Identification And Harmfulness Of Parasitic Nematode Species On Peanut

From 2005 to 2007, plant nematodes were identified and surveyed from some peanuts growing areas in China. Peanut root-knot nematodes (Meloidogyne) and the yield losses caused by root-knot nematodes were studied in China.The pathogenicity of Ditylenchus destructor to the peanut and the resistance of peanut varieties to D. destructor were studied. Main research results were as follows:Eight species of plant parasitic nematodes were identified from roots and rhizosphere soil of peanuts by the light microsope and the scan electron microsope in Fujian Province and Shandong Province of China. They were Meloidogyne hapla, Meloidogyne arenaria, Macroposthonia ornata, Helicotylenchus dihystera, Paratylenchus bukowiinensis, Tylenchorhynchus annulatus, Aphelenchus avenae , Aphlenchoides composticola. The results showed that Macroposthonia ornata caused the peanut yellow and reduced the hight and root of the peanut. Small necrotic lesions were often superficial,but serious necrosis lesions usually extended into the tissues.The pathogenicity of D. destructor to the peanut was confirmed by inoculation tests to peanuts in pot. The nematode infected the roots, pegs and pods of peanuts, and reduced the numbers and the weight of pods. Peanut pegs were seriously infected by the nematodes. Roots and pods were relatively weak. The differences of the symptoms and resistance to D. destructor were studied by inoculation tests on twenty peanut varieties. The results showed that all cultivars were susceptible and the northern peanut seeds were more susceptible than the southern ones.Investigation of peanut root-knot nematodes population in Shandong Province showed that Meloidogyne hapla combined with Meloidogyne arenaria infected peanuts.The dominate specie was M. hapla, the rate of in the population was more than 85 %.Galls on peanut roots, pods,and pegs caused by M. hapla,liked rice.Roots caused by M. hapla enlarged and formed roots mission. While Galls caused by M. arenaria did not have fibrous roots. The rate of pod was 50.4 % and the rate of fruit was 3.4 %.There were no punctations in the end of M. hapla by the scan electron microsope. In fact, the punctuations were contributed to convex-concave cuticle thickening.