Seleção de estirpe fraca do Zucchini Yellow Mosaic Vírus (ZYMV) e controle dos mosaicos comum (Papaya ringspot vírus) e amarelo (ZYMV) por dupla premunização em abobrinha-de-moita. / Selection of mild strain of Zucchini Yellow Mosaic Virus (ZYMV) and control of Papaya ringspot virus and ZYMV by double cross protection in zucchini squash.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2002

RESUMO

Due to the present high incidence of Zucchini yellow mosaic virus (ZYMV) and the damage it causes to cucurbit crops, studies were carried out to select mild strains of the virus and evaluate their efficiency for the control of the disease by cross protection in zucchini squash (Cucurbita pepo L. cv. Caserta). Studies were also done to evaluate the efficiency of double cross protection for the control of ZYMV and Papaya ringspot virus – type W (PRSV-W) in zucchini squash under greenhouse and field conditions. Searching for mild strains was carried out as follows: a) from local lesions caused by ZYMV on indicator hosts maintained under green house conditions; b) from local lesions caused on indicator hosts maintained at 15 °C; and c) from local lesions caused on indicator hosts inoculated with suspension of purified ZYMV, exposed to ultra-violet light. Only one very mild strain of the virus, named ZYMV-M, was obtained in zucchini squash plant directly inoculated with suspension of purified ZYMV exposed to ultra-violet light for 30 minutes. This mild strain remained stable for a period of 15 months, after 12 successive transfers in zucchini squash plants. Experiments carried out under greenhouse showed that zucchini squash plants protected with ZYMV-M, at the cotyledonal stage, did not show severe symptoms of the disease after double challenge inoculation with severe strains of the virus, obtained from three regions of the State of São Paulo. Plants inoculated with the mild strain ZYMV-M and a mild strain of PRSV-W, named PRSV-W-1, were also protected against superinfection with severe strains of both viruses. Field test carried out with zucchini squash protected with ZYMV-M and doubly protected with ZYMV-M and PRSV-W-1, showed that this technology was effective for the control of the mosaic diseases caused by severe strains of these viruses. The yield of marketable fruits from plants protected with ZYMV-M, or doubly protected, were 1.85 kg and 1.70 kg of fruits/plant, respectively. These yields were, respectively, 101 % and 85 % higher than the yield of marketable fruits from plants inoculated with a mixture of severe strains of both viruses. Studies are necessary to evaluate the efficiency of double cross protection for the control of ZYMV and PRSV-W in other cucurbit species susceptible to these viruses.

ASSUNTO(S)

anatomia vegetal plant anatomy potyvirus zucchini squash abobrinha mosaic (plant disease) mosaico (doença de planta)

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