RESUMO
Colletotrichum boninense was isolated from pepper (Capsicum annuum) fruits (cv. Amanda) with preharvest anthracnose symptoms collected in the Brazilian states of Rio Grande do Sul and São Paulo in July of 2005. In the field, the disease affected mature fruits and leaves with an incidence near 25%. Typical symptoms in fruits were circular, sunken lesions with orange spore masses in a dark center. Three single conidia isolates were obtained from infected fruits. When grown on potato dextrose agar at 25°C with a 12-h photoperiod, these isolates produced white colonies with a cream-to-orange color in the opposite side, but no sclerotia. Conidia were cylindrical, had obtuse ends and a hilum-like low protuberance at the base, and measured 13.5 to 15.5 × 4.6 to 5.1 µm. Conidial length/width ratio was 2.8 to 3.0. These morphological characteristics are consistent with the description of C. boninense (1). To confirm pathogen identity, the internal transcribed spacer rRNA region was sequenced (GenBank Accession Nos. FJ010199, FJ010200, and FJ010201) and compared with the same region of C. boninense (GenBank Accession No. DQ286160.1). Similarity between these sequences was 98 to 99%. The pathogenicity of the three isolates was determined on pepper fruits cv. Amanda. Attached as well as detached fruits from potted plants were inoculated. Inoculation was performed by depositing 40-µl droplets of a suspension (105 conidia per ml) on the surfaces of nonwounded (detached n = 5; attached n = 5) and wounded (detached n = 5; attached n = 5) fruits with a sterilized hypodermic needle. Incubation took place in a moist chamber for 12 days at 25°C with a 12-h photoperiod. Inoculation of control fruits was similar in procedure and number to that of test fruits, except sterile distilled water was used instead of the conidial suspension. Symptoms, observed in wounded and nonwounded test fruits 3 to 5 days after inoculation, were characterized by necrotic, sunken zones containing acervuli, black setae, and orange spore masses. Control fruits presented no symptoms. Pathogens reisolated from infected fruits showed the same morphological and molecular characteristics of the isolates previously inoculated. To our knowledge, this is the first report of C. boninense infecting pepper in Brazil. Reference: (1) J. Moriwaki et al. Mycoscience 44:47, 2003.
RESUMO
Powdery mildew is an important disease of melons (Cucumis melo L.) cultivated in greenhouses in Brazil. Currently, there are 5 races of Podosphaera xanthii (formerly known as Sphaerotheca fuliginea) and 2 races of Golovinomyces cichoracearum (formerly known as Erysiphe cichoracearum) described on melons worldwide, but only race 1 of P. xanthii has been reported in Brazil (1). However, typical whitish powdery fungal growth was observed on an experimental hybrid yellow melon resistant to race 1 of P. xanthii during the summer of 2000 in a greenhouse in Bragança Paulista, State of São Paulo. Conidia collected from diseased leaves were spread onto 0.5% water agar medium and maintained at 22°C for 24 h with 12 h of light and 12 h of darkness. Most of the germinated conidia displayed fibrosin inclusion bodies when observed in a solution of 3% potassium hydroxide (KOH), and approximately 1 of 50 also displayed forked germ tubes. These features allowed us to identify P. xanthii as the causal agent. Conidia raised on the susceptible yellow melon 'Amarelo CAC' were used to inoculate cotyledons of the differential melon lines (2) 'Hale's Best Jumbo' (susceptible to races 1, 2, and 3 of P. xanthii), 'PMR-45' (resistant to race 1 and susceptible to races 2 and 3), and 'PMR-6' (resistant to races 1 and 2 and susceptible to race 3). Inoculations were performed on 10 plants of each differential line and replicated four times. The presence or absence of symptoms was evaluated 18 days after inoculation. 'Hale's Best Jumbo' and 'PMR-45' were rated as susceptible while 'PMR-6' was rated as resistant, thus indicating the presence of race 2 of P. xanthii in Brazil. During field surveys from 2001 to 2003, this race was found on squash (Cucurbita moschata), summer squash (C. pepo), and melons in São Paulo. References: (1) F. J. B. Reifschneider et al. Plant Dis. 69:1069, 1985. (2) C. E. Thomas et al. Cucurbit Genet. Coop. 7:126, 1984.
