Assessments of salt tolerance in a bottle gourd line expressing the Arabidopsis H+-pyrophosphatase AVP1 gene and in a watermelon plant grafted onto a transgenic bottle gourd rootstock

In this study, we developed transgenic bottle gourd lines expressing the Arabidopsis H+-pyrophosphatase AVP1 gene and confirmed the stable integration of AVP1 in the genomes of bottle gourd T-2 homozygous lines and its transcription. Additional analyses of the AVP1-expressing lines indicated that AVP1 expression in bottle gourds could improve salt tolerance in the greenhouse, as the lines maintained higher relative water content under salt stress regime. Moreover, the axillary shoots of AVP1-expressing lines recovered gradually when the soil was desalinized, whereas wild-type plants died. Watermelon plants grafted onto the transgenic bottle gourd rootstock also exhibited greater salt tolerance than those grafted onto wild-type bottle gourd rootstock, by generating higher biomasses and photosystem II quantum yields. Therefore, the expression of AVP1 enhanced salt tolerance in the bottle gourd, and the use of a rootstocks improved by genetic engineering is one of the effective methods in improving the agronomic traits of watermelon.