Evidence of Intergenomic Relationships in Triploid Hybrids of Coffee (Coffea sp.) as Revealed by Meiotic Behavior and Genomic in Situ Hybridization

摘要

Interspecific hybrids involving the cultivated C. arabica (2n=4x=44, EaEaCaCa) and two related diploid species (2n=2x=22), C. eugenioides (EE) and C. liberica (LL), were produced and analyzed for their relative genome affinity using different complementary approaches, including chromosome association analysis, genomic in situ hybridization (GISH) and pollen fertility. The mean arm pairing frequency (c) and the relative affinity index (x) of triploid hybrids with known genome combinations were used asa measure of chromosome homology. Triploid hybrids were highly sterile as a result of meiotic abnormalities (fertility ranged from 1 to 15 %). Nevertheless, all hybrids exhibited a significant occurrence of genome affinities (x=0.96 for EaCaE and 0.81 for EaCaL). Further analysis using the GISH approach revealed that C. eugenioides was more closely related to C. arabica than to C. liberica, which was in agreement with the ancestral history of the allotetraploid C. arabica. The absence of incompatibility barriers at the stylar level in the flowers of the triploid hybrids indicates the possibility of desirable gene transfer through breeding strategies.