Submitted to: Crop Science Society Of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/5/1999
Publication Date: N/A
Citation: ULLOA, M., CANTRELL, R.G., PERCY, R.G., LU, Z., ZEIGER, E. GENETIC VARIATION FOR STOMATAL CONDUCTANCE AND RELATIONSHIP TO AGRONOMIC PERFORMANCE IN AN INTERSPECIFIC COTTON POPULATION. CROP SCIENCE SOCIETY OF AMERICA. 1999. Interpretive Summary: Cotton lint yield can be dramatically reduced by extended periods of high temperatures during peak bloom in irrigated Southwestern U.S. conditions. The plant's physiological process of stomatal conductance (gs) may confer some adaptive advantage to cotton varieties that experience supra-optimum temperatures. The primary objectives of this research were to practice divergent selection for gs and to identify molecular markers associated to gs in order to determine its effect on cotton lint yield. Replicated experiments of 20-selected breeding lines (10 high gs and 10 low gs) were grown in Maricopa AZ and Las Cruces NM. Lint yield was significantly affected by selection for gs in Maricopa AZ. The high gs group produced the highest cotton lint yield. Two molecular markers for gs were also identified on two cotton chromosomes. The two selected groups were not significantly different for gs at Las Cruces NM. The advantages for this physiological trait would be small or non-existent in temperature zones where enhanced evaporative cooling would not be expected to enhance lint yield. The association of molecular markers to gs is especially interesting to breeders in that it opens the door to more precise manipulation of the trait.
Technical Abstract: Extended periods of high temperature can reduce cotton (Gossypium hirsutum L. and G. barbadense L.) lint yield, even under adequate irrigation. High stomatal conductance (gs) may confer some adaptive advantage to genotypes that experience supra-optimum temperatures. Divergent selection was practiced for gs in a segregating population (n=118 F2.3 progenies) derived from the cross NM24016 X TM1. Divergent selection for high and low gs was practiced in Maricopa, AZ in 1996. DNA was isolated from all 118 F2 plants in 1995 and a linkage map produced with 199 RAPD and SSR DNA markers. Genetic analysis of the replicated F3 families in 1996 at Maricopa permitted identification of quantitative trait loci (QTL) influencing gs. Replicated experiments of 20-selected F2.4 eny (10 high gs and 10 low gs) were grown in Maricopa and Las Cruces in 1997. The 10 families selected for high stomatal conductance in 1996 averaged 542.6 mmol H2O m**-2 s**-1 at Maricopa in 1997 and were significantly (P>0.0001) different from the mean of the low families (472 mmol H2O m**-2 s**-1). The two selected groups were not significantly different for stomatal conductance at Las Cruces (P>0.0631). The absence of high temperatures during the growing season at Las Cruces may explain this difference. Lint yield was significantly (P=0.0027) affected by selection for stomatal conductance in Maricopa. The high gs F3.4 family group produced the highest cotton lint yield averaging 1842 g plot**-1 while the low gs family group averaged 1655 g plot**-1. Two putative QTLs for gs were identified on two