CREA Journals (Consiglio per la ricerca in agricoltura e l’analisi dell’economia agraria)
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Assessment of interrelationships among grain yield and secondary traits of early-maturing maize inbred lines under drought and well-watered conditions
Get PDFKnowledge and understanding of interrelationships between grain yield and yield-related traits would ensure progress from selection in maize breeding programs through the use of appropriate selection indices. One hundred and fifty-sixearly-maturing maize inbreds were evaluated at fiveenvironments in Nigeria, for 2 years to assess the relationship between grain yield and yield-related traits of maize inbreds under drought and well-watered conditions. Genotypes, and genotype × environment interaction mean squares were significant(P<0.05) for grain yield and other measured traits under drought and well-watered conditions. Under drought, plant and ear aspects, ear height, ears per plant (EPP), leaf senescence, number of seeds per ear, and seeds per row had direct effects on grain yield, accounting for 76% of total variation. Under well-watered conditions, days to silking, ear aspect, ear height, EPP, ear length, 100-kernel weight, number of seeds per row, plant height, and stalk lodging had significantdirect effects on yield. Genotype main effect plus genotype × environment interaction (GGE) biplot identifiedplant and ear aspects, days to anthesis and silking, ASI, EPP, stay green characteristic, plant and ear heights, ear diameter, number of seeds per ear, number of seeds per row, and ear length as the most reliable traits for indirect selection for grain yield improvement under both research conditions. Plant and ear aspects, ear height, stay green characteristic, number of seeds per ear, and number of seeds per row were identifiedby both path–coefficientand GGE biplot analyses as the most reliable traits for selecting for grain yield under drought. Ear aspect, EPP, days to silking, plant and ear heights, number of seeds per row, and ear length were the most reliable traits for selecting for improved grain yield under well-watered conditions
A review of genetic analysis and response to selection for resistance to Busseola fusca and Chilo partellus, stem borers in tropical maize germplasm: A Kenyan perspective
Get PDFThis paper provides a review on the context for the research in maize improvement for resistance to stem borers (Chilo partellus and Busseola fusca) in tropical environments. The following aspects are reviewed a) major productions constraints in East Africa, b) the stem borer problem in maize, c) genetic studies on maize resistance to stem borers. The explanations of key technical issues on progress and challenges in breeding for stem borer resistance in maize, inheritance of stem borer resistance and combining ability in maize, maize heterotic patterns, determination of heterotic orientations, application of the line x tester mating design, screening methods, selection indices, genotype x environment interactions, and response to selection for resistance to stem borers are addressed. Therefore, this paper forms a setting of reference for the study
Gene action controlling stability and adaptability in maize
Get PDFLimited knowledge about the genetic merit of maize landraces contributes to their little use in breeding, al- though some reports pointed them as a source of useful alleles. Repeated cultivation of landraces for many generations could make them a useful germplasm source to enhance yield stability. This study pretends to determine if such statement holds, and to analyze stability in terms of gene action involved. Twenty Argentine landraces were testcrossed to three US and two Argentine elite lines, and evaluated in 13 environments. Effects of general and specific combining ability for grain yield and ecovalence, as well as for regression coefficients of response to en- vironments were also predicted. Non-additivity resulted more important than additivity for controlling ecovalence, and frequently resulted detrimental to stability. Although landraces contributed to ecovalence, their importance was less than that of lines. Testcrosses´ adaptability to environments was variable depending on the line tester considered. Relative greater importance of lines´ general combining ability for ecovalence than landraces’ general combining ability could be attributed to a successful selection for stability during the development of inbred lines. Sixty percent of landraces appeared more adapted to unfavorable environment, which suggests their higher level of rusticity. Argentine lines provided greater stability to their testcrosses than US lines. Correlation between grain yield and stability was mainly dependent upon non additive effects. More productive testcrosses tend to have greater ecovalence (less stability) due to specific combining ability effects. Inbred lines selected for greater general combining ability effect tend to provide their testcrosses higher stability
Line x testers analysis of tropical maize inbred lines under heat stress for grain yield and secondary traits
Get PDFThe combining ability and mode of gene action in tropical maize germplasm is not extensively studied. In the present study, a line x tester analysis involving 290 test-cross hybrids developed by crossing 145 tropical maize inbred lines with two testers and four standard checks was conducted for grain yield and other agronomic traits under heat stress during summer 2013 at B gudi agriculture research station. The main objective of the investigation was to study mode of gene action governing the traits under heat stress along with identification of superior inbred lines based on combining ability to develop heat tolerant hybrids. Analysis of variance showed that mean squares for genotypes was highly significant for grain yield, days to anthesis and silking, anthesis silk interval, plant height and ear height under heat stress. The combining analysis for lines (GCA), tester (GCA) and line x tester (SCA) showed significant difference (P < 0.01) for all the traits under study except ASI for LXT interaction. This indicates that both additive and non additive gene action control the expression of these traits under heat stress. The low GCA variance to SCA variance ratio for all the traits showed preponderance of non-additive gene action in the inheritance of the traits. Among 145 inbred lines used for study, the inbreds L78, L73, and L37 showed good general combining ability for grain yield. The crosses L118 x L2 and L143 x L1 were having good specific combiners ability for grain yield under heat stress. These inbreds can be used in breeding program for development of heat tolerant hybrids through exploitation of dominant gene action
Influence of titanium foliar application on antioxidant enzyme activity and some biochemical attributes of corn
Get PDFThis study was conducted to evaluate the effect of solution titanium dioxide and titanium oxide on antioxidant enzyme activity and some biochemical attributes of corn during 2010 growing season in the research farm of Islamic Azad University of Shahryar –Shahr-e Qhods. The experimental design was randomized complete blocks arranged in factorial with four replications. The factors were included two growing stages i.e. four leafy stage and stem elongation for titanium application and five titanium concentration and sources including control (water), titanium oxide (Bulk) and three concentrations of 0.01%, 0.02%, and 0.03% of titanium dioxide nanoparticles. Antioxidant enzymes activity, malondialdehyde and 8-hydroxyguanosine, dityrosine, protein and membrane sta- bility were assayed. The results showed that there was significant difference between growing stages regarding catalase, glutathione peroxidase, malondialdehyde, dityrosine and protein content. In addition, titanium caused an increase in antioxidant enzyme activity and decrease in malondialdehyde accumulation. In general titanium dioxide nanoparticle (0.03%) application improved antioxidant enzymatic system and prevent lipid peroxidation in corn plants. So it can be recommended to use this material on stressed plants
Diallel analysis and inbreeding depression of commercial maize hybrids aiming the formation of base populations
Get PDFThe development of base populations derived from high yield commercial hybrids is considered one of the main strategies to initiate a maize breeding program, mainly because these hybrids have already been tested in many environments, and so, associating high yield and a large proportion of favorable loci fixed. Therefore, the objective of the present study is to estimate the combining abilities and inbreeding depression of commercial maize hybrids for agronomic traits. Eighteen commercial hybrids divided in two groups accordingly to their respective companies, seventy-two F combinations from a partial diallel scheme, eighteen S populations and one check were evaluated in a randomized complete block design in two experiments, both in Sementes Balu Experimental Unit, Sabáudia (PR), Brazil, for growing seasons from 2011/2012 and 2012/2013. The Griffing method (1956), adapted to a partial diallel by Geraldi and Miranda Filho (1988) was applied for the evaluation of the general com- bining ability (GCA) and specific combining ability (SCA). The hybrids P1630, P4285, 30B39Y and DKB370 showed increased yield, and hybrids P1630, 32R22H, and DKB615 showed reduced plant and ear height. These hybrids can be recommended for the extraction of inbred lines and formation of composites followed by intrapopulation selection. The combinations P1630 x DKB330, P4285 x DKB245, 30F53 x DKB370, and 32R22H x DKB370 showed desirable SCA effects for grain yield and are recommended for use in interpopulation breeding programs. Among the hybrids with desirable GCA effects, 30B39Y showed the lowest inbreeding depression effect for the analyzed traits
Significance of irrigation treatments and weather conditions on European corn borer appearance
Get PDFIncreased average air temperatures, winter temperatures, wind, amount of rainfalls and water shortages are climate factors that affect pest invasion. The aim of this study was to determine the effects of weather conditions on occurrence of European corn borer (ECB) (Ostrinia nubilalis Hubner) on different maize genotypes under three irrigation levels. This study was conducted at the Agricultural Institute in Osijek (Croatia) during three years period (2012 - 2014). Trials included three levels of irrigation (A1 – control, A2 60% - 100% water field capacity (WFC), A3
80% - 100% WFC) and four maize genotypes (OSSK: B1-596; B2-617; B3-602 and B4-552). At the end of each growing season ear weight (g), tunnel length (cm), ear shank damage (cm), number of larvae in maize stem, ear shank and total number of larvae were recorded. Unfavorable environmental conditions delayed ECB appearance for more than 10 days. In 2014, the lowest average air temperature in vegetation season (18.23˚C) and the greatest amount of rainfalls (523.3 mm) were recorded, whereas intensity of ECB attack was the lowest compared to other two years. The highest air temperatures were recorded in 2012, in average 19.95˚C while the rainfalls were 291.2 mm and ECB attack in this year was the highest. The lowest damage of plants was at the highest level of irrigation and hybrid B1 was the most susceptible to ECB. Although appearance of ECB was similar on tested variants, in all tested years, with increased air temperatures and an average rainfalls we can expect greater ECB potential to damage maize
Genetic variability, heritability and genetic advance studies in top- cross and three-way cross maize (Zea mays L) hybrids
Get PDFUnderstanding the genetic variability, heritability and genetic advance of traits in any plant population is an im- portant pre-requisite for selection program. This study was designed to assess the magnitude of genetic variabili- ty, heritability and genetic advance of traits in top-cross and three-way cross maize (Zea mays L) hybrids evaluated at three locations in South-Western Nigeria. The trial consisted of ten genotypes each of top-cross and three-way cross hybrids arranged in randomized complete block design with three replications. Data on grain yield and other desirable traits across the three locations were used to estimate the genetic variability parameters, heritability and genetic advance (GA). Highly significant (P ≤ 0.01) differences were detected within each hybrid class for all the traits. Traits evaluated in this study exhibited different levels of variability, heritability and genetic advance between the two hybrid classes. Low to moderate phenotypic coefficient of variation (PCV) and genotypic coefficient of variation (GCV) were recorded. Also, low to very high heritability and low to high GA values were recorded for all the traits measured in the top-cross hybrids, whereas the three-way cross hybrids exhibited low to moderately high heritability estimates and low to moderate GA values. Grain yield and field weight showed moderate GCV, moderately high heritability and high GA values in top-cross hybrids. These characters exhibited moderate GCV but low heritability and GA values in three-way hybrids. More characters in top-cross hybrids revealed sufficient amount of variability than in three-way cross hybrids, thus offer scope for genetic improvement through selection
The maize (Zea mays) b-32 protein shows RIP activity in yeast cells
Get PDFRibosome-inactivating proteins (RIPs) are either single-chain (type 1) or two-chain (type 2) toxins. They are toxic to eukaryotic cells by cleaving a N-glycosidic bond in an extremely conserved loop located in the 28S RNA. This releases a specific adenine and inactivates the ribosome, ultimately inhibiting protein synthesis. Plant RIPs have been intensely investigated because of their projected antiviral, antifungal and insecticidal activity. RIPs also have biomedical applications as the toxic mojety of immunotoxins. Given their biotechnological potentials, it is strategic to develop platforms to rapidly evaluate the activity of recombinant RIPs. This investigation fills this need in that it reports that the yeast Saccharomyces cerevisiae is a model system to assess the impact of genetic manipulations on the functionality of a recombinant Zea mays RIP named b-32
Nutritional and phenotypical characterization of two South African maize (Zea mays L) varieties sampled in the Qwa-Qwa region
Get PDFZea mays L represents one of the main source of energy in the diet in many African countries, especially in the sub-Saharan regions. White maize varieties, characterized by the lack of carotenoids, are usually widely preferred in Africa for human consumption, and this contributes to the occurrence of Vitamin A deficiency; yellow varieties, often derived from commercial hybrids, are usually destined for animal feeding. In this study we characterized from the phenotypical and nutritional points of view one white and one yellow South African landrace maize cultivar obtained directly from the farmers in the rural region of Qwa-Qwa (Free State Province). Calorific value, oil, protein, starch, minerals, flavonoids and carotenoids content were determined, together with free and phytic phosphorus (P). Both of the varieties showed lower protein and Fe content in comparison to the ones used as control, and the yellow one also had a low content of Zn. The white variety was characterized by a higher free P content but also by a very low level of carotenoids. Our data show that there are no nutritional reasons to prefer the white variety for human consumption, with the exception of the large size of the seeds, which make them particularly adapted for milling; hence the nutritional value of these varieties, and in particular of the white one, should be improved (protein, Fe and carotenoids), contributing in this way to tackle the problem of malnutrition in South African rural areas