This book focuses on early germination, one of maize germplasm most important strategies for adapting to drought-induced stress. Some genotypes have the ability to adapt by either reducing water losses or by increasing water uptake. Drought tolerance is also an adaptive strategy that enables crop plants to maintain their normal physiological processes and deliver higher economical yield despite drought stress. Several processes are involved in conferring drought tolerance in maize: the accumulation of osmolytes or antioxidants, plant growth regulators, stress proteins and water channel proteins, transcription factors and signal transduction pathways. Drought is one of the most detrimental forms of abiotic stress around the world and seriously limits the productivity of agricultural crops. Maize, one of the leading cereal crops in the world, is sensitive to drought stress. Maize harvests are affected by drought stress at different growth stages in different regions. Numerous events in the life of maize crops can be affected by drought stress: germination potential, seedling growth, seedling stand establishment, overall growth and development, pollen and silk development, anthesis silking interval, pollination, and embryo, endosperm and kernel development. Though every maize genotype has the ability to avoid or withstand drought stress, there is a concrete need to improve the level of adaptability to drought stress to address the global issue of food security. The most common biological strategies for improving drought stress resistance include screening available maize germplasm for drought tolerance, conventional breeding strategies, and marker-assisted and genomic-assisted breeding and development of transgenic maize. As a comprehensive understanding of the effects of drought stress, adaptive strategies and potential breeding tools is the prerequisite for any sound breeding plan, this brief addresses these aspects.

Maize is the most important cereal crop grown in areas of South Africa by both small-scale and commercial farmers. Maize monocropping without sufficient input and declining soil nitrogen content are some of the factors that limit yield. The objective of the study was to evaluate the effect of different cowpea cultivars and populations on growth, yield and yield components of succeeding maize. The effects of cropping systems on soil N content were also observed. Field experiments were conducted during the 2005/2006 and 2006/2007 growing seasons at Potchefstroom and Taung in North West province. The trial consisted of four cowpea cultivars: PAN 311 (short duration cowpea cultivar), CH 84, Bechuana white (medium duration cowpea cultivar) and TVU 1124 (long duration cowpea cultivar) and, four planting densities (10 000, 15 000, 20 000 and 40 000 plants ha-1). Maize was used as sequential test crop to determine the residual effect of previous cowpea treatments. Cowpea grain yield increased as planting density increased at both localities. TVU 1124 gave highest grain yield of all cowpea cultivars at both localities. Total dry matter yield also increased with increasing planting density. After cowpea soil NO3- and NH4+ content increased with increasing density. Similarly, soil NO3- content of maize following cowpea showed a considerable improvement, compared to maize monocropping. The highest soil NO3- and NH4+ content was observed when maize followed Bechuana White. Significant differences were also observed in soil microbial activities among the cultivars. Maize grain yields and plant height responded positively to the previous cowpea crop, compared with maize monocropping at both locations, but especially at Taung. Maize stover yield, cob length and KNC significantly responded to maize and cowpea rotation compared to maize monocropping at Taung. These results further confirm the potential of using cowpea to contribute soil N to subsequent maize crops in a rotational system. Copyright.