Cacao breeding in Bahia, Brazil - strategies and results

Cacao was introduced in Bahia in 1756, becoming later the largest producer state in the country. In order to supportthe planting of cacao in the region, a breeding program was established by CEPEC at the beginning of the 1970s. For a long time,the program consisted in testing new hybrids (full-sibs) and releasing a mixture of the best ones to farmers. Lately, particularly afterthe witches´ broom arrival in the region, in 1989, recurrent breeding strategies were implemented, aiming mainly the developmentof clones. From 1993 to 2010, more than 500 progenies, accumulating 30 thousand trees, were developed by crossing many parentswith resistance to witches´ broom, high yield and other traits. In this period, more than 500 clones were put in trials and 39 clonesand 3 hybrids were released to farmers. In this paper the strategies and results achieved by the program are reviewed. Overall theprogram has good interface with pathology and genomic programs

Parent selection for cocoa resistance to witches'- broom

O objetivo deste trabalho foi identificar genótipos com alta capacidade geral de combinação quanto à resistência à vassoura-de-bruxa (Moniliophthora perniciosa), em populações formadas a partir do primeiro ciclo de seleção recorrente. Clones altamente produtivos e resistentes à vassoura-de-bruxa, de diferentes procedências, foram intercruzados com uso do delineamento Carolina do Norte II. Como progenitores paternos, foram utilizados os clones SCA 6, CSUL 7, RB 39, CEPEC 89, OC 67, BE 4, EEG 29 e ICS 98 e, como maternos, NA 33, CCN 10, IMC 67, P 4B, CCN 51, CEPEC 86, SGU 54 e ICS 9. Vinte dias após a germinação, 56 plântulas de cada cruzamento (quatro repetições de 14 plântulas) receberam inoculação de 1 mL de suspensão com 7,5x 104 basidiósporos mL-1. Os sintomas foram avaliados 60 dias após a inoculação. Foram observadas diferenças significativas, entre os progenitores paternais e entre os progenitores maternais, quanto à resistência à vassoura-de-bruxa avaliada pela proporção de plântulas das progênies com sintomas da doença. Diferenças também foram observadas entre grupos de progenitores paternais ou maternais previamente definidos como resistentes, e grupos previamente definidos como suscetíveis. É possível obter, diretamente de primeiros ciclos de seleção recorrente, uma combinação de genes que possa aumentar a resistência à vassoura-de-bruxa.The objective of this work was to identify genotypes with high general combining ability for resistance to witches'-broom (Moniliophthora perniciosa) in populations formed from a first cycle of recurrent selection. Highly productive and resistant clones from different origins were interbred using the North Carolina II design. The clones SCA 6, CSUL 7, RB 39, CEPEC 89, OC 67, BE 4, EEG 29 and ICS 98 were used as paternal parents, while the maternal ones were NA 33, CCN 10, IMC 67, P 4B, CCN 51, CEPEC 86, SGU 54 and ICS 9. Twenty days after germination, 56 seedlings of each cross (four replicates of 14 seedlings) received the inoculation of a 1-mL suspension with 7.5x 104 basidiospores mL-1. Symptoms were evaluated 60 days after inoculation. Significant differences were observed among paternal and among maternal parents, for resistance to witches'-broom assessed according to the proportion of progeny seedlings with the disease symptoms. Differences were also observed between groups of mothers or fathers previously defined as resistant, and groups previously defined as susceptible. It is possible to obtain a combination of genes that can increase the level of resistance to witches'-broom directly from the first cycle of recurrent selection

Genetic divergence in cocoa progenies for backcrossing program to witches' broom disease resistance

Backcrossing has been little used in cacao breeding, particularly due to the long time required to transfer genes and recover the genetic background of the recurrent parent. The objective of this study was to select individuals, resulting from the backcross CEPEC-42 x SIC-19, genetically related to the recurrent parent SIC-19 by using RAPD molecular markers, among those with resistance to witches' broom. Of the 31 plants that clustered with SIC-19, 18 from the replanted material remained free of the disease in the field, with good vegetative aspect and, therefore can be used for backcross to reach the desired objective

Microsatellite diversity and heterozygosity of parents of a cocoa breeding population

The purpose of this study was to determine the genetic diversity and heterozygosity of 26 clones used asparents of 27 families. The populations are being evaluated by the Comissão Executiva do Plano da Lavoura Cacaueira(CEPLAC), in the state of BA. Nine of these clones are currently being recommended to farmers, while six others were used ascontrol. The seven microsatellite generated 52 alleles with a mean of seven alleles/locus and genetic distance ranging from0.17 to 0.90. This indicates a wide distribution of accessions and high variability. The heterozygosity ranged from 20% to86%, and more than 50% of the loci were heterozygous in 79% of the clones. Although the selection of the parents forpopulations was not based on genetic distances, the high genetic diversity and heterozygosity of parents indicate highlysegregating populations that make the selection of trees of interest possible, due to the variability