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POSTERS: Genetics of resistance

Evaluating Bacterial Wilt Resistant Tomato Lines for Resistance QTLs and Their Disease Reaction Against Phylotypes I and II Strain of Ralstonia spp.
Sanju Kunwar - University of Wisconsin-Madison. Yun-che (Grace) Hsu- The World Vegetable Center, Peter Hanson- The World Vegetable Center, Shufen Lu- The World Vegetable Center

Bacterial wilt caused by Ralstonia spp. causes substantial yield losses on tomato. Disease management by chemicals are limited and host resistance is the cheapest and easiest means of control. However, the location and strain specific nature of resistance makes it difficult to breed varieties that are resistant across wide geography. We characterized a global set of bacterial wilt resistance tomato sources available at the World Vegetable Center, Taiwan, for presence of two major disease resistance QTLs, Bwr-6 and Bwr-12. We also correlated the genotypes of the resistant sources with their disease reactions against one strain each of phylotype I (R. pseudosolanacearum; Pss4) and phylotype II (R. solanacearum; Pss1632) by drench inoculation (108 CFU/ml) in the greenhouse. Out of sixty-seven entries tested, five had Bwr-6, nineteen had Bwr-12 and six entries had both QTLs present. Bwr-12 contributed to stable resistance against phylotype I but not against phylotype II strain. Bwr-6 contributed to stable resistance against both phylotypes I and II. The entries with both QTLs performed the best overall. Interestingly, entry ‘94T765-24-79’ that lacked both QTLs demonstrated high resistance against the phylotype II strain and may be a source of new disease resistance QTL/s. Understanding the interaction between distribution of resistance QTLs and corresponding disease reaction against phylotype I and II strains may help to unravel molecular genetics behind location specific and strain specific nature of bacterial wilt resistance in tomato for effective disease management.