Stress tolerance indexes of Maize ( Zea mays L. ) grown in the southwestern savannah in the Democratic Republic of Congo

Twenty maize varieties were evaluated in southwestern savannah of DR. Congo during two years for their grain yield potential under optimum and water deficit conditions. A factorial experimental design with three replicates was adopted. Grain yield obtained under optimum was considered as yield potential (Ri) while the one in water deficit conditions was considered as yield performance under stress (Rs). Six stress tolerance indexes, including Stress Tolerance Index (STI), the Sensitivity to Stress Index (SSI), mean productivity (MP), geometric mean productivity (MGP), the stability index Performance (ISR) and stress tolerance (TOL) were used to identify genotypes tolerant to drought. Linear regressions were done between Ri and Rs yields and between six stress tolerance indexes. High positive correlations were revealed between Ri and Rs yields and indexes STI, MP and MGP. Furthermore SSI and TOL indexes were highly correlated positively and negatively to SRI at Rs. High significant correlations were observed between STI, MP and MGP while SRI, SSI and TOL are highly correlated, and are slightly or not correlated with STI MP and MGP. Varieties ranking based on STI, MP and MGP is similar to that based on the combination of the two rankings prepared on Ri and Rs. For maize, ranking varieties based on SSI and TOL is in the opposite direction of that obtained according to the Ri and Rs yields. The selection of lines based on the index can be more effective by combining high values of STI and MP at low to moderate values of SSI and TOL.