Resumo

PERDOMO, Rosaura et al. Characterization and evaluation of virulence in rhizoctonia solani kühn isolates, causal agent of leaf banded spot on maize. INCI [online]. 2007, vol.32, n.1, pp.48-54. ISSN 0378-1844.

In Venezuela, banded leaf spot caused by Rhizoctonia solani Kühn is a widely distributed disease in the most important maize growing areas, causing important yield losses. In 2004, experiments were conducted with the purpose of characterizing and evaluating the virulence of 25 isolates of R. solani. Characterization tests were performed throughout cultural, microscopic, and molecular evaluations, the latter using a specific ribosomal internal transcribed spacer region (rADN-ITS). Virulence tests were performed on the maize inbred lines CML-254 y L-82201-22-1-1, both in the laboratory using KIN solution (6-furfurilaminopurine), and in a greenhouse inoculating seedlings. Characterization tests demonstrated that all isolates belong to R. solani, although differences were observed in colony color, mycelial growth and sclerotia size, among others. Molecular analysis classified all isolates within the R. solani anastomosis group AG1-IA. Virulence tests performed in the laboratory showed that the isolates G1SOM1 and P2TUR3 had the highest virulence index. In greenhouse tests B1TOR1, P2TUR6, and B2SAB1 resulted more virulent. In both virulence tests, the line CML-254 showed the highest level of resistance to disease. The isolates identified and characterized in this study may be used by maize breeding programs looking for resistant sources and improved cultivars.

Palavras-chave : Grupo de Anastomosis ; Maíz ; Mancha Bandeada; Rhizoctonia solana ; Virulencia ; Zea mays .