The Long and the Short of Soybean Petioles.

Increases in the world population have led to rising demands for sustainable sources of plant protein and oil.  Modifications to plant canopy architecture could play an important role in meeting these demands, as was demonstrated during the Green Revolution in the 1960's and 1970's.  Petioles are an important component of canopy architecture as they connect the leaflets to the stem in dicot species, but many of the mechanisms controlling petiole length are largely unknown.  To our knowledge, no previous study has identified the causal polymorphism for a soybean short petiole mutant and conducted yield and physiological studies on the effects of short petioles.  Kilen (1983) identified a short petiole soybean mutant, lps1, that segregated as a single, recessive locus. The mutation was first observed in 1976 segregating in an F₃ row in a population generated from a cross between Forrest(2) x (PI 229358) and D71-6234. D71-6234 was derived from a cross between a high protein Lee type and PI95960. None of the four parents were observed to have the short petiole phenotype which suggests that the mutation occured spontaneously. This study was undertaken to identified the causal polymorphism underlying the lps1 short petiole phenotype as well as to test the utility of the lps1 for improving soybean yield, agronomics, and physiology using Near Isogenic Lines (NILs) generated during the trait mapping process. At this time, a candidate mutation has been identified for lps1 and yield testing of NILs started during the summer of 2015.