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Some Factors Affecting Penetration of Bean Roots by Larvae of Meloidogyne incognita and M. javanica. B. W. Ngundo, Nematologist, Plant Pathology and Nematology Division, East African Agriculture and Forestry Research Organization, P.O. Box 30148, Nairobi, Kenya; D. P. Taylor, Nematologist, Plant Pathology and Nematology Division, East African Agriculture and Forestry Research Organization, P.O. Box 30148, Nairobi, Kenya, Present address of second author: Laboratoire de Nematologie, O.R.S.T.O.M., B.P. 1386, Dakar, Senegal. Phytopathology 65:175-178. Accepted for publication 23 August 1974. DOI: 10.1094/Phyto-65-175.

Twenty-four-hour-old larvae of Meloidogyne incognita and M. javanica, at inoculum levels of 100 larvae per seedling, failed to penetrate roots of any of six bean (Phaseolus vulgaris) cultivars after exposure periods of 12, 24, or 48 hours. Under glasshouse conditions (21-24 C), freshly hatched larvae of both species, at an inoculum level of 300, penetrated roots in 48 hours. In later experiments in which the inoculum was applied to the root tips, there was penetration of the roots at inoculum levels of 100, 150, 200, and 250. There were no significant differences in penetration percentage between the cultivars and the species when the experiment was conducted under conditions of low and fluctuating temperature. In a growth chamber at higher temperature (29 and 23 C for day and night, respectively), and using larvae of variable age, significantly more M. incognita penetrated roots of all six cultivars than did M. javanica. In a similar experiment in which all larvae were of the same age, significantly more M. incognita penetrated roots of bean cultivars Kikara, Canadian Wonder, Masterpiece, Marathon, and Premier than did M. javanica, but there were no significant differences in penetration of Mexico 142 between the two species.