ASSESSMENT OF HORTICULTURAL CHARACTERISTICS OF AUB TOMATO LINES GROWN UNDER BEKAA CONDITIONS AND THEIR RESISTANCE TO TOBRFV

Abstract

Tomato (Solanum lycopersicum) is one of the most economical and important vegetable crops cultivated worldwide. In Lebanon and many other Mediterranean countries, Tomato brown rugose fruit virus (ToBRFV) has been a rising concern for tomato farmers. In South Lebanon, the incidence may reach 100% of tomato greenhouses in some regions. ToBRFV is a Tobamovirus belonging to the same family of Tobacco mosaic virus (TMV) and Tomato mosaic virus (ToMV) which are transmitted mechanically with no specific vector reported. The most effective and economic management strategy to decrease the virus incidence is to find resistant varieties. At present, only one intermediate-resistant variety (TT-708) is available commercially. This study aims to test the yield performance and tolerance to ToBRFV of AUB developed tomato lines carrying resistance to Tomato yellow leaf curl virus (TYLCV) as compared to an intermediate-resistant variety (TT-708) and a commercially high-yielding variety (Catrina). Yield performance was evaluated in the Bekaa under hot dry weather during the spring -summer period. Data were collected on major horticultural characteristics. AUB-bred lines 1, 9, and 47 performed similarly to the commercial variety in the total yield and average fruit weight; while the average fruit weight of lines 13 and 42 was significantly higher than the commercial variety. ToBRFV resistance of AUB-bred tomato lines was evaluated in a controlled environment greenhouse following ToBRFV mechanical inoculation of seedlings. Data were collected on disease severity indices on leaves and fruits, as well as, on the relative virus concentration using RT-qPCR protocol. All tested tomato lines/varieties showed ToBRFV leaf symptoms during the hot summer growing conditions; however, the intermediate-resistant commercial variety and AUB lines 1, 6, 9, 13, and 47 did not show fruit symptoms. AUB lines 9, 10, 13, and 47 had a significantly lower viral concentration than TT-708. A survey on the distribution of ToBRFV in South Lebanon showed that spread of the disease is expanding from one season to the other since no commercially resistant varieties are available and farmers are not aware of management strategies they can adopt to reduce the virus spread. The preliminary results observed on tolerance of some AUB tomato lines to ToBRFV fruit symptoms are very promising. Their testing under farmers’ field conditions is recommended. If the results are confirmed this may be considered a major achievement and may help farmers mitigate damage caused by infections with two major viruses TYLCV and ToBRFV.