Morphophysiological traits of soybean leaflets and their relationship with crop agronomic performance

Soybean genotypes have distinct morphophysiological traits, which may influence the crop agronomic performance. The aim of this work was to evaluate the productive parameters of three contrasting soybean genotypes for leaf morphophysiological traits. The experiment was carried out at in a typical Distroferric Red Latosol, located at latitude 25º41'52" S and longitude 53º03'94" W; in the 2015/16 (CY1) and 2016/17 (CY2) seasons. The genotypes tested were: BS 2601 RR® (lanceolate and smaller leaflets); NS 6006 IPRO® (triangular and intermediate leaflets) and homozygous lineage CI 21 IPRO® (oval and larger leaflets). The gas exchange, chlorophyll index, leaf area, leaflet length and width, and petiolulus length were evaluated when plants of each genotype were at the beginning of flowering. At harvest, the variables analyzed were: first pod insertion, plant height, number of pods and grains per plant, grains per pod, mass of one thousand grains and grain yield. The design used was randomized blocks with four replicates. Photosynthesis per leaf area unit was higher in CY2, and is related to greater stomatal conductance, higher chlorophyll index, lower transpiration and lower leaf area of plants. The lanceolate leaf cultivar showed higher grain yield due to the higher number of grains and the greater mass of these grains in the two crop years. In addition, it was the one that obtained lower leaf area and lower transpiration. The cultivar NS 6006 presented greater productive stability, but this trait does not confer greater productive potential.