Reação de híbridos interespecíficos de Passiflora spp. à Xanthomonas axonopodis pv. passiflorae

Abstract

Avaliou-se o grau de resistência de 36 clones de maracujazeiro obtidos por seleção massal de sete progênies de híbridos interespecíficos a três isolados de Xanthomonas axonopodis pv. passiflorae. As progênies foram obtidas por meio de cruzamentos entre a cultivar comercial Passiflora edulis "flavicarpa" com as espécies silvestres P. caerulea, P. edulis "roxo" e P. setacea. Os isolados da bactéria foram obtidos em Rio Claro-SP, Planaltina-DF e Limeira-SP. Clones individuais foram inoculados com solução bacteriana na concentração de 108ufc ml-1 aos 120 dias da semeadura. As avaliações ocorreram aos 5, 10 e 15 dias após a inoculação, medindo-se o diâmetro longitudinal e transversal das lesões. Em seguida, calculou-se a área abaixo da curva de progresso da lesão (AACPL). O delineamento experimental foi em blocos ao acaso com parcelas subdivididas, sendo os genótipos os tratamentos distribuídos em quatro blocos com parcelas de três plantas para cada genótipo. Em cada parcela, plantas individuais foram inoculadas com um dos isolados da bactéria, totalizando três plantas com isolados diferentes. Plantas das espécies genitoras P. caerulea (AACPL=0,17) e P. setacea (AACPL=14,50) apresentaram alto grau de resistência, quando comparadas às plantas da testemunha BRS Gigante Amarelo (AACPL=4089,25), enquanto genótipos híbridos apresentaram valores intermediários (AACPL de 15,67 a 768,42), indicando a importância desses materiais como fontes de resistência à bacteriose.

Yellow passion fruit reaction to Xanthomonas axonopodis pv. passiflorae and to Cowpea aphid-borne mosaic virus

“…Moreover, analysis of genetic diversity among Xap and CABMV isolates reported existence of variability for aggressiveness within and among Xap populations (Nakatani et al 2009), as well as genetic variability among CABMV isolates (Melo et al 2015). This information supports the possibility of existing pathogen-host interactions, which could lead to different responses from genotypes to pathogen isolates (Lopes et al 2006, Fuhrmann et al 2014. Therefore, it is essential to consider plant and pathogen genetic variability as well as pathogen aggressiveness when establishing strategies for a breeding program.…”

“…Studies have pointed towards a difficulty in distinguishing genotypes for disease resistance. Meanwhile, it is important to recognize that in breeding programs with focus on disease resistance, any minimal difference between and within progenies or genotypes is useful in providing information for resistance selection (Kudo et al 2012, Fuhrmann et al 2014.…”

“…EC-L-7 (41%) and MAR20#12 (33%) were the progenies with the greatest numbers of resistant plants at the end of the study, contrasting with BRS GA1 (11%) and MAR20#24 (9%) ( Table 2). According to Junqueira et al (2003), disease resistance variability in yellow passion fruit is low, but it may occur within plants of the same cultivar (Fuhrmann et al 2014).…”

Reaction of yellow passion fruit to passion fruit woodiness disease and to bacterial spot

“…For this reason, not only statistical but also genetic analyses are very useful tools in breeding programs with focus on disease resistance. In this context, any minimal differences between and within genotypes are useful in providing information for resistance selection and should not be underestimated or discarded (JUNQUEIRA et al, 2003;KUDO et al 2012, FUHRMANN et al 2014).…”

Sample size for estimate the average of Passiflora caerulea fruits traits

“…The wild passion plant has also been used as rootstocks of commercial passion fruit plants. In this sense, FUHRMANN et al (2014) emphasized that P. caerulea demonstrated high degree of resistance to bacterial spot disease caused by Xanthomonas axonopodis pv. passiflorae, allowing it to be used as a disease resistance source.…”