Evaluation of drought tolerance in different genotypes of foxtail millet during the entire growth period

Drought significantly affects foxtail millet [Setaria italica (L.) Beauv.] yield, and its adverse effects can be mitigated via genetic improvement to generate drought‐tolerant varieties. This study aimed to screen drought‐tolerant materials and genes in foxtail millet germplasm resources to improve the efficiency of breeding for drought tolerance. A field experiment was conducted in a randomized incomplete block design (α‐lattice design) and repeated thrice with 30 foxtail millet genotypes treated under drought stress or normal water supply (control) for 2 yr. The agronomic traits and drought tolerance coefficient (DC) of each genotype were assessed during the entire growth period. The soil water environment and genotype significantly affected the indices. Moreover, the interaction between genotype and soil water environment significantly affected the growth traits of foxtail millet. A genotype plus genotype × environment interaction (GGE) biplot revealed mixed correlations among the DC indices. Various indices had different effects on the drought tolerance of foxtail millet. The drought tolerance performance and evaluation indices of foxtail millet were ranked according to the distance from the “ideal” drought tolerance genotype and index. The drought tolerance was classified into five categories according to the comprehensive evaluation index (D‐value) cluster analysis. Discriminant analysis showed that the plant height and spike weight could be used as indices for identifying drought tolerance identification in foxtail millet. The GGE biplot results were consistent with the results based on the D‐value. Therefore, multiple agronomic traits combined with D‐value as an evaluation parameter can effectively and accurately identify drought‐tolerant foxtail millet. Core ideas Evaluation of drought tolerance in foxtail millet based on agronomic traits was practical. The GGE biplot accurately visualized drought tolerance in foxtail millet. Plant height and spike weight could serve as drought tolerance indices for foxtail millet.