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Incidence of viruses in pepper production

To minimize productivity losses, it is important to be aware of aspects such as correct diagnosis, transmissibility and variability of viruses.

19.05.2020 | 20:59 (UTC -3)

Pepper production in Brazil is severely limited by the incidence of viruses such as Begomovirus, Tospovirus and Potyvirus. To minimize productivity losses, it is important to pay attention to aspects such as correct diagnosis, transmissibility and variability of viruses.

Viruses are one of the limiting factors for pepper production in several growing regions, causing losses in productivity. The symptoms of viral infection manifested in pepper are broad, and mixed and simple infections can occur. However, some viral species may present identical symptoms in different pepper species, resulting in difficult diagnosis in the field.

Species of the genus Begomovirus have been reported causing disease in pepper. This genus belongs to the Geminiviridae family. Its transmission occurs through the whitefly Bemisia tabaci to dicotyledonous plants. Begomovirus species have already been reported infecting several crops, such as: beans, tomatoes, peppers and peppers. The symptoms associated with begomovirus infection in pepper present themselves in a variety of ways, from leaf distortion to yellow mosaic.

There are also reports of incidence of the genus Tospovirus - species (Tomato spotted wilt virus - TSWV, Groundnut ringspot virus - GRSV and Tomato chlorotic spot virus -TCSV. This genus belongs to the Bunyaviridae family and are spread by thrips in a circulative-propagative way. This means that thrips acquire and transmit the virus after a long period of incubation and once viruliferous it perpetuates the virus for life. Viruses belonging to this genus can infect several species of plants, including cultivated plants, weeds and ornamental plants. The infections caused caused by tospoviruses, they cause significant damage, especially in vegetables, with chlorotic lesions often occurring.

A genus that stands out in the incidence of viruses in pepper is Potyvirus, belonging to the Potyviridae family, being considered the most numerous, with more than 100 classified species. It is transmitted by aphids in a non-circulating way. PVY is considered the “type” species of the genus Potyvirus and several strains have already been identified. The occurrence of the disease in Brazil caused by PVY was initially reported in potato plantations and then in peppers. In pepper and pepper, PVY strains induce mosaic, mottling and necrosis symptoms, with the symptom depending mainly on the Capsicum genotype evaluated. The PepYMV species was identified infecting peppers in several Brazilian states, and is considered a new species of the Potyvirus genus. This virus is the main problem in pepper cultivation and occurs in all producing regions of Brazil, and can cause mosaic symptoms on the leaves, yellowing, leaf distortion and reduction in fruit size.

Importance of diagnosis

A good measure of controlling diseases caused by viruses in the field depends on accurate diagnosis. In the diagnosis of plant viruses, biological testing methods (host range and symptoms), vector transmission, serological and molecular tests are used.

A basic premise to aid virus diagnosis are incidence survey studies in the field. Therefore, to diagnose the species of pepper cultivated, production and phytosanitary problems, a survey was carried out with small producers in the municipality of Humaitá, Amazonas, in 2012.

Preliminary results indicated a predominance of cultivation of Malagueta pepper (C. frutescens), De Outubro pepper (C. chinense) and Murupi pepper (C. chinense), with a greater predominance of cultivation for De Ardor pepper. A high incidence of viruses was observed in these crops, presenting intense mosaic symptoms and leaf deformation. Malagueta pepper leaf samples were collected and sent to the Phytosanitary laboratory at the Federal University of Amazonas - Institute of Education, Agriculture and Environment (UFAM-IEAA).

Preliminary test

With the aim of verifying transmission via buffered plant extract, a preliminary test was carried out with healthy plants of chili pepper, Murupi pepper, De Oleiro pepper, Dedo de Moça pepper, Tekila pepper (C. chinense), Long Sweet Pepper (C. annuum) and Yolo Wonder peppers (C. annuum). Commercial substrate was used for sowing. The seedlings were transplanted into plastic pots, containing soil and commercial substrate, in a 3:1 ratio, respectively, remaining in the greenhouse, where they were inoculated 30 days after emergence.

For the inoculation procedure, young leaves of Malagueta pepper collected with typical virus symptoms were macerated in a mortar in the presence of phosphate buffer (0,05 M, pH 7,0), plus the antioxidant sodium sulfite (0,01 M) and of celite abrasive (0,05%). After maceration, the resulting extract was filtered through double gauze and mechanically inoculated into Capsicum leaves by rubbing pieces of gauze soaked in the plant extract on the adaxial surfaces. Immediately after inoculation, the leaves were washed with distilled water. After carrying out the procedure, the plants remained in the greenhouse.

In Malagueta, Doce Comprida, De Outubro, Murupi and Tekila pepper plants inoculated with the plant extract obtained from infected plants, the presence of symptoms of mild mosaic, severe mosaic and leaf deformation was observed. However, Malagueta and Tekila presented a more expressive intensity of symptoms, accentuating possible necrosis. The Dedo de Moça pepper plant showed no symptoms of infection. In relation to the Yolo Wonder pepper, a smooth mosaic was observed. The plants that showed symptoms are being evaluated for viral etiology, giving evidence of infection with species of the Potyvirus genus. Molecular analyzes are being carried out.

In view of the results obtained, it was found that the Malagueta pepper isolate caused more severe symptoms in pepper than in bell pepper. This result, although preliminary, has helped in the development of other research. Surveys are being carried out with the aim of collecting samples of pepper plants with viral infection in the state of Amazonas, aiming to study the variability of these viruses and possible sources of resistance.

General control measures

- The use of resistant varieties is considered one of the most efficient methods for controlling viruses;

- Use of healthy seedlings in planting;

- Elimination of contaminated host plants;

- Plant plantings separately from each other with the best possible isolation;

- Do not plant new crops next to fields with a high incidence of the disease;

- Insect-vector control (when applicable).

Peppers in Brazil

The Capsicum genus is among the most economically important vegetables in Brazil, being cultivated in all states, under different climatic conditions. The pepper species assigned to this genus constitute a very peculiar group characterized by their “sweet” or spicy flavor. Attributed to these characteristics, they present great variation in the shape, size and color of the fruits. In addition to the pepper (Capsicum annuum var. annuum), different types of peppers belonging to the four domesticated species are cultivated in Brazil: C. annuum (jalapeño), C. baccatum (dedo-de-moça), C. frutescens (chilli pepper) and C. chinense (pepper, goat, cumari-do-Pará). The production of pepper culture is distributed in all regions of Brazil, however in the North region, pepper, in addition to being present in regional cuisine, its cultivation is considered an activity of great socio-economic importance, being one of the best examples of family farming, contributing as a source of income on small properties and in settling people in rural areas.

Due to the diversity of pepper found in the Amazon region, its planting is being widely explored. However, with the expansion of cultivation, phytosanitary problems, mainly of viral etiology, may arise and pose a serious risk to productivity, resulting in losses for the producer.