Anthracnose caused by Colletotrichum species is the most important disease of chayote (Sicyos edulis) in Brazil. The etiology of chayote anthracnose has been assigned to the species C. orbiculare, an important plant pathogenic fungus also reported as the causal agent of anthracnose in other cucurbits worldwide. However, there is no recent survey of the Colletotrichum species causing anthracnose in chayote in Brazil. In this study, Colletotrichum isolates associated with anthracnose on the fruit and leaves of chayote, from various producing regions in Brazil, were collected and identified. Haplotype analysis based on sequences of the β-tubulin genomic region (TUB2) of 44 Colletotrichum isolates was carried out as a first measure of genetic diversity. A subset of 22 isolates were sequenced using the partial sequences of actin (ACT), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and the rDNA ITS (ITS) region. Maximum likelihood analysis was performed using the concatenated sequences. The multilocus sequence analysis revealed four previously described species, Colletotrichum chrysophilum, C. menezesiae, C. plurivorum, and C. karsti, and two novel species, named C. cucurbitacearum and C. sicyi. All species were able to induce typical symptoms of anthracnose in chayote fruits but varied in their aggressiveness. The species C. menezesiae and C. sicyi were the most aggressive, while C. plurivorum was the least aggressive. The species C. orbiculare was not found to cause chayote anthracnose in Brazil.

Scarlet eggplant (Solanum aethiopicum var. gilo) is a Solanaceae with an appreciated peculiar bitter taste, which plays a significant role in family farming in Brazil. Fruit anthracnose is the main pre- and postharvest disease that affects scarlet eggplant in Brazil. This study aimed to evaluate the effect of chitosan-based coating on in vitro inhibition of Colletotrichum tamarilloi and anthracnose control of scarlet eggplant fruits. Chitosan was dissolved in a 2% citric acid solution at 40°C and then homogenized with potato dextrose agar (PDA), and poured into Petri dishes, as follows: 1) PDA + 0.1% chitosan, 2) PDA + 0.2% chitosan, 3) PDA + 0.3% chitosan, 4) PDA + 0.4% chitosan, and 5) pure PDA as control. Discs of 5 mm diameter of pure fungus culture were placed on the center of the culture medium in the plates. The plates were then maintained in BOD at 25°C and 12-h photoperiod for 10 days. Colony characteristics, mycelial growth rate, and mycelial growth inhibition were evaluated. Afterward, the effect of chitosan coating was evaluated in fruit inoculated or not with C. tamarilloi. The treatments were: T1) uncoated and injured uninoculated fruits, T2) uncoated and inoculated fruit, T3) fruits coated with 0.1% chitosan and inoculated, T4) fruits coated with 0.2% chitosan and inoculated, and T5) fruits coated with chitosan at 0.3% and inoculated. For inoculation, 15 μL of a conidial suspension (2 x 10⁵ conidia/mL) were deposited on an injury caused by a needle, and the fruits were coated by immersion into the different concentrations of chitosan gel. Fruits were placed on expanded polystyrene trays. Fresh weight loss, the mean incidence of disease, and lesion diameter were measured. All concentrations of chitosan reduced the in vitro growth of C. tamarilloi. The treatment T4 reduced the severity of anthracnose but did not prevent its incidence in scarlet eggplant fruits.

A new pathogenic Colletotrichum species was isolated from chayote (Sicyos edulis) leaves and fruit presenting typical anthracnose symptoms from fields in Ibirité (Minas Gerais state) and Tijucas (Santa Catarina state), Brazil. The species Colletotrichum menezesiae sp. nov. is described and illustrated. Multilocus phylogenetic analyses based on combined ACT, GAPDH, nrITS and TUB2 partial sequences revealed that Colletotrichum isolates from chayote form a distinct clade within the C. orbiculare species complex. This clade does not contain the ex-type of any species previously described and is also recognized as an independent lineage according to the GCPSR criteria.