On-Farm Grafted Tomato Trial to Manage Bacterial Wilt

Grossing over $33.7 million in annual sales, North Carolina ranks 7th in the US for the production of tomatoes (Solanum lycopersicum). A replicated on-farm trial was conducted in Rowan County, NC. On May 30th, 2013, 8.1 ha of two bacterial wilt (BW; R. solanacearum (race 1)) resistant rootstocks were planted. The objective of this trial was to evaluate disease susceptibility and production in fields with BW history. In addition, plant spacing and training systems were compared. Two experimental sites, one fumigated and one non-fumigated, were arranged in a randomized complete block design with four replications, each consisting of 91.4 m-rows in a commercial plasticulture system. Each row contained 13 10-plant treatment plots (2x2x3 Factorial + Control): two rootstocks ('801', '802'; Rijk Zwaan), two training systems (single-leader, double-leaders), three between-plant spacings (45.7, 61.0, and 76.2 cm) with 'Mountain Fresh' as the scion and a non-grafted 'Mountain Fresh' control spaced at 45.7 cm. Wilt incidence was collected during the two harvests. Fruit were harvested twice at 69 and 84 days after transplanting. Wilt incidence was lower in the non-fumigated field and no differences in yield between the grafted and non-grafted plants were observed. In the fumigated field, the main effect of grafting tended to increase yield. Both the main effect of training system and spacing significantly affected yield in the grafted treatments. BW incidence was significantly higher in the non-grafted treatment (29.08%) than '801' and '802' rootstocks (0.909 and 0.183%, respectively) (P<.0001). Single-leader grafted plants had 2.54% more BW incidence than double-leader plants (P=0.0007). Grafted tomatoes offered an alternative method to fumigation as a means to reduce BW loss and sustain marketable yield.