Identification of Tropical Maize Germplasm with Tolerance to Drought, Nitrogen Deficiency, and Combined Heat and Drought Stresses

The objective of this study was to evaluate Maize (Zea mays L.) elite lines currently available in CIMMYT's lowland tropical breeding program in Latin America under multiple abiotic stresses and identify lines with tolerance to drought, N deficiency, and combined heat and drought stress (HTDS). An incomplete line-by-tester design was used to evaluate 436 testcrosses under non-stressed conditions, 507 under N deficiency, 417 under drought stress (DS), and 368 under HTDS in 30 season-by-location combinations between 2012 and 2015. Elite lines CLRCY016, CML269, CML550, and CML551 performed well across all conditions, while CLQRCWQ118, CLWN306, and CML576 showed good performance under DS and N deficiency. CML574 was tolerant to DS and HTDS. Moreover, CML550 and CML574 are known for their partial tolerance to maize lethal necrosis. Grain yield measured under DS was to some extent predictive of attainable grain yield under N-deficient conditions (r = 0.65; P < 0.01) and HTDS (r = 0.54; P < 0.01) as indicated by the correlation across treatments. The fact that only a few lines were tolerant across treatments re-emphasizes the need to separately screen germplasm under each abiotic stress. Based on high best linear unbiased predicted general combining ability (BLUP GCA), it will be possible to develop hybrids tolerant to multiple abiotic stresses without incurring any yield penalty under nonstressed conditions using these inbred lines.