Plant breeding involves a reduction of genetic diversity that could hinder the expected response to further selection, and the magnitude of that detrimental effect depends on both breeding population and breeding program design. The objective of the current study was to evaluate the effect of selection for reduced anthesis-silking interval in an Algerian maize (Zea mays L.) population in order to assess the potential value of this population and breeding strategy for subsequent breeding programs. We genotyped Cycle 0 and Cycle 3 from selection for reduced anthesis-silking interval under drought conditions of the Algerian maize population LOM, which was the best performing population in a previous breeding program, with 34 polymorphic simple sequence repeat markers. These selected markers were highly informative with Polymorphism Information Content values = 0.72 and genetic diversity was maintained over the selection cycles. The genetic distance (Nei's, 1978) between the two cycles was 0.47 and the genetic identity was 0.62. These results indicate that the population LOM was highly variable and that the genetic diversity was not significantly reduced for most genetic parameters by this selection program for reduced anthesis-silking interval. However, genetic selection has caused several genetic changes in Cycle 3 respect to Cycle 0, generating a large genetic divergence between the two cycles of selection. Variations in allelic frequency suggest that further studies could reveal markers associated with selection that could be useful for identifying quantitative trait loci.
Drought stress negatively affects germination, vegetative growth, biomass production, and yield traits in maize (Zea mays L.). In this study, we investigate the effects of osmotic stress induced by polyethylene glycol (PEG) solutions on germination, early seedling growth traits, and the physiological response of ten maize genotypes in Yucatan, Mexico. Additionally, drought tolerance indices were calculated and used to differentiate drought-tolerant genotypes. The data were examined by two-way analysis of variance and multivariate analysis. The results showed that PEG treatments significantly reduced germination and retarded seedling growth of maize genotypes. The physiological response of maize genotypes was also affected. Under drought stress, maize genotypes showed reduced carbon assimilation, stomatal conductance, and transpiration, but increased water use efficiency. Additionally, variability was observed in drought tolerance traits among different maize genotypes. According to PCA analysis based on variation in drought tolerance indices, three maize genotypes are drought-tolerant, including NTR, NTA, and NTB. These genotypes are suitable for cultivating areas where water availability is limited and for selecting tolerant genotypes to drought in breeding programs.
A study was conducted to assess the yield stability of 45 single cross maize (Zea mays L.) hybrids across five locations in North India, namely Samastipur, Muzaffarpur, Meerut, Kannauj, and Varanasi. Of the 45 hybrids tested, 21 displayed a higher-than-average yield (3.76 t/ha) across all environments. The analysis of variance showed that environment contributed to 88.4% of the total variation, followed by genotype x environment (7.9%) and genotype (3.7%). The first two significant interaction principal component axes accounted for about 81.54% of the total variation for grain yield. Hybrid 39 had the highest yield under diverse environments. Meerut and Muzaffarpur were identified as being more representative for grain yield compared to Kannauj, Samastipur, and Varanasi. Meerut was found to be the most discriminating environment. Hybrid 27, with an AMMI (Additive main effects and multiplicative interaction) stability value (ASV) of 0.00, was widely adapted. Hybrids specifically adapted to Samastipur (2), Muzaffarpur (2), Meerut (1), Kannauj (2), and Varanasi (2) were identified. With the least yield stability index (YSI), Hybrid 40, is recommended for cultivation during the monsoon in Northern India. Meerut and Muzaffarpur sites are recommended for evaluating early stages of maize test crosses.
Adjuvants are critical in enhancing herbicide efficacy, resulting in reduced herbicide application cost, less environmental pollution, and more sustainable weed management. To check the role of adjuvants (alkyl ether sulphate sodium salt, rapsoel methyl ester, fatty alcohol ethoxylate, and ammonium sulphate) in improving the efficacy of nicosulfuron-atrazine-propisochlor (NAP), a repeated warehouse experiment was conducted to optimize the NAP at 100% and 75% of the recommended label dose and adjuvants combinations against five different types of weeds and maize plants. NAP at a reduced dose (75% label dose) plus rapsoel methylester at 400 ml ha-1 provided 100% and 97% control of Trianthema portulacastrum and Dactyloctenium aegyptium. While NAP at reduced dose plus alkyl ether sulphate sodium salt 400 ml ha-1 provided 91%, 86%, and 87% control of Amaranthus viridis, Echinochloa colona and Cyperus rotundus, respectively. The addition of adjuvants did not cause any phytotoxic effect on maize growth and grain yield. All tested adjuvants enhanced the NAP efficacy, however, change in efficacy depended on the adjuvant added and the type of weed species. Hence, tested adjuvants can be used to reduce herbicide doses up to 25%, representing a promising strategy to reduce herbicide input to cope with increasing herbicide-resistance development and environmental pollution to ensure sustainable weed control in maize.
Fall armyworm (Spodoptera frugiperda (J.E. Smith)) (FAW) impacts maize (Zea mays L.) production. No maize genotype is completely resistant to FAW. This experiment was conducted in Calabar, Cross River State, with twenty maize genotypes using a randomized complete block design with three replications. These maize genotypes varied in responses to FAW scores, plant height, leaf count, plant standability and performance, days to 50% anthesis and silking, anthesis-silking interval, fresh and de-husked cob weight and length, husk proportion, ear rating, grains per cob, 100-seed weight, and grain yield. FAW score perfectly correlated with plant and ear ratings. Grain yield is strongly associated with cobs per plant and grains per cob. The study of this genetic variability showed that while seedling emergence, days to 50% anthesis, and 50% silking showed moderate genetic gain, all other traits showed high genetic gain. This suggests that under FAW pressure, it might be possible to choose maize genotypes that have these traits. FAW score, plant standability and performance, and ear rating were all found to be in the same cluster in the principal component and genotype-by-traits biplot analyses. This proved that they were useful for the identification of maize genotypes that are tolerant to FAW pressure. In one cluster were cobs per plant, husk covering, cob length, and grains per cob with grain yield. This further confirmed the importance of these traits in selecting maize genotypes with high yield potential under FAW pressure. Despite FAW pressure, maize genotypes AS2001-20, AS2001-24, M1628-8, AS2106-63, and FAW 2212 demonstrated high grain yields considerable for inclusion in further FAW-related studies.
