Evaluatoin of the resistance of some citrus rootstocks to the citrus nematode, Tylenchulus semipenetrans, in Fars province, Iran

The citrus nematode, Tylenchulus semipenetrans, is widely distributed in the citrus orchards of Fars province, Iran. The nematode causes slow decline and serious crop losses. Host resistance is the most effective method for controlling the disease. Seedlings of some rootstocks including Minneola (C. paradise × C. reticulata), Citrus ourantium, C. lmettioides, C. aurantifolia var. Ahvazi (a natural hybrid), C. maxima, Fortunella margarita, C. medica, C. medica var. Otroj, C. lemonia var. Lisbon, C. taivanica, C. volkameriana, C. lemonia var. Eureka, C. aurantifolia, C. grandis, C. lemonia var. Rough Lemon, C. macrophylla (Alemow), Poncirus trifoliata, Swingle Citromelo(C. paradise × P. trifoliata) were evaluated for their resistance to the citrus nematode. The seedlings were planted in the pots and citrus orchard. In case of pot experiments, the three months old rootstock seedlings were transplanted to the pots with 40 J2/g of soil. The roots of seedlings were scored for nematode infestation after six months. For orchard experiments, the five months old rootstock seedlings were transplanted to naturally infested soil in a citrus orchard with 25 J2/g of soil. The roots of these seedlings were evaluated for nematode infestation 4.5 and 15 months after transplanting. The susceptibility of rootstocks to citrus nematode was evaluated on the base of the number of penetrated females per gram of feeder roots. In both experiments P. trifoliata, Swingle citromelo and Citrus ourantium were resistant to citrus nematode, whereas the other rootstocks supported a high population of the nematode.