National Conference on Frontiers in Plant Physiology Towards Sustainable Agriculture, 5-7 November, 2009, Jorhat, Assam Invited Talk 1 National Conference on Frontiers in Plant Physiology Towards Sustainable Agriculture, 5-7 November, 2009, Jorhat, Assam SINGLE CROSS HYBRID TECHNOLOGY FOR MANAGING ABIOTIC STRESSES IN MAIZE Sain Dass and Ishwar Singh Directorate of Maize Research, Pusa Campus, New Delhi 110012 Maize (Zea mays L.) is the most widely cultivated crop of the world being grown in tropics, sub-tropics and temperate regions under irrigated to semi-arid conditions. It is crop of more than 150 counties. The major maize growing countries are USA, China, Brazil, Mexico, France and India. It is third most important cereal crop in India after rice and wheat that occupies about 8.12 million hectares having production of 19.3 million tones with average productivity of 2.37 tonnes/ ha during 2007-08. It is an important crop that holds a unique position in world agriculture, for food (25%), animal feed (12%), and poultry feed (49%), starch (12%), brewery (1%) and seed 1%. Apart from normal maize it has many other types viz. quality protein maize (QPM), sweet corn, baby corn, pop corn, waxy corn, high oil, etc. It generates employment for many million people in the world. Single cross hybrids (SCH) are most productive among the other types of hybrids and composite varieties of maize. Productive inbred lines are the strength of hybrid development programme. As many as 44 single cross hybrids of different maturity have been developed in a short span of period for different agro-ecological conditions. Because of their high yield potential, uniformity and resistant to various abiotic and abiotic stresses single cross hybrids are most acceptable to the farmers. The adoption of this technology has made maize a global productive crop. The cultivation of high yielding, stress resistant/tolerant single cross hybrids offers viable, sustainable and profitable option for Indian farmers. The impact of single cross hybrid adoption has already been witnessed in USA, China and many other countries of world. Even in India by hardly covering 20% area under single cross hybrids. The crop growth rate with respect to production and productivity of maize has increased significantly in many states of the country, which is probably highest among food crops. This technology is certainly going to provide solution to the climate change that is rising temperature in eastern and some part of central India, lowering water table in rice dominated area and weed menace in wheat belt etc., because of high productivity of single cross hybrids. Therefore it is a potential technology in achieving the nutritional and food security of the nation. With the change in global climatic scenario, maize has emerged as an alternative for diversification of rice-wheat cropping system. Temperate germplasm, being highly productive, has been introgressed for desirable gene(s) into promising tropical/sub-tropical genetic backgrounds to develop productive inbreds suitable for different agro-climatic conditions of the country. Winter maize is gaining popularity in north and eastern India. Hence, late maturing productive hybrids have been developed by using temperate as well as late maturing tropical and sub-tropical inbred lines. With the lowering of water table, rice- area from different states in various seasons has been shifted/likely to be shift more to maize. For these areas productive hybrids have been recommended for sustainability of the agriculture. More than 80% area of maize grown in India is rainfed and is subjected to the vagaries of monsoon. Cultivation of early maturing single cross hybrids has helped in reducing the yield loss on farmer field in the current century’s severe drought year. 3 National Conference on Frontiers in Plant Physiology Towards Sustainable Agriculture, 5-7 November, 2009, Jorhat, Assam SCREENING TECHNIQUE FOR DEVELOPMENT OF IDEOTYPES IN COTTON (G. HIRSUTUM) UNDER RAINFED CONDITIONS B.S. Janagoudar Dean and Professor of Crop Physiology, College of Forestry, Sirsi University of Agricultural Sciences, Dharwad 580 005, Karnataka [email protected] Since water is a limiting resource under dry land conditions, cotton crop improvement and research activities are therefore, compelled to develop or screen high yielding genotypes with low leaf area and higher total biomass under rainfed conditions rather than those producing higher leaf area and higher biomass. This necessitates the identification and breeding of cotton genotypes with low leaf area and higher total biomass for obtaining higher yield. It would be helpful in identifying the cotton genotypes with higher photosynthetic rate thereby improving the yield potential of cotton genotypes under limited water conditions. One of the possible approaches is to search for cotton ideotypes with specific and distinct characters or combination of characters that are known to influence the photosynthesis, growth and production of economically important plant parts, as are expected to perform better under adverse environmental conditions. Development or identification of such cotton ideotype is possible either by regular breeding programme or by screening from the existing cotton germplasm under rainfed conditions. In broad sense, an ideotype is a biological model which is expected to perform or behave in a predictable manner in a defined environment. For the identification of ideotype in cotton, a wide range of cotton cultivars with a genetic diversity for various traits is required (Blixt and Vose, 1984). Application of ideotype concept in cotton with higher photosynthetic rate, higher yield, pest and disease resistance and better fibre character lies in the extent of understanding about plant growth and morpho- physiological characters in enhancing yield including the nature of interrelationships between different characters. Seed cotton yield is stagnated for the last 10 years and India’s productivity (338 kg/ha) is very low as compared to the world average (478 kg/ha). It appears that, the frequent occurrence of natural vagaries of various kinds of stress, lack of scientific crop production technology and the low yielding nature of present genotypes except hybrid cottons resulted in lower productivity in India. In this direction, efforts need to be made in elucidating the principal factors limiting seasonal yield under rainfed conditions. To meet the challenges of productivity, Gossypium hirsutum sp. offers better scope for genetic improvement among the four cultivated species of cotton. Majority of cotton produced by G. hirsutum sp. is medium and long staple and it has very high adoptability with rich diversity for yield and yield related characters. Initially 228 genotypes were evaluated under rainfed conditions for only yield and morpho–physiological characters. Based on this preliminary investigation results in the successive years totally 62 G. hirsutum L. genotypes were evaluated in detail for morpho-physiological, biophysical and biochemical parameters apart from growth, yield and yield attributing characters, to identify desirable plant characters for ideotype under rainfed condition. Among the genotypes, Alleppo x Rex, DS-44, DRC-264, IC-376, NA-1269, DRC-19 and CPD-4-4-5 produced significantly higher yield as compared to the checks Abadhita and Sharada. The increase in yield was to the extent of 45 to 70 per cent. Among the high yielding genotypes, DS-44 and IC-376 were categorized as low LA types, because of low LA/TDM ratio’s. These genotypes also had high NAR, SLW and TDM/LAD ratio as compared to other genotypes and both the checks. In addition, these genotypes had higher chlorophyll content at all the growth stages indicating better photosynthetic capacity of the leaves which might have resulted in higher dry matter accumulation per unit leaf area. The higher yield obtained in the above mentioned genotypes was ascribed to accumulation of higher total biomass and greater partitioning into 4 National Conference on Frontiers in Plant Physiology Towards Sustainable Agriculture, 5-7 November, 2009, Jorhat, Assam reproductive parts as evidenced by the higher degree of association with TDM (r=0.629*) and harvest index (r=0.460*). In addition, the higher yield obtained in these genotypes was associated with higher boll number (r=0.832**), bartlett’s index (r=0.278*), LAR at 60 DAS (r=0.317**), SLW at 90 DAS (r=0.289*), RGR (r=0.268*) and NAR (r=0.282*) between 60-90 DAS and the negative association with LAI at 60 DAS (r=- 0.312*) and stomatal conductance at 120 DAS (r=-0.368*). All the fibre properties studied in these genotypes were on par with checks Abadhita and Sharada. Based on the above investigations, it could be concluded that the desirable plant characters for ideotype of plant under rainfed conditions are with low leaf area between 12-18 dm2 / plant at peak growth stage, NAR of 0.04 to 0.07g/dm2/plant between 60-90 DAS, CGR of 2.0 to 3.0 g/dm2/day at 90 DAS, lower stomatal conductance 2 (3 to 4 cm/sec), lower transpiration rate (45 to 50 μg H2O/cm /sec) and higher NAR to stomatal conductance ratio (0.0645 to 0.0812) during peak growth period, higher photosynthetic rate (Low LA/ TDM ratio), higher productivity per day, higher yield per unit functional LA, total biomass of 90 to 130 g/plant at harvest, higher HI of 22-35 percent, and more number of good bolls per plant (6-8) and with medium maturity(160-165 days) and the resultant genotypes identified based on these characters as ideotype cottons are DS-44, IC-376 and CPD-4- 4-5. From the field studies conducted at Dharwad for many seasons the following cotton ideotype characters have been proposed under rainfed conditions. 1. Short compact plant structure with open canopy. 2. Smaller leaves well inclined to intercept maximum light and showing heliotropic movements. 3. Short multinodal sympodia (2 to 4 nodes).