Location: Subtropical Plant Pathology Research
Title: First report of Colletotrichum lupini on Lupinus hartwegii and L. mutabilis Authors
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 8, 2013
Publication Date: N/A
Interpretive Summary: Florida producers of cut flowers grow many species and varieties to meet market demands. They must often rotate crops in order to avoid producing plants that are highly susceptible to plant diseases and nematodes. In the late 1930s, anthracnose of lupin was reported from North Florida on the species Lupinus angustifolius. The disease was caused by the fungus, Glomerella cingulata. Since that time, different species of lupin have been grown by commercial producers. In 2013, a severe epidemic of anthracnose was observed at a commercial flower farm, on another lupin species, L. mutabilis. The fungus that was isolated from these plants was tested for pathogenicity to L. mutabilis and L. hartwegii, two more commonly grown species of lupin. The isolate was pathogenic and was identified using DNA sequencing and morphological characters as Colletotrichum lupini, a recently defined species. Although it is not possible to determine if these two isolates represent the same fungus, it does not seem likely. Finding of a lupin anthracnose in southeastern Florida is important to both the cut flower producers as well as vegetable producers who might consider some species of Lupinus as potential green manure crops. To the best of our knowledge, this is the first report of C. lupini or any Colletotrichum species on L. hartwegii and L. mutabilis in Florida.
Technical Abstract: During the 2013 winter cut flower production season, a severe anthracnose epidemic was observed on Lupinus mutabilis (syn L. cruckshanksii) on a commercial flower farm in Martin County, FL. Approximately 50% of the crop was lost to the disease. Symptoms included mild leaf spots, but more typically, stems were severely twisted, forming a distinctive necrotic crook. Margins of necrotic lesions were excised and surface sterilized by immersion in 1% sodium hypochlorite for 90 s, rinsed in sterile deionized water, and plated onto potato dextrose agar (PDA). Plates were incubated at approximately 27°C with cycles of 12 h light/12 h darkness. Infected tissue consistently produced colonies that were typical of the genus Colletotrichum. Conidia were primarily oval, with one rounded end and one pointed end. Cultures were gray with orange spots, and no setae were observed. These morphological characteristics are consistent with those of Colletotrichum lupini (2). Identification of this species was confirmed by performing a BLASTn search with ITS sequence data (primers ITS4 and ITS5), which shared 99% identity with GenBank submission AJ301968, C. lupini var. setosum strain BBA 71310, isolated from L. luteus in Poland. Inoculum was produced on PDA; the plates were flooded with sterile deionized water, scraped with a rubber policeman, and the liquid passed through 4 layers of sterile cheesecloth. This preparation was used to inoculate 10 L. mutabilis and 10 L. hartwegii plants by injecting 10 µl of a suspension of 105 conidia/ml into the stem using a hypodermic needle (1). Ten additional plants were injected with sterile deionized water and maintained with the inoculated plants in the greenhouse for four weeks. All of the inoculated plants developed the previously-observed necrotic crook in the stem, whereas control plants developed no symptoms. The same organism was isolated from all inoculated plants. The ITS region was again sequenced, and the Polish strain was the closest match. The Floridian isolate’s sequence was deposited in GenBank (accession KF207599). In 1939, research plots of L. angustifolius were found with symptoms of anthracnose caused by Glomerella cingulata (3). Although it is not possible to determine if this isolate would be redefined as C. lupini, it does not seem likely since pathogenicity was confirmed on L. angustifolius and L. albus, but it did not cause infection on L. luteus (3) as has been reported for C. lupini (2). Finding of a lupin anthracnose in southeastern Florida is important to both the cut flower producers as well as vegetable producers who might consider some species of Lupinus as potential green manure crops. To the best of our knowledge, this is the first report of C. lupini or any Colletotrichum species on L. hartwegii and L. mutabilis in Florida.