Abstract
The objective of this work was to identify expressed simple sequence repeats (SSR) markers associated to leaf miner resistance in coffee progenies. Identification of SSR markers was accomplished by directed searches on the Brazilian Coffee Expressed Sequence Tags (EST) database. Sequence analysis of 32 selected SSR loci showed that 65% repeats are of tetra-, 21% of tri- and 14% of dinucleotides. Also, expressed SSR are localized frequently in the 5'-UTR of gene transcript. Moreover, most of the genes containing SSR are associated with defense mechanisms. Polymorphisms were analyzed in progenies segregating for resistance to the leaf miner and corresponding to advanced generations of a Coffea arabica x Coffea racemosa hybrid. Frequency of SSR alleles was 2.1 per locus. However, no polymorphism associated with leaf miner resistance was identified. These results suggest that marker-assisted selection in coffee breeding should be performed on the initial cross, in which genetic variability is still significant.
Highlights
The species Coffea arabica is an allotetraploid with 2n = 4X = 44, as a result of a natural hybridization of the diploid species C. eugenioides and C. canephora
Simple sequence repeat loci in coffee exhibited complex repeated motifs, being 65% of tetranucleotide repeats, 21% of tri- and 14% of dinucleotides
Dinucleotides motif copy numbers were higher than others, and ranged from 17 to 30 copies
Summary
The species Coffea arabica is an allotetraploid with 2n = 4X = 44, as a result of a natural hybridization of the diploid species C. eugenioides and C. canephora. Overall genetic variability of C. arabica is very restricted, in cultivated materials and in wild accessions. This is a consequence of the mode of reproduction, of the narrow center of origin and of low number of seeds used for world dispersion (Maluf et al, 2005). The leaf miner Leucoptera coffeella (GuérinMéneville, 1842) (Lepidoptera: Lyonetiidae) represents the major plague in coffee plantations, and production losses due to insect infestation can reach 50%. The leaf miner is an obligate parasite and requires coffee plants to complete its life cycle. Upon oviposition on leaves, ecloded larvae feed directly from parenchyma tissues, Pesq. agropec. bras., Brasília, v.42, n.3, p.377-384, mar. 2007
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