Epidemiologia e controle da antracnose em Capsicum spp. e identificação de Colletotrichum spp. associados às solanáceas cultivadas

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

Although pepper and sweet-pepper anthracnose may be caused by several Colletotrichum species, most domestic (Brazilian) reports identify Colletotrichum gloeosporioides as the main causal agent, with rare records of other species. Twenty-two Colletotrichum isolates were studied as to their mycelial growth, colony coloration and conidial morphology and morphometrics, as well as to their aggressiveness to Capsicum fruits and plantlets. All five pepper isolates belonged to the C. gloeosporioides taxon, as well as the majority of sweet-pepper isolates and one S. gilo isolate. Most of the remaining isolates were identified as C. acutatum. C. acutatum was the predominant species among S. gilo isolates. The most aggressive isolates on S. gilo fruits were the ones that were originally isolated from this same species, and they were generally pathogenic to sweetpepper as well. In agreement, most aggressive isolates to sweet-pepper were obtained from pepper and sweet-pepper, but these were not capable of inducing symptoms on S. gilo fruits. The most aggressive isolates to S. gilo fruits belong to C. acutatum, while most aggressive isolates to sweet-pepper belong to C. gloeosporioides. Almost none of the isolates was able to induce symptoms on plantlets. The results from plantlet inoculation were insufficient to differentiate among isolates according to their host specificity or aggressiveness. This work studied the reaction of green and mature fruits to inoculation with different Colletotrichum spp. isolates onto 11 Capsicum genotypes (fruits of the species Capsicum annuum, C. baccatum e C. chinense). Green fruits of C. annuum were consistently more susceptible than mature fruit, irrespective of the isolate tested. When inoculated with the C. gloeosporioides isolates, C. baccatum and C. chinense fruits responded the same way. However, when these Capsicum species were inoculated with the C. acutatum isolate, larger lesions were verified in mature fruit. All three Capsicum species presented genetic variability as to susceptibility to Colletotrichum spp., from extremely susceptible to resistant, demo nstrating that the genus includes promising sources for breeding for anthracnose resistance. The effects of chemical control, soil mulch and nitrogen fertilization on the progress of sweet-pepper anthracnose were studied in two series of field experiments. Experiments were conducted in the winter (March to July) and summer (September to December) seasons, with sweet-pepper hibrid Maximos F1. Chemical treatments were Potassium phosphate dibasic (K2HPO4) and Chlorotalonil, and soil mulch treatments were plastic mulch and organic (Andropogon sp.) mulch, in a total of four treatment-combinations, in a randomized complete block design (RCBD), replicated four times. In separate experiments, the effect of four levels of nitrogen fertilization (0 Kg/ha, 50 Kg/ha , 150 Kg/ha and 450 Kg/ha de N) were tested in the winter and summer seasons. Nitrogen was applied in the form of urea (45-46 % N) and the experiments followed a RCBD, with four replicates. Results showed that severity of sweet-pepper anthracnose is affected by planting season, soil mulch and chemical control. Disease severity was much larger in the summer than in the winter season, larger with K2HPO4 than Chlorotalonil, and also larger with plastic mulch than organic mulch. In the winter season, the effect of the organic mulch was better noted under K2HPO4, while disease progress rates were uniformly low with Chlorotalonil, irrespective of mulch type. On the other hand, on the summer season, the effect of organic mulch was better noted under Chlorotalonil, while disease progress rates were uniformly high with K2HPO4, irrespective of soil cover type. In the summer, however, no treatmentcombination gave sufficient disease control. The highest nitrogen dose (450 Kg/ha) resulted in significantly larger disease severities in both seasons, while anthracnose levels did not differ among the remaining doses from 0 to 150 Kg/ha.

ASSUNTO(S)

solanáceas antracnose ciências biológicas capsicum colletotrichum

ACESSO AO ARTIGO

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