CROSS-INFECTION OF SUBTROPICAL AND TEMPERATE FRUITS BY COLLETOTRICHUMSPECIES FROM VARIOUS HOSTS

Forty-two isolates of Colletotrichum gloeosporioides for almond, apple , avocado, mango, pecan, and eight isolates of C. acutatum from apple, peach and pecan were compared by molecular analyses and a pathogenici ty assay in order to determine genetic variability and host specificit y. Polymerase chain reaction (PCR) amplification of genomic DNA using four different primers and HaeIII digestion pattens of genomic DNA (A + T-rich DNA) grouped the C. acutatum isolates separately form the C. gloeosporioides isolates. Based on arbitrarily primed PCR (ap-PCR), in traspecies similarity among the isolates of C. acutatum and C. gloeosp orioides ranged from 78 to 93% and from 0 to 38%, respectively. Simila rity between the isolates of C. acutatum and C. gloeosporioides ranged from 0 to 26.5%. A + T-rich DNA grouped the C. acutatum isolates sepa rately from those of C. gloeosporioides, corresponding to ap-PCR analy ses. Artificial inoculations with nine representative isolates on almo nd, apple, avocado, mango and nectarine fruit showed a variation in le vels of infection. The C. gloeosporioides isolates from almond grew mo re slowly, causing significantly smaller lesions on all inoculated fru it than the other isolates. The C. acutatum isolates from apple and pe ach and caused similar levels of infection on all fruit, but differed significantly from the C. gloeosporioides isolate from apple. Variatio n in lesion size was also observed with isolates of C. gloeosporioides from apple, avocado and mango for most fruit inoculations. (C) 1996 A cademic Press Limited.