Submitted to: Jordan Journal of Agricultural Sciences
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/26/2013
Publication Date: N/A
Citation: Interpretive Summary: Production costs in irrigated apple orchards are rising, due in part to increased competition for urban-directed water supplies and to drought episodes which have lowered the availability of water in natural aquifers. Since most commercial cultivars are grown on different rootstocks, it is important to be able to recognize drought tolerant rootstocks, as well as rootstocks that have superior water use efficiency. This paper describes work done in collaboration with Syrian scientists to analyze rootstocks based on whether they possess specific genes known to be associated with drought resistance. Out of five Syrian cultivars examined, four showed no change in leaf traits usually associated with drought response, whereas one variety showed a significant loss of leaves. This variety also lacked two of the genes studied, suggesting that these genes might be required for effective drought tolerance. Development of new varieties of apple with superior water use and drought tolerance could result in significant savings in production costs and could be useful if drought episodes in the US continue or increase in the near future.
Technical Abstract: This investigation was conducted to detect the drought tolerant genes (four genes) within seedling apple rootstocks derived from five apple genotypes, including Syrian apple cultivars. The results showed that the gene MdPepPro (a cyclophilin) was found in all studied genotypes and their progenies except for one plant in genotype B. This was followed by the gene encoding an apple heat shock protein (MdHSP18), while the other two genes, MdDhn1 (Dehydrin1) and MdERC (transcription coactivator), were present in fewer of the progenies of the studied genotypes. On the other hand, the plants derived from the local apple cultivar 'Sukari 2' were distinguished with a high number of plants having all four genes among the studied genotypes, while the genotype B plants had the lowest number of individuals possessing the four genes, in particularly MdDhn1 and MdHSP18, compared to the other genotypes. This information together with evaluation of leaf phenotypes, suggest that genotype B plants are the least drought tolerant of those studied. Consequently, this study provides a rapid method for screening apple genotypes for potential drought tolerance. Further study of the expression of these genes under deficit water will also aid in identifying apple rootstocks with better drought tolerance.