How to manage CBMV virus in passion fruit

The genus Passiflora has approximately 500 described species, of which around 120 are endemic to Brazil. Of the Brazilian Passiflora species, commercially exploited, the sour passion fruit and the sweet passion fruit are the most important. However, due to its use, both for fresh consumption and for the concentrated juice industry, sour passion fruit is the most produced with a cultivated area of ​​62 thousand hectares and an average annual production of 920 thousand tons. This fact gives Brazil the position of largest producer in the world, with the Northeast, Southeast and North regions being the most important and responsible for 94% of national production. Most of the passion fruit produced in Brazil meets the industry's demand for the production of concentrated juice, which supplies both the domestic consumer market and that aimed at export.

As a result of intensive production, which began in the state of São Paulo in the 1960s, sour passion fruit crops began to be affected by various diseases induced by fungi, bacteria, phytoplasmas, nematodes and, mainly, viruses. To date, in Brazil, the following definitive virus species, accepted by the International Committee on Taxonomy of Viruses (ICTV), have been reported infecting passion fruit plants: Cucumber mosaic virus (CMV, Cucumovirus), Passionfruit vein clearing virus (PVCV, Potyvirus), Passion fruit yellow mosaic virus (PFYMV, Tymovirus) and Cowpea aphid-borne mosaic virus (CABMV, Potyvirus). However, other virus species, not yet accepted as definitive by the ICTV, were originally and exclusively described in passion fruit trees in Brazil: Purple granadilla mosaic virus (PGMV, species with undetermined taxonomy), Passion fruit green spot virus (PFGSV, Cytorhabdovirus), Passion flower little leaf mosaic virus (PLLMV, Begomovirus), Passion fruit severe leaf distortion virus (PSLDV Begomovirus) and, more recently, Passion fruit chlorotic mottle virus (PCMoV, Begomovirus). 

In Brazil, CABMV is responsible for causing passion fruit fruit hardening (EFM), one of the most important passion fruit diseases. CABMV is a species of virus belonging to the genus Potyvirus, family Potyviridae. Its first occurrence was recorded in 1978 in commercial sweet passion fruit orchards, in the municipality of Feira de Santana (BA). This virus quickly spread to orchards in all Brazilian producing regions, with the first records of a drop in production being reported in the state of São Paulo, in the 1990s, causing losses of up to 80% in the production of sour passion fruit in the regions of the Valley. Ribeira and Alta Sorocabana. Since then, in scientific work carried out, it has been observed that at least 16 species of wild passion fruit (or species that have the potential for commercial exploitation as fruit or ornamental) are susceptible to CABMV. Currently, CABMV has been responsible for frequent epidemics, occurring in all commercial passion fruit orchards in the states of Bahia, Pernambuco, Ceará, Sergipe, São Paulo, Paraná, Minas Gerais, Mato Grosso do Sul, Goiás, Distrito Federal and Santa Catarina. 

In the Northeast region, in addition to infecting passion fruit, CABMV is also one of the main pathogens of cowpea (Vigna unguiculata), Fabaceae (or Leguminosae), important because it is one of the species that constitute the basis of the diet of the Northeastern people. . Other cultivated legumes such as peanuts (A. hypogaea), soybeans (Glycine max) and several cultivars of beans (Phaseolus vulgaris) have also been reported as susceptible to this virus. In experiments carried out at the Phytovirology and Pathophysiology Laboratory of the Instituto Biológico, it was demonstrated that CABMV isolates, from passion fruit samples collected in the state of São Paulo, are also capable of infecting food legumes such as peas (Pisum sativum) and lupine (Lupinus albus). The researchers also found that species used in the production of green biomass and nitrogen fixation in the soil (green manure) such as sunn hemp (Crotalaria juncea, C. incana and C. spectabilis), mucuna beans (Mucuna aterrina and M. cinerea), Jack beans (Canavalia ensiformes), pigeon peas (Cajunus cajan) and siratro (Macroptilium atropurpureum), as well as those used in the formation of intercropped pastures such as perennial soybeans (Neonotonia wightii), behaved as susceptible to the virus. Furthermore, fedegoso (Senna occidentalis), a perennial shrub legume native to South America, was also susceptible, proving to be a potential reservoir for CABMV. All species or commercial varieties of passion fruit, when infected by this virus, develop mosaic foliar symptoms, blisters and deformations. The fruits do not develop and are often deformed, with a hardened and thick pericarp. The deformation and malformation of the fruits, combined with the shortening of the production period and the reduction in pulp content, significantly reduce production with a consequent loss of commercial value.

Initially, passion fruit cultivation was semi-perennial, with orchards being replaced every three to four years. After the spread and given the severity and losses caused by CABMV, in areas destined for intensive production, producers began to adopt the annual renewal of orchards as management. Another important factor that drove the renewal of orchards annually was the difficulty in obtaining varieties resistant to this virus. Associated with the annual renewal of orchards, it has been recommended as a cultural practice, to minimize the losses caused by CABMV, the introduction of sour passion fruit seedlings with more advanced stages of development, that is, at least 0,8m, and reaching 1,5m high. These seedlings must be kept, from sowing, in anti-aphid screens before being taken to the field.

CABMV is not transmitted by passion fruit seeds, however, its dispersion in the field is carried out efficiently by several species of aphids (aphids). However, aphids do not colonize passion fruit plants. This fact often causes doubt and surprise among producers, who claim that they do not notice the presence of these insects in their orchards. Although they do not colonize passion fruit, most aphid species colonize a multitude of weed and cultivated plants, including other fruit species, which favors the maintenance of populations and constant flocks of these insects in the field throughout the entire development cycle, i.e. from introduction, development to orchard production. The transmission of CABMV, as well as other potyviruses, occurs in a non-persistent (non-circulating) manner, that is, the virus is acquired by the aphid in a few seconds and, after acquisition, it can be immediately transmitted, and the inoculation of the virus also occurs within a few seconds. This type of transmission, carried out during test bites, occurs in the cells of the epidermis and mesophyll of the leaves. Aphids are characterized by being insects that suck sap from the phloem of their host plants, where they establish themselves forming large colonies. However, the test bites (in mesophyll cells) serve to recognize their hosts. The mouthparts of these insects consist of a stylet, which allows the aphid to pierce and suck out the contents of the cell. When it recognizes the host, the aphid continues to lengthen its style in the spaces between the cells until it reaches the phloem vessels, where it will remain feeding on sap. After the test bites, if the aphid does not recognize the plant as a host, it will collect its stylet and take flight in search of a new host.

When carrying out test bites on an infected passion fruit plant, generally in orchards at the end of their cycle or already abandoned, the aphids quickly acquire CABMV particles that will be retained on the tip of the stylets for minutes or a few hours. As aphids do not colonize passion fruit plants, after test bites on an infected plant, they will carry out reconnaissance flights in search of a new host. In intensive cultivation regions, there is a high probability that successive landings will occur on other sour passion fruit plants (healthy or infected) and, therefore, in the subsequent feeding processes, the virus will be inoculated and, consequently, the EFM will be dispersed in the orchard. In epidemiological studies carried out in different regions of the state of São Paulo, it was found that the spread of EFM can be very rapid, especially in traditional passion fruit planting areas. In Vale do Ribeira, for example, in approximately six months, a passion fruit orchard could have 100% of its plants infected by CABMV.

HOW TO MANAGE

As aphids behave like visitors to sour passion fruit orchards, controlling these insects with the application of agrochemicals is not a recommended practice to contain the spread of CABMV, as transmission will occur during test bites before the insecticide take effect. It is worth mentioning that the spread of the virus, in addition to the important role of aphid vectors, can also be enhanced through the use of contaminated cutting tools during cultural practices, such as grafting and pruning. 

Epidemiological studies, also carried out by researchers from the Laboratory of Phytovirology and Pathophysiology of the Instituto Biológico, to monitor aphid populations in passion fruit orchards located in the East of São Paulo and Vale do Ribeira regions, São Paulo, made it possible to verify the occurrence of intense flocks of aphids during the entire sour passion fruit production cycle. Yellow sticky traps and yellow water traps (Moericke) were used throughout the sour passion fruit production cycle, with the aim of collecting and identifying the main aphid species involved in transmission. The largest flocks were recorded during the winter period when, normally, temperatures are milder and rainfall is lower. Sixteen aphid species were classified as visitors to the monitored orchards: Aphis fabae, Aphis craccivora, Aphis gossypii, Aphis nasturtii, Aphis nerii, Aphis spiraecola, Aulacorthum solani, Brevicoryne brassicae, Hyperomyzus lactucae, Macrosiphum euphorbiae, Myzus persicae, Pemphigus spp., Pentalonia nigronervosa, Toxoptera aurantii, Toxoptera citricidus, Uroleucon ambrosiae. Species of the genus Aphis were the most constant (always present) and abundant (with the highest numbers of individuals), mainly A. fabae and A. gossypii. Experimental transmission tests showed that A. fabae was capable of transmitting CABMV with an efficiency of up to 40%, which indicated that this aphid species is strongly related to the dispersion of the virus in the field. When comparing the behavior of more developed seedlings (1,5m) with seedlings up to 30cm tall, in the face of CABMV pressure, it was found that regardless of the size of the seedling, the entry of the virus into the orchard occurred simultaneously. However, in the developed seedlings, there was a delay in the appearance of symptoms, allowing the production of fruits with commercial value for up to two years.

Due to the expansion of sour passion fruit cultivation in the South, Southeast, Center-West and Northeast regions of Brazil and given the edaphoclimatic diversity of these regions, which directly interferes with the aphid population, it is difficult to recommend a single management for the passion fruit culture. However, knowledge of the behavior of flocks of aphid populations is important to adopt EFM management and control strategies. This principle is valid mainly for the adoption of virus control strategies in crops where there is no supply of varieties with specific resistance genes, as is the case with the CABMV-passion fruit interaction.

Despite production difficulties, and while obtaining resistant commercial varieties is not yet a reality, some phytosanitary and cultural management measures for passion fruit cultivation are essential, regardless of the region (Table 1). Finally, the incessant work of researchers at research institutes and universities has guaranteed Brazil the position of largest producer of sour passion fruit, appreciated throughout the world.

SOURCE 

Cultivated plants originate from wild ancestral species from so-called “centers of diversity” or “centers of origin”. These centers correspond to geographically delimited areas, which are of great use for genetic improvement programs that seek to rescue genes of interest, present in wild species, such as those that confer resistance to abiotic and biotic factors. Almost exclusively, genes that confer some level of resistance to biotic factors, such as pests and diseases, are rescued in their respective centers of origin. From the plant origin center called “Brazil-Paraguay” numerous species of agricultural importance originated, such as peanuts (Arachis hypogaea), mate tea (Ilex paraguayensis), cassava (Manihot esculenta) and rubber trees (Hevea brasiliensis). , in addition to a great diversity of fruit species with potential for commercial exploitation, such as sour passion fruit (Passiflora edulis) and sweet passion fruit (P. alata), guava tree (Psidium guajava), pitan tree (Eugenia uniflora), uvai tree (E. uvalha), grumixameira (E. dombeyi), cabeludinha (E. tomentosa), jabuticaba tree (Myriaria jaboticaba), pineapple tree (Ananas comosus), cocoa tree (Theobroma cacao), Brazil nut tree (Bertholletia excelsa) and cashew tree (Anacardium occidentale) . The sour passion fruit, one of the native Brazilian species, is the most commercially exploited, only surpassed by the cultivation of introduced species such as orange, banana, grape, papaya, apple and mango, which has its center of origin in other regions of the world.

Alexandre Levi Rodrigues Chaves, Marcelo Eiras, Leilane Karam Rodrigues and Addolorata Colariccio, Instituto Biológico

Growing Vegetables and Fruits February 2019

With each new edition, Cultivar Hortaliças e Frutas publishes a series of technical content produced by renowned researchers from all over Brazil, which address the main difficulties and challenges encountered in the field by rural producers. Through research focused on controlling the main pests and diseases in vegetable and fruit cultivation, the Magazine helps farmers in the search for management solutions that increase their profitability. 

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