Characteristics and Control of Colletotrichum gloeosporioides Isolates in Behera Governorate, Egypt

Eight isolates of Colletotrichum gloeosporioides were recovered from guava and banana fruits showed anthracnose symptoms collected from different orchards in Behera Governorate. Isolates were characterized according to types of colony colour, colony diameter, conidium shape and size, appressorium shape and size and the effect of different temperature degrees on isolates radial growth. The isolates showed mostly gray colony phenotype while the olive-gray and the dark-gray phenotypes were also existed in four out of the investigated eight isolates. Diameter of the developed colonies ranged between 80 and 85 mm. Conidia of the developed eight isolates were mostly monomorphic and exhibited cylindrical, hyaline conidia with size ranged between 14.5 and 19.1 μm for length and 4.4 and 6.5 μm for width. Clavate appressoria were recorded in all isolates. Irregular appressoria were also recorded accompanied with the clavate ones in five of the eight investigated isolates. The optimal temperature for radial growth was 25°C with rate of 8.0 - 8.37 cm, five days after inoculation. All isolates were pathogenic on different host species Guava cv. Balady, Apple cv. Golden Delicious, Banana cvs. Balady and Grantidin, Mango cv. Ewasy and Pepper cv. Balady. Apple fruits were the most susceptible for the infection by C. gloeosporioides isolates while pepper was the most tolerant for the infection. Moreover RAPD-PCR analysis using five random oligonucleotide primers revealed DNA fingerprints and considerable variations were revealed with primers tested. However, the RAPD-PCR phylogenetic analysis did not reveal known genetic entities for isolates from each guava and banana, since it did revealed two clusters for the highly virulent isolates and the moderately virulent isolates in the dendrogram of the tested C. gloeosporioides isolates. Anthracnose control of fruits by chitosan as a natural product was tested. The in vitro 2.5 % chitosan application significantly inhibited the growth of C. gloeosporioides isolates tested by 96.6 % on agar plates. The in vivo tests on fruits of different species, i.e. banana, mango, apple and guava confirmed the in vitro results. The chitosan treatment to artificially infected fruits reduced the development of symptoms, at the different chitosan concentrations, i.e. 1.5%, 2% and 2.5%. The 2.5% chitosan was the most affective concentration for anthracnose control in the different fruit species. The study supported the view that chitosan offers a safe alternative to synthetic fungicides in postharvest anthracnose diseases control and could be considered as a potential agrochemical of low environment impact.