Predicting Tillering of Diverse Sorghum Germplasm across Environments

Abstract

Prediction of fertile tiller number (FTN) is important for predicting crop leaf area development and provides an avenue to identify genotypes with specific adaptation to variable environments. However, previous tillering prediction models in sorghum [Sorghum bicolor (L.) Moench] were limited to only a few genotypes. This study aimed to develop an approach to predict FTN for a large number of genotypes grown in multiple environments. A set of 756 genotypes from 17 diverse families of a backcross‐derived, sorghum nested association mapping population were evaluated in test cross combinations with a single female tester. Plants were grown in five environments, but not all genotypes were included in all environments. One of the environments was space planted for expression of tillering propensity. Three predictors of tillering were considered: tillering propensity, incident radiation per unit thermal time during the tillering stage, and plant density. These represent the genotypic, environmental, and management effects on FTN, respectively. Based on these predictors, a robust model was developed for 125 genotypes grown in the spaced planting and all four test environments (R2 = 0.85, n = 500). For the independent set of remaining genotypes, the model predicted FTN in each of the four test environments with an accuracy and precision close to that for the training set (R2 = 0.69–0.74). The implications for crop improvement of this predictive capability of FTN are discussed in relation to the opportunities for assessing genetic and management options for specific adaptation, and for removing confounding effects in the analysis of breeding trials.

Statistical Modeling of Phenotypic Plasticity under Abiotic Stress in Triticum durum L. and Triticum aestivum L. Genotypes

“…For example, PPs of fertile tillers and kernels m −2 were closely clustered in both genotypes (Figure 2), and they responded similarly to stress phases, growth stages, and abiotic stress treatments. Also, PP of fertile tillers, being partly regulated by leaf area dynamics [68], is correlated with PP of grain yield because it leads to larger canopy leaf area and number of spikes m −2 .…”

“…Therefore, the decreasing plasticity of wheat in the order: fertile tillers > kernels m −2 > kernel weight can be attributed to differential costs and contributions to yield components, stabilizing selection for kernel weight, and directional changes in resource (i.e., light, water, and nutrients) availability during plant ontogeny [25,27]. Tillering is a complex and dynamic wheat yield component; its plasticity is partly controlled by the regulation of plant leaf area dynamics, which determines the carbon balance during the vegetative growth stage [67,68]. As a major determinant of grain yield, tillers plasticity was impacted by environmental (PTQ), edaphic (ECa) stressors, and by most (77.0%) covariates, fixed factors, and their interactions (Table 2); thus, ontogenically, tillering could be the most reliable yield component to use in selecting for tolerance to abiotic stress [35,62].…”

“…A steady increase in population density has been a driver of maize- [74], sorghum- [68], but not wheat-yield improvements, where higher-yielding environments have maximum yields at higher population density. Despite the negative relationship between population density and fertile tillers [32,69], their plasticity estimates covaried positively ( Figure 3); thus, confirming that a trait and its plasticity can be independent, and PP is under its own genetic control under a specific abiotic stress [28].…”

The Impacts of Flowering Time and Tillering on Grain Yield of Sorghum Hybrids across Diverse Environments

“…Thus, phenotypic variations in flowering time [22] and tillering [23] can complicate the interpretation of breeding trials and the selection of superior parents for hybrid production. To improve the accuracy of selection in sorghum breeding programs, it will be beneficial to minimise these confounding effects of flowering time and tillering on grain yield.…”

The Impacts of Flowering Time and Tillering on Grain Yield of Sorghum Hybrids across Diverse Environments

“…Thus, phenotypic variations in flowering time [22] and tillering [23] can complicate the interpretation of breeding trials and the selection of superior parents for hybrid production.…”