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Background Passion fruit ( Passiflora edulis [Sims]) is an important economic fruit crop in Kenya, grown for domestic, regional and international markets. However, passion fruit production is constrained by both biotic and abiotic stresses. Passion fruit woodiness disease (PWD) complex is the most injurious viral disease responsible for yield losses of up to 100%. In East Africa , it is caused by potyviruses. The most effective way to manage PWD is by using resistant cultivars. The objectives of this study were to determine the occurrence of passion fruit woodiness disease in selected counties at the Coastal lowlands of Kenya and screen farmer preferred passion fruit genotypes for resistance to PWD. Results In the present study, it was established that all surveyed farms in Kwale and Kilifi counties displayed passion fruit woodiness virus disease symptoms. The highest disease incidence of 59.16% and 51.43% was observed at Kilifi and Kwale counties, respectively. A significant difference ( p  < 0.05) in symptom severity was observed within the tested genotypes with purple and banana passion fruits having the highest and lowest AUDPC values, respectively, both under greenhouse and field conditions. ACP ELISA assays using universal potyvirus antiserum (Agdia Inc., Elkhat, IN) confirmed that the observed characteristic symptoms of woodiness disease were as a result of potyvirus infection. Conclusions The findings herein indicate that PWD is widespread in both Kilifi and Kwale counties with low to moderate disease incidence and severity. The observed prevalence, incidence and severity levels of PWD in Kwale and Kilifi counties could be aggravated by poor management practices such as non-sterilization of pruning tools, intercropping with target crops and crop rotation with the same target crops. Response of passion fruit genotypes to woodiness viruses was genotype dependent. There is need to sensitize farmers on the cause and spread of PWD and management strategies in order to increase production and enhance the quality of fruits.

In Brazil, the passion fruit woodiness disease is caused by the cowpea aphid-borne mosaic virus (CABMV). It is considered one of the most economically important diseases in the passion fruit (Passiflora edulis Sims). This study aims to implement the recurrent selection to develop passion fruit cultivars resistant to CABMV and with good agronomic performance. The experiment was led in Campos dos Goytacazes, Rio de Janeiro–Brazil, in a randomized block design with 90 full-sib families, three replications, and three plants per plot. The area below the mean disease progress curve (AUDPCM) was estimated, and the total production per plant (TPP) was evaluated. The estimate analysis of variance components and prediction of genetic gains were performed using the REML/BLUP procedure (Restricted Maximum Likelihood/Best Linear Unbiased Prediction). At the end of the evaluations, all plants presented symptoms of the disease, with different levels of severity. For families RS32 and RS33, the largest number of individuals selected for TPP was obtained. A AUDPCM values ranged from 468.75 to 1717.50 for individuals 438 and 604, respectively. In the selection for AUDPCM, families RS91 and RS84 stood out, with the highest number of resistant individuals selected. Genotypes 497, 582, 438, 495, 581, 92, 791, 506, 552, 183, 443, 669, 219, 724, 189, 378, 477, 244, 239, 126, and 174, are promising and can be used as parents to obtain progenies, to compose the next cycle of recurrent selection.

The passion fruit woodiness disease, caused by the cowpea aphid-borne mosaic virus (CABMV), is the most important disease and represents a limiting factor for culture. Cultivars with resistance levels are being developed from backcrosses associated with a recurrent selection program. Studies showing how segregating populations respond to infection over time and describing resistance are necessary and make it possible to characterize the genotypes and select the most promising ones. Therefore, the present study aimed to describe the pathogenesis; evaluate resistance in the Passiflora sp. × CABMV pathosystem; and select the most resistant individuals for generation advance in the recurrent selection program in passion fruit. Five generations of crossbreeding were used, namely, interspecific hybrid, backcrosses BC1.1 and BC1.2 and parents P. edulis and P. setacea. The plants were inoculated in a greenhouse and evaluated for resistance to CABMV. The area under the disease progress curve (AUDPC) was calculated and variance components and genetic values were estimated for the populations under study. High genetic variability was observed between the individuals, ranging from asymptomatic plants to plants exhibiting the most severe symptoms of the disease. Four phenotypic groups were formed, allowing greater differentiation between the generations and their parents. The presence of CABMV was confirmed in plants of the BC1.1 generation and of P. edulis, with characteristic symptoms of the virus. In asymptomatic plants, 75% of the individuals were considered resistant by PTA-ELISA and RT-PCR. The majority of individuals selected for resistance to CABMV belonged to the BC1.2 generation, which might thus be included in the recurrent selection program.

Developing yellow passion fruit cultivars capable of combining precocity, productivity and resistance to Cowpea aphid-borne mosaic virus (CABMV) is essential to passiculture. The aim of the current study is to evaluate vegetative and reproductive precocity, as well as resistance to CABMV, in a population of third generation backcross (BC3) involving an interspecific hybrid (P. edulis x P. cincinnata) followed by three backcrosses with com P. edulis. Eight hundred and thirty-three (833) progenies, 22 BC3 families and 10 yellow passion fruit (controls) accessions were evaluated. Phenological stages were assessed based on the number of days after planting (DAP) when progenies presented primary, secondary and tertiary branches, flowers and fruits in these branches. CABMV severity was analyzed under field conditions based on a rating scale that ranged from 1 (resistant) to 4 (highly susceptible); values were converted into McKinney's disease index (DI%). Overall, BC3 families were superior to control treatments (P. edulis accession), since they presented greater precocity, productivity and resistance to CABMV. Based on CABMV’s classification, 34 progenies were considered resistant (DI from 0.0 to 14.81%) and 299 were moderately resistant (DI from 16.67 to 30.0%). Findings in the current study have shown that BC3.A, BC3.B and BC3.G families have potential to be used in breeding programs, since they showed more precocious vegetative and reproductive vigor, accumulated production higher than 70 fruits per plant and resistance to CABMV.

Passion fruit woodiness disease, which is caused by the potyvirus Cowpea aphid borne mosaic virus (CABMV), is the primary constraint for passion fruit production in Brazil. Transgenic Passiflora alata lines that contain a CABMV-derived coat protein gene fragment in a hairpin configuration were obtained via Agrobacterium tumefaciens -mediated transformation. The plants were propagated and the reaction to CABMV infection was evaluated after three mechanical and one viruliferous vector inoculations. After three mechanical inoculations, two lines from a total of 21 transgenic lines tested maintained all four propagated clones symptomless. After the fourth inoculation, all transgenic lines presented at least one propagated clone infected with CABMV. However, 20 propagated clones from different transgenic lines remained asymptomatic. These asymptomatic plants were analyzed by RT-PCR and CABMV was detected in 17 plants. The estimated viral titers in these plants, which were determined by RT-qPCR, were consistently low compared with those of the positive control (non-transgenic inoculated plants). A biological virus recovery test was performed using leaf extracts from the three RT-PCR negative propagated clones and the absence of the CABMV was confirmed. The results of the present study indicate that the incorporation of CABMV-gene fragments into the Passiflora genome may influence the resistance of these plants to the pathogen.

Yellow passion fruit (Passiflora edulis Sims) yield and longevity have been drastically reduced by bacterial spot (Xanthomonas axonopodis pv. passiflorae- Xap) and passion fruit woodiness disease (PWD) (Cowpea aphid-borne mosaic virus – CABMV). This study was aimed at evaluating the reaction of 11 genotypes of yellow passion fruit, based on the reaction of their progenies, to both mechanically inoculated Xap and CABMV, under greenhouse conditions. There was a progressive increase in bacterial spot and PWD severity with time. BRS Gigante Amarelo, MAR20#12, and MAR20#34 were selected as the progenies with lowest bacterial spot severity and disease progress over time. MAR20#2005, EC-L-7, UnB2015-1, and EC-3-0 presented the lowest PWD severity and disease progress over time. These progenies, along with individual plants from other progenies in which disease severity was significantly low until the last evaluation, will be cloned and tested again for Xap and CABMV, including other isolates. Get the article here. (PDF)

Based on filamentous particles, aphid transmission, and symptoms of distorted, size-reduced, woody fruits, the major potyvirus associated with passionfruit woodiness disease (PWD) in Taiwan has been regarded as Passionfruit woodiness virus (PWV) for decades. In this study, the genomes of four potyvirus isolates, originally collected from orchards with PWD in Taiwan and re-designated as Poty-TW, Poty-0920-6, Poty-dpd and Poty-pt, were sequenced for molecular characterization. Our results revealed that the CP genes of Poty-TW and Poty-0920-6 share nucleotide (nt) identities/amino acid (aa) identities of 97.7/95.9 and 98.5/97.2%, respectively, with that of East Asian passiflora virus (EAPV) isolate AO of Japan, and the CP genes of Poty-dpd and Poty-pt share nt/aa identities of 95.3/96.2 and 94.9/97.6% respectively, with that of EAPV isolate IB of Japan. The genomic sequences of PWD-associate viruses in Taiwan also share high degrees of homology with that of EAPV-AO (TW and 0920-6 isolates > 98%) and EAPV-IB (dpd and pt isolates > 88%). However, the CP genes of four PWD-associated viruses from Taiwan share only 67.6–69.4% nt identities with that of PWV Australia MU isolate, does not satisfy the ICTV criteria (> 76%) to be regarded as a strain of PWV. A field survey with 175 samples from different areas of Taiwan demonstrated that the PWD-associated potyvirus is mainly caused by EAPV. Hence, our results indicate that the major potyvirus causing PWD in Taiwan should be reclassified as EAPV.

Passion fruit woodiness disease induced by Cowpea aphid-borne mosaic virus (CABMV) is currently the most harmful viral disease affecting passion fruit crops. Given the economic importance of this fruit crop in Brazil, it is essential that passion fruit breeding programs invest in developing resistant and productive cultivars. The goals of this study were to estimate genetic parameters of agronomic and resistance traits via restricted maximum likelihood (REML) and select individuals found to be resistant to CABMV and agronomically superior, in order to provide the basis for further studies on passion fruit breeding, with the aim to develop cultivars resistant to CABMV. The study was conducted in randomized block design, with four replicates. Three full-sib families from the recombination of RC1 parents were evaluated. Based on the severity data, the area below the mean disease progress curve (AUDPCM) was estimated. Five traits relating to fruit yield and quality were also assessed. The components of variance and genetic values were estimated by the REML/best linear unbiased prediction (BLUP) mixed model methodology. A difference in the severity of CABMV symptoms was recorded among the 119 genotypes evaluated. AUDPCM values varied from 750 to 1252.5 for individuals 202 and 161, respectively. Family 1 distinguished itself with the largest number of individuals selected for resistance; for agronomic traits, families 1 and 2 contributed most of the selected genotypes. Genotypes 167, 24, 34, 23 and 202 achieved the lowest AUDPCM values, being selected for most of the agronomic traits; these results indicate the potential of these genotypes to be chosen and recombined for the advancement of generations in breeding programs aimed at developing resistance to CABMV. The strategy of recombining resistant genotypes from RC1 populations appears to be promising for breeding for resistance to CABMV, of which the heritability is complex.

Passion fruit woodiness disease is responsible for severe losses in passion fruit production around the world. The disease is caused by Cowpea aphid-borne mosaic virus (CABMV), an aphid-transmitted potyvirus . Traditional sanitary measures against the disease, such as vector elimination and cross protection, have not been successful, resulting in elimination and replanting of passion fruit plants each season. To find new alternatives for disease control, we tested the use of a peptidogalactomannan (pGM) extracted from the fungus Cladosporium herbarum to activate passion fruit defense mechanisms, enabling plants to tolerate passion fruit woodiness disease (PWD) . Passion fruit seedlings were spray-treated with pGM in a greenhouse three days before mechanical inoculation with CABMV. Experiments were set up in a completely randomized design, and disease incidence and severity were compared between water- and 100 μg ml −1 pGM-treated plants. Woodiness symptoms and certain developmental parameters of water- and pGM-treated plants were evaluated over five weeks. pGM treatment did not affect plant normal development. Plants that were both treated with pGM and inoculated with the virus showed very mild or no foliar CABMV disease symptoms and had the same growth and developmental patterns as the healthy uninoculated control plants. pGM led to the accumulation of antioxidant enzymes such as peroxidase and superoxide dismutase in the leaf tissues as well as their respective mRNAs. In addition, a ten- and twofold transcription induction of the mRNAs of the defense-related genes such as chitinase I ( PR-3 ) and phenylalanine ammonia-lyase ( PAL ), respectively, were observed in pGM-treated seedlings. These results suggested that pGM enables plants to respond more intensely to CABMV infection, mitigating woodiness symptoms and maintaining normal plant growth.

East Asian Passiflora virus (EAPV) causes passionfruit woodiness disease, a major threat limiting passionfruit production in eastern Asia, including Taiwan and Vietnam. In this study, an infectious cDNA clone of a Taiwanese severe isolate EAPV-TW was tagged with a green fluorescent protein (GFP) reporter to monitor the virus in plants. Nicotiana benthamiana and yellow passionfruit plants inoculated with the construct showed typical symptoms of EAPV-TW. Based on our previous studies on pathogenicity determinants of potyviral HC-Pros, a deletion of six amino acids (d6) alone and its association with a point mutation (F8I, simplified as I8) were conducted in the N-terminal region of the HC-Pro gene of EAPV-TW to generate mutants of EAPV-d6 and EAPV-d6I8, respectively. The mutant EAPV-d6I8 caused infection without conspicuous symptoms in N. benthamiana and yellow passionfruit plants, while EAPV-d6 still induced slight leaf mottling. EAPV-d6I8 was stable after six passages under greenhouse conditions and displayed a zigzag pattern of virus accumulation, typical of a beneficial protective virus. The cross-protection effectiveness of EAPV-d6I8 was evaluated in both N. benthamiana and yellow passionfruit plants under greenhouse conditions. EAPV-d6I8 conferred complete cross-protection (100%) against the wild-type EAPV-TW-GFP in both N. benthamiana and yellow passionfruit plants, as verified by no severe symptoms, no fluorescent signals, and PCR-negative status for GFP. Furthermore, EAPV-d6I8 also provided complete protection against Vietnam’s severe strain EAPV-GL1 in yellow passionfruit plants. Our results indicate that the attenuated mutant EAPV-d6I8 has great potential to control EAPV in Taiwan and Vietnam via cross-protection.