Incidência de viroses e enfezamentos e estimativa de perdas causadas por molicutes em milho no Paraná

Abstract

Resumo -O objetivo deste trabalho foi avaliar a incidência de viroses e enfezamentos e estimar as perdas causadas por enfezamentos na cultura do milho safrinha. Os diagnósticos baseados em sintomas foram confirmados por PCR ou RT-PCR. Em todas as lavouras, foram identificadas plantas com sintomas de enfezamentos, em incidência de 6,2% a 49,9% (média de 20,7%). Na identificação de insetos vetores desses patógenos, a cigarrinha Dalbulus maidis foi detectada em 20 lavouras das 24 amostradas, constituindo 66,6% do total de espécimens de cigarrinhas coletadas. A perda potencial causada pelos enfezamentos no período foi estimada em cerca de 16,5 milhões de dólares. A ocorrência de plantas com sintomas de "Maize rayado fino virus" e "Maize dwarf mosaic virus" foi baixa e o diagnóstico confirmado por RT-PCR. A análise de 441 amostras suspeitas de infecção por "Mal de Río Cuarto virus", por DAS-ELISA, mostrou ausência desse vírus. Resultados de PCR indicaram a presença de um possível fitoplasma distinto de "Maize bushy stunt phytoplasma" em duas plantas apresentando nanismo acentuado, folhas estreitas, enrijecidas, com deformações, e grãos na inflorescência, havendo necessidade de mais estudos para a confirmação da identidade desse possível novo fitoplasma.Termos para indexação: Zea mays, espiroplasma, doença das plantas. Occurrence of viruses and stunting diseases and estimative of yield losses by mollicutes in corn in Paraná State, BrazilAbstract -The objective of this work was to evaluate the occurence and yield losses by corn stunting diseases and maize viruses in "safrinha" season. Disease diagnostics based on plant symptoms were confirmed by PCR or RT-PCR assays. Insect samples were collected in 24 fields for identification of vectors of the pathogens. Corn stunting diseases symptoms were observed in all crops evaluated, with incidence levels ranging from 6.2% to 49.9% (average 20.7%) and the presence of the leafhopper Dalbulus maidis, was detected in 20 of the 24 areas evaluated. This insect species was prevalent, representing 66,6% of total leafhoppers specimens collected.

Incidence of corn stunt disease in off-season corn hybrids in different sowing seasons

“…Therefore, the incidence of corn stunt disease increased with the delay in sowing (Figure 2), as also observed by Oliveira et al (2003). This may be explained by the fact that corn leafhoppers, which acquire Mollicutes by ingesting the infected sap of diseased plants, only become permanently infectious after three to four weeks (Orlovskis et al, 2017).…”

Assessing the impact of climate change on the worldwide distribution of Dalbulus maidis (DeLong) using MaxEnt

“…Transmission of these pathogens occurs in a persistent and propagative manner, and can result in high infestation rates . In Central America, Peru, Brazil and Argentina, infestations by these pathogens can affect 100% of the plants in some areas, which translates into yield losses of up to 90% . Therefore, direct (i.e.…”

Preliminary Observations on Zelus obscuridorsis (Stål) (Hemiptera: Reduviidae) as Predator of the Corn Leafhopper (Hemiptera: Cicadellidae) in Argentina

“…It only feeds on plants of the genus Zea (maize and teosintes) [1]; and it efficiently transmits three important plant pathogens: Corn stunt spiroplasma (CSS), maize bushy stunt phytoplasma (MBSP) and maize rayado fino virus (MRFV) [2]. The distribution of the CSS has increased significantly in South America [3]. In Argentina, CSS disease is present with incidences of up to 100% in the subtropical region [4,5].…”