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POSTERS: Cultural control

Resistance to Non-Race 1 Verticillium dahliae in Tomatoes Suppresses Necrosis and Chlorosis Symptoms in Infected Plants
Thomas Ingram - North Carolina State University. Ralph Dean- North Carolina State University, Yeon Yee Oh- North Carolina State University, Randolph Gardner- North Carolina State Univ, Frank Louws- North Carolina State University

In 2017 and 2018 field trials were conducted in Mills River, NC to evaluate grafted and non-grafted tomatoes with reported resistance to non-race 1 Verticillium dahliae. In 2017 ‘NC-7GEM’ (7-1K), had significantly lower AUDPC scores than the susceptible ‘Red Defender’ (RD). 7-1K also had less disease than non-fumigated RD. However, when 7-1K was used as a rootstock for RD, it did not prevent the susceptible scion from wilt symptoms. The susceptible RD scion grafted on to 7-1K was just as susceptible as non-grafted and self-grafted RD. When the trial was repeated in 2018, similar results were found. In 2018 similar results were found, but we included 7-1K grafted onto RD, and showed that even with a susceptible rootstock, the 7-1K prevented disease symptoms in the foliage. In 2017 yields from RD/7-1K, RD/‘Maxifort’, and RD were 48,876, 70,285, and 58,323 lb/A respectively; in 2018 the yields were 37,717, 37,439, and 26,830 lb/A respectively. These results indicate that vigorous rootstocks such as ‘Maxifort’ play a bigger role in boosting yields in V. dahliae infested fields than resistant rootstocks such as 7-1K. In both years non-grafted 7-1K had the lowest AUDPC. V. dahliae can be isolated from symptomless 7-1K, indicating the resistance may prevent symptoms caused by the pathogen, but not growth. 7-1K has been developed into ‘NC-7GEM’, as an inbred parent line for future varieties. These results imply that a combination of vigorous rootstocks, and resistant scions or standalone varieties would be the optimal way to manage non-race 1 V. dahliae.