Herrera J C, Combes M C, Cortina H, Alvarado G, Lashermes P
Centro Nacional de Investigaciones de Cafe, CENICAFE, AP 2427, Manizales, Colombia.
Heredity (Edinb). 2002 Dec;89(6):488-94. doi: 10.1038/sj.hdy.6800171.
Interspecific triploid hybrid plants between the tetraploid species Coffea arabica L. and the diploid species C. canephora P. were backcrossed to C. arabica. Although characterised by a low production and an important fruit dropping, all attempted crosses (ie, 6) generated BC(1) progenies. Flow cytometric analysis of the nuclear DNA content revealed that most of the BC1 individuals were nearly tetraploid. Among the male gametes produced by the interspecific triploid hybrids, those presenting a high number of chromosomes appeared strongly favoured. Only pollen mother cells having nearly 22 chromosomes were effective, the others leading to deficient endosperm and fruit dropping. Molecular markers (ie, microsatellite and AFLP) combined with evaluations of morphological characteristics and resistance to leaf rust were applied to verify the occurrence of gene transfer from C. canephora into C. arabica, and to estimate the amount of introgression present in BC(1) individuals. The results reveal a strong deficiency in the C. canephroa alleles indicating a severe counter-selection against the introgression of genetic material from C. canephora into C. arabica by way of triploid hybrids. However, introgressants displaying desirable traits such as a high resistance to leaf rust were obtained. The low level of introgression could be an advantage by facilitating the recovery of the recurrent parent and possibly reducing the number of required backcrosses. On the other hand, this could be a limitation when attempting the transfer of a complex trait or several simply inherited traits.
四倍体物种阿拉伯咖啡（Coffea arabica L.）与二倍体物种卡内弗拉咖啡（C. canephora P.）之间的种间三倍体杂交植物与阿拉伯咖啡进行了回交。尽管产量低且落果严重，但所有尝试的杂交（即6次）都产生了BC1后代。对核DNA含量的流式细胞术分析表明，大多数BC1个体接近四倍体。在种间三倍体杂交产生的雄配子中，那些染色体数目较多的配子似乎受到强烈青睐。只有染色体数目接近22条的花粉母细胞是有效的，其他的则导致胚乳发育不良和落果。结合形态特征评估和对叶锈病抗性的分子标记（即微卫星和AFLP）被用于验证从卡内弗拉咖啡到阿拉伯咖啡的基因转移的发生，并估计BC1个体中渗入的基因数量。结果显示卡内弗拉咖啡等位基因严重不足，表明通过三倍体杂交将卡内弗拉咖啡的遗传物质渗入阿拉伯咖啡存在严重的反选择。然而，获得了表现出如对叶锈病高抗性等理想性状的渗入系。低水平的渗入可能是一个优势，有助于轮回亲本的恢复，并可能减少所需的回交次数。另一方面，在尝试转移复杂性状或几个简单遗传性状时，这可能是一个限制。
