The Long and Short of Soybean Petioles: The Effect of a 3-bp Insertion on Plant Architecture and Harvest Index

Modifications to plant canopy architecture could play an important role in meeting increased global food demands, as was demonstrated during the Green Revolution. In dicot species, petioles are an important component of canopy architecture as they connect the leaflets to the stem. However, many of the mechanisms controlling petiole length are unknown, and to our knowledge, the effect of short petioles on seed yield has not been studied. Kilen (1983) identified a short petiole soybean mutant, lps1, that segregated as a single, recessive locus. The mutation was first observed segregating in an F₃ row in a population derived from four parents: Forrest, PI229358, Lee, and PI95960. The four parents were not observed to have the short petiole phenotype, suggesting the lps1 mutation occurred spontaneously. This study was undertaken to first identify the lps1 causal polymorphism and then to use Near-Isogenic Lines (NILs) to characterize the phenotype and assess the utility of lps1 to improve soybean agronomics. Whole-genome resequencing-based bulked segregant analysis was used to locate the chromosomal region harboring the lps1 mutation. Diversity analysis of sequences within this interval identified an in frame 3-bp insertion in an uncharacterized gene. Silencing of this gene by virus-induced gene silencing successfully produced a short petiole plant. Preliminary yield trials in 2015 of the NILs in narrow row spacing indicated that lps1 does not negatively impact yield and may improve soybean agronomics through increased harvest index and decreased plant height.