Black pepper and water stress

Abstract

Black pepper is mainly grown as a rainfed crop. Total rainfall and its distribution influence pepper productivity. Heavy rains during flowering reduce the rate of pollination and continuous heavy rainfall promotes vegetative development and limits flowering. On the other hand, break in the rainfall experienced at different stages during critical period following flower initiation leads to severe reduction in yield. Black pepper needs to be irrigated in summer to harvest good crop. Low spike intensity in rainfed situation is due to staggered and delayed spiking, lower bisexual flowers, anthracnose incidence, and spike shedding. Both plant height and leaf area are affected by water stress. Tolerant genotypes maintain higher root growth, higher relative water content, and lower cell membrane leakage under stress condition. In general, tolerant genotypes accumulated all the amino acids in higher quantities compared to susceptible ones during water stress. A, gs, and E decreased drastically, while Tleaf increased after 6 days of stress induction. Water stress reduced the activity of catalase and acid phosphatase and increased the activities of peroxidase, glutathione reductase, and polyphenol oxidase enzymes. Lipid peroxidation was high in drought-susceptible cultivars compared to tolerant cultivars. There was no difference in the expression profile of isoforms of catalase and peroxidase enzymes between control and stress, while super oxide dismutase showed an additional isoform in some genotypes under stress condition. Studies on 2D SDS gel electrophoresis indicated that the proteins relevant to photosynthesis were downregulated during drought suggesting reduced photo oxidative stress and protection of photosynthetic machinery during stress. Studies on exogenous application of ABA indicated a role for ABA in stress tolerance. Gene expression studies showed higher expression levels of dehydrin, osmotin, and DREB genes in tolerant genotype, implicating their possible role in imparting drought tolerance.