heterosis, Potence Ratio and Genetic Distance for yield and yield contributing traits in single cross maize hybrids
Get PDFThe study is concerned with the development of single cross heterotic hybrids and to understand the underlying genetic principle for heterosis as well as to establish its relation with parental genetic divergence to formulate a breeding strategy for maize improvement. Heterosis was trait dependent exhibiting high level for plant height, cob characters and grain yield/plant. Two hybrids were better than standard checks, but only DMR QPM 103 x CML 539 recorded 26-28% heterosis over both checks and also displayed positive heterosis for cob characters as well for grain weight. Significanly it was almost seven days earlier in floweringwhich favoured pollination advantage with better floweringsynchrony. Cob characters were positively correlated with yield heterosis’s cob diameter was positively correlated with all cob characters. Cob diameter heterosis could be effective predictor for grain yield heterosis. Majority of the traits were controlled by over dominance gene effect, where more than 80% of hybrids recorded over dominance gene effect for plant height and cob characters. The breeding strategy has to be adopted to maximize heterosis. In this context it appears that inbred tester would improve the population more than the population tester because in an inbred, alleles are fixed whereas in population they are intermediate in frequency. As many as 34 hybrids recorded mid parent heterosis of 100% or above. Of them 25 (74%) belonged to the medium parental divergence group having parental grain yield of 50 g or above. It was observed that parents with high per se performance and intermediate genetic divergence produced highly heterotic and high yielding hybrids
Assessing seed regeneration in chestnut coppices: a methodological approach
Get PDFOver the last decades, the abandonment of the traditional management due to many adverse factors caused a general aging of chestnut coppices; this led to an increased mortality of the chestnut stools and a consequent replacement with the entry of other species. Preservation and improvement of the chestnut coppice emphasize the importance of natural regeneration for future forest management: seed regeneration contributes to provide new stools for future coppice generations and promotes a proper development of the stand in terms of specific and structural diversity. In this study, we propose a method for investigating the relationship between density, diversity, development of natural regeneration and possible driving forces in terms of site conditions and stand parameters. At this purpose, a survey based on mixed sampling plots was conducted in different coppice systems (simple coppice, coppice with standards), 4÷8 years after the coppicing: measurements on stools, shoots and standards, as well as seed regeneration were carried out. Chestnut seed regeneration was characterized by taller individuals in simple coppice plots, even though the seedlings were fewer than those in coppice with standards treatment. Canopy cover and amount of standards, density of stools and resprouting shoots negatively influenced the establishment of chestnut seed regeneration: likewise, within the same treatment, plots with greater site index promoted the development of chestnut regeneration.The proposed methods allowed a characterization of the dynamics related to the natural regeneration of classical chestnut coppice systems, identifying the main controlling factors. Among them, factors modifiable by management, such as stand structure and amount of standards, offer forest managers multiple silvicultural options to control seed regeneration processes
Microsatellite marker dependent genetic divergence assessment within and among heterotic groups of tropical maize inbred lines
Get PDFUse of microsatellite markers can be helpful in assessing the nature and extent of genetic diversity among inbred lines, assigning inbred lines efficienly to heterotic groups and making the choice of heterotic parents to develop new hybrids. A study was conducted to determine the heterotic groups of 18 inbred lines of maize including three inbred testers and to examine the nature and extent of divergence within and between heterotic groups of inbred lines based on the analysis of targeted microsatellite sites. Using hybrid index and hybrid mean values obtained from the results of experimental trials conducted over the two seasons as the indices, inbred lines were classifie into three heterotic groups. Microsatellite profiing with a panel of 28 primer pairs covering all chromosomes revealed ample genetic polymorphism, which allowed unique genotyping and unambiguous classificaion of inbred lines. Basically, the inbred lines and testers were differentiated into four genotypic groups. Principal coordinate analysis based on similarity indices and spatial ordination of the genetic profile showed four well define genotypic groups of 18 inbreds. The distribution pattern of the entries into different heterotic groups formed on the basis of hybrid index value and hybrid mean value corresponded with the microsatellite markers based groups to the extent of 75% and 67% in the firs heterotic group, 40% and 29% in the second heterotic group and 33% and 40% in the third heterotic group, respectively. Overall coincidences of inbred lines in heterotic groups based on microsatellite markers with the hybrid index value and hybrid mean value based heterotic groups (47% and 40%, respectively) indicated that microsatellite markers may be effectively and efficienly utilized to assign the inbred lines to heterotic groups for the purpose of reducing the number of single crosses to be generated and evaluated. Average genetic divergence revealed within and between heterotic groups by the microsatellite markers may be utilized as the criterion for parental line selection during development of experimental hybrid
Investigating the unusually high cell wall digestibility of the old INRA early flint F4 maize inbred line
No full textThe old INRA flint early line F4, which belongs to the Northern Flint group, is typified by its high cell wall digestibility which reaches values as high as those observed in several brown-midrib bm3 mutant lines. The F4 line thus appeared as a model that could contribute to the understanding of genetic mechanisms involved in variation of secondary wall traits. Different strategies and results were thus gathered including especially cell wall biochemical and digestibility investigations, expression approaches, QTL investigations, and colocalizations between QTLs and candidate genes. Lignin content was lower in F4 than in other lines, with a tendency to lower p-coumarate content. The S/G (Syringyl/Guaiacyl) ratio was similar in F4 as in other lines, but this ratio was nearly not reduced in F4bm3, conversely as what is observed in bm3 mutants. In comparison with the INRA F2 control line, expressions of three PAL genes including the ZmPAL, of the ZmF5H1 and the ZmCOMT genes were significantly reduced in F4 lignifying ear internodes at early silking stage. In the F7025 x F4 RIL progeny, seven QTLs were shown with favorable alleles (increasing cell wall digestibility) originating from F4. Two strong QTLs were located in bins 1.03 and 2.03 colocalizing with the ZmMYB019 and ZmSWN6 transcription factors, respectively. Orthologs of ZmMYB09 have been shown to be involved in lignin biosynthesis, and the PpMYB8 ortholog was shown to regulate PAL gene expression in maritime pine. The ZmSWN6 NAC transcription factor is an upstream master regulator of the secondary wall biosynthetic programs. At the other QTL positions, colocalizations were also shown with other secondary wall related ZmMYB, but also with BAHD genes involved in arabinoxylan feruloylation, and with the position of the bm6 mutation. Three QTL positions were shown with favorable alleles originating from F7025, which colocalized with ZmMYB and ZmSWN2 transcriptions factors. This latter fact indicates that, despite its high cell digestibility, the F4 line does not gather all alleles possibly available for this trait improvement. As a tentative conclusion, the F4 unusually high cell wall digestibility is likely related to the altered working of at least two major transcription factors regulating cell wall biosynthesis and assembly