Evaluation of Agronomical traits and Drought Tolerance Indices in Some Corn (Zea mays L.) Hybrids under Water Deficit Stress

Corn is an important crop that is cultivated in many parts of the world. One of the major factors limiting the plant growth is lack of water, which reduces plant growth and survival in arid and semi-arid areas. For this purpose, evaluation of the effect of drought stress on plant cultivars and identification of the tolerant genotype is of particular importance.

In this research, nine corn hybrids (including three promising hybrids H1 (SC01; TS01×MS02), H2 (KLM77021/4-1-2-1-2-4-1× K47/3), and H3 (K47/2-2-1-4-2-1-1-1× MO17) and six commercial H4 (NS640), H5 (SC703), H6 (SC704), H7 (SC720), and H9 (SC715) grain corn hybrids as late and medium maturity groups) were planted in split plots in the form of a complete random block design in three replicates at Research Unit of Moghan Agro-Industry and Livestock Company, Ardabil in spring and summer 2022. The main plots include two levels of normal irrigation (10 times of atmospheric and stack irrigation according to the region's custom) and drought stress (interruption of irrigation during the flowering and seed filling stages: eight times of atmospheric and stack irrigation so that the interruption of irrigation at the end of flowering continued to grain filling for 18 days) and the sub-plots included six varieties and three hybrids of corn. In both irrigation conditions, yield and seed yield components were evaluated. To identify the tolerant genotype based on grain yield under stress and normal conditions, stress tolerance indices (STI), stress sensitivity (SSI), tolerance (TOL), mean productivity index (MP) and geometric mean yield (GMP) were calculated. Correlation and grouping was performed based on tolerance indices of drought stress in different corn hybrids.

Dehydration stress significantly reduced the yield and yield components of corn cultivars. The H7 (SC703) and H6 (SC704) hybrids were the ones with the highest plant height, hundred seed weight, number of seed rows in cob, and number of seeds in each cob row. Further, the hybrid H1 (SC01), H6 (SC704), H7 (SC703) and H3 (K47/2-2-1-4-2-1-1-1× MO17) have the highest seed yield in both conditions of normal stress and dehydration. The correlation between grain yield and grain yield components was significant and positive. The data obtained from the evaluation of drought tolerance indices showed that there was a significant difference between different corn hybrids. As the hybrid H6 (SC704) and promising hybrid H1 (SC01) allocated the highest MP, GMP and STI, and the promising hybrid H3 (K47/2-2-1-4-2-1-1-1× MO17) showed the highest SSI value. Correlation analysis between drought tolerance indices also showed a significant positive relationship between STI, SSI, TOL, MP and GMP. The cluster analysis of the studied corn hybrids based on drought tolerance indices divided the corn hybrids into three separate groups, such that the hybrids H1 (SC01), H3 (K47/2-2-1-4-2-1-1-1× MO17), H6 (SC704) and H7 (SC703) were classified as drought tolerant hybrids within the same group.

It seems that by simultaneous trait evaluation of the grain yield and grain yield components along with drought tolerance indices, it is possible to identify the genotype with high grain yield under water deficit stress. The information acquired by the study might be applied in the future remedial programs.