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Abstract

A field experiment was conducted using twenty hybrids, twelve inbreds and four check varieties of Maize (Zea mays L.) under different level of moisture and nitrogen stress. Inbreds were crossed in line/tester mating design at National Maize Research Program, Rampur to produce hybrids. The inbreds and their hybrids were grown in the field to quantify secondary traits and study stress indices for selecting the best genotype for both drought and low nitrogen stress tolerance. The secondary traits do not affect the yield under stressed condition directly but assist in selecting the tolerant genotypes. The correlation of those traits with grain yield under stressed condition was studied. Canopy temperature depression (r=0.61**) and SPAD reading (r= 0.50**) showed positive correlation while leaf rolling score (r=0.49**), leaf senescence score (r=-0.57**) and anthesis silking interval (r=0.15) showed negative correlation. Cluster analysis showed six distinct clusters and cluster 4 represented tolerant genotypes. Hybrids were concentrated at a place while inbreds were scattered as shown by the Principal component analysis. The secondary traits along with stress tolerance indices (TOL and STI) were found useful for selecting stress tolerant genotypes. Based on quantification of secondary traits and stress indices, the hybrids were found to be more tolerant as compared with their inbred parents. The hybrids RML-4/RML-17, RML-32/RML-17, RML-8/RML-17, RML-32/RL-111 were found to be more tolerant compared with other hybrids based on secondary trait quantification and stress indices.

Keywords: Secondary traits; Drought stress; Tolerance; Correlation; Stress indices