ISHS Acta Horticulturae 535: First International Citrus Biotechnology Symposium
EVALUATION OF LEMON SOMACLONES FOR TOLERANCE TO MAL SECCO DISEASE BY ARTIFICIAL INOCULATION |
| Authors: | A. Gentile, Z.N. Deng, E. Tribulato, A. Vardi, G. Albanese, V. Grimaldi, A. Catara |
| Keywords: | Citrus limon, in vitro selection, Phoma tracheiphila, disease resistance, PCR analysis |
| Abstract:
Phoma tracheiphila causes a serious tracheomycotic disease in various Citrus species, especially in lemon. In vitro selection of Femminello lemon calli with toxin produced by the pathogen resulted in a cell line named Femminello-S, from which plants tolerant to the toxin were regenerated and planted in the field in 1992. In the present study, two somaclones (FS01 and FS11) were used to evaluate their in vivo response to artificial inoculation in comparison with the susceptible Femminello and the tolerant Monachello lemons. Twelve young plants of each genotype, grafted on sour orange, were stem-inoculated with a conidial suspension of a virulent isolate of P. tracheiphila. Inoculated stems were monitored through observation and evaluation of xylem colonization. Five stem segments were sampled from each plant at regular intervals of 10 cm from below the inoculation point. Each segment was divided into two parts, one for potato-dextrose agar (PDA) plating and the other for polymerase chain reaction (PCR) analysis. The four genotypes gave quite different in vivo responses to fungus inoculation. Observed symptoms were strongly confirmed by PDA plating and PCR analysis. The two laboratory tests that were applied gave the same results, revealing the presence of the pathogen in the inoculated plants, but the PCR test produced results earlier, without any doubt about the identity of the detected fungus. The disease symptoms observed after the artificial inoculation were in full agreement with the field observations of Monachello (tolerant) and Femminello (susceptible) lemons. This indicated that the in vivo test reflected the real host-pathogen relationship. The two analyzed somaclones, especially FS01, showed mild symptoms indicating the same tolerance to mal secco as that of Monachello. Although the results obtained are preliminary, they seem promising. | |
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