Abiotic Stresses in Major Pulses: Current Status and Strategies
Environmental stresses such as erratic and insufficient rainfall, extreme temperatures, salinity, alkalinity and aluminium toxicity limit the yield and productivity of many cultivated crops including pulses. Pulses are leguminous plants whose grains are u
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Abstract
Environmental stresses such as erratic and insufficient rainfall, extreme temperatures, salinity, alkalinity and aluminium toxicity limit the yield and productivity of many cultivated crops including pulses. Pulses are leguminous plants whose grains are used exclusively for food and are generally grown in harsh environments. Therefore, pulses encounter a number of abiotic stresses during various stages of their life cycle. Each type of stress hampers the growth of the plant by disturbing the normal physiology and morphology. The exact mechanisms governing the cause and effect of abiotic stresses in pulses are very complex and difficult to understand. Due to changing environmental conditions, very often referred to as ‘climate change’, pulses have become more prone to oxidative damage by overproduction of toxic reactive oxygen species (ROS) such as superoxide radicals, hydrogen peroxide and hydroxyl radicals. These radicals disturb the cellular homeostasis of the cell resulting in significant yield losses. In North India, high temperatures (>30 C) coupled with drought stress during flowering stage produce distinct effect on the grain yield of chickpea and lentil, whereas in pigeon pea, low temperatures (35 C). Among warm season pulses, pigeon pea is the crop which encounters
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low temperature stress during winter months in North India. Low temperature adversely affects growth, survival and reproductive capacity of plants if the minimum temperature falls below 10 C. Conclusive evidence for the presence of genetic variability vis-a`-vis cold tolerance was provided by Sandhu et al. (2007). They screened for cold tolerance in a set of 480 pigeon pea lines at Ludhiana. During the first fortnight of January, minimum temperature more often touches 0 C, which was good enough to assess cold reaction. As many as 32 genotypes were rated cold tolerant as the plants retained their normal morphology with intact floral buds. They suggested utilising these genotypes to enhance cold tolerance of sensitive varieties and study the genetics of cold tolerance. However, they did not report any data on other reproductive traits. Low temperature primarily affects development and growth of flower buds and opening of flowers (Choudhary 2007). In some sensitive genotypes such as ‘IPA 209’ and ‘IPA 06-1’, filaments of stamens fail to enlarge at low temperature and thus affect opening of flowers. Pollen dehiscence does not occur too, although pollens are fully fertile. As a consequence, unfertilised flowers wither and fall down, resulting in no pod formation in these genotypes under low temperature (IIPR Annual Report 2008–2009). It appears that formation of floral buds, number of blossomed flowers and pod setting at low temperature can be used as selection criterion to identify tolerant genotypes in pigeon pea. These traits need to be investigated also in wild relatives of pigeon pea so as to screen tolerant wild accessions as have been done in wild relatives of mung bean and urd bean, IC 251372 in V. glabrescens and IC
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