Theses and Dissertations

ORCID

https://orcid.org/0000-0002-9609-0084

Issuing Body

Mississippi State University

Advisor

Bheemanahalli, Raju

Committee Member

Reddy, K. Raja

Committee Member

Reddy, Krishna N.

Committee Member

Wijewardane, Nuwan K.

Date of Degree

5-12-2023

Document Type

Graduate Thesis - Campus Access Only

Major

Agronomy

Degree Name

Master of Science (M.S.)

College

College of Agriculture and Life Sciences

Department

Department of Plant and Soil Sciences

Abstract

Soybean (Glycine max L.) is an important legume crop often exposed to heat and drought stresses during reproductive and early-seed setting stages, resulting in lower yields and seed quality. Ten soybean cultivars were phenotyped for individual (drought or heat) and combined stress tolerance. Under drought, reduced stomatal conductance and increased canopy temperature significantly reduced seed number (46%) and weight (35%). Heat stress alone reduced seed number (19%) and weight (23%) compared to control. Moreover, a degree increase in daytime temperature above 32 °C during the reproductive stage reduced seed weight by 4% and 7% under well-watered and drought conditions, respectively. Seed protein was increased under drought, while it declined under heat and combined stress compared to control. In contrast, oil content showed the opposite trend. Weak correlations between phenotypic traits under individual and combined stress suggest that selecting cultivars for individual stress tolerance may not work under combined stress conditions.

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