Assessment of Yield-based Drought Tolerance Indices and Physiological Traits for Screening Pomegranate (Punica granatum L.) Genotypes

The present research considered identifying drought tolerant genotypes through an index-based analysis of stress tolerance and physiological traits in pomegranates. Ten local pomegranate genotypes in Iran were evaluated for drought stress tolerance in two different irrigation regimes, i.e. normal conditions and severe drought stress (SDS). The experiment was arranged in a randomized block design with three replications and took two consecutive years to accomplish (2019-2020). Indices for stress tolerance were estimated from the fruit yield of a single tree under each irrigation regime. There were significantly positive correlations among several parameters, including Yp (fruit yield under normal condition), Ys (fruit yield under SDS), mean productivity (MP), geometric mean productivity (GMP), stress tolerance index (STI), and proline (Pro) content. Therefore, these indices were applicable to the identification of drought tolerant genotypes under SDS and normal conditions. The Pro content was introduced as the best physiological index to assist in the indirect selection of drought-tolerant genotypes. Meanwhile, a negative correlation was noticed between Ys and stress susceptibility index (SSI). This index may assist in identifying susceptible genotypes. Based on principal component analysis (PCA), two genotypes (MTS and PSS) performed best in terms of fruit yield and showed a high Pro content under the SDS condition.