Yellow Maize Population Research Articles

Heterotic Patterns for Twelve Exotic and Local Yellow Maize Populations in Egypt

The concept of heterotic groups and patterns is fundamental to hybrid breeding theory and practice, the objective of this study was to determine heterotic patterns among twelve yellow maize populations, eight of these populations were exotic germplasm, six from China (Ch2, Ch6, Ch8, Ch12, Ch14, and Ch15), one from France (Fr.), and one from CIMMYT (DTPY); and four local populations contain mixture of Local and exotic germplasm (NYP, NDTYP, Sk21, and Gm YP). Half diallel was performed among the populations at 2018 summer season. Twelve parents and their 66 crosses were evaluated at three locations in 2019 summer season. Data were collected for grain yield, number of days to mid-sulking, plant and ear heights. Results showed that High significant differences were observed among locations, entries and their partition i.e., general and specific combining abilities (GCA and SCA) effects for all the studied traits. Also, locations by entries interaction was significant or high significant for all studied traits, while location by GCA effects interactions was highly significant and significant for plant height and ear height respectively. In addition, location by SCA effects interaction was highly significant to differ for plant height. This study showed that, Ch2, Ch12, Gm YP and Sk 21 have good Potentials for use in the National Maize Research Program (NMRP) as new heterotic patterns to develop new yellow diverse inbred Lines. The combinations (Ch14xSk21), (Ch2xGmYP), and(Ch2XDTPY) Showed desirable Specific Combining ability effects for grain yield and therefore, recommended to use in inter and intra population breeding program.

Efficiency of Index-Based Selection Methods for Stem Borer Resistance in Maize (Zea mays L.)

Breeders need a simple and reliable index that could be used to make selection quickly in a breeding program. A study was conducted at the International Institute of Tropical Agriculture, Nigeria, to compare efficiency of four selection indices in selecting the best genotypes in a population improvement program involving a yellow-grained (DMR ESR-Y) and white-grained (DMR ESR-W) maize (Zea mays L.) population under artificial stem borer infestation. Rank summation index (RSI), Base index (BSI), Multiplicative index (MI), and Optimum index that uses heritability as weight (OI) were compared using grain yield, plant aspect, ear aspect, stalk breakage, and tolerance to stem borer as selection criteria. The selection criteria had moderate to high narrow-sense heritability. Each of the traits had a significant correlation with all selection indices, except MI in DMR ESR-Y. The BSI had the highest selection differential (23.32%) followed by OI (21.45%) in the white maize population. It also had the highest (29.11%) followed by RSI (20.99%) in the yellow maize population. The BSI also had strongest correlation with RSI in the white (−0.95**) and the yellow maize population (−0.90**). Percentage similarity was highest between BSI and RSI in the white (82.6%) and yellow maize populations (72.3%). This suggested that both BSI and RSI are good selection indices that could be used in improvement programs for stem borer resistance in maize.

Genetic Variances and Heritabilities of Traits of an Early Yellow Maize Population after Cycles of Improvement for Striga Resistance and Drought Tolerance.

Drought and Striga are principal constraints to maize (Zea mays L.) production in sub-Saharan Africa. An early yellow maize population, TZE-Y Pop DT STR, which had undergone five cycles of selection for resistance to Striga, followed by three cycles of improvement for drought tolerance, was investigated for yield gains, changes in genetic variance, and interrelationships among traits under drought stress and optimum environments. Two hundred and forty S1 lines comprising 60 each from the base population and subsequent populations from three selection cycles improved for grain yield and drought tolerance were assessed under drought and optimal environments in Nigeria from 2010 to 2012. Genetic improvements in grain yield of 423 and 518 kg ha–1 cycle–1 were achieved under drought stress and optimal environments. Predicted improvements in selection for yield were 348 and 377 kg ha–1 cycle–1 under drought stress and optimum environments, respectively. The highest yield observed in C3 was accompanied by reduced days to silking and anthesis–silking interval, improved plant aspect and ear aspect, and increased plant height and ears per plant across research environments, as well as improved stay-green characteristic under drought. The level of genetic variability for yield and a few other traits were maintained under drought and optimal environments in the population. The presence of residual genetic variability for yield and other assayed traits in C3 indicated that progress could be made from future selection in the population depending on the ability of breeders to identify outstanding genotypes and the precision level of experimentation. Substantial improvement has been made in yield and drought tolerance in C3 of the population.

Correlation between agronomic and stem borer resistant traits in maize: Implications in selection

Objective : The interrelationship between agronomic and resistant traits of two stem borer species, and its influence on selection was studied in a yellow maize population, DMR ESR-Y, at Ibadan between 2009 and 2010. Methodology and results: Two hundred and fifty (250) full-sib progenies of the population with three checks were evaluated. Resistant traits had negative correlations with most agronomic traits including grain yield (GY). GY had significant relationship with days to 50% pollen shed, (DTA) (rg = 0.49**), plant height (PH) (rg = 0.46**) and ear aspect (EA) (rg = -0.98**). Indirect selection of GY via DTA and PH gave gains that were a little lower than direct selection for GY, but they have higher heritability. Indirect selection of stem tunnelling and cob damage through EA would give gains of 150.64 % and 106.94 % respectively. Conclusion and application of results : This result suggested that either days to 50% pollen shed or plant height could be considered in selection for stem borer resistance. Ear aspect is another good criterion to consider instead of cob damage and stem tunnelling to hasten selection. The result indicated that breeders selecting for stem borer resistance and high yield could consider plant height, days to 50% pollen shed, ear aspect and grain yield itself as criteria for selection. In selecting the best genotypes in any crop improvement study therefore, breeders need to consider not only the magnitude of the correlation between pairs of traits, but the desirability of their relationship, ease of measuring the traits, correlated response among the traits, and heritability of the secondary trait selected. Keywords : Correlated responses, heritability, secondary traits, selection, stem borer resistance

Response of recurrent selection on yield, kernel oil content and fatty acid composition of subtropical maize populations

High oil maize (HOM) has been successfully achieved by a long-term breeding program. The aim of this study was to evaluate eight cycles of recurrent selection for agronomic traits and HOM content in four subtropical white and yellow maize populations and the effect of selection on yield, kernel physical properties, oil content, fatty acid (FA) profile and lipophilic antioxidant (LAOX) capacity. Through the selection cycles the agronomic traits showed a low but significant increase of grain yield and reduction in diseases. These positive changes significantly affected kernel physical properties and distribution of ground particles related to grain hardness. Oil content in kernels increased through cycles of selection and had a positive correlation (r<0.001) with the germ size. The improved kernels belonging to the last cycles contained from 33 to 60% more oil compared to original counterparts. Oleic acid (OLA) and linoleic acid (LOA) accounted for approximately 79–85% of total FA and the relative proportions of these FA slightly decreased during selection. The percentage of Ω-3 linolenic acid increased in the oil belonging to the advanced HOM populations whereas LAOX significantly decreased with cycles of selection. There was not a relationship between the observed oil increase with grain yield; however, the monounsaturated oleic proportion tended to decrease in kernels belonging to the yellow populations. Fatty acids and LAOX capacity had a positive correlation with OLA and negative (r>0.65) with LOA. This research demonstrated that it was feasible to develop high-yielding subtropical populations with HOM content and acceptable agronomic performance and grain physical properties.

Genetic Variability for Grain Yield and Its Components in an Early Tropical Yellow Maize Population Under Striga hermonthica Infestation

A major problem that usually confronts the breeder is ensuring that there is sufficient genetic variability in a population for the trait being improved because this determines the breeding schemes to use for improvement and whether or not sufficient progress could be made. Three hundred full-sib families from cycle 3 of the early maturing yellow endosperm maize (Zea mays L.) population, TZE-Y Pop DT STR, were evaluated under artificial Striga hermonthica infestation at Mokwa and Abuja, Nigeria in 2003. The objectives of this study were to investigate the type of gene action involved in the inheritance of S. hermonthica resistance in TZE-Y Pop DT STR C3, determine the extent of genetic variability available in the population after three cycles of S1 recurrent selection, and the phenotypic and genetic correlation coefficients among the traits used for selecting for resistance to S. hermonthica. Estimates of dominance variances were larger than additive genetic variances for grain yield, plant height, ear height, number of ears at harvest, and Striga damage rating at 8 weeks after planting (WAP). Even though h2 estimates were generally low for most traits (< 0.40), moderate-to-large additive genetic variances, and wide ranges were obtained in TZE-Y Pop DT STR C3 for most traits, suggesting that there was adequate genetic variation for improving Striga resistance and grain yield in the population. Highly significant phenotypic correlation coefficients were obtained between grain yield and ears per plant, plant height, ear height, days to anthesis and silking, anthesissilking interval, and Striga damage score at 10 WAP. Recurrent selection methods that capitalize on both additive and dominance variances would be effective for improving the population for Striga resistance and grain yield.

Combining ability and heterosis in diallel crosses of maize

The present investigation involved crosses among 20 elite yellow maize populations. These were evaluated in four environments in a randomized block design with four replications in each environment. Variety Cuba was observed to be the best general combiner for grain yield, followed by St Croix and Prolific. No clear association could be discerned between general combining ability (GCA) effects for grain yield and its components, and mean grain yield performance and GCA effects. Heterosis was observed in general and all the crosses involving Cuba yielded better than the midparent. The five hybrids, Kisan × Cuba, Antigua 3D × St Croix, Prolific × St Croix, Vijay × Antigua Gr. I and A 23 × Cuba, yielded more than the standard check. Significant yield superiority of these varietal hybrids over the best commercial composite (Jawahar) suggested the possibility of their commercial exploitation.

Estimation and inheritance of stability parameters of grain yield in maize

SUMMARYOne hundred and ninety hybrids involving 20 broad-based yellow maize populations were evaluated together with their parents for stability in expression of their grain yield potential by means of linear regression on to an environmental index. Both linear and non-linear components were observed to be significant; the linear component, in general, being the more important. Two high yielding parents, namely variety A 3D and composite Jawahar, had general adaptability, while synthetic A 22 was suited to poor environment and variety SO 4D to good environment. Seventeen hybrids had above average yield and the majority of these exhibited general adaptability.Combining ability analysis revealed that GCA (general combining ability) was more important than SCA (specific combining ability) in the expression of mean yield. Inheritance of linear regression was controlled predominantly by GCA whereas both GCA and SCA were equally important in the expression of non-linear fluctuations. Variety Cuba was the most desirable parent, as it transmitted to its progeny high grain yield potential and low linear response. The other good combiners for grain yield were variety SC 4D and Prolific composite but these transmitted above average linear response.Lack of association between grain yield and linear regression of both parents and GCA effects indicated their independent mode of inheritance. It suggested, therefore, that high yield can be combined with general adaptability or responsiveness to either good or poor environment.

Determination of Heterotic Groups in Nepalese Yellow Maize Populations

Assigning germplasms into different heterotic groups is fundamental for exploitation of heterosis for hybrid development. An experiment was conducted in order to establish heterotic groups of some maize populations. Line x tester design was used for making crosses. Ten open pollinated varieties were used as lines and four as testers. Forty crosses along with their parents were evaluated in a randomized complete block design with three replications. Three testers were open pollinated varieties and one tester was a NML-2, an inbred line developed by CIMMYT. Basis of grouping the germplasms into different heterotic groups was specific combining ability (SCA) effects for grain yield. Population 46C1, Rampur So3Eo2, and Rampur So3Fo2 showed positive SCA effects with NML-2, and negative with Arun-4. These germplasms were assigned into heterotic group A. Similarly, Upahar, Across 9331, Population 35C5 and Narayani had positive SCA effects with Arun-4 and negative with NML-2 and grouped into heterotic group B. Likewise, Manakamana-2 and Hill Pool Yellow were placed into AB heterotic group, which displayed positive SCA effects with both testers. Khumal yellow had shown negative effects with both testers and put into undetermined group. This way, three heterotic groups were established based on the SCA effects. These heterotic groups are potential sources for inbred line development.Keywords: Lines; Testers; Heterotic effects; Specific combining ability effects; Heterotic groupingsDOI: 10.3126/njst.v10i0.2802Nepal Journal of Science and Technology Volume 10, 2009 December Page: 1-8