INFECTIVITY AND IN VITRO PRODUCTION OF SWEET POTATO SCAB FUNGUS (Sphaceloma batatas Saw.) INOCULUM

Abstract

Sweet potato stem agar and exposure to continuous darkness supported the most abundant conidial production of Sphaceloma batatas. Saw. Sweet potato stem agar produced 19 times more conidia than sweet potato tuber agar and almost 3 times more conidia than potato dextrose agar. Sporulation in carrot agar peaked at 12-15 days after seeding and harvestable conidia generally declined after 18 days of incubation. Multipoint seeding of agar slants hastened sporulation and increased conidial production by almost 6 times compared to single-point seeding. Infectivity of conidia decreased with age of agar culture probably due to the drastic decline in conidial viability with age. Conidia from 1-week old agar cultures were most infective on sweet potato internodes and leaves.