Articles
Comparison between field and greenhouse phenotyping to identify sources of resistance to mal secco in lemon hybrids
Article number
1412_57
Pages
383 – 390
Language
English
Abstract
Mal secco, caused by the fungus Plenodomus tracheiphilus, is a xylematic disease that represents a limiting factor for lemon (Citrus limon) production in the Mediterranean.
Resistance or field tolerance are major goals for lemon breeders.
However, there is little information regarding the heritability of mal secco resistance in breeding populations.
As for other vascular diseases, phenotyping is the bottleneck for the reliable estimation of resistance/susceptibility, and a validated protocol for greenhouse phenotyping would be valuable to accelerate the selection of tolerant individuals before field evaluation.
Here we report phenotyping in field and greenhouse conditions of one C. latipes (resistant to mal secco) × lemon population consisting of 148 individuals.
Field evaluation was performed on all hybrids for two or three consecutive years on trees subjected to high natural pathogen pressure.
Detection of the fungal infection was performed by visual observation and real time PCR. The first infections occurred about six months after planting, but two years of observations occurred for a reliable estimation of susceptibility.
Three years after planting, hybrids clustered into three groups (susceptible, resistant and with intermediate phenotype) based on symptom progression.
A subset of 65 self-rooted hybrids was also subjected to stem inoculation in cold greenhouse, with two to ten biological replicates per hybrid.
Three months after inoculation, the individuals were monitored for symptoms appearance.
We observed a low (R=0.42) but significant (p<0.001) correlation between field and greenhouse phenotypes, indicating that in our conditions field evaluation remains the best method to assess the tolerance to the disease.
However, artificial inoculations might be helpful to discard the highly susceptible hybrids before field evaluation.
Resistance or field tolerance are major goals for lemon breeders.
However, there is little information regarding the heritability of mal secco resistance in breeding populations.
As for other vascular diseases, phenotyping is the bottleneck for the reliable estimation of resistance/susceptibility, and a validated protocol for greenhouse phenotyping would be valuable to accelerate the selection of tolerant individuals before field evaluation.
Here we report phenotyping in field and greenhouse conditions of one C. latipes (resistant to mal secco) × lemon population consisting of 148 individuals.
Field evaluation was performed on all hybrids for two or three consecutive years on trees subjected to high natural pathogen pressure.
Detection of the fungal infection was performed by visual observation and real time PCR. The first infections occurred about six months after planting, but two years of observations occurred for a reliable estimation of susceptibility.
Three years after planting, hybrids clustered into three groups (susceptible, resistant and with intermediate phenotype) based on symptom progression.
A subset of 65 self-rooted hybrids was also subjected to stem inoculation in cold greenhouse, with two to ten biological replicates per hybrid.
Three months after inoculation, the individuals were monitored for symptoms appearance.
We observed a low (R=0.42) but significant (p<0.001) correlation between field and greenhouse phenotypes, indicating that in our conditions field evaluation remains the best method to assess the tolerance to the disease.
However, artificial inoculations might be helpful to discard the highly susceptible hybrids before field evaluation.
Authors
M. Cortese, C. Arlotta, A. Ciacciulli, D. Pietro Paolo, R. Russo, G. Licciardello, C. Licciardello, S. Di Silvestro, M. Caruso
Keywords
artificial inoculation, citrus, disease resistance, Plenodomus tracheiphilus, lemon breeding
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