Antagonism of white mold (Sclerotinia sclerotiorum) of bean by fungi from bean and rapeseed flowers

Abstract

1989. Antagonism of white mold (Sclerotinia sclerotiorum) of bean by fungi from bean and rapeseed flowers. Can. J. Bot. 67: 1775-1781. Filamentous fungi from white bean and rapeseed flowers were isolated, characterized, and evaluated for potential as antagonists to Sclerotinia sclerotiorum (Lib.) de Bary. Various fungi were isolated from surface-sterilized petals sampled from four developmental stages ranging from freshly opened flowers to petals that had lodged on plant surfaces. Alternaria and Cladosporium spp. were the dominant mycoflora and were isolated from 65-100% of the petals that developed fungal colonies. All isolates, except one, restricted ascospore germination by the pathogen on water agar by 16-66%, and 13 of 28 isolates restricted mycelial growth on potato dextrose agar by 29-46%. Bean flowers were inoculated with spore suspensions of S. sclerotiorurn and of individual antagonists and were then placed on detached bean leaves, bean seedlings, and flowering bean plants. On detached leaves in a laboratory environment, 16 of 28 isolates suppressed white mold lesion diameter by 10-100%. On bean seedlings in a growth room, 8 isolates suppressed the percentage of flowers developing lesions by 42-loo%, and 12 of 13 isolates reduced mean lesion diameter by 14 -100%. On flowering bean plants in a greenhouse, 6 of 11 isolates suppressed the percentage of flowers developing lesions by 14 -90%. The most disease-suppressive fungi included isolates of Drechslera sp., Epicoccum purpurascens, Fusarium graminearum, and Fusarium heterosporum; isolates of Myrothecium verrucaria ind ~richodermi viride were effective in some trials. BOLAND, G. J., et INGLIS, G. D. 1989. Antagonism of white mold (Sclerotinia sclerotiorum) of bean by fungi from bean and rapeseed flowers. Can. J. Bot. 67 : 1775 -1781. Les auteurs ont is016 des champignons filarnenteux i partir de fleurs de haricot blanc et de colza et ils ont CvaluC leur potentie1 comme antagonistes contre le Sclerotinia sclerotiorum (Lib.) de Bary. 11s ont isolt divers champignons i partir de pttales stCrillisCs superficiellement et CchantillonCs i quatre stades de dtveloppement i partir de la fleur fraichement Cclose jusqu'aux petales tombts sur les surfaces de la plante. Les Alternaria et les Cladosporium spp. dominent la flore et proviennent de 65 21 100% des pCtales qui ont dtveloppC des colonies fongiques. Tous les isolats, sauf un, attCnuent la germination des ascospores entre 16 et 66% sur eau gClosCe, et 13 des 28 isolats diminuent la croissance mycClienne entre 29 et 46% sur extrait de pomme de terre gClosC. Des fleurs de haricot ont Ctk inoculCes avec des suspensions de spores du S. sclerotiorum et celles des antagonistes individuels et ont ensuite kt6 plactes sur des feuilles de haricot dCtachCes, sur des plantules de haricot et sur des plants de haricot en fleur. Sur feuilles dCtachtes en conditions de laboratoire, 16 des 28 isolats ont dirninuC le dCveloppernent des lCsions fongiques en diamktre entre 10 et 100%. Sur les plantules de haricot en chambre de cr...

Interactions of air temperature, relative humidity and biological control agents on grey mold of bean

“…Thebehaviour of E. purpurascens may be attributable to its ecological competence or to a different mechanism of biocontrol action, such as antibiosis, which might be independent of the atmospheric environment. Studies of the mechanism(s) of action of this B CA have reported that both competition and antibiosis may be important in disease suppression [Boland and Hunter, 1988;Boland and Inglis, 1989;Mercier and Reeleder, 1987;Zhou and Reeleder, 1990;Zhou etal., 1991].…”

“…After plants had started flowering (3-4 wk), bean petals at stages A (attached, recently opened flowers) and B (attached flowers that had started to wilt or senesce) [Boland and Inglis, 1989] were collected daily until flowering ceased. The petals were sterilized using propylene oxide according to Inglis [1989]. Aliquots of 2 ml propylene oxide at 4 ~ were pipetted into desiccation chambers where the petals were arranged in single layers on a perforated screen.…”

“…Isolates of A. alternata (B639), and E. purpurascens (D224) were cultured from rapeseed petals [Inglis, 1989]. Drechslera sp.…”

“…ex Steudel (B24), and Trichoderma viride Pers. ex (BC34) were isolated from rapeseed or bean petals [Boland and Inglis, 1989]. Isolates of Gliocladium roseum Bain.…”

“…In each trial, inoculated plants were incubated for 96 h, the optimum time required for disease development according to preliminary experiments [Inglis, 1989], and disease was then assessed. The diameter of lesions that formed beneath the infested petals on bean leaves were measured using callipers.…”