title: Genetic Determinism of Sensitivity to Corynespora cassiicola Exudates in Rubber Tree (Hevea brasiliensis).
abstract: An indirect phenotyping method was developed in order to estimate the susceptibility of rubber tree clonal varieties to Corynespora Leaf Fall (CLF) disease caused by the ascomycete Corynespora cassiicola. This method consists in quantifying the impact of fungal exudates on detached leaves by measuring the induced electrolyte leakage (EL%). The tested exudates were either crude culture filtrates from diverse C. cassiicola isolates or the purified cassiicolin (Cas1), a small secreted effector protein produced by the aggressive isolate CCP. The test was found to be quantitative, with the EL% response proportional to toxin concentration. For eight clones tested with two aggressive isolates, the EL% response to the filtrates positively correlated to the response induced by conidial inoculation. The toxicity test applied to 18 clones using 13 toxinic treatments evidenced an important variability among clones and treatments, with a significant additional clone x treatment interaction effect. A genetic linkage map was built using 306 microsatellite markers, from the F1 population of the PB260 x RRIM600 family. Phenotyping of the population for sensitivity to the purified Cas1 effector and to culture filtrates from seven C. cassiicola isolates revealed a polygenic determinism, with six QTL detected on five chromosomes and percentages of explained phenotypic variance varying from 11 to 17%. Two common QTL were identified for the CCP filtrate and the purified cassiicolin, suggesting that Cas1 may be the main effector of CCP filtrate toxicity. The CCP filtrate clearly contrasted with all other filtrates. The toxicity test based on Electrolyte Leakage Measurement offers the opportunity to assess the sensitivity of rubber genotypes to C. cassiicola exudates or purified effectors for genetic investigations and early selection, without risk of spreading the fungus in plantations. However, the power of this test for predicting field susceptibility of rubber clones to CLF will have to be further investigated.
authors.affiliation: Rubber Research Institute of Vietnam, Ho Chi Minh City, Vietnam.|CIRAD, UMR-AGAP, F-34398 Montpellier, France.
authors.forename: Dinh Minh
authors.initials: DM
authors.lastname: Tran
authors.affiliation: CIRAD, UMR-AGAP, F-34398 Montpellier, France.
authors.forename: André
authors.initials: A
authors.lastname: Clément-Demange
authors.affiliation: UCA, INRA, UMR PIAF, 63000 Clermont-Ferrand, France.
authors.forename: Marine
authors.initials: M
authors.lastname: Déon
authors.affiliation: CIRAD, UMR-AGAP, F-34398 Montpellier, France.
authors.forename: Dominique
authors.initials: D
authors.lastname: Garcia
authors.affiliation: CIRAD, UMR-AGAP, F-34398 Montpellier, France.
authors.forename: Vincent
authors.initials: V
authors.lastname: Le Guen
authors.affiliation: CIRAD, UMR-AGAP, F-34398 Montpellier, France.
authors.forename: Anne
authors.initials: A
authors.lastname: Clément-Vidal
authors.affiliation: Société Africaine de Plantations d'Hévéas, 01 BP 1322 Abidjan 01, Côte d'Ivoire.
authors.forename: Mouman
authors.initials: M
authors.lastname: Soumahoro
authors.affiliation: Société des Caoutchoucs de Grand-Béréby, Grand-Béréby, Côte d'Ivoire.
authors.forename: Aurélien
authors.initials: A
authors.lastname: Masson
authors.affiliation: UCA, INRA, UMR PIAF, 63000 Clermont-Ferrand, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Label
authors.affiliation: Rubber Research Institute of Vietnam, Ho Chi Minh City, Vietnam.
authors.forename: Mau Tuy
authors.initials: MT
authors.lastname: Le
authors.affiliation: CIRAD, UMR-AGAP, F-63000 Clermont-Ferrand, France.
authors.forename: Valérie
authors.initials: V
authors.lastname: Pujade-Renaud
mesh_terms: D000483:Alleles; D001203:Ascomycota / Q000502:physiology*; D005838:Genotype; D028482:Hevea / Q000235:genetics* / Q000382:microbiology* / Q000502:physiology; D018895:Microsatellite Repeats; D010641:Phenotype; D010935:Plant Diseases / Q000235:genetics* / Q000382:microbiology*; D018515:Plant Leaves / Q000235:genetics / Q000382:microbiology; D040641:Quantitative Trait Loci