First Report of Colletotrichum chrysophilum Causing Anthracnose on Blueberry in Brazil.

Highbush (Vaccinium corymbosum L.) and rabbiteye (V. ashei R.) blueberry are the most important export small fruit crops in southern Brazil. Anthracnose has been considered one of the most destructive disease and exclusively associated with C. karstii in Brazil (Rios et al. 2014). In November 2019, severe anthracnose symptoms including leaf spots but particularly twig blights and fruit rots were observed on all blueberry plants (V. ashei) in one organic orchard in Santa Catarina state, Brazil (27º43'48.96"S, 49º0'57.79"W). Four isolates were obtained from necrotic lesions and monosporic cultures were grown on potato dextrose agar at 25°C and with a 12 h photoperiod under near ultra violet light. After 15 days, colonies showed upper surface color varying from grayish-white to pale-orange and the reverse side pale-orange. Conidia were hyaline, cylindrical with rounded ends, and their length and width ranged from 9.5 to 15.5 µm (x ̅=11.8) and 6.5 to 3.5 µm (x ̅=4.9), respectively. The isolates were identified by multilocus phylogenetic analyses using nucleotide sequences of actin (ACT), ß-tubulin (TUB2), calmodulin (CAL), glyceraldehyde-3-phosphate-dehydrogenase (GAPDH), glutamine synthetase (GS), internal transcribed spacer (ITS) and the intergenic spacer between DNA lyase and the mating-type locus MAT1-2-1 (ApMAT). Nucleotide sequences exhibited from 95 to 100% sequence identity to Colletotrichum chrysophilum ex-type (CMM4268) and were deposited in GenBank database (MW868219 to MW868222, MW868211 to MW868214, MW868215 to MW868218, MW868223 to MW868226, MW868202 to MW868205, MW793353 to MW793356, and MW868207 to MW868210). C. chrysophilum belongs to the C. gloeosporioides species complex and was previously described as C. ignotum in banana and other tropical fruits in Brazil (Vieira et al. 2017; Veloso et al. 2018). In addition, this species was recently reported on apple fruit in New York, USA (Khodadadi et al. 2020). To confirm pathogenicity, one-year-old blueberry plants were inoculated by spraying a suspension of 1×106 conidia/ml, incubated in a moist chamber in the dark for 48 h and then kept in the greenhouse. Plants sprayed with sterile distilled water served as control. Additionally, fruits were immersed for 2 min in a conidial suspension (1×106 conidia/ml) and incubated at 25°C and 12 h photoperiod for 20 days. Inoculated plants exhibited first symptoms in twigs at 10 days after inoculation (dai). Infected twigs showed initially dark brown spots that coalesced and became necrotic. On leaves, reddish-brown lesions with less than 2 mm appeared at low intensity at 15 dai. On fruits, sunken areas associated with an abundant orange mucilaginous mass of acervuli and conidia were seen at 7 dai. Symptoms on plants were identical to those observed under field conditions, and the pathogen was re-isolated from lesions fulfilling Koch's postulates. To the best knowledge, this is the first report of C. chrysophilum causing anthracnose on blueberries in Brazil. The identification of this species causing blueberry anthracnose is crucial to improve the disease control strategies and resistance breeding.

First Report of Colletotrichum karstii Causing Anthracnose on Strawberry in Brazil.

Strawberry (Fragaria x ananassa Duch.) is one of the most important fruit crops worldwide. With increasing cultivated area in the last decades, Brazil has become the largest strawberry producer in South America. Anthracnose caused by Colletotrichum spp. has been considered one of the most destructive diseases in Brazil. In May 2019, irregular and circular dark brown leaf spots sometimes associated with chlorosis and petiole necrosis were observed on strawberry plants (cv. Pircinque) organically cultivated in Santa Catarina state, Brazil (27°45'40"S, 49°59'06''W). The Colletotrichum isolate was obtained from leaf, and monosporic culture was grown on potato dextrose agar at 25°C and 12-h photoperiod under near ultraviolet light. Colonies at the age of 15 days showed upper surface color varying from white to orange and the reverse side grayish to orange. Conidia were hyaline, cylindrical with rounded ends, 13.9 to 9.2 × 4.2 to 6.7 µm ((x ) ̅= 11.3 × 5.2, n = 100). Perithecia were produced in vitro and their diameter ranged from 265.2 to 142.5 µm ((x ) ̅= 198.4). Asci were 47.3 to 39.9 × 5.2 to 7.2 µm ((x ) ̅= 42.8 × 5.9, n = 50), and ascospores 12.6 to 8.1 × 4.3 to 2.1 ((x ) ̅= 10.3 × 2.9, n = 100). To confirm pathogenicity, 90-day-old plants of strawberry (cv. Pircinque) were inoculated by spraying a suspension of 1×106 conidia/ml, incubated in a moist chamber in the dark for 48 h and then kept in a greenhouse for further 30 days. Plants sprayed with sterile distilled water served as control. Additionally, detached leaves were inoculated with six drops of 10 µl (1×106 conidia/ml) onto abaxial surface and incubated in a moist chamber at 25°C and 12 h photoperiod for 15 days. Inoculated plants exhibited first symptoms in both leaves and petioles at 15 days after inoculation (dai). On leaf, irregular and circular dark brown spots evolved to necrotic lesions and were frequently surrounded by chlorotic halos. In petioles, lesions were reddish-brown, elongated, and depressed. Typical anthracnose symptoms on fruits at 6 dai showed as circular, slightly sunken lesions that enlarged over time and produced an abundant orange mucilaginous mass of acervuli and conidia, and after 20 days, fruits became mummified. In the detached-leaf-assay, symptoms appeared at 7 dai, with presence of circular dark brown lesions measuring 1 to 15 mm and then evolved to necrosis. The same pathogen was consistently re-isolated from the inoculated leaves, petioles, and fruits, and confirmed by morphological characterization and molecular assays as described in this note. A representative isolate (MANE189) was molecularly identified using genomic regions of actin (ACT), ß-tubulin (TUB2), calmodulin (CAL), glyceraldehyde-3-phosphate-dehydrogenase (GAPDH), glutamine synthetase (GS), and internal transcribed spacer (ITS). Nucleotide sequences exhibited 100% homology to the typical Colletotrichum karstii strains (CBS:127535, CBS:128500 and ML1792) and were deposited in GenBank database (MW396420, MW396430, MW396460, MW396440, MW396450, and MW331606). This species belongs to the C. boninense species complex (Damm et al. 2012) and was previoStrawberry (Fragaria x ananassa Duch.) is one of the most important fruit crops worldwide. With increasing cultivated area in the last decades, Brazil has become the largest strawberry producer in South America. Anthracnose caused by Colletotrichum spp. has been considered one of the most destructive diseases in Brazil. In May 2019, irregular and circular dark brown leaf spots sometimes associated with chlorosis and petiole necrosis were observed on strawberry plants (cv. Pircinque) organically cultivated in Santa Catarina state, Brazil (27°45'40"S, 49°59'06''W). The Colletotrichum isolate was obtained from leaf, and monosporic culture was grown on potato dextrose agar at 25°C and 12-h photoperiod under near ultraviolet light. Colonies at the age of 15 days showed upper surface color varying from white to orange and the reverse side grayish to orange. Conidia were hyaline, cylindrical with rounded ends, 13.9 to 9.2 × 4.2 to 6.7 µm ((x ) ̅= 11.3 × 5.2, n = 100). Perithecia were produced in vitro and their diameter ranged from 265.2 to 142.5 µm ((x ) ̅= 198.4). Asci were 47.3 to 39.9 × 5.2 to 7.2 µm ((x ) ̅= 42.8 × 5.9, n = 50), and ascospores 12.6 to 8.1 × 4.3 to 2.1 ((x ) ̅= 10.3 × 2.9, n = 100). To confirm pathogenicity, 90-day-old plants of strawberry (cv. Pircinque) were inoculated by spraying a suspension of 1×106 conidia/ml, incubated in a moist chamber in the dark for 48 h and then kept in a greenhouse for further 30 days. Plants sprayed with sterile distilled water served as control. Additionally, detached leaves were inoculated with six drops of 10 µl (1×106 conidia/ml) onto abaxial surface and incubated in a moist chamber at 25°C and 12 h photoperiod for 15 days. Inoculated plants exhibited first symptoms in both leaves and petioles at 15 days after inoculation (dai). On leaf, irregular and circular dark brown spots evolved to necrotic lesions and were frequently surrounded by chlorotic halos. In petioles, lesions were reddish-brown, elongated, and depressed. Typical anthracnose symptoms on fruits at 6 dai showed as circular, slightly sunken lesions that enlarged over time and produced an abundant orange mucilaginous mass of acervuli and conidia, and after 20 days, fruits became mummified. In the detached-leaf-assay, symptoms appeared at 7 dai, with presence of circular dark brown lesions measuring 1 to 15 mm and then evolved to necrosis. The same pathogen was consistently re-isolated from the inoculated leaves, petioles, and fruits, and confirmed by morphological characterization and molecular assays as described in this note. A representative isolate (MANE189) was molecularly identified using genomic regions of actin (ACT), ß-tubulin (TUB2), calmodulin (CAL), glyceraldehyde-3-phosphate-dehydrogenase (GAPDH), glutamine synthetase (GS), and internal transcribed spacer (ITS). Nucleotide sequences exhibited 100% homology to the typical Colletotrichum karstii strains (CBS:127535, CBS:128500 and ML1792) and were deposited in GenBank database (MW396420, MW396430, MW396460, MW396440, MW396450, and MW331606). This species belongs to the C. boninense species complex (Damm et al. 2012) and was previously reported causing anthracnose on strawberry leaves in Taiwan (Chung et al. 2020). To our knowledge, this is the first report of C. karstii causing anthracnose on strawberry in Brazil. The accurate identification of the pathogen will assist in the disease management and resistance breeding. usly reported causing anthracnose on strawberry leaves in Taiwan (Chung et al. 2020). To our knowledge, this is the first report of C. karstii causing anthracnose on strawberry in Brazil. The accurate identification of the pathogen will assist in the disease management and resistance breeding.

Herbaspirillum seropedicae promotes maize growth but fails to control the maize leaf anthracnose.

Herbaspirillum seropedicae is an endophytic diazotrophic bacterium and a plant growth promoting bacteria. Colletotrichum graminicola causes the anthracnose, one of the most destructive maize diseases worldwide. The main objective of this work was to evaluate the effects of H. seropedicae SmR1 strain on the plant growth and leaf anthracnose of maize plants grown in substrate amended or not amended with humic substances. In the first assay, plants were pre-treated with H. seropedicae and inoculated with C. graminicola at 7, 14 and 21 days after treatment (DAT). In the second assay, plants were treated with H. seropedicae, grown in substrate amended with humic substances and inoculated at 3 and 7 DAT. The anthracnose severity was assessed by measurement of necrotic and chlorotic leaf area, and bacteria were quantified in leaves by quantitative PCR. H. seropedicae did not affect the disease severity in maize leaves, although it efficiently colonized the leaf tissues and it promoted maize leaf growth. Humic substances improved H. seropedicae colonization in maize.

Extracellular enzymes of Colletotrichum fructicola isolates associated to Apple bitter rot and Glomerella leaf spot.

Colletotrichum fructicola causes two important diseases on apple in Southern Brazil, bitter rot (ABR) and Glomerella leaf spot (GLS). In this pathosystem, the Colletotrichum ability to cause different symptoms could be related to differences of extracellular enzymes produced by the fungi. Thus, the objectives of this study were to compare the production of these enzymes between ABR- and GLS-isolate in vitro and to evaluate their involvement on infected apple leaves with C. fructicola. In agar plate enzymatic assay, ABR- showed significantly higher amylolytic and pectolytic activity than GLS-isolate. In contrast, for lipolytic and proteolytic no significant differences were observed between isolates. In culture broth, ABR-isolate also had higher activity of pectin lyase (PNL), polygalacturonase (PG) and laccase (LAC). Notably, LAC was significantly five-fold higher in ABR- than GLS-isolate. On the other hand, in infected apple leaves no significant difference was observed between isolates for PNL, PG and LAC. Although differences in extracellular enzymes of ABR- and GLS-isolate have not been observed in vivo, these results contributed to highlight the importance to investigate such enzymes in depth.

Modulation of oxidative responses by a virulent isolate of Colletotrichum fructicola in apple leaves.

Apple bitter rot (ABR) and Glomerella leaf spot (GLS) can be caused by Colletotrichum fructicola. Although both diseases can occur simultaneously in orchards, some isolates show clear organ specialization. Thus, this work was aimed to compare microscopically the development of preinfective structures of ABR- and GLS isolates and their impact on the enzymatic oxidant defense system during the leaf infection process. On leaves, conidial germlings of GLS-isolate formed appressoria mostly sessile. In contrast, those of ABR-isolate were pedicellate and formed multiple melanized appressoria probably as a sign of unsuccessful infection attempts. Neither ABR- nor GLS isolate triggered hypersensitive response in apple leaves. In overall, the activity of scavenging enzymes was higher and long-lasting in leaves inoculated by GLS- than by ABR isolate and control. Guaiacol peroxidase, catalase, and glutathione reductase had activity peaks within 24 h after inoculation (HAI). Ascorbate peroxidase activity was higher only in GLS-infected leaves at 6 HAI, while superoxide dismutase remained unaltered. A lower level of hydrogen peroxide (H2O2) was determined in GLS-infected plants at 48 HAI, but the electrolyte leakage markedly increased. Disease symptoms in leaves were only caused by GLS-isolate. Results suggest that the virulent isolate coordinately downregulates the oxidative plant defense responses enabling its successful establishment in apple leaves.

New insights into the characterization of Colletotrichum species associated with apple diseases in southern Brazil and Uruguay.

Colletotrichum species are associated with Apple bitter rot (ABR) and Glomerella leaf spot (GLS). Whereas both apple diseases occur frequently in Brazil, only the former has been reported in Uruguay. This work was aimed at identifying and comparing morpho-cultural characteristics and pathogenic variability of thirty-nine Colletotrichum isolates from both countries. Sequencing of the internal transcribed spacer (ITS) rDNA, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and ß-tubulin (TUB2) allowed the identification of three species causing ABR and GLS in Brazil, i.e., Colletotrichum fructicola, Colletotrichum karstii, and Colletotrichum nymphaeae; and three species causing ABR in Uruguay, i.e., C. fructicola, Colletotrichum theobromicola, and Colletotrichum melonis. Six groups of colony colours were recorded with group 1 (mycelium white to pink and in reverse pinkish) and group 2 (mycelium white to grey and in reverse pinkish) the most frequent. Isolates of C. fructicola and C. theobromicola were sensitive to benomyl, while C. karstii, C. nymphaeae, and C. melonis were resistant. Conidia were predominantly cylindrical for C. fructicola and C. karstii, fusiform for C. nymphaeae and C. melonis, and obclavate for C. theobromicola. Brazilian isolates caused ABR in wounded fruits, but only five in non-wounded ones. Uruguayan isolates produced symptoms in fruits with or without previous wounding. All Brazilian isolates from GLS and twelve from ABR were able to cause GLS symptoms, while a sole Uruguayan ABR-isolate caused leaf spot symptoms. This study gives a better insight on the new species causing apple disease in both countries and discusses their pathogenic potential.