In the light of climate changes and global warming, as well as the rapid expansion in sugar beet (Beta vulgaris L.) cultivation in Egypt, the development of sugar beet varieties with improved tolerance to high temperature and deficit irrigation is of great importance. The objective of this study was to evaluate sugar beet genotypes under high temperatures and deficit irrigation conditions for further identification and selection of heat and drought tolerant genotypes. In the current study, a panel of 18 sugar beet breeding lines produced at the USDA–ARS–NWISRL, Kimberly, ID, and the commercial sugar beet cultivar Kawimera were evaluated for yield and quality under high temperature. Six promising lines in terms of yield and quality were further evaluated under both high temperature and deficit irrigation for two growing seasons.

All lines performed differently under deficit irrigation, indicating a high degree of genetic variability in the evaluated lines. Additionally, yield traits showed negative effect due to deficit irrigation. A significant positive correlation was observed between stress tolerance index (STI), and average root and sugar yields under stressed and non‐stressed conditions. A linear relationship between STI and average root and sugar yields indicates that STI is a reliable stress index to select high yielding genotypes under both optimum‐ and deficit‐irrigation conditions. USKPS25 and USC944‐6‐68 breeding lines are most likely adapted to deficit irrigation and high temperature and suitable to be utilized in the proposed sugar beet breeding programs in Egypt.