The relationship between the amount of Verticillium dahliae in soil and the incidence of strawberry wilt as a basis for disease risk prediction

Abstract

The incidence of wilt was recorded in runner and fruiting crops of 13 strawberry cultivars at 72 locations in southern England in 1989 and 1990, and soil samples from the sites were analysed for Verticillium dahliae. Linear regressions of wilt incidence on inoculum concentration in soil for runner crops of the susceptible cv. Elsanta in both years were significant whilst that for runner crops of the susceptible cv. Hapil in 1989 approached significance; the regression for cv. Elsanta fruiting crops in 1990 was not significant. The inclusion of sand content of soil in the regression model improved the fit for the cv. Hapil data but not for the cv. Elsanta data; neither clay nor silt content of soil significantly improved the fit of the models for any data set. There were insufficient data in either year for regression analysis for other cultivars, but the levels of wilt generally corresponded with the degree of soil infestation and broadly reflected known field resistance. The data were used to estimate an inoculum concentration which corresponds to 5% wilt incidence (IC5) for cv. Elsanta. It is suggested that this could be used as a yardstick for determining the risk of unacceptable levels of wilt in susceptible cultivars on the basis of pre‐planting soil analysis. For the 44 sites where the cropping history over the 15 years prior to soil analysis was available there was no clear association between any crop and soil infestation levels at or above the IC5. However, V. dahliae was more common at sites with a history of vegetatively propagated crops than at sites which had only supported crops grown from true seed.

Spatiotemporal Analysis of Spread of Infections by Verticillium dahliae Pathotypes Within a High Tree Density Olive Orchard in Southern Spain

“…In our study, the distribution of Verticillium wilt-diseased olive trees in the orchard followed aggregated patterns, similarly to that described for diseases caused by other soilborne pathogens (7). An aggregated pattern of diseased plants may correspond to an aggregated distribution of the pathogen in the primary source of inoculum, but also results from secondary infections by the spread of inoculum from primary foci to healthy plants (15) (4,18,34) at planting play a critical role in the spatial patterns of diseased plants and wilt development in many crops.…”

Comparison of Crop Rotation for Verticillium Wilt Management and Effect on Pythium Species in Conventional and Organic Strawberry Production

“…Another potential explanation is that even low densities of V. dahliae may incite high wilt incidences on strawberries. Harris and Yang (15) reported that on very susceptible cultivars, 3.8 CFU/g of soil incited 29% wilt. In our study, densities of V. dahliae in fumigated soils were lower than 2 CFU/g of soil, and wilt incidences in these soils were 15.3 and 24.4% in 2001 and 2002, respectively.…”

Verticillium wilt caused by Verticillium dahliae in woody plants with emphasis on olive and shade trees

“…Also, there is a correlation between inoculum density and final disease incidence values (López Escudero and Blanco-López 2007; Bejarano- Alcázar et al 1995). Moreover, it has been observed that for a given inoculum density, disease incidence varies greatly depending on the crop (Berbegal et al 2007;Xiao and Subbarao 1998;Grogan et al 1979;Harris and Yang 1996;Atallah et al 2011). Consequently, validation and standardization of V. dahliae inoculation methods and inoculum density is needed to provide accurate assessment of wilt resistance in tree hosts.…”