Field screening of tomato genotypes for resistance to TYLCV disease in Senegal

Date de mise à jour : 22 novembre 2016

The tomato (Solanum lycopersicum L.) is one of the most widely consumed vegetables in the world, second only to potato. Average yields are around 20 t/ha in Senegal, whereas yields of 100 t/ha are obtained in several countries (Laterrot, 1994). Over two hundred diseases are Iisted worldwide (Gry, 1994). ln addition to fungal and! or bacterial diseases, there are pests and viral diseases. of which Tomato yellow leaf cu ri virus (TYLCV) disease is the most important and the most dangerous (Pico et al.. 1996; Moriones and Navas­Castillo, 2000). TYLCV causes tomato leaves to curl and turn yellow. The virus, which is transmitted by the whitefly, Bemisia tabaci Gennadius. belongs to the group of "Geminiviruses" (Cohen and Harpaz, 1964; Czosnek et al., 1989; Czosnek and Laterrot, 1997; Fauquet et al.. 2003).

Following transmission, the virus is usually localized in the tissues of the plant, thereby disrupting its growth. The plant becomes dwarfed and takes on a bushy appearance, leaflet size is reduced and the leaves curl (Cohen et al., 1974). The symptoms are ail the more severe the more the variety is susceptible and the more edapho-c1imatic conditions are difficult. Harvests are virtually nil wh en the virus is transmitted before flowering. If transmission occurs after flowering, the few flowers formed give very small fruits resulting inlosses of75% (Anon, 1998). Harvests are therefore virtually nil wh en an attack occurs in the nursery (Laterrot, 1994). Thus, the damage caused by TYLCV can reach 50-70% if the attack is late and 100% if it occurs in the nursery (Pico et al.. 1996; Vidavsky and Czosnek, 1998; Moriones and Navas­Castillo, 2000; Ciss, 2004).

ln Senegal, the disease appeared in 1980 in the Kaolack and Ziguinchor regions (Ciss, 2004). The appearance of the disease was probably due to the proximity of cotton crops which harbour the insect vector, B. tabaci. Today, it has spread to the entire national terri tory and is a serious threat to tomato production in the country, or even in the region (Huat, 2006).

Date de mise à jour : 22 novembre 2016

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