Spatial analysis of garlic viruses in the Alto Paranaíba region, Minas Gerais

Abstract The Alto Paranaíba region, located in Minas Gerais State, Brazil, is one of the largest garlic producers in Brazil, but little is known about the occurrence and incidence of viral diseases in the region. In this study, a survey of the viral species presents in 10 areas in the municipality of São Gotardo. Each sampled area was divided into 3 subareas, and in each subarea, 1290 plants were visually evaluated for the presence or absence of symptoms and 25 leaves each with and without symptoms were collected to identify the viruses present by means of RT‒PCR. The incidence of viruses in the ten areas was quite variable, and four of them had a lower incidence, ranging from 2.9–16.7%. Two of the others presented incidences of 42.9% and 86.4%, while four showed an incidence of 100%. The infected plants showed an aggregated spatial distribution pattern in 90% in the run test and a random distribution in 63.3% in the doublet test. The dispersion index in 63.3% of the blocks indicated a regular spatial pattern. All symptomatic samples collected were positive for the presence of one or more virus species belonging to the genera Potyvirus, Carlavirus and Allexivirus, indicating possible transmission by the cloves used in planting. These results demonstrate the importance of vector control and the use of virus-free propagation material because the presence of the inoculum at the beginning of the crop cycle means a longer time for dissemination and impairment of productivity.