ISHS Acta Horticulturae 706: IV International Symposium on Brassicas and XIV Crucifer Genetics Workshop
CLUBROOT CONTROL USING BRASSICA BREAK CROPS |
| Authors: | L.H. Cheah, S. Gowers, A.T. Marsh |
| Keywords: | biofumigants, Brassica crops, clubroot, isothiocyanates, Plasmodiophora brassicae |
| Abstract:
Clubroot of brassicas, caused by Plasmodiophora brassicae, is the most serious disease of New Zealand’s vegetable Brassica crops, reducing marketable yields and sometimes totally destroying crops. The potential of Brassica break crops containing high levels of glucosinolates for use in an integrated clubroot management strategy has been investigated. Two trials were carried out to compare the efficacy of two species of Brassica break crops (B. rapa and B. napus), and to investigate the optimum time required for break crop residues to decompose and provide clubroot control. Seedlings of Brassica break crops were grown to about 70 days, ploughed and rotary-hoed to a depth of 12 cm. The plant material was left to decompose for about 1, 2 or 3 months before cauliflower or broccoli were planted as main crops. In the first trial B. rapa reduced the mean clubroot severity score on cauliflower root systems, and increased plant top weights compared to plants from untreated plots or from plots treated with cauliflower residues. Brassica napus did not reduce the clubroot score. Gas chromatography analysis showed that B. rapa had a higher total isothiocyanates (ITCs) than B. napus. B. rapa released larger quantities of 4-pentenyl ITC than B. napus. In the second trial it was found that both 2- or 3-month decomposition treatments reduced clubroot severity compared to the untreated or broccoli residue treatments. The 3-month decomposition treatment gave slightly better disease control than the 2-month treatment. The treatments had little effect on plant top weight. | |
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