Genetic Analysis of Vegetative Branching and Rhizomatousness in Sorghum

Axillary bud initiation and outgrowth are vital plant development processes in determining plant architecture. The axillary buds ultimately develop into either vegetative branches or subterranean rhizomes depending on different developmental orientations. We are using forward genetics to study vegetative branching patterns and rhizomatousness in sorghum. We have developed a system to quantify the branching pattern and classify the position and the maturity of each branch, and to measure the number of rhizomes as well as the distance of rhizome-derived vegetative shoots to the crown. With the help of single sequence repeat (SSR) markers, genetic mapping is being used to discover quantitative trait loci (QTL) responsible for these traits in a recombinant inbred line derived from a cross between cultivated sorghum (Sorghum bicolor) and a wild relative (Sorghum propinquum (Kunth) Hitchc) indigenous to southeast Asia that is rhizomatous and highly branched. As a complement to genetic mapping, association genetics will assist to identify and pinpoint candidate genes from an established sorghum diversity panel. Better characterizing the genetic basis of these two traits promises to shed light upon plant growth regulation, with a wide range of applications ranging from suppressing the growth of weeds to facilitating the breeding of perennial sorghum.