Genetic analysis in some citrus accessions using microsatellites - and AFLP-based markers [electronic resource].

Includes references.

Twelve lSSR primers, five SSR primer pairs and five AFLP primer combinations were used to estimate the level of polymorphism among 14 Citrus genotypes. The two types of lSSR primers (unanchored and anchored) showed different levels of polymorphism. All of the unanchored primers successfully amplified bands with a total number of 54 of which 44 were polymorphic, representing a percentage of polymorphism of 79.14% and 8.8 polymorphic bands per primer. While, three out of the four 5'-anchored primers amplified scorable bands revealing a total number of34 bands of which 28 were polymorphic. corresponding to 82.4% polymorphism and an average of 9.3 polymorphic bands per primer. On the other hand, the 3'-anchored primers failed to amplify reproducible patterns even with the modification ofthe PCR-reaction and temperature profile. Four sets out of five SSR primer pairs amplified a total number of 23 alleles revealing 100% polymorphism, with an average of 5.8 polymorphic alleles per loci. The SSR markers revealed allele frequency ranging from 0.04 to 0.52 . The expected heterozygosity ranged from 0.65 to 0.83 and the effective alleles per locus ranged from 2.9 to 5.9. The five AFLP primer combinations amplified a total number of 311 amplicons, where 304 were polymorphic representing 97. 7% polymorphism and 60.8 polymorphic amplicons per primer combination. The microsatellite basedmarkers revealed genetic similarity ranging from 55.4 [between Ruby red grapefruit (RRG) and Troyer citrange (TC)] to 94.9 [between Washington navel orange (WNO) and Valencia orange (Va)]. While, the highest similarity percentage (73.9%) detected by AFLP markers was between Volkamer lemon (VOL) and Rangpure lime (RL), and the lowest percentage of similarity (8.3%) was observed between Troyer citrange (TC) and Balady sour orange (BSO).Generally. the dendrograms based on the two types of markers (microsatellites and AFLPs) revealed nearlv similar topology separating Troyer citrange from the other Citrus genotypes. Moreover, accessions belonging to the same species always clustered together except for the sweet orange group (Valencia orange. Washington navel orange and Robertson navel orange) only in the AFLP dendrogram. All the tested ISSR primer (8) identified ten accessions, and both of Mic4 and Amicl detected the highest number of identified accessions (4). Moreover, four SSR primer pairs identified six Citrus accessions (Rangpure lime, Willowleaf mandarin, Cleopatra mandarin, Troyer citrange, Robertson navel orange and Abdel Razek mandarin). In addition, SSR markers exhibited species-specific markers. Three species out of eight (c. aurantium, C. deliciosa and C. paradisi) were characterized by specific allele sizes. The AFLP had the potentiality to characterize all the lesled accessions by unique markers. Combination MeagXEaag characterized the highest number of Citrus genotype (10). While, combination MereXEage characterized the lowest number of accession (5). In addition. the genomic DNA of Valencia orange scions grafted onto three different rootstocks (Volkamer lemon. Troyer citrange and Cleopatra mandarin) was analyzed with five different AFLP primer combinations. All the tested combinations revealed new bands (1-6) in the graft-induced variants except for combination Met! X Eaer with Troyer citrange and Meag X Eaer with Cleopatra mandarin. On the other hand. some bands which were present in the scion and (or) stock disappeared in the graft induced variant. The number of these bands ranged from I to 7. Moreover. it seems that the examined rootstocks transmitted bands to the graft induced variants, ranging in number from I to 6. While, the conserved bands from the scion ranged from 2 (with combination MeaeXEaee on both of Troyer citrange and Cleopatra mandarin) to 9 (with combination MeteXEage on Volkamer lemon). These results indicated the presence of a genetic relationship between the scion and the stock. however. further studies are needed to elucidate this relationship at the molecular level.

Summary in Arabic.

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