Browsing by Person "Abdulai, Alhassan Lansah"

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    Genotypic responses of rainfed sorghum to a latitude gradient
    (2016) Abdulai, Alhassan Lansah; Asch, Folkard
    Climate change poses various challenges to crop production systems. Coping with the changing climate requires adaptation strategies that will enhance the resilience of crop production systems to the resultant aberrant weather. However, the impacts of the changing climate are extremely difficult to predict because the associated extreme events result in a complex of abiotic stresses. These stresses act singly or in synergy with others to affect physiological processes at the different growth and development stages of crop plants. Currently, the physiological and phenological (developmental) response mechanisms of crops, as well as adaptation of cultivars to these stresses are not very clear and well understood. The complex interactions between crops and abiotic stresses make it difficult to accurately predict crop responses to climate change using the available crop growth models that have been parameterized and validated using some climate scenarios. While prediction of the complex ideotype-trait combinations may benefit breeders, physiological models that are well validated for target environments are equally important. Therefore, this study investigated elite grain sorghum genotypes from three races (Caudatum, Durra, and Guinea) and a Guinea-Caudatum composite, with different degrees of sensitivity to photoperiod and adaptation to a wide range of latitude locations, for their grain yield and yield stability responses to different environments. The aim was to calibrate growth models in for use in quantifying climate change effects on rainfed sorghum production systems. Field experiments were established to investigate the yield performance and yield stability of ten genotypes in eighteen environments created from a factorial combination of three locations (along a latitudinal gradient) and three monthly-staggered dates of sowing within years in 2008 and 2009. Field trials to study the phenology of seven of the ten genotypes were also established in a similar fashion in 2009 and 2010. Data were also collected on yield and other traits for the first two dates of sowing on six of the genotypes used for the yield performance trial to analyze the relations between grain yield and the selected traits and also evaluate the potential of path analysis in improving understanding of trait yield relations of grain sorghum. Mean grain yields of 0 to 248 g m were recorded across environments and from 74 to 208 g m-2 across the 10 genotypes and generally reduced with delayed sowing. Grain yield was significantly influenced by the main and interactive effects of location, year, sowing date, and genotype, necessitating the assessment of yield superiority and stability for each of the ten cultivars. The only two Caudatum cultivars (Grinkan and IRAT 204) were ranked among the top three by six of the indices. The study also brought to the fore that some yield stability indices correlate perfectly or very highly and could be substituted one for the other when assessing yield stability of sorghum. Very strong correlations were found between grain yield and each of shoot biomass, panicle weight, the number of grains per panicle, and threshing ability across environments, but path coefficient analysis confirmed that these traits are auto-correlated, with grains per panicle being the major mediating trait in all the relationships. Relationships between grain yield and the remaining traits were weak to medium and very inconsistent across the environments. This study brings to the fore, the location- and / or environment-specific adaptation of existing genotypes which should be exploited for tactical adaptation to changed climates, whiles genotypes with general or wider adaptations to environments are being sought. The phenology study showed that for photoperiod sensitive (PPS) genotypes, the number of days from emergence to panicle initiation and the number of leaves increased with latitude and decreased with sowing date, a day-length difference between locations of < 8 minutes increasing crop duration of some varieties by up to 3 weeks and decreasing number of leaves by up to 11 for the same sowing date. Some varieties exhibited photoperiod-insensitivity at one location and photoperiod-sensitivity at another location, indicating the complex nature of photoperiod responses. The study also showed that existing models do not accurately simulate the effect of latitude on the phenology of PPS sorghum, and latitude has to be taken into account in adjusting coefficients to improve the accuracy of such simulations. We conclude that genotypic response of rainfed sorghum is influenced by latitude, sowing date, and their interactions, but very little by years. Some existing cultivars could be deployed as tactical adaptive measures, while efforts are intensified to develop strategic adaptive measures. If changes in rainfall and temperature reduce the length of growing seasons, genotypes which are currently adapted to higher latitudes could easily be shifted southwards to lower latitudes, while those at lower latitudes may fit poorly into the new environments. A large potential for contributing to food security exist for the low latitudes if climates change in the direction predicted in future. It is absolutely necessary to develop new models that will be able to accurately simulate effects of sowing date and latitude on phenology. More research is needed to understand physiological response mechanisms of the pronounced latitude effects on sorghum phenology.