Yield -based evaluation of low nitrogen tolerance indices for screening of [Sorghum bicolor (L.) Moench] genotypes

Nitrogen stress is one of the key factors limiting sorghum crop productivity. To identify desirable sorghum genotypes best suited to nitrogen stress, the response of 300 sorghum landraces and two standard checks: KS78, and BCK60 were evaluated using yield-based indices. The experiment was conducted under nitrogen stress and ideal conditions for two years using a split-plot in RCBD design with two replications. Nitrogen treatments were assigned to the main plots, and sorghum genotypes were assigned to the subplots. Fourteen nitrogen stress screening indices, namely, the yield stability index (YSI), stress tolerance index (STI), modified stress tolerance index (KSTI), low nitrogen tolerance index (LNTI), relative decrease in yield (RDY), tolerance index (TOL), yield index (YI), stress susceptibility index (SSI), stress susceptibility percentage index (SSPI), and harmonic mean (HM), were computed using grain yield. The yield under optimal and stress conditions was significantly positively correlated with the HM, MP, GMP, STI, HM, YI, and modified STI. The results from the cluster analysis, PCA biplot, and 3D biplot classified the genotypes into three groups: nitrogen stress tolerant, nitrogen stress susceptible, and poor performers under both environments. Using STI, GMP, and MP, Genotypes (G80) ETSL101255, (G216) ETSL101006, (G35) ETSL101258, (G146) ETSL100813, and genotypes (G244) ETSL100292, (G161) ETSL100539, (G240) ETSL100890, (G93) ETSL101845, (G261) ETSL100625, (G248) ETSL100874, (G258) ETSL100752, (G142) ETSL100921, (G135) ETSL100307 were identified as top nitrogen stress tolerant, and susceptible genotypes respectively. We conclude that the indices MP, GMP, and STI can help in improving sorghum yield by selecting nitrogen efficient genotypes.