Plant & Animal Genomes XI Conference Plant & Animal Genomes XI ConferenceJanuary 11-15, 2003
Town & Country Convention Center
San Diego, CA
Workshop: Abiotic Stress
We are identifying QTL conditioning water use efficiency (WUE) in rice and tomato. WUE is defined as the ratio of transpiration to net carbon assimilation during photosynthesis. Discrimination against naturally occurring, stable, heavy isotopes of carbon during photosynthesis is employed in genetic screens to identify genotypes with lowered intercellular CO2 concentrations and consequently higher WUE. Initial QTL scans were performed on stable mapping populations derived from crosses between strongly contrasting Indica and Japonica varieties in rice, and between S. lycopersicon and related wild species in tomato. Several candidate loci enhancing high WUE were identified in both crops. In tomato, QTL associated with high WUE were consistently associated with low specific leaf area (m2 leaf area/g dry weight) and high nitrogen contents per unit leaf area. These traits would be consistent with increased biochemical capacity for carboxylation rather than stomatal closure being responsible for increased WUE. QTL scans were performed on both well-watered and drought-stressed tomato plants. Under drought-stress, all genotypes shifted to lower intercellular CO2 and higher WUE, but the range of values associated with genetic differences in the employed mapping populations decreased and no significant QTL candidates were identified under drought with the sample sizes employed.