Identification of quantitative trait loci for adaxial and abaxial stomatalfrequencies in Oryza sativa

Stomatal frequency is one of the main factors that determine photosynthetic ability and stomatal conductance. However, the genetic basis for stomatal frequency is still poorly understood. The genetic relations between adaxial and abaxial stomatal frequencies have been studied in rice (Oryza sativa L .) with quantitative trait loci (QTL) analysis approach on a population of backcross inbred lines of japonica Nipponbare x indica Kasalath. Four QTLs controlling adaxial and abaxial stomatal frequencies were identified. On ch romosome 3 of rice, QTL for adaxial stomatal frequency overlapped that for abaxial stomatal frequency. There was a high correlation (r = 0.660, P < 0. 01) between them, and the allele that increases the expression was contribu ted by Kasalath for both traits. These results suggest that the same gene m ay pleiotropically control the stomatal frequency on both surfaces of the l eaf. QTLs for leaf rolling related to osmotic stress were also mapped. The absence of overlap in QTLs fur leaf rolling and stomatal frequency suggests that osmotic tolerance is at least partly independent. of stomatal frequen cy. The generic relationship between stomatal frequency and yield is also d iscussed. (C) 2001 Editions scientifiques et medicales Elsevier SAS.