IARI
The Water Technology Centre at the Indian Agricultural Research Institute (IARI), New Delhi, investigates plant characteristics related to yield responses of wheat to water stress conditions. The studies on the importance for potassium accumulation and certain amino acids for osmo­regulation, help to understand the structure of drought­resistant varieties. This could be of great interest for the development of this trait in other varieties.

In 1992, the Water Technology Centre took up a World Bank supported project for understanding the tolerance mechanisms of crops in drought and thermal stress environments. The project aims at evaluating the importance of stress proteins, osmotic adjustment and ability to keep green leaves (leaf senescence) for drought tolerance in wild and cultivated wheat, chickpea and sorghum. This study includes the relationship between drought tolerance and drought induced proteins. The later proteins include dehydrins, responsive to abscissic acid (RAB) protein, and water stress proteins (WSP). This four­year project has a budget of US$ 7 million.
Production of drought­tolerant varieties is also studied at the IARI's Nuclear Research Laboratory. It was reported that the relative drought tolerance of wheat genotypes can be assessed quickly by measuring the leaf water spin­lattice relaxation time (a method to determine the plant water status and water availability in different plant tissues) at tillering stage under either irrigated or stressed conditions. The specific relaxation times of 20 varieties of wheat with different drought tolerance levels was measured in vivo with the help of low­resolution nuclear magnetic resonance.

Groundnut
At the International Crops Research Institute for the Semi­Arid Tropics (ICRISAT), Hyderabad, South India, drought tolerance research has been carried out on sorghum, pearl millet and groundnut. Groundnut is an important source for edible oil. India's groundnut production suffered a decrease in production because of adverse weather conditions during a critical crop stage in the 1991­1992 season.

ICRISAT's collaborative research with the Australian Centre for International Agricultural Research (ACIAR) demonstrated that the carbon isotopic composition of groundnut leaves is well correlated with water­use efficiency. The carbon isotopic composition itself showed to be connected with the thickness of leaves. Especially the second characteristic could be used as a rapid and inexpensive criterion in the selection of drought­tolerant varieties. Unfortunately, groundnut varieties that turned out to be efficient water users failed to efficiently partition dry matter to their pods. Therefore, ICRISAT, in collaboration with ACIAR and the Indian Council of Agricultural Research (ICAR) is now studying the selection possibilities for both water use and dry matter partitioning efficiencies in groundnut. This new initiative will also include the testing of the stabilities of the selected genotypes across a range of environments in India.
Research on drought resistance in groundnut is also carried out at the Central Research Institute for Dryland Agriculture, in Hyderabad, India. By exposing suspension cultures to drought stress, this institute developed variant clones of two existing groundnut cultivars with an enhanced drought resistance of 15 per cent.
ICRISAT has collaborated with the Institute of Grassland and Environmental Research (IGER), UK, on comparative methods of selection thermo­tolerance of seedlings in elite cultivars. It was demonstrated that germination at high temperature is not an effective selection criterion. Therefore, the research partners are now trying to identify markers for genes contributing to seedling heat tolerance.

Rice
India's rice production is also badly affected by erratic monsoons. In the case of rice, the research institutes are focusing more on drought avoidance rather than resistance to it. For drought­prone rainfed upland, a new hybrid variety (PNR­570) has been released which matures in 65­67 days, with a yield potential of 4,500 kilo/ha. The United Nations Development Programme (UNDP) has sanctioned US$ 3 million for the network on Development and Use of Hybrid Rice Technology at twelve Indian centres.
Sachin Chaturvedi

Sources
International Crops Research Institute for the Semi­Arid Tropics (1993), Annual Report, 1992. Hyderabad, India: ICRISAT.

Central Research Institute for Dryland Agriculture (1992), Annual Report 1991­92. Hyderabad, India.

P.N. Tiwari et. al. (1993), "Assessment of Relative Tolerance of Wheat (Triticum aestivum) Varieties by Nuclear Magnetic Resonance". Indian Journal of Agricultural Sciences, 63 (7), July 1993.