Seleção de plantas resistentes e de fungicidas para o controle da podridão do pé do maracujazeiro causada por Phytophthora nicotianae

The stem rot of passion fruit is one of the main problems of the crop in most of the producing areas in Brazil, being responsible for the decrease in yield and constant migrations of the crop. The death of the plants is preceded by wilt as a consequence of stem girdling from collar rot and root rot. The control of the disease is basically preventive, aiming not to introduce the pathogen in the area. The objectives of this research were to evaluate methods for inoculation of Phytophthora nicotianae in plant roots and stem, assess the susceptibility of Passiflora edulis f. flavicarpa at different ages; to evaluate the behavior of different species of the genus Passsiflora and different genotypes of P. edulis f. flavicarpa to the pathogen; to carry out tests for chemical control in vitro, and to evaluate eradicative chemical treatment and curative chemical treatment in P. edulis f. flavicarpa for P. nicotianae. Inoculations in the collar zone of P. edulis f. flavicarpa plants provided higher levels of disease compared to the inoculations in the radicular system. Mortality was higher when the inoculation was carried out in younger plants. Amongst the 17 species of genera Passiflora tested for resistance to the pathogen, P. suberosa, P. morifolia, and P. foetida were the least affected. P. sidaefolia, P. edulis f. flavicarpa, and P. edulis were the most susceptible, having symptoms that culminated with the death of the plants. The most resistant genotypes of P. edulis f. flavicarpa to P. parasitica were those from Morretes (PR), Jaboticabal (SP), and L13P2 (IAC). The Sul-Brasil, Maguari and Livramento (BA) varieties were highly susceptible to the pathogen, having symptoms that culminated with the death of plants. The fungicides kif, dimethomorph, metalaxyl+mancozeb, mancozeb, cymoxanil+maneb, and copper oxychloride controlled eradicatively P. nicotianae, inhibiting the incidence of the disease in six-weeks-old plants. The tested fungicides in curative treatment inhibited the development of the disease with better effect when applied two days after the inoculation, compared to seven days. Kif, dimethomorph, metalaxyl+mancozeb, and cymoxanil+maneb showed similar efficiency and were superior to fosetyl-Al in the control of P. nicotianae.