PATHOGENICITY OF A SPECIES OF PHOMOPSIS CAUSING A SHOOT BLIGHT ON PEACH IN GEORGIA AND EVALUATION OF POSSIBLE INFECTION COURTS

A species of Phomopsis was isolated consistently from blighted shoots of peach trees in Georgia and Alabama. Isolates of the fungus caused c haracteristic cankers on current season's shoots of Babygold-7 peach t rees when wounded or nonwounded dormant buds, breaking buds, and natur al or artificially-created leaf scars were inoculated with conidia of the fungus. Mean canker length for the isolates was 35 mm 30 days afte r inoculation. No disease developed on control trees. There was no sig nificant difference between the canker length on inoculated wounded do rmant buds (59 mm) and nonwounded breaking buds (54 mm). However, cank ers from both sites of inoculation were significantly longer than thos e resulting from inoculated artificially-created leaf scars (33 mm), n atural leaf scars (33 mm), and non-wounded dormant buds (30 mm). There was no significant difference in virulence among the 5 isolates of Ph omopsis sp. tested, and multi-locus DNA fingerprint analysis resulted in a similarity coefficient of 0.94 among the isolates. Additionally, results of the internal transcribed spacer (ITS) regions sequence comp arisons for the isolates were consistent with the multi-locus polymera se chain reaction profiles, and the nucleotide sequences of the ITS re gion were identical for all 5 isolates. This is the first documentatio n of the pathogenicity of a Phomopsis sp. associated with shoot blight of peach in Georgia. Rapid development of disease in breaking buds in dicates that they may be the primary site of invasion by the fungus. N atural leaf scars and dormant buds may also serve as possible infectio n courts.