Monday, November 13, 2006

Assessing Genotypic Variability of Cowpea to Current and Projected Ultraviolet-B Radiation.

Shardendu Kumar Singh, Giridara Kumar Surabhi, and K. Raja Reddy. Mississippi State Univ, Dept of Plant and Soil Sciences, 117 Dorman Hall, Box 9555, Mississippi State, MS 39762

Current and projected terrestrial UV-B radiation may affect growth and reproductive potential of many crops.  Better understanding of genotypic variability to UV-B radiation is a prerequisite in developing tolerant cultivars to current and projected changes in UV-B radiation. An experiment was conducted in sunlit, controlled environment chambers known as Soil-Plant-Atmosphere-Research (SPAR) units to evaluate sensitivity of cowpea cultivars to a range of ultraviolet-B radiation. Six cowpea cultivars (Prima, CB-5, CB-27, CB-46, Mississippi Pinkeye and UCR-193) differing in their sensitivity to abiotic stresses were grown at 30/22 °C day/night temperatures from seeding to 60 days after emergence (DAE).  Four biologically effective ultraviolet-B radiation treatments of 0 (control), 5, 10, and 15 kJ m-2 d-1 were imposed from 10 DAE to end of the experiment. Plants were irrigated with half-strength Hoagland’s nutrient solution, three times a day.  Physiological, vegetative and reproductive parameters were measured during and at the final harvest. Significant genotypic variability was observed for vegetative and reproductive parameters among the cowpea genotypes. The magnitude of the sensitivity to UV-B radiation also varied among cowpea genotypes.  Plants grown in elevated UV-B radiation significantly decreased net photosynthesis, electron transport rate and caused reductions in plant height, total dry matter, pollen viability and seed yield in Prima, CB-27 and CB-46 cultivars. The reductions were less in CB-5 and UCR-193, and none in Mississippi Pinkeye.  Based on the total stress response index (TSRI) calculated as sum of individual physiological, vegetative and reproductive component responses over all the UV-B radiation treatments, the cultivars were classified as tolerant (Mississippi Pinkeye and CB-5), intermediate (CB-46 and UCR-193) and sensitive (CB-27 and Prima) to UV-B radiation. The differences in sensitivity among the cowpea cultivars imply the options for selecting or developing cultivars with tolerance to a niche environment based on current and projected UV-B radiation.  

Handout (.pdf format, 337.0 kb)