Interaction of Root-Knot Nematode Meloidogyne incognita and Vascular Wilt Fungus Verticillium dahliae on Cotton

The interaction of root-knot nematode (Meloidogyne incognita) and the vascular wilt fungus (Verticillium dahliae) on two cotton cultivars Aleppo 90 and Dir-Al-Zor 22 was studied in a pot experiment under plastic house conditions. Four treatments were examined to study the pathogenicity of the nematode and the fungus separately or together, and to determine their effects on the growth of cotton plants. Results showed that plant lengths were increased significantly (P = 0.05) by the treatment with nematode plus fungus in comparison with fungus alone inoculation on Dir-Al-Zor 22 cultivar, as well as in comparison with fungus and nematode inoculations separately on Aleppo 90 cultivar without significant differences compared with the control on both cultivars. All treatments have greatly suppressed plant weight and root weight of both Aleppo and Dir-Al-Zor cultivars, but without significant differences. The percentage of plants showing vascular discoloration was increased from 20 % in the inoculation with fungus alone to 70 % in the inoculation with fungus plus nematode on Dir-Al-Zor 22 cultivar, while no fungal infection was observed on Aleppo 90 plants. The (fungus/ nematode) combination reduced the number of root galls caused by root-knot nematode (reduction of 52.63%) on Dir-Al-Zor 22, while the root knot index was increased from 1.68 in the nematode alone treatment to 3.36 in the (fungus/ nematode) treatment on Aleppo 90 cultivar. We suggest to take root-knot nematode control into consideration in the integrated management of cotton vascular wilt.