Resistance to Cowpea aphid-borne mosaic virus in in vitro germinated genotypes of Passiflora setacea

ABSTRACT Passion fruit (Passiflora edulis) is a fruit species of great relevance for Brazilian economy. However, it is highly susceptible to the Cowpea aphid-borne mosaic virus (CABMV). The species P.setacea, on the other hand, is resistant to the disease. The present study aimed to identify CABMV-resistant P. setacea genotypes for the introgression of genes into sour passion fruit genetic breeding programs. The seeds of passion fruit genotypes were germinated in vitro in MS culture medium. The seedlings were acclimatized in a growth chamber at the temperature of 27 ± 2ºC, photoperiod of 16:8 hours and 80% of relative humidity. Thirty plants of each genotype were mechanically inoculated with extract prepared from leaves collected from passion fruit plants with symptoms of CABMV for the assessment of resistance to CABMV. The severity of leaf symptoms was evaluated by means of a grading scale of visual signs. After the visual evaluation and identification of the asymptomatic genotypes of P. setacea, the PTA-ELISA test was carried out for 30 selected genotypes. According to the visual evaluation, all P. setacea genotypes were highly resistant to CABMV, while the P. edulis genotypes were highly susceptible. Out of the 30 genotypes selected, only PsRJ 4 was considered susceptible by PTA-ELISA. The other genotypes of P. setacea were considered resistant and present great potential for use in passion fruit genetic breeding programs. RESUMO O maracujazeiro-azedo (Passiflora edulis) é uma espécie frutífera de grande importância econômica para o Brasil, porém altamente susceptível ao vírus Cowpea aphid-borne mosaic vírus (CABMV). A espécie P. setacea, em contrapartida, apresenta resistência à doença. O objetivo deste estudo foi identificar genótipos de P. setacea resistentes ao CABMV, visando à introgressão de genes em programas de melhoramento genético do maracujazeiro-azedo. As sementes dos genótipos de maracujazeiro foram germinadas in vitro em meio de cultura MS. A aclimatização das plântulas ocorreu em câmara de crescimento com temperatura de 27± 2 ºC, fotoperíodo de 16h8 e 80% de umidade relativa. Para avaliar a resistência ao CABMV, foram utilizadas 30 plantas de cada genótipo, inoculadas mecanicamente com extrato preparado a partir de folhas coletadas de plantas de maracujazeiro-azedo com sintomas de infecção pelo CABMV. A severidade dos sintomas foliares foi avaliada por meio de uma escala de notas visuais. Após a avaliação visual e a identificação dos genó