Articles
Revisions to class-based eastern filbert blight ratings to reflect variation in quantitative resistance
Article number
1379_21
Pages
141 – 148
Language
English
Abstract
The causal pathogen of eastern filbert blight (EFB), Anisogramma anomala, is genetically diverse across its endemic range in the eastern US. Recent evidence at Rutgers University shows the existence of fungal populations that can overcome some major resistance genes.
Efforts to develop durable resistance are now under consideration, including pyramiding single R-genes, enhancing quantitative resistance (QR), and breeding single genes into QR backgrounds.
Fortunately, many new sources of QR have been identified in Corylus americana and C. avellana at Oregon State University and Rutgers University, and studies of QR genetic control are expanding.
Evaluation of QR in clonal genotypes and full-sibling mapping populations has included the measurement of the total canker length (TCL) and proportion of diseased wood (PDW) in 6- to 7-year-old trees, which is effective but laborious and not scalable for large segregating populations.
A qualitative 0-5 EFB rating system has been used for such populations; however, it does not capture sufficient resolution of the variation observed in intermediate QR genotypes.
Here, we present EFB incidence for 35 American × European F1 hybrid selections that express a range of disease reflective of QR. Relationships are reported between the 0-5 rating, TCL, PDW, number of cankers (NC), and average canker length (ACL) and are considered in proposing a new class-based rating system that better captures variation in QR. Simple linear regression between TCL and NC showed good fit (R2=0.87), while the fit of ACL to TCL (R2=0.66) was moderate.
Interestingly, the relationship between NC and ACL has a rather poor fit (R2=0.33), suggesting these characters represent distinct variation.
As expected, multiple regression using NC and ACL as explanatory variables was significant (P-value <0.001) and improved R2 to 0.994. Using this information, we preliminarily propose nine NC classes and conditional weights based on ACL to form an NC+ACL rating system.
Future research will include assessing the proposed NC+ACL rating system in large seedling families for accuracy and efficiency.
Efforts to develop durable resistance are now under consideration, including pyramiding single R-genes, enhancing quantitative resistance (QR), and breeding single genes into QR backgrounds.
Fortunately, many new sources of QR have been identified in Corylus americana and C. avellana at Oregon State University and Rutgers University, and studies of QR genetic control are expanding.
Evaluation of QR in clonal genotypes and full-sibling mapping populations has included the measurement of the total canker length (TCL) and proportion of diseased wood (PDW) in 6- to 7-year-old trees, which is effective but laborious and not scalable for large segregating populations.
A qualitative 0-5 EFB rating system has been used for such populations; however, it does not capture sufficient resolution of the variation observed in intermediate QR genotypes.
Here, we present EFB incidence for 35 American × European F1 hybrid selections that express a range of disease reflective of QR. Relationships are reported between the 0-5 rating, TCL, PDW, number of cankers (NC), and average canker length (ACL) and are considered in proposing a new class-based rating system that better captures variation in QR. Simple linear regression between TCL and NC showed good fit (R2=0.87), while the fit of ACL to TCL (R2=0.66) was moderate.
Interestingly, the relationship between NC and ACL has a rather poor fit (R2=0.33), suggesting these characters represent distinct variation.
As expected, multiple regression using NC and ACL as explanatory variables was significant (P-value <0.001) and improved R2 to 0.994. Using this information, we preliminarily propose nine NC classes and conditional weights based on ACL to form an NC+ACL rating system.
Future research will include assessing the proposed NC+ACL rating system in large seedling families for accuracy and efficiency.
Publication
Authors
R.S. Revord, T.J. Molnar, D. Hlubik, N.A. Meier
Keywords
Corylus avellana, Corylus americana, Anisogramma anomala, disease, breeding, durability
Groups involved
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