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Temperature and leaf wetness duration affect phenotypic expression of Rlm6 ‐mediated resistance to Leptosphaeria maculans in Brassica napus
Author(s) -
Huang YongJu,
Evans Neal,
Li ZiQin,
Eckert Maria,
Chèvre AnneMarie,
Renard Michel,
Fitt Bruce D. L.
Publication year - 2006
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.2006.01651.x
Subject(s) - leptosphaeria maculans , biology , brassica , conidium , inoculation , spots , botany , horticulture , phenotype , plant disease resistance , gene , genetics
Summary• Near‐isogenic Brassica napus lines carrying/lacking resistance gene Rlm6 were used to investigate the effects of temperature and leaf wetness duration on phenotypic expression of Rlm6 ‐mediated resistance. • Leaves were inoculated with ascospores or conidia of Leptosphaeria maculans carrying the effector gene AvrLm6 . Incubation period to the onset of lesion development, number of lesions and lesion diameter were assessed. Symptomless growth of L. maculans from leaf lesions to stems was investigated using a green fluorescent protein (GFP) expressing isolate carrying AvrLm6 . • L. maculans produced large grey lesions on Darmor (lacking Rlm6 ) at 5–25 °C and DarmorMX (carrying Rlm6 ) at 25°C, but small dark spots and ‘green islands’ on DarmorMX at 5–20°C. With increasing temperature/wetness duration, numbers of lesions/spots generally increased. GFP‐expressing L. maculans grew from leaf lesions down leaf petioles to stems on DarmorMX at 25°C but not at 15°C. • We conclude that temperature and leaf wetness duration affect the phenotypic expression of Rlm6 ‐mediated resistance in leaves and subsequent L. maculans spread down petioles to produce stem cankers.