Temperature and leaf wetness duration affect phenotypic expression of Rlm6-mediated resistance to Leptosphaeria maculans in Brassica napus.
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 degrees C and DarmorMX (carrying Rlm6) at 25 degrees C, but small dark spots and 'green islands' on DarmorMX at 5-20 degrees 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 degrees C but not at 15 degrees 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.
Huang
Yong-Ju
YJ
Rothamsted Research, Harpenden, Herts, AL5 2JQ, UK.
Evans
Neal
N
Li
Zi-Qin
ZQ
Eckert
Maria
M
Chèvre
Anne-Marie
AM
Renard
Michel
M
Fitt
Bruce D L
BD
D001203:Ascomycota / Q000254:growth & development; D029688:Brassica napus / Q000033:anatomy & histology / Q000235:genetics* / Q000382:microbiology*; D003433:Crosses, Genetic; D017343:Genes, Plant; D007113:Immunity, Innate / Q000235:genetics; D008954:Models, Biological; D010641:Phenotype; D010935:Plant Diseases / Q000382:microbiology*; D018515:Plant Leaves / Q000033:anatomy & histology / Q000235:genetics / Q000382:microbiology; D018547:Plant Stems / Q000033:anatomy & histology / Q000235:genetics / Q000382:microbiology; D013696:Temperature; D013997:Time Factors; D014867:Water
D014867:Water