Multi-Seeded Sorghum Mutants As a Genetic Resource for Enhancing Sorghum Yield.

Sorghum (Sorghum bicolor L. Moench) has highly branched panicles with primary, secondary, and tertiary branches. The flower branch ends with a terminal triplet spikelets, one sessile spikelet that is directly attached to the branch and two pedicellate spikelets that are attached to the branch through a short pedicel, followed by one or more spikelet pairs (one sessile and one pedicellate). In BTx623 and most other known lines, only the sessile spikelets can develop into seeds and the pedicellate spikelets, occasionally develop anthers, will eventually abort. We isolated a series of multi-seeded (msd) mutants, in which all spikelets are fertile. In addition, the mutants displayed increased length and total number of primary and secondary inflorescence branches. In most of the msd mutants, the seed number per panicle increased by three fold as the wild type BTx623 and the seed weight per panicle doubled. All msd mutations are monogenic recessive. Ongoing genetic complementation indicates these msd mutants represent at least three loci. We are in the process of cloning the first complementation group, MSD1. This collection of mutants may serve as an important genetic resource to boost sorghum grain yield and unravel mechanisms of the abortion of pedicellate florets in many grass species.