Differential production of sclerotia by isolates ofSclerotinia sclerotiorumfrom Alaska

Abstract

Sclerotinia sclerotiorum was isolated from lettuce (Lactuca sativa) grown in Alaska. Sections of cabbage (Brassica oleracea var. capitata) and lettuce were inoculated with isolates A and B. Sclerotia of S. sclerotiorum were counted and weighed after the host tissue decomposed. Isolate A produced a mean of 42 sclerotia weighing 1.9 g on 100 g of cabbage 'Balbro', which was twice the number of sclerotia and triple the biomass produced by isolate B. On three cultivars of lettuce, isolate A had a greater mass and a similar number of sclerotia compared with isolate B. Carrot (Daucus carota subsp. sativus) and celery (Apium graveolens) were also inoculated to measure production of sclerotia. Differences between isolates of S. sclerotiorum were less pronounced on carrot and celery, but the difference between hosts was significant. The mean mass of sclerotia for isolate A was 73 mg on carrot and 18 mg on celery. Isolates A and B were distinct in the rDNA intergenic spacer sequences. Isolate A had identical sequences to those reported for some isolates from United States and Canada, whereas isolate B matched different isolates from United States, Canada, and New Zealand. Both isolates belong to a relatively recently evolved group exhibiting significant associations between genotype and both geography and host species. In agricultural fields, one infection of S. sclerotiorum on lettuce or cabbage can produce hundreds of new sclerotia that may affect levels of disease in future years. Cultural control can include minimizing the amount of sclerotia on crop residue by disking soon after harvest. Résumé :Le Sclerotinia sclerotiorum a été isolé de laitues (Lactuca sativa) cultivées en Alaska. Des sections de chou (Brassica oleracea var. capitata) et de laitue ont été inoculées avec les isolats A et B. Les sclérotes de S. sclerotiorum ont été comptées et pesées après la décomposition des tissus de l'hôte. L'isolat A a produit, en moyenne, 42 sclérotes pesant 1,9 g par 100 g de chou 'Balbro', ce qui est deux fois le nombre de sclérotes et trois fois la biomasse produits par l'isolat B. Avec trois cultivars de laitue, l'isolat A a produit une plus grande masse que l'isolat B, mais un nombre semblable de sclérotes. Afin de mesurer la production de sclérotes, des carottes (Daucus carota subsp. sativus) et du céleri (Apium graveolens) ont aussi été inoculés. Les différences entre les isolats de S. sclerotiorum étaient moins grandes avec la carotte et le céleri, mais les différences entre les hôtes étaient significatives. La masse moyenne des sclérotes de l'isolat A était de 73 mg avec la carotte et de 18 mg avec le céleri. Les séquences des espaceurs intergéniques d'ADNr étaient différentes pour les isolats A et B. L'isolat A avait des séquences identiques à celles publiées pour certains isolats des États-Unis et du Canada, alors que l'isolat B correspondait à d'autres isolats des États-Unis, du Canada et de la Nouvelle-Zélande. Les deux isolats appartiennent à un groupe qui a évolué relativement récemment et pour lequel sont observé...

Volatiles from biofumigant plants have a direct effect on carpogenic germination of sclerotia and mycelial growth of Sclerotinia sclerotiorum

“…The number of sclerotia produced by S. sclerotiorum on different plant tissues is also variable and is an important factor in determining the inoculum levels in soil following an infected crop. For instance, an infected cabbage head was found to produce 250 to 500 sclerotia, (Leiner and Winton 2006) while an infected carrot root produced up to 30 (Jensen et al 2008). …”

Inoculum potential of Sclerotinia sclerotiorum sclerotia depends on isolate and host plant

“…In the same work, the weight of sclerotia produced by two different S. sclerotiorum isolates on three different iceberg lettuce varieties was in the range of 14-26 mg. By comparison, an almost identical weight range for S. sclerotiorum sclerotia produced on lettuce (13-28 mg) was observed in the current study, but much smaller sclerotia were produced on carrot (12-14 mg), with the largest sclerotia produced on OSR (33-60 mg). Leiner & Winton (2006) also estimated that 250-500 sclerotia might be produced on a single iceberg lettuce plant depending on S. sclerotiorum isolate, which is substantially more sclerotia than observed on the infected butterhead lettuce in this work (55-122 per plant). However, this might be explained by iceberg lettuce forming a dense compact head similar to a cabbage, which would have a much greater biomass and hence sustain a greater level of sclerotial production than the open, leafy butterhead type of lettuce used here.…”

“…Interestingly, the three S. sclerotiorum isolates showed a consistent pattern of sclerotial production irrespective of crop type; L6 produced large numbers of small sclerotia while L44 produced small numbers of large sclerotia, with L17 intermediate between the two. Leiner & Winton () also observed that one of the two S. sclerotiorum isolates they examined consistently produced more sclerotia on cabbage, carrot, celery and lettuce tissue. As well as being more numerous, the sclerotia from this isolate were also larger.…”

“…However, few researchers have attempted to investigate and quantify the effect of crop type and S. sclerotiorum isolate on the production of sclerotia and hence understand how these factors might influence subsequent inoculum pressure. This is the first study to investigate differences in sclerotial production on whole plants rather than on detached tissue, which was the approach used in a previous study by Leiner & Winton (2006). Here, a greater number of sclerotia were produced on carrot pieces compared to celery and these were also larger, with weights in the range of 38-90 mg compared to 14-18 mg (Leiner & Winton, 2006).…”

“…This is the first study to investigate differences in sclerotial production on whole plants rather than on detached tissue, which was the approach used in a previous study by Leiner & Winton (). Here, a greater number of sclerotia were produced on carrot pieces compared to celery and these were also larger, with weights in the range of 38–90 mg compared to 14–18 mg (Leiner & Winton, ).…”