Abstract
Thirty-two species of nematodes belonging to 20 genera were detected in mulberry fields and 20 species of 11 genera were found to be parasitic to mulberry. Ogma coffeae, Paratylenchus elachistus, Xiphinema bakeri, Helicotylenchus erythrinae, Meloidogyne mali, Gracilacus yokooi, M. javanica, M. arenaria, H. dihystera and Cryphodera sp. were observed with a high frequency. Nematode fauna of mulberry fields is characterized by a large variety of species including most of the Meloidogyne and Xiphinema species which have been reported in Japan along with the frequent occurrence of G. yokooi and O. coffeae which are seldom observed on other crop plants. On the other hand the occurrence of Pratylenchus, which is often detected in other crops, was unfrequent. M. mali shows a wide geographical distribution in mulberry fields unlike M. hapla and M. incognita. Although the geographical distribution of the nematodes in the fields does not always corespond to the natural distribution dues to the widespread introduction of mulberry saplings infected with nematodes, the following 4 groups can be distinguished: 1. Nematodes observed all over Japan such as P. elachistus, O. coffeae and X. bakeri; 2. Nematodes adapted to low temperature areas including both M. hapla and M. mali; 3. Nematodes occurring in warm areas including Hoplolaimus sp. which is mainly detected in subtropical Okinawa, M. incognita, M. javanica and H. dihystera; and 4. Nematodes adapted to temperature ranges intermediate between those in the cold and warm areas including species such as M. arenaria, Cryphodera sp. and G. yokooi. Both Meloidogyne sp. and Nothocriconemella mutabilis which were only detected in Suginami, Tokyo and Nothocriconema yakushimense in Yakushima Is. do not belong to any of the above 4 groups, suggesting a narrow range of distribution.
