A.E. KRETSCHMER Jr, R.M. SONODA and G.H. SNYDER

Abstract

Carpon desmodium (Desmodium heterocarpon cv. Florida) a long-lived, high seed producing, perennial tropical forage legume for grazing, was released for commercial use in south Florida in 1979. It is susceptible to root-knot nematodes (Meloidogyne spp.). A greenhouse and a field experiment were used to assess root-knot nematode resistance or tolerance of other carpon desmodium accessions to determine resistance of several commercial tropical legumes and to compare first season productivity of tropical legumes.
Two of eight carpon desmodiums, Desmodium adscendens, greenleaf desmodium (Desmodium intortum cv. Greenleaf), centro (Centrosema pubescens), siratro (Macroptilium atropurpurem cv. Siratro), stylo (Stylosanthes guianensis cv. Cook), Caribbean stylo (S. hamata cv. Verano), and joint vetch (Aeschynomene americana cv. American), were apparently resistant to Meloidogyne spp. No galls were noted on roots of these species from nematode infested soil. Moderate to severe galling was found on roots of Florida and four other carpon accessions and on a Centrosema pascuorum accession. Very slight galling was found on roots of one carpon desmodium accession and on calopo.
Yield and survival of affected plants were less than those of plants from inoculated or fumigated plots.
In the, absence, of root-knot, yields of the two resistant carpon desmodiums were considerably less than that of Florida carpon while in the presence of root-knot their yields were significantly higher.
Finding nematode resistance in carpon desmodium is encouraging for future selection and breeding programmes.