Introgression of Sub1 QTL alters aerenchyma-mediated gas exchange and stored carbohydrates to maintain yield under flooding stress in rice

Floods can completely submerge rice fields. When rice is submerged, various anatomical and physiological changes occur at cellular and whole plant levels. New submergence tolerant varieties have been developed for the benefit of farmers in flooded areas. The present investigation comprised of evaluating a Sub 1introgressed CO 43 variety (CO 43 Sub 1 Nil) along with its donor (FR13A) and cultivated variety CO 43, for different anatomical and physiological traits underlying flooding stress tolerance. The results revealed that one of the adaptive trait of rice is the constitutive development of aerenchyma when submerged. It also showed that lesser porosity or air cavities in the leaf, stem and root aerenchymas of the tolerant varieties (FR13A and CO43 Sub 1 Nil) showed limited gas exchange and conserved the stored carbohydrates. The susceptible variety (CO 43) showed higher percentage increase in porosity in all the tissues studied. The plants also showed limited underwater elongation and higher survival percentage for seven days of flooding stress. The yield advantage of CO 43 Sub 1 Nil showed a two fold increase in all the yield components compared to CO 43 following submergence. This was due to its ability to utilize the stored carbohydrate immediately after withdrawal of stress to enhance photosynthetic rate and conductance, for greater biomass and yield. A strong positive correlation exists between leaf and stem carbohydrate contents and the survival percentage before and after submergence. The paper highlights the role of aerenchyma in regulating the gas exchange and stored carbohydrates in improving the tolerance of CO 43 Sub 1 Nil to flooding stress. © 2022, The Author(s), under exclusive licence to Korean Society of Crop Science (KSCS).