BP Singh

226 Ra'anplanting should be recommended. A number of such alternativesare available. For example stem cuttings of potato, cassava andsweet potato do not carry nematodes whereas tubers or roots oftencontain Meloidogyne and other nematodes. Seeds of pyrethrum arefree of M. hapla. Stolons taken from the base of vines of blackpepper (Piper nigrum L.) could carry R. simi/is and MeloidogJ-Jne sp.but the movement of stem cuttings will ensure that gennplasmexchanged is free from nematodes. In yam (Dioscorea spp.) the useof tuber pieces rather than mature whole tubers for exchange willenable the examination for symptoms of dry rot caused byScutellonema bradys or P. coffeae and other nematodes.The leaf bearing tips of mature corms of taro (c. esclilenta)are generally free from H. miticallsa and should be used inpreference to cormels or suckers which can be infected. In additiontransport of nematodes on planting material can be prevented byacquring seeds rather than seedlings, e.g., with perennial cropssuch as coffee which can be infested with the root parasitesMeloidogyne, PratylencJllls and other genera. Use of tissue culturefor exchange of germplasm can prohibit entry of several pests andpathogens. Techniques have been standardised in case of severalcrops, e.g., garlic, banana, etc.ConclusionsGermplasm procured for import or export to some countryneeds examination and presence of nematodes which is very likelyin underground parts and vegetatively propagative materialsrequire some treatment to make it healthy for exchange.Treatment schedules are carefully planned recommendationsfor salvaging plant or plant parts with 100 1 )10 efficiency ofelimination of nematodes without any or very less damage to thehost plant. For such recommendations thorough investigations aremade with regard to temperature and time interval- tolerance incase of heat treatment and concentrations time as well astemperature in case of nematicidal dip treatments. Specialprecautions are needed as most of the times the treatment whichis lethal to the nematodes is also lethal to the host. To meet suchconditions either dormant stages of the host or uninfestedpropagative parts of the plant or heat hardening of such parts bypre treatment is suggested. Treatments vary from host to host andspecies to species of nematode infesting it. Development and