DROUGHT AND LOW NITROGEN TOLERANCE IN EGYPTIAN MAIZE (Zea mays L.) GENOTYPES

Abstract

Exposing maize plants to drought stresses results in a huge reduction in grain yields. The expected future shortage in irrigation water in Egypt necessitates that maize breeders should pay great attention to develop drought-tolerant cultivars. Moreover, using lower rates of nitrogen (N) fertilizer by most of Egyptian farmers than the recommended rates, because of their low purchasing power and high price ratio between fertilizer and grain, is one of the reasons responsible for low productivity of maize. Current breeding programs should therefore pay attention to develop hybrid corn of high tolerance to the low soil nitrogen along with drought stresses. To start a successful breeding program for improving low N tolerance as well as drought tolerance, available maize germplasm should be screened for productivity and agronomic and physiological performance under Low-N and/or drought conditions in order to identify the best genotypes that could be used directly or indirectly as suitable sources for developing tolerant hybrids to these stresses. The objectives were: (i) to screen 19 maize genotypes(14 hybrid cultivars and five populations) for tolerance to drought and/or to Low-N and to identify tolerant ones,(ii) to describe the effects of drought and Low-N on agronomic and yield traits of maize, (iii) to estimate heritability and predicted genetic advance from selection under both stresses, (iv) toidentify the traits of strong association with drought and/or Low-N tolerance and recommend the selection criteria, and (v) to assess maize