16 Breeding strategies to mitigate abiotic stresses in pulses A K Choudhary 1 , Rafat Sultana 2 , S K Chaturvedi 3 , Rajveer Sharma 1 , B P Bhatt 4 and S P Singh 5 1 ICAR RCER Regional Centre, Darbhanga 846 005; 2 Bihar Agricultural University, Sabour; 3 Indian Institute of Pulses Reseach, Kanpur 208 024; 4 ICAR RCER, Patna 800 014; 5 CSAUAT, Kanpur; E-mail: akicar1968@gmail.com Pulses are an important source of dietary protein especially for millions of vegetarians of India. The group comprises chickpea, pigeonpea, mungbean, urdbean, lentil, field pea, rajmash and grass pea besides several other grain legumes of local importance such as cow pea, moth bean, horse gram, faba bean, rice bean, and the like. The dry grains of pulses are used mainly as ‘dal’ as a supplement to cereals, making the food as a perfect mix. However, in India and some parts of the world, immature seeds are also used as vegetables. Besides this, they also add significant amount of nitrogen to the soil by fixing atmospheric nitrogen in their root nodules. In the developing countries like India, pulses are still crops of typically low input agriculture, which hardly receives better than average management practices. Such environments are prone to large errors, less differentiation between genotypes, and less repeatability across years (Allard, 1999). The prediction and management of such environments have become even more difficult under changing climatic scenario. Components of such environments largely include abiotic stresses such as extremes of moisture (waterlogging/drought) and temperature (high/low), salinity and mineral stresses (such as Al toxicity in acid soil). In low-input agriculture and/ or low productivity environments in which most variables are unpredictable, high G-E interactions are observed. Consequently, identification of superior genotypes becomes very difficult (Sultana et al., 2014). Before suggesting breeding strategies, it is pertinent to understand the nature and complexity of abiotic stresses. 1. Nature of abiotic stresses in pulses Abiotic stress is deviation from optimum production condition arising due to non-living components of environment (such as high or low temperature and moisture, high salinity or acidity in soil, etc) that adversely affect growth and reproduction of crop plants. Breeding for abiotic stress is considered more difficult because of: (a) complexity of conditions causing abiotic stresses, (b) complex nature of abiotic resistance in a variety, (c) occurrence of one stress more often in conjunction with the other, (d) low heritability of abiotic resistance, and (e) variable intensity of such stress under field condition (Choudhary and Vijayakumar, 2012). The actual mechanisms employed by individual crop plants vary greatly, and are not homogeneous. The tolerance to abiotic stress is often conditioned by quantitative trait loci (QTLs) with complex interactions. Besides these, high G×E interactions and lack of precise screening techniques make the task of breeder even more challenging. Pulses encounter a number of abiotic stresses during various stages and phases of their life cycle. The nature of abiotic stresses may vary depending upon species, prevailing weather conditions and the type of soil. For example, winter grain legumes (cool season pulses) such as chickpea, lentil, peas and faba beans, which relatively tolerate low temperature, more often experiences terminal heat stress during their reproductive period. In low input agriculture, this condition is often intertwined with moisture stress. Warm (rainy) season pulses (e.g., pigeonpea, mungbean, urdbean, etc) often experience temporary waterlogging that may vary from hours to a few days. Although urdbean tolerates excess moisture to a greater extent, yield level is adversely affected in case excess water is not drained out after 2-3 days. This group of pulses also encounter moisture deficit owing to uneven rainfall pattern. Besides these, this group is relatively sensitive to low temperature stress. Pigeonpea, which is perennial by nature but is cultivated as a rainy season annual, encounter almost all such stresses such as waterlogging (during seedling stage) and drought and low temperature stresses (during reproductive stage). Depending upon the edaphic conditions, pulses may also face stresses imposed by salinity/alkalinity (high pH), Al toxicity and sodicity. Response of each grain legume to each stress may vary; the expression of stress (strain) may be manifested through effects on different traits. Consequently, different screening techniques and a different kind of breeding strategy is needed to mitigate abiotic stresses. 2. Screening techniques and marker traits Genetic variations have been noticed for almost all the abiotic stresses wherever a large number of genotypes have been screened. Marker traits conditioning tolerance to such stress(es) have also been identified. In the following section, we will discuss the specific screening technique(s) and the marker traits apt to differentiate genotypes for such a stress. 2.1. Drought The kind of drought that is of our interest is the agricultural drought that occurs where soil moisture and rainfall are inadequate during the growing season to support healthy crop growth to maturity and cause extreme crop stress and wilting of plants (Choudhary and Vijayakumar, 2012). A plant can resist drought condition through reduced water loss from aerial portions, increased water uptake from deep layers of the soil or by giving more yield at low water potentials. The maintenance of water uptake under drought condition is related to several properties concerning roots of plants such as root size and efficiency, root density, size of xylem vessel, and the like. _________________________________________________________ Lead Paper presented during the National Conference on “Emerging challenges and opportunities in biotic and abiotic stress management (ECOBASM-2014)” held at Directorate of Rice Research, Hyderabad, India during December 13-14, 2014, pp. 16-21.