Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/7/2016
Publication Date: 10/26/2016
Citation: Tolk, J.A., Schwartz, R.C. 2016. Do more seeds per panicle improve grain sorghum yield. Crop Science. 57:1-7.

Interpretive Summary: Both seed number and seed weight are important to grain yield, but seed number is often considered to be the more important of the two. ARS scientists at Bushland, Txcompared the yields of two grain sorghum hybrids. One was a specially developed grain sorghum hybrid (tri-seed hybrid) with a greater number of seeds but they were smaller in weight. The other was a normal hybrid (parent hybrid) with fewer but larger seeds. Although the tri-seed hybrid had significantly more seeds compared with the other hybrid, the increased seed number did not adequately compensate for the significantly smaller seed weight. Increased seed number gave no yield advantage.

Technical Abstract: Seed number rather than seed mass is largely considered to be the most important yield component of grain sorghum [Sorghum bicolor (L.) Moench]. An experimental sorghum hybrid with enhanced seed number (tri-seed) was grown at the Soil-Plant-Environment Research (SPER) facility, USDA-ARS, Bushland, TX, in 2014 and 2015 to provide field validation of the hybrid’s ability to increase yield. The SPER facility had a rain shelter to control the soil water balance. The parent hybrid line, BTx623, and the hybrid tri-seed line, MSD-P5, which originated as a mutant of BTx623, were grown in weighing lysimeters with undisturbed soil profiles of four agriculturally productive soils (Pullman clay loam, Ulysses silt loam, Amarillo sandy loam, and Vingo fine sand) of the US Great Plains. Planting density was 16 plants m-2, and the crops received either 18 or 36 mm of irrigation weekly. The MSD-P5 tri-seed hybrid produced significantly smaller grain yield, seed mass, and total biomass compared with the BTx623 hybrid. Although it did produce a significantly more seeds compared with the parent line, the increase in seed number by the tri-seed hybrid did not compensate for the decreased seed mass which consequently failed to increase grain yield or harvest index (HI). The mass panicle-1 were similar between hybrids, but a significantly larger proportion of the tri-seed hybrid panicle was non-grain panicle mass. While both hybrids exhibited some plasticity in seed mass to accommodate assimilate as it became available, this also did not result in a significant increase in HI for the tri-seed hybrid, supporting previous research that sorghum yield is source limited.