How soybean plants develop compound leaf?

Abstract

Soybean (Glycine max L.) leaves show morphological alteration from simple leaf to compound leaf in accordance with the transition from juvenile phase to adult phase in vegetative development. In order to reveal the genetic mechanism of such a leaf development, the variation of leaf shape was investigated using a variety of soybean groups. The most popular mature leaf phenotype was trifoliate (with three leaflets), but the number of leaflet was increased more than three in accordance with the plant development in some varieties. Morphological analysis suggested that they could be classified into two groups; one is attributable to the multi-foliation of lateral leaflets and the other to the multi-foliation of terminal leaflet. While the mature leaves of the former varieties stably show pentafoliate phenotype (with five leaflets), the latter range from three to seven. For the identification of the genetic factor(s) that cause the morphological alteration in soybean leaves, the M₂ lines derived from the EMS treatment of variety Peking with trifoliate phenotype were investigated. Among them, several lines showed 5-foliate phenotype attributable to the multi-foliation of lateral leaflets in accordance with the plant development. Therefore, it was considered that at least two kind of factors control leaf morphology in soybean; one promotes alteration from simple to compound leaf in accordance with the phase transition and the other repress the number of leaflets.