LEVANTAMENTO DE FUNGOS CAUSADORES DE PODRIDÃO DE ESPIGA EM MILHO E VARIABILIDADE GENÉTICA EM Stenocarpella maydis

Abstract

The objective of this study was to survey the main fungi that cause ear rot in corn grains and to estimate the genetic variability of S. maydis using ISSR molecular markers. Samples of corn grains collected in different municipalities were subjected to seed pathology test (Blotter Test). For the mycelial growth of S. maydis test, the experiment was completely randomized design (CRD) in a factorial arrangement 4 (culture media) x 2 (antibiotic) x 2 (light regime), with four replications. The tested media were oatmeal agar (AA), potato dextrose agar (PDA), potato sucrose agar (BSA) and medium carrot (MC) and the antibiotic used was chloramphenicol 150 mg L?¹. For mycelial growth and competition test fungi that cause ear rot, Aspergillus spp., Fusarium spp., Penicillium spp. and S. maydis fungi were used for selection of primers and evaluation of the genetic variability of the DNA isolated from S. maydis was extracted by the CTAB method and the amplification of the fragments by PCR technique using 42 ISSR primers. The PIC (polymorphic information content), MI (marker index) and RP (resolving power) indices were calculated to determine the 10 ISSR primers more information. The results of the grain pathology test indicated that the fungus Stenocarpella spp was the one with the lowest incidence (1.13%) and Fusarium spp. the highest (49.56%). For mycelial growth, the BDA and BSA media stood out. Regarding the mycelial growth and competition of fungi that cause ear rot, stood out the fungus Penicillium spp., as evidenced high antagonism to the pathogen S. maydis. In relation to genetic variability, the 42 primers, 50% showed good amplification products. Cluster analysis allowed separate isolates of S. maydis the same city (I2, I3, I5 and I6 - Vitorino) in different groups and did not group the I4 (Guarapuava) to other strains. UBC primers 848, 873, 808, 811, 807, 827, 861, 868, 809 and 835 showed the best results for the analysis of genetic variability. The mean genetic similarity among isolates was 34%, showing the existence of high genetic variability among the six isolates of S. maydis.