Evaluation of groundnut genotypes for heat tolerance under field conditions in a Sahelian environment using a simple physiological model for yield

Heat tolerance of groundnut (Arachis hypogaea L.) was evaluated under field conditions using physiological traits identified in a yield model [crop gr ow th rate (C). reproductive duration (D-r) and partitioning (p)], In 1991. 625 diverse genotypes were initially screened under irrigation during the hottest months (February to Mag;). Subsequent tests consisted of 16 contras ting genotypes selected based on a combination of high pod yield and partit ioning coefficient of > 0.50. Large variation was observed among the 625 ge notypes for pod yield and physiological traits. C was a powerful factor inf luencing pod yield. Eight genotypes combining high pod yield and a partitio ning coefficient greater than 0.6 were identified. These included two relea sed cultivars (55-437 and 796) in the Sahel. Correlations between seasons w ere significant for p (r = 0.84), but nun-significant For pod yield (r = 0. 40), C (r = 0.39), and D-r (0.36). Date of sowing and genotypes had signifi cant effects on pod yield and C, but were slight on p and D-r. pod yield of most genotypes declined by more than 50% when flowering and pod formation occurred when maximum temperatures averaged 40 degreesC. The results reveal ed that estimates of p would be a more reliable selection criterion for ide ntification of genotypes tolerant to heat than yield. Further research is s uggested to maximize crop growth rate and partitioning of genotypes growing under supra-optimal temperatures.