A Model Integrating Components of Rate‐reducing Resistance to Cercospora Leaf Spot in Sugar Beet

Abstract

Four components of rate‐reducing resistance to Cercospora leaf spot in sugar beet (infection efficiency of conidia RC1, incubation period RC2, size of necrotic spots RC3 and spore yield RC4), previously measured in single infection cycle experiments, were integrated into a model simulating the chain of infection cycles under field conditions, as influenced by weather. To integrate resistance components, variables accounting for infection frequency, incubation period, affected leaf area, and infectiousness – which are computed for a susceptible cultivar – were modified by means of coefficients which reduced (RC1, RC3, RC4) or increased (RC2) them. Outputs obtained by running the model and changing resistance components actually reduced the rate of disease progress and the area under the disease progress curve of epidemics (AUDPC), as happens at field level; therefore, the approach may be considered successful. Changes in single resistance components were closely correlated with changes in AUDPC: improvements in RC1, RC3 or RC4 reduced AUDPC by the same, over the whole range of variation in infection frequency, affected leaf area, and infectiousness; on the contrary, little improvements in RC2 were more effective than stronger ones. When components acted simultaneously, each of them reduced disease progress in proportion to its magnitude; when all components were improved by the same amount, they had about the same effectiveness in slowing the epidemic. Changing more components simultaneously reduced the disease development slightly more than additively. Advantages for plant breeders in improving their selection strategies are outlined.

Trichoderma as a potential biocontrol agent for Cercospora leaf spot of sugar beet

“…The reduction of the spore yield is considered a very important parameter for the control of C. beticola and one of the most effective resistance components for sugar beet genotypes (Rossi et al 2000).…”

“…This type of resistance is rate-reducing, i.e. it reduces the rate of the disease progress, and is characterised by several components: length of incubation, infection efficiency of conidia, size of necrotic spots, conidiation length and spore yield on necrotic spots (Rossi et al 1999(Rossi et al , 2000. Since a high degree of resistance correlates with low-yielding genotypes, most commercial varieties are only moderately resistant and repeated fungicide applications are needed, especially in more affected areas (Weiland and Koch 2004).…”

Non-Invasive Spectral Phenotyping Methods can Improve and Accelerate Cercospora Disease Scoring in Sugar Beet Breeding

“…vulgaris) are frequently infested by the fungal pathogen Cercospora beticola that occurs in moderate climatic areas and causes yield loss between 40% and 100% [1,2]. Plant protection against Cercospora leaf spot (CLS) usually includes crop rotation, fungicide application, and the use of resistant cultivars [1].…”

Cercosporoid fungi of Poland

“…The progressive infection process as well as withering of other leaves and production of new leaves lead to formation of distinctive conical roots. As a result, inhibition of the weight increase occurs, accompanied by a decline in the sugar content and technological quality of juice [109,116,117].…”