Reaction of Cucurbita pepo e C. moschata tomlxed infection of papaya ringspot virus-W (PRSV -W) with watermelon mosaic virus-2 (WMV-2) or with zucchini yellow mosaic virus (ZYMV)

Avaliou-se os efeitos das infecções mistas do VMM-Me com O VMAA ou com o VMMe-2 nas cvs. Caserta e Piramoita. Foram conduzidos 4 experimentos sendo cada um com 10 tratamentos. Os tratamentos foram: 1. Inoculação simples com o VMM-Me; 2. Inoculação simples com o VMAA (ou VMMe-2); 3. Inoculação simultânea dos vírus; 4, 5 e 6. Inoculações com o VMM-Me seguidas pelo VMAA (ou VMMe- 2) com intervalos de 24, 48 e 72 h, respectivamente; 7, 8 e 9. Inoculação com o VMAA (ou VMMe-2) seguidas pelo VMM-Me com intervalos de 24, 48 e 72 h, respectivamente; 10. Testemunha, sem inoculação. Aos 15 dias após inoculação foram avaliados: sintomas, área foliar, pesos seco e fresco e concentração dos vírus através do ELISA-indireto. Os resultados mostraram que o genótipo do hospedeiro, o intervalo de tempo e a ordem das inoculações influenciaram a sintomatologia reduzindo a área foliar e alterando a concentração dos vírus VMMe-2 e do VMAA nas plantas quando inoculadas em infecções mistas com o VMM-Me. Nas infecções mistas avaliadas a interação tipo antagonismo foi a mais frequente. A infecção simples pelo VMAA foi a mais severa quando comparada com as infecções mistas. O VMM-Me apresentou concentrações de partículas superiores aos outros dois vírus, apresentando maior velocidade na replicação nestes hospedeirosMultiple resistance to PRSV-W, WMV-2 and ZYMV is a priority for squash and summer squash breeding. This present research look for an explanation of PRSV-W interations with WMV-2 and ZYMV, in Cucurbita sp. to support further squash breeding for virus resistence. The effects· of mixed infections by PRSV-W with ZYMV or with WMV-2, was elaluated on young plants of cv. Caserta (Cucurbita pepo) and cv. Piramoita (Cucurbita moschata). Four experiments were carried out in greenhouses and each experiment cosisted of 10 treatments and 12 repetitions. The treatments were: 1. Single inoculation with PRSV-W; 2. Single inoculation with WMV -2 (or ZYMV); 3. Simultaneous inoculation with PRSV -W and WMV-2 (or ZYMV); 4, 5 and 6. Mixed inoculations of PRSV-W before WMV-2 (or ZYMV) with 24, 48 and 72 h. of the intervals between inoculations (respectively); 7, 8 and 9. Mixed inoculations of WMV-2 (or ZYMV) before PRVS-W with 24, 48 and 72 h. of the intervals between inoculations (respectively); 10. Health controI. It was evalueted symptoms, foliar area, fresh and dry weight of leaves and viral concentration throught inderect-ELISA fifteen days after inoculation. The results showed that genotype, time interval and inoculations sequence influence symptoms, reduction foliar area and viral concentration of WMV -2 and ZYMV in mixed inoculated plants with PRSV-W. The antagonism was the most frequent effect observed in the double inoculations. The ZYMV was more severe than PRSV-W or WMV-2. PRSV-W showed higher viral concentration tahn the ZYMV or WMV-2, with faster replication. Symptoms severity were directily proporcional to reduction of foliar area in all treatments in both cultivars. Foliar area reduction was an excellent parameter to evaluate severity degree in the infected host. Cv. Piramoita tolerance to PRSV-W, was confirmed, although viral concentration was higher than in cv. Caserta, considered to be highly sensitive to PRSV-W. The antagonism effect on cv. Caserta concerning viral concentration and foliar area was observed when PRSV-W inoculations preceded ZYMV or WMV-2 inoculations. No antagonism was observed when WMV-2 or ZYMV inoculations preceded PRSV-W. Mixed infections of WMV-2 inoculations preceded by PRSV-W at 48 h. (T8) intervals inoculation on cv. Piramoita showed antagonism with PRSV-W viral concentration reduction. Both cultivars showed severe symptoms when double infected by PRSV -W with WMV-2 or with ZYM