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Title: QTLs for downy mildew resistance and their association with LRR-RLK resistance gene analogs in cucumber

Author
item WANG, YUHUI - University Of Wisconsin
item VANDENLANGENBERG, KYLE - North Carolina State University
item WEHNER, TODD - North Carolina State University
item Weng, Yiqun

Submitted to: Cucurbitaceae Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 8/1/2014
Publication Date: 10/16/2014
Citation: Wang, Y., Vandenlangenberg, K., Wehner, T.C., Weng, Y. 2014. QTLs for downy mildew resistance and their association with LRR-RLK resistance gene analogs in cucumber. Cucurbitaceae Proceedings. p. 31.

Interpretive Summary:

Technical Abstract: Downy mildew (DM) caused by the obligate oomycete Pseudoperonospora cubensis is an important disease of cucumber and other cucurbit crops. For more than 50 years, DM was effectively controlled in cucumber through host resistance. The dm-1 gene became less effective in 2004 due to the appearance of a new pathotype. Resistance sources (for example, K8, PI 197088 and PI 330628) against the new DM strain have been identified. Several QTL mapping studies have revealed the recessive and quantitative nature of DM resistance in these materials. QTLs for DM resistance were detected in K8, PI 197088 and PI 330628, and have been mapped in five (1, 2, 4, 5, and 6) of the seven cucumber chromosomes. Previous studies in other plant species suggested that the leucine-rich repeat (LRR)-receptor-like kinases (RLKs) may be responsible for recessively inherited host resistance against oomycete pathogens. For better understanding of the molecular mechanisms of DM resistance in cucumber, we performed genome-wide identification of LRR-RLKs type resistant gene analogs (RGAs) in the cucumber genome, aiming for possible association of these RGAs with DM resistance QTLs. From the Gy14 and 9930 draft genome assemblies, we identified 181 LRR-RLKs RGAs carrying the transmembrane (TM), LRR and serine/threonine kinase (STK) domains. Several LRR-RLKs in chromosomes 4 and 5 were found to be co-localized or near the major effect QTLs from different resistance sources, but further evidence is needed to establish any association of these resistance gene analogs with the QTLs for downy mildew resistance.