R. C. Nageswara Rao

Effect of Drought on oil, fatty acids and protein contents of groundnut (Arachis hypogaea L.) seeds.

The rainfed groundnut (Arachis hypogaea L.) crop suffers from moisture stress of varying intensity at different growth stages. The effect of drought on oil, protein and fatty acid contents were studied in 12 genotypes that differed in seed quality traits. The genotypes were subjected to mid-season and the end-of-season drought in field experiments at ICRISAT Asia Center (IAC), Patancheru, India, conducted during the 1991/92 and 1992/93 postrainy (November-April) seasons. Mid-season drought was imposed between 40 and 80 days after sowing (DAS). The crop received normal irrigation, 50 mm at 10 day intervals, before and after the imposition of mid-season drought until harvest. Using the line-source sprinkler technique, end-of-season drought of varying intensity was imposed from 80 DAS until harvest. Mid-season drought had no significant effect on the content of oil, protein and fatty acids other than eicosenoic fatty acid. End-of-season drought significantly reduced total oil, and linoleic and behenic fatty acid content, and significantly increased total protein and stearic and oleic fatty acid content. However, genotype by treatment interactions were found. In ICGVs 88369, 88371, 88381, 88382 and 88403, total oil content remained unaffected while oleic fatty acid content increased under end-of-season drought. These were identified as desirable parents for a breeding program to develop cultivars suitable for rainfed cultivation.

The Physiological Basis for Yield Differences between Four Genotypes of Groundnut ( Arachis Hypogaea ) in Response to Drought. I. Dry Matter Production and Water Use

Four genotypes of groundnut grown with limited irrigation in a medium depth Alfisol in Central India transpired similar total amounts of water (220–226 mm) over the season, but produced different amounts of shoot dry matter (390–490 g m−2 ). The extraction front of Kadiri 3 moved most rapidly down the soil profile which may have enabled it to maintain the fastest rates of transpiration when soil water depletion was greatest. Tap root extension rates of Kadiri 3 in the first 32 days after sowing were also the fastest. NC Ac 17090 was more efficient than the other genotypes in extracting water immediately after irrigation from the upper 40 cm of the soil, but this had little value in determining the pattern of water availability in this experiment. Differences in the water extraction characteristics of these genotypes explain little of the variation in dry matter:water ratio, and do not account for the major variation in harvest index associated with drought.

The Physiological Basis for Yield Differences between Four Genotypes of Groundnut (Arachis hypogaea) in Response to Drought. II. Solar Radiation Interception and Leaf Movement

Four genotypes of groundnut grown with limited irrigation during the post-rainy season in Central India produced similar amounts of dry matter per unit of intercepted solar radiation (e) before pod-filling, although different e values were observed during pod-filling. The relation between cumulative transpiration and intercepted radiation was similar for all genotypes. When drought became severe, fractional radiation interception (f) was reduced by folding of leaves, with little decrease in leaf area (L). The ratio f/√L was used as an index of the degree of leaf folding and was correlated with leaf water potential. The degree of folding varied with genotype and may have contributed to the observed differences in e and the dry matter:water ratio (q). The genotype EC76446(292) had the smallest q and largest f/√L ratio (the poorest radiation avoidance), while Kadiri 3 had the largest q and smallest value of f/√L

Population, Growth and Water Use of Groundnut Maintained on Stored Water. III. Dry Matter, Water Use and Light Interception

At a field site in central India, four populations of groundnut (Arachis hypogaea L.) were grown on stored water to investigate how the production of shoot and root dry matter is related to transpired water and intercepted radiation. Throughout the season, total dry matter was closely related to transpiration (slope = 3.0 mg dry matter g−1 water) and the amount of radiation intercepted by foliage (slope = 0.74 g dry matter MJ−1 radiation intercepted). Accumulated transpiration increased linearly with intercepted radiation at 0.37 kg water MJ−1 in the sparser stands. In the densest spacing, the initial slope of the relation at 0.28 kg MJ−1 decreased later in the season because water deficits curtailed growth without a concomitant reduction in the interception of radiation.

A comparative assessment of water use efficiency in groundnut (Arachis hypogaea) grown in containers and in the field under water-limited conditions

Water use efficiency (WUE) was measured on fourteen genotypes of groundnut (Arachis hypogaea L.) grown in containers under adequately irrigated and water-limited conditions. The genotypes used similar amounts of water but produced different quantities of dry matter. WUE accounted for > 92% of the variation in dry matter production under both irrigated and water-limited conditions. There was a significant increase in WUE under water-limited conditions. Four genotypes selected from the container experiment as having either a high or a low WUE under non-limited or limited water input conditions were further tested under prolonged water deficit conditions in a field experiment. WUE varied significantly between genotypes and there was a positive correlation between WUE and the quantity of dry matter produced by the genotypes. The results suggested that, in three out of four genotypes, the WUE measured in the container experiment was positively correlated with the WUE estimated under field conditions.

Population, Growth and Water Use of Groundnut Maintained on Stored Water. I. Root and Shoot Growth

The growth of roots and shoots was measured in stands of groundnut grown at a number of populations on stored water in central India. Total weight and length of roots per unit land area increased with population density, but the proportional increases were much less than for shoot weight. Consequently the root:total weight ratio increased from 0.3 in the densest stand to almost 0.5 in the widely spaced crop. The denser stands produced a greater proportion of their roots at depth. In wide rows there was little change in rooting density across the inter-row space. Total dry matter per unit land area increased with population, although the weight per plant was less in denser stands. Although the crops were harvested prematurely, pod yield per unit land area, unlike total dry matter, was no greater in dense stands than in more widely spaced crops. The greatest number of pods per unit land area was recorded at an intermediate population density.

A hand-held red-infrared radiometer for measuring radiation interception by crop canopies

A simple and portable two-band radiometer to measure simultaneously, reflectance of red (r) and near infrared (ir) radiation from canopies of peanut (Arachis hypogaea L.) is described. A strong linear relationship (r2 = 0.94) was observed between the normalised reflectance ratio (NR) calculated from r and ir reflected, and the fraction of incident photosynthetically active radiation (PAR) intercepted by peanut canopies up to a leaf area index of 3.0. The importance of and scope for measurements on radiation interception in crop improvement programs is discussed.

A method for calculating the population/yield relations of groundnut (Arachis hypogaea) in semi-arid climates

Between 1980 and 1986, six field experiments were conducted to investigate the relations between planting density, total dry matter and pod yield of groundnut (Arachis hypogaea L. cv. TMV2) grown at different levels of irrigation and rainfall at two sites in central India. In general, the relationship between total dry matter and planting density for most treatments was well described by the function: 1/W = 1/w m P + 1/W m where W is the crop dry weight per unit ground area, w m is the maximum weight per plant, W m is the maximum crop weight per unit ground area and P is the plant population (.)

Intercropping Short and Long Duration Groundnut ( Arachis Hypogaea ) Genotypes to Increase Productivity in Environments Prone to End-of-season Droughts

Three short duration and one long duration groundnut genotypes, grown either ‘sole’ or as intercrops (in 1:1 ratios of the short duration with the long duration genotypes), were compared in four trials. The intercrop treatments resulted in Land Equivalent Ratios (LERs) of up to 1.25 for pod yield and total biomass despite moderate or severe water deficits at the end of the season. Specific combinations of genotypes were necessary to maximize the LER. The results indicate there is scope for achieving greater productivity in environments with a variable season length by growing late and early genotypes together in an intercrop system