Identificação molecular de isolados do fitoplasma do enfezamento vermelho do milho coletados no Estado de São Paulo.

Abstract

In order to identify isolates of phytoplasma associated with the red stunt (maize bushy stunt), corn plants were collected in four regions where corn is grown in Sao Paulo State. The symptoms exhibited by each plant were registered. Detection was made by nested PCR, using the universal primer pair mF2/R1 followed by F2n/R2. Identification was made also by nested PCR using mF2/R1 in the first reaction, followed individually by R16(1)F1/R1 and R16(III)F2/R1, which are specific pairs to identify phytoplasmas belonging to Groups I and III, respectively. The identification also was conduced by RFLP analysis with the restriction enzymes Alu I, Hha I, Kpn I, Mse, I e Rsa I. In this case, DNA fragments amplified by nested PCR with universal primer pairs R16 mF2/R1 e R16 F2n/R2 were used. The symptoms were mainly reddening of leaves, reduction in height, ear proliferation and stunting. Seventy isolates, detected with universal primer pairs were randomly selected. Fifty two were positive according to the PCR tests using Group I specific pair. Positive results were not obtained for any isolate when specific primers for Group III were used. Using RFLP, 29 isolates randomly chosen were confirmed as being of Group I. All of them were detected with universal primer pairs, but only 14 were detected with specific primer pair for Group 1. RFPL analysis demonstrated that for each enzyme the isolates showed band profiles identical to each other and belonging to Group 1, Subgroup B on the basis of the pattern currently adopted to classify phytoplasmas.