Late blight resistant West Virginia ’63 tomato is a favorite to organic and small growers in West Virginia. However, its susceptibility to Septoria leaf spot caused by the fungal pathogen Septoria lycopersici concerns growers.
Cornell University released a F₁ hybrid, Iron Lady, with resistance to Septoria leaf spot and late blight resistance partly obtained from the WV ’63. We crossed the WV ’63 with the Iron Lady and selected field-grown plants resistant to Septoria leaf spot. We tested for this tolerance by inoculating six-week old, nutrient-stressed plants in the greenhouse. The WV ’63 plants were killed; whereas, the hybrid selections survived.
Progenies from these plants were then grown in field plots under naturally occurring disease pressure and selected for genetic homogeneity. Two selected lines had greener foliage at the end of the growing season compared to the original WV ’63. These two selections, tentatively named WV ’17A and ‘17B, are being released in honor of the 150th anniversary of WVU Davis College of Agriculture, Natural Resources and Design.
Both selections carry single-gene and multiple-gene resistance to late blight and the dominant Ve-gene and I-gene for Verticillium and Fusarium wilt resistance. The vine type of both selections is indeterminate, and the fruit carried the uniform ripening gene and high color. Fruit set is higher in the WV ‘17A and is more firm than that of WV ’63. Fruit of WV ‘17B is similar to a beefsteak type and is sweeter with significantly higher brix content compared with the WV ’63.
During the 2016 WVU Organic Farm Field Day, we conducted a taste test of these tomatoes where 90 percent of the testers preferred the WV ’17B over the WV ’63. More than 300 seed packets containing 10 seeds from each of the two lines and WV’63 were distributed to interested growers. We’re asking growers to provide feedback on the total yield, disease resistance against late blight and Septoria leaf spot, as well as taste and fruit firmness. Data will be utilized to select one of these two lines to release as named tomato variety.
Although we expect these new lines will tolerate Septoria leaf spot better than the WV’63, growers are advised to take precautions that are normally followed for managing the disease. Some common cultural adjustments that can prevent, or reduce, Septoria leaf spot severity include rotating the growing area with non-solanaceous crops, using certified or treated seeds, removing infected plant debris at season’s end, removing lower leaves touching the soil line, using plastic or other mulch, using drip irrigation instead of a sprinkler and adopting methods such as wide spacing or row orientation for air movement and sunlight penetration that facilitate quick foliage drying.
Growers may also use bio-rational products, such as fixed copper (Kocide, Champ, Copper sulfate etc.), Regalia, Serenade or Actinovate, if a rainy and cloudy weather persists for a long time during the growing season. Considering the level of tolerance these lines possess against Septoria leaf spot, growers may not need to use any harsh chemicals to control the disease.