ISHS Acta Horticulturae 663: XI Eucarpia Symposium on Fruit Breeding and Genetics
COMBINATION OF A TRANSGENE-MEDIATED DEFENSE MECHANISM WITH A NATURAL RESISTANCE GENE INCREASES APPLE SCAB RESISTANCE |
| Authors: | E. Chevreau, M. Faize, F. Dupuis, S. Sourice, L. Parisi |
| Keywords: | chitinase, disease resistance, genetic engineering, gene expression, Malus x domestica, puroindoline, Venturia inaequalis |
| Abstract:
Apple (Malus x domestica) conventional breeding successfully released scab resistant cultivars. However, the discovery of new strains of Venturia inaequalis overcoming the Vf gene highlighted the importance of combining several defense mechanisms to obtain durable resistance. This study reports for the first time the combination of a transgene-mediated defense mechanism with a conventionally-bred resistance. Two cultivars of apple (‘Galaxy’, scab susceptible, and ‘Ariane’, carrying the Vf resistance gene) were transformed with endochitinase and exochitinase genes derived from the biocontrol fungus Trichoderma atroviride, or with the gene encoding wheat puroindoline B (pinB), all under the control of the CaMV35S constitutive promoter. PCR, semi-quantitative RT-PCR, ELISA or enzymatic activity analyses confirmed both the presence and the expression of the transgenes in 67 lines selected via resistance to kanamycin. All transgenic lines were tested in growth-chamber for their resistance to two races of the pathogen V. inaequalis: the common race 1 and the race 6 which overcomes resistance conferred by the Vf gene. Among lines expressing chitinases, a negative correlation between endochitinase activity and growth was observed. Scab inoculation of chitinase lines with normal vigor revealed 5 lines with significantly enhanced resistance. A significant negative correlation between disease susceptibility and PinB content was observed after inoculation of both transgenic lines of ‘Ariane’ and ‘Galaxy’ with the race 6 of the pathogen. Such a moderate resistance was not detected in transgenic lines of ‘Galaxy’ after inoculation with the race 1. Our overall results indicate that the concept of combining an antifungal transgenic mechanism with a natural single gene resistance holds promises to increase apple scab durability. | |
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