Mapping quantitative trait loci for bean traits and ovule number inTheobroma cacaoL.

Abstract

Quantitative trait loci (QTL) mapping for bean traits and the number of ovules per ovary was carried out in cocoa (Theobroma cacao L.) using three test-cross progenies derived from crosses between a lower Amazon Forastero male parent (Catongo) and three female parents: one upper Amazon Forastero (IMC78) and two Trinitario (DR1 and S52). RFLP (restriction fragment length polymorphism), microsatellite, and AFLP (amplified fragment lengthpolymorphism) markers were used for mapping. Between one and six QTL for bean traits (length, weight, and shape index) and one and four QTL for the number of ovules per ovary were detected using composite interval mapping (CIM). Individual QTL explained between 5 and 24% of the phenotypic variation. QTL clusters were identified on several chromosomes, but particularly on chromosome 4. QTL related to bean traits were detected in the same region in both Trinitario parents and in a close region in the upper Amazon Forastero parent. In reference to a previous diversity study where alleles specific to Criollo and Forastero genotypes were identified, it was possible to speculate on the putative origin (Criollo or Forastero) of favorable QTL alleles segregating in both Trinitario studied.

Caracterização de frutos de clones de cacaueiros na região litorânea de São Mateus, ES

“…Variações na forma da amêndoa, como o comprimento, largura, espessura e peso, em T. cacao, têm sido relacionados à origem genética (Clement et al, 2003 O método de Singh (1981), baseado em D² de Mahalanobis, considera de menor importância características que expressam menor variabilidade. As características peso total do fruto (49,31%), peso total da casca (41,85%) e peso total da polpa (7,57%) foram as que mais contribuíram na diversidade genética dos genótipos (Tabela 7).…”

A new cacao linkage map based on codominant markers: development and integration of 201 new microsatellite markers

“…These maps were based on codominant markers such as restriction fragment length polymorphisms (RFLPs), isoenzymes and a small number of simple sequence repeats (SSRs) and, in some of the maps, associated with dominant amplified fragment length polymorphisms (AFLP) and random amplified polymorphic DNA (RAPD) markers. They have been used to locate quantitative trait loci (QTLs) affecting traits of interest, such as disease resistance and yield factors (Crouzillat et al 2000;Flament et al 2001;Clement et al 2003;Queiroz et al 2003;Risterucci et al 2003).…”

Inheritance of the Number of Ovules per Ovary and Selection of Cacao Genotypes

“…It was previously proved that this characteristic is determining for the potential number of seeds per fruit once that it presents a positive correlation with number of seeds per fruit [3,4]. Also in relation to production, evidences of gene grouping were detected with NoOV and other characteristics of the seed, in the form of QTL co-location for both in a same region of chromosome 4 [16], indicating a possible grouping of genes genetically linked and with effects on these characteristics. Therefore, the plants selected in the progeny resulting from the crossing of TSH 1188 × CCN 51 represent an elite in terms of potential for the seed production in this population.…”

“…The intermediate categories (49 to 60 ovules) were the most frequent (185 plants, 88.5% of the progeny). The polygenic nature of this characteristic in this population is according to the data from a different genetic background of cocoa [16], which mapped eight quantitative trait loci (QTL) related to NoOV, distributed into six different chromosomes in segregating populations resulting from the crossing of the forasteiro high Amazon clone IMC 78 and two trinitario materials: DR1 and S52. Among these eight loci, four alleles were identified as favorable to the increase of NoOV, supposedly from forasteiro ancestry.…”

“…This number of ovules is considered high for cacao [8]. Additionally, a more large range of NoOV was observed for the progeny involving the crossing of the clone IMC 78 with Catongo (NoOV = 58.7 ± 2.10; extremes 52.7 to 63.5) [16]. The progeny studied on this work ( Table 3: NoOV = 54.3 ± 4.03; extremes 44.1 and 67.5) shows higher NoOV variation than that involving IMC 78 and Catongo (NoOV = 58.7 ± 2.10).…”