Potato early blight

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Early blight, caused by the fungal pathogen Alternaria solani Sorauer, is a serious foliar disease of potato and tomato worldwide.  It is characterized by substantial yield loss resulting from severe defoliation, especially under hot, humid conditions.  Fungicides are the main method of control, however they are undesirable due to their economic, environmental, and health consequences.  Host resistance is the most optimal solution, yet cultivated varieties offer only a few sources of moderate resistance, most of which are associated with late maturity.  Strong levels of resistance have been identified in wild species, and breeding efforts to introgress this resistance into cultivated potato offer promise in controlling the disease more sustainably.  

This project is focused on understanding early blight resistance from different wild species sources.  First, we are working with resistance derived from the species Solanum brevidens.  Resistance derived from this species was introduced by somatic fusion with the tetraploid potato cultivar Superior (work done by Dr. John Helgeson several years ago).  The progeny have been crossed several times with other cultivated varieties and we are now working to combine early blight resistance with late blight resistance derived from S. bulbocastanum (the RB gene).

Second, we are studying novel resistance derived from S. tarijense (2n = 2x = 24) and S. berthaultii (2n = 2x = 24).  Resistance from S. tarijense is very strong and does not appear to be related to maturity of the plant, which will be a benefit for potato breeders.  Populations derived from these wild species are being evaluated in a major potato production area for early blight development under field conditions without fungicides using natural inoculum.  The data gathered will be used to estimate the heritability and inheritance patterns of early blight resistance derived from these species.