Researchers identify viruses in garlic

Around 50 samples of garlic plants with symptoms of viruses, collected in Vale do Itajaí, in Santa Catarina, were analyzed at the Virology and Molecular Biology Laboratory of Embrapa Hortaliças (DF) and the results of the serological tests confirmed the occurrence of species of virus in fields in the region. “This is the first record in this location of the occurrence of Onion yellow dwarf virus (OYDV), of the genus Potyvirus, and species of the genus Allexivirus, which are transmitted, respectively, by aphids and mites”, indicates researcher Mirtes Freitas Lima, virologist at Embrapa Hortaliças. The viruses had previously been reported infecting garlic fields in other Brazilian regions.

The collection of samples from the noble garlic cultivars Quitéria and Ito was carried out by technicians from the Agricultural Research and Rural Extension Company of Santa Catarina (Epagri-SC) based on the observation of symptoms such as banded mosaic (streaks that vary from green- light to yellow) and dwarfism (reduction in plant development). Tests with antisera identified OYDV as the most common virus, having been detected in 38% of samples from the Quitéria cultivar and in 18,5% of samples from Ito garlic. In these two cultivars, virus species of the genus Allexivirus were present in 4,7% and 3,7%, respectively.

The results of laboratory analyzes detected a single sample with the presence of both viruses, which characterizes a mixed infection, which can result in more severe symptoms and further affect the plant's yield. “The infection reduces the productive potential of the plant and, in the case of garlic, there is an aggravating factor, as it is a vegetatively propagated crop, because new plantings are made from bulbils collected in the previous planting, that is, from propagation vegetative”, summarizes Mirtes, explaining that, over generations of planting, as the viral load increases, the productivity and vigor of the plant are compromised, which is known as crop degeneration.

Santa Catarina is the second largest garlic producing state in the country, with around 20% of national production, behind only Minas Gerais. Most of Santa Catarina's garlic production is concentrated on the mountain plateau, in the Curitibanos region, but there is a prospect of expanding cultivation to new areas, such as the Itajaí Valley.

“The importance of detecting viruses in garlic in the Alto Vale do Itajaí is due to the fact that the Allexivirus genus has never been reported in the state of Santa Catarina. Furthermore, the presence of the Onion yellow dwarf virus serves as a warning for the region, since this same virus can also infect onions, which are the main vegetable produced in the Itajaí Valley”, argues agronomist Edivânio Araújo, researcher at the Epagri Experimental Station in Ituporanga (SC).

Virus-free garlic seed

Vegetative propagation is the main cause of the spread of viruses in garlic crops, therefore, using healthy propagation materials, such as virus-free seed garlic, with guaranteed origin, is essential to ensure the quality of new plantings, a since chemical control is not very effective in reducing the spread of viruses, as it affects insect vectors - aphids (aphids) or mites, but these may have already transmitted the viruses through crops.

“The adoption of virus-free seed garlic in commercial crops has provided very significant increases in productivity when compared to garlic propagated by the conventional method”, comments researcher Francisco Vilela, from Embrapa Hortaliças, when quantifying that, depending on the level of infection of the variety, the productivity of the virus-free clone can increase between 30 and 50% in relation to infected garlic.