Effects of brassica-leaf green manures and crops on activity and reproduction of Meloidogyne javanica

Green manures (chopped leaves) of 15 brassica potentially useful as inter-r ow crops in vineyards were incorporated into soils inoculated with second s tage juveniles (J2) of root-knot nematode Meloidogyne javanica to compare t heir antinematode activity. With application rates of 10 and 20 g/kg soil, all green manures substantially lowered nematode numbers and there were sig nificant treatment effects at both application rates. However, treatment ef fect was not closely related to estimated addition of glucosinolate, which ranged from 8 to 46 nM/g soil. When J2 were exposed to volatiles from rewet ted freeze-dried brassica tissue in sealed dishes in the absence of soil, t here was evidence of a relation between effect and glucosinolate dose, esti mated to be equivalent to a range of 1 to 40 nM/g soil. Egg production on 2 5 brassica crops was investigated to assess the scope for selection of crop s that support less nematode reproduction. M javanica produced more eggs on tomato (cv. Grosse Lisse) than on most of the brassicas, although egg prod uction on Polybra fodder turnip was not significantly lower than on tomato. However, egg production was substantial on all but four of the brassicas. Egg production was low on Adagio, SCO 7024, Nemex and Pegletta oilseed radi shes, cultivars bred in Europe to resist beet cyst nematode (Heterodera sch achtii). Egg production was not related to innate total root glucosinolate concentrations of cultivars as measured 3 months after sowing. Nor was ther e a connection between higher concentration of the dominant glucosinolates (progoitrin [2-hydroxy-3-butenyl], glucobrassicanapin [4-pentenyl] and gluc onasturtiin [2-phenylethyl]) and low egg production. Very low egg productio n on Adagio oilseed radish was associated with the presence of dehydroeruci n (4-methylthio-3-butenyl). It is concluded that mechanisms other than gluc osinolate-derived toxicity are important in the antinematode activity of br assica-leaf green manures and cultivars. The results indicate that there is little scope for selecting very low egg producing crops from amongst the b rassica crops currently available for use as inter-row crops in vineyards. The role of glucosinolate derivatives in relation to resistance to Meloidog yne is discussed..