Etiologia da antracnose da fava e resistência de genótipos a doença

Abstract

The pathogenic fungi may be associated with adaptation in a given geographical condition and the high genetic variability that have. The study evaluated the pathogenicity twelve Colletotrichum truncatum against seven genotypes of Phaseolus lunatus with known resistance to anthracnose in the field. The isolates collected in five municipalities of Alagoas, Messias (01, 17) São José da Laje (03, 04), União dos Palmares (05, 06), Murici (07, 11, 12, 13) and Rio Largo (18, 20) they were inoculated in healthy leaves of lima bean. The inoculatin consisted of mycelium discs containing pathogen structures. Assessment of pathogenicity was assessed by the weighted average injury to three leaflets seven days after inoculation. The design was completely randomized with five repetitions and subjected to analysis of variance by the program SISVAR 5,6 and testing Tukey with a probability of 5 %. The leaves used showed lesions with dark brown coloring and depressed spots, or reddish-brown and depressed spots with soaked appearance and with black fruiting bodies of the pathogen training and growing along the leaf veins. All isolates tested were pathogenic in endurance tests to the host. After inoculation of the pathogen on leaves with injury, symptoms appeared three or four days after inoculation the genotypes G10 (AS) and G65 (AR), respectively. Through phylogenetic analysis of GAPDH gene it was possible to identify the species C. truncatum in the 12 isolates obtained in the state of Alagoas. The mycelial growth it has variation of 3.7 cm to 7.9 cm. Cultural assessment mycelia present with brown coloring, gray, dark green and cream in the center. Edges with white color, cream, green and dark green and perithecia in agglomerate in some. Growth type observed was the sector with interspersed areas of light and dark mycelia. The star type growth was observed in an isolated. Topography varied in small, moderate, abundant and aerial mycelium. In the pathogenicity test, it was possible to observe isolated ICT20 caused smaller size on G65 genotype, and The Isolated ICT03, ICT07, ICT11, ICT12 and ICT13 LARGEST caused injuries. WHEN we compare ourselves Isolated inoculated in different genotypes, What we observe the G65 genotype, considered resistant, showed less damage size compared to all isolates, and the sizes of the lesions differed significantly for ICT01, ICT03, ICT05, ICT07, ICT11, ICT12, ICT13 and ICT20. It was possible to select for resistance evaluation in five genotypes of fava isolated ICT ICT07 and ICT12 (Murici). In the resistance analysis of the isolated C. trucatum more aggressive, the genotypes G17, G22, G32 had minor lesions when inoculated ICT07 the isolates and genotypes G62, G69 had the highest lesion. The ICT12 was less aggressive to G32 and G69 genotypes. The G17 genotype was more susceptible to the isolated ICT12 presenting the larger lesions. Lesion size only differed statistically for G17 and the only genotype that behaved in both resistant isolates was G32, which may be indicated for further anthracnose resistance studies.