Water deficit and heat stress induced alterations in grain physico-chemical characteristics and micronutrient composition in field grown grain sorghum

Authors: SOMAYANDA, IMPA - Kansas State University; PERUMAL, RAMASAMY - Kansas State University; Bean, Scott; SUNOI, JOHN - Kansas State University; JAGADISH, KRISHNA - Kansas State University

Submitted to: Journal of Cereal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/29/2019
Publication Date: 1/30/2019
Citation: Somayanda, I., Perumal, R., Bean, S.R., Sunoi, J., Jagadish, K. 2019. Water deficit and heat stress induced alterations in grain physico-chemical characteristics and micronutrient composition in field grown grain sorghum. Journal of Cereal Science. 86:124-131. https://doi.org/10.1016/j.jcs.2019.01.013.
DOI: https://doi.org/10.1016/j.jcs.2019.01.013

Interpretive Summary: The surge in sorghum-based foods as a cost-effective and gluten-free alternative for cereals like wheat, has directed sorghum research towards understanding and improving grain quality parameters. Since sorghum is usually grown in arid and semi-arid environments, is often prone to terminal water deficit and heat stress, inducing significant yield and quality losses. Field experiments were carried out to assess the effect of water deficit and heat stress on grain physico-chemical, and micronutrient composition in diverse sorghum varieties. Drought stress increased kernel hardness and total protein in grain, decreased protein digestibility, kernel diameter, kernel weight and micronutrient composition. However, heat stress decreased total protein, protein digestibility, micronutrient composition and increased kernel hardness. Irrespective of the stress, larger kernels had higher total protein, higher protein digestibility and micronutrient composition, but a lower total starch and kernel hardness. All the measured grain micronutrients (Zn, Fe, Mn and Cu) were reduced under both the stresses except for grain Fe under water-deficit stress, which increased. Sorghum varieties were identified which had the ability to maintain desired grain quality parameters under stress conditions, which will be useful for sorghum breeders developing sorghum to grow in areas prone to heat or drought stress.

Technical Abstract: The surge in sorghum-based foods as a cost-effective and gluten-free alternative for cereals like wheat, has directed sorghum research towards understanding and improving grain quality parameters. Since sorghum is usually grown in arid and semi-arid environments, is often prone to terminal water deficit and heat stress, inducing significant yield and quality losses. Field experiments were carried out to assess the effect of water deficit and heat stress on grain physico-chemical, and micronutrient composition in 24 sorghum diverse genotypes that originated from major sorghum growing regions of the world. In Exp. 1, the 24 genotypes were grown in irrigated and dryland fields, wherein, the irrigated field in addition to the rainfall received two irrigations one at flowering and the other at grain-filling stage. The dryland field experienced water-deficit stress during these critical stages. In Exp. 2 heat stress was imposed by placing custom-built field-based heat tents on already established plants at the start of booting until maturity.Water-deficit stress increased kernel hardness and total protein in grain, decreased protein digestibility, kernel diameter, kernel weight and micronutrient composition. However, heat stress recorded a lower total protein, protein digestibility, micronutrient composition and higher kernel hardness than controls. Irrespective of the stress, larger kernels recorded higher total protein, higher protein digestibility and micronutrient composition, but a lower total starch and kernel hardness. All the measured grain micronutrients (Zn, Fe, Mn and Cu) were reduced under both the stresses except for grain Fe under water-deficit stress, which increased by 12% compared to control. Identified genotypes having the ability to maintain desired grain quality parameters under stress conditions, such as SC372 and RTx7000 would help in selection of appropriate nested association mapping populations for further genetic mapping studies or used as donors in abiotic stress breeding programs.