Location: Soil and Water Management Research
Title: Yield component analysis of grain sorghum grown under water stress Authors
Submitted to: Field Crops Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 6, 2013
Publication Date: March 20, 2013
Citation: Tolk, J.A., Howell, T.A. 2013. Yield component analysis of grain sorghum grown under water stress. Field Crops Research. 145:44-51. http://dx.doi.org/a0.1016/j.fcr.2013.02.006 Interpretive Summary: A plant that can keep its leaves green for longer period of time compared with what is traditional can produce more food for its grain and produce bigger grain yields. This is called "stay-green". For two years, we compared the grain yields of a stay-green grain sorghum crop with the yields of a grain sorghum crop that did not have the stay-green trait. We wanted to see what part of the yield (seed number per unit area, seed size) was different between the two crops. When the crops had adequate water and air temperatures were mild, the stay-green crop had smaller yields compared with the non-stay-green crop, primarily because the seed size was smaller. When the crops had little water and air temperatures were hot, the stay green crop produced larger yields compared with the other crop, primarily because it produced a greater number of seeds. The stay green trait helped maintain yields when water was limited.
Technical Abstract: Delayed leaf senescence, or 'stay green', in grain sorghum (Sorghum bicolor Moench L.) allows continued photosynthesis under drought conditions which can result in normal grain fill and larger yields compared with senescent cultivars. The objective of this study was to compare the yield response of a sorghum hybrid with stay green genetics and a sorghum hybrid with senescent genetic traits to differing levels of water stress to identify traits leading to increased yield under water stress. A stay green (SG) and a senescent (SN) hybrid of grain sorghum were grown in 2010 and 2011, which had contrasting environmental conditions, in 48 weighing lysimeters containing soil monoliths of four regional soils - clay loam, silt loam, sandy loam or fine sand (12 each) at Bushland, TX, USA. Plant density was 16 plants m**92; irrigation treatments were 19 mm or 28 mm applied weekly. Under water and heat stress (2011), the SG hybrid produced significantly larger grain yield due to a greater seed number (seeds m**2) compared with the SN hybrid, both with similar amounts of evapotranspiration (ET). Panicle biomass growth rate from flag leaf emergence to beginning seed fill was identified as a period critical for determining seed number. Panicle biomass (g m**2) at maturity, as an integrated measure of panicle growth rate during this period, was linearly related to seed number in the water stress treatments, with the SG hybrid producing a greater number of seeds compared with the SN hybrid with the same panicle mass. The seed mass of the SG hybrid was fairly constant in both minimum stress and stress environments, which was in general significantly smaller than the seed mass of the SN hybrid under all conditions. Under drought conditions, the stay green hybrid maintained yield by retaining greater seed numbers.