ISHS Acta Horticulturae 605: II International Symposium on Fig
THE USE OF MICROSATELLITE MARKERS FOR IDENTIFICATION AND GENETIC DIVERSITY EVALUATION OF THE FIG COLLECTION IN CBNMP |
| Authors: | B. Khadari, I. Hochu, L. Bouzid, S. Santoni, J.P. Roger, F. Kjellberg |
| Keywords: | SSR markers, heterozygosity, null alleles, distinctness, genotypes similarity |
| Abstract:
In this study, we describe genetic parameters of eight SSR loci previously developed (Khadari et al., 2001) and we report the result on SSR characterisation of CBNMP fig accessions. For all eight loci, the number of alleles detected per locus was similar in the 14 CBNMP cultivars and the 16 Moroccan cultivars. However, additional alleles were detected in the 70 fig samples which corresponds to a large set of genotypes. A significant deficit of heterozygous individuals over Hardy-Weinberg expectations was observed in CBNMP cultivars at loci MFC1 and MFC7 suggesting the occurrence of null alleles. This hypothesis seems however not to be valid because the observed level of heterozygosity was higher than expected in Moroccan cultivars and in the two wild-growing populations from France at all eight loci (Khadari et al., 2001). The analysis of 70 fig trees based on 5 microsatellite loci and 25 alleles allowed to identify 52 different SSR profiles. UPGMA phenogram based on the proportion of shared alleles showed two main clusters of genotypes which were distinguished by 8 to 9 alleles. Despite the limited number of loci examined, there is a very low probability of 2 genotypes sharing the same SSR profile (ranging from 7.2 10-9 to 1.7 10-4 under the hypothesis of independence between markers). Hence, it is most likely that only 52 genotypes are represented in the 70 trees analysed. Nevertheless, results on genotypes that are distinguished by only one allele have to be confirmed by using more markers. For several cases, pomological characterisation and molecular analysis were in disagreement. For example, accession n° 8-1 and accession n° 7-24 which were identified according pomological descriptors as “Lampeira” and “Pittalusse” cultivars respectively were characterised by one SSR profile. These results may be explained by environmental difference of some pomological traits or by a few SSR loci examined. Conversely, several accessions which were identified as a defined cultivar according to pomological descriptors displayed several SSR profiles. These results, especially related on genotypes which were distinguished by more than 2 alleles, showed the limits of pomological characterisation. | |
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