BREEDING OF ARABICA COFFEE AT IAC, BRAZIL: OBJECTIVES, PROBLEMS AND PROSPECTS

Brazil is the world’s leading Arabica coffee (Coffea arabica) producer. Ninety percent of cultivars grown derive from the Instituto Agronômico (IAC) breeding program, based on exploitation of large germplasm, long-run efforts for artificial hybridizations, and evaluations in representative growing regions. Since the species is predominantly self-pollinated, breeding strategies aim to produce homozygous lines developed mainly by pedigree or backcross methods. Yield is outstanding in modern cultivars. To be increased, genotype × environment interactions must be exploited or exotic polygenes introgressed. Bean size is minimum in cultivar ′Mokka′ (momo) and maximum in the cultivar ′Maragogipe′ (MgMg). ′Bourbons′ (tt) have smaller beans than common cultivars but superior beverage quality. The Ct allele is the basis of several short-stature releases. Further reduction in plant size might be achieved by combining Sb and Vl but selection is hampered by a double-dominant epistatic interaction at the nursery stage. Nine SH genes for leaf-rust resistance in Coffea are counteracted by nine pathogenicity v genes in Hemileia vastatrix. SH_1,2,4,5 from Ethiopian accessions, SH₃ from C. liberica, and the remaining from C. canephora were bred into C. arabica. Changes in prevalent rust races have overcome several resistances. Lm₁ and Lm₂ genes for leaf-miner resistance from C. racemosa were transferred to C. canephora × C. arabica backcross derived lines but cultivar release awaits uniform advanced lines. Breeding for nematode resistance identified in C. canephora derivatives and Ethiopian accessions needs basic studies and integration with molecular markers. The ′Mokka′ accession has superior cup quality but the momo gene block reduces bean size and yields. C. eugenioides, a diploid ancestor of C. arabica, is a source of fine flavor. Initial backcross lines are extremely late with low yields but show a distinct cup profile. Presently, 65 cultivars are recommended by IAC for plantings in diverse edaphoclimatic regions of Brazil.