The reaction of some of tobacco varieties to Fusarium wilt (Fusarium oxysporum f.sp. nicotianae), root knot nematode (Meloidogyne incognita) and their interaction

Fungal fusarium wilt and root knot nematodes are distributed in all tobacco-producing regions of the world and can result in yield losses in almost all tobacco-growing areas. Fungal soilborne pathogens can attack tobacco at any growth stage causing seedling death in both seedbeds and fields. Control of fungal soil-borne pathogens and root knot nematodes are accomplished through the use of pesticides، crop rotation and resistant cultivars. The use of resistant cultivars is preferable economic management because pesticides are expensive and may pollute the environment. According to these reasons this research was done with two aims; observation on the reaction of different flue-cured and air-dried tobacco varieties against fungal soil-borne pathogens and root knot-nematode، Meloidogyne incognita and identification of resistant cultivars to these pathogens. Therefore، this study evaluated reaction of 35 flue-cured and air-dried tobacco varieties to Fusarium oxysporum f. sp. nicotianae، and M. incognita in a factorial experiment with two factors including: tobacco type (flue-cured and air-dried tobacco varieties) and inoculum type (1-fungus alone، 2-Nematode alone and 3- fungus and Nematode) based on Completely Randomized Design with 6 replications in greenhouse at 25+3oC in Tirtash Research and Education Center in 2012. Each tobacco seedling was inoculated with 3000 eggs and second stage juveniles (J2) at transplanting into 1. 5 Kg pot and inoculated with the fungus 10-15 days later. After 70 days، number of egg masses، number of eggs per mass، reproductive factor، weight of leaves and roots were determined. The results showed a synergistic interaction between nematode and fungus on tobacco. Simultaneous inocoulation of nematode and fungus had greatly increased ratings of the symptoms and root necrosis severity. Results of variance analysis showed that there were significant differences among these cultivars and they had different reactions to fungal fusarium wilt and root knot nematode and that not all tobacco cultivars were resistant to pathogens. Based on ratings of the symptoms، varieties Bel 61-10، NC 100، Burley orumieh3 and HB4105P، showed resistance. Speight G-28، Ergo and Burley 21 were very susceptible.