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

Rod W. Mcleod, Chris C. Steel

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Abstract

Green manures (chopped leaves) of 15 brassica potentially useful as inter-row crops in vineyards were incorporated into soils inoculated with second stage juveniles (J2) of root-knot nematode Meloidogyne javanica to compare their antinematode activity. With application rates of 10 and 20 g/kg soil, all green manures substantially lowered nematode numbers and there were significant treatment effects at both application rates. However, treatment effect 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 rewetted freeze-dried brassica tissue in sealed dishes in the absence of soil, there was evidence of a relation between effect and glucosinolate dose, estimated to be equivalent to a range of 1 to 40 nM/g soil. Egg production on 25 brassica crops was investigated to assess the scope for selection of crops that support less nematode reproduction. M. javanica produced more eggs on tomato (cv. Grosse Lisse) than on most of the brassicas, although egg production 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 radishes, cultivars bred in Europe to resist beet cyst nematode (Heterodera schachtii). Egg production was not related to innate total root glucosinolate concentrations of cultivars as measured 3 months after sowing. Nor was there a connection between higher concentration of the dominant glucosinolates (progoitrin [2-hydroxy-3-butenyl], glucobrassicanapin [4-pentenyl] and gluconasturtiin [2-phenylethyl]) and low egg production. Very low egg production on Adagio oilseed radish was associated with the presence of dehydroerucin (4-methylthio-3-butenyl). It is concluded that mechanisms other than glucosinolate-derived toxicity are important in the antinematode activity of brassica-leaf green manures and cultivars. The results indicate that there is little scope for selecting very low egg producing crops from amongst the brassica crops currently available for use as inter-row crops in vineyards. The role of glucosinolate derivatives in relation to resistance to Meloidogyne is discussed.

Original languageEnglish
Pages (from-to)613-624
Number of pages12
JournalNematology
Volume1
Issue number6
DOIs
Publication statusPublished - Oct 1999

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