Mapping QTLs for Resistance to Frosty Pod and Black Pod Diseases and Horticultural Traits in Theobroma cacao L.

Abstract

A heterozygous F1 mapping population of cacao (Theobroma cacao L.) was created and evaluated for resistance to frosty pod [caused by Moniliophthora roreri (Cif. and Par.) Evans et al.], and black pod [caused by Phytophthora palmivora (Butl.) Butl.] and for five horticultural traits at CATIE in Turrialba, Costa Rica. The population consisted of 256 F1 progeny from the cross ‘Pound 7’ × ‘UF 273’. Progeny were used to form a linkage map using 180 markers. The linkage map contained 10 linkage groups (LGs), numbered as the LG in the cacao reference map, and was used to locate putative quantitative trait loci (QTL) for resistance to the aforementioned diseases and five horticultural traits. Resistance to frosty pod was measured by internal and external pod resistance. Five QTLs for frosty pod resistance were found on three LGs, 2, 7, and 8, with UF 273 appearing to be the source of resistance. These alleles are being used for scoring progeny in ongoing cooperative marker‐assisted selection projects, and constitute the first QTLs identified for frosty pod resistance. Three QTLs for black pod resistance were found on LG 4, 8, and 10, with the most favorable alleles coming from Pound 7. One QTL was found on LG 4 for average trunk growth rate, and two QTLs for height of first jorquette were identified on LGs 4 and 6. One QTL each for average trunk diameter growth and pod color was found on LG 4.

Assessing microsatellite linkage disequilibrium in wild, cultivated, and mapping populations of Theobroma cacao L. and its impact on association mapping

“…Evidence suggests, however, that other phenotypes of cacao are likely products of far more complex interactions between genes, regulatory elements and the environment. Pod color also has a very strong genetic component compared to other cacao phenotypes (e.g., Brown et al 2007Brown et al , 2005. While this makes it difficult to make specific recommendations about marker density, it does suggest that association analyses will require a higher density to maintain the power to detect associations.…”

EFFECTIVE CACAO SOMATIC EMBRYO REGENERATION ON KINETIN SUPPLEMENTED DKW MEDIUM AND SOMACLONAL VARIATION ASSESSMENT USING SSRs MARKERS

“…Cacao breeding usually take a long time and this is because of the long life cycle and the narrow genetic background (Brown et al, 2007). Utilizing plant tissue culture technology and molecular biology is expected to accelerate constrain in achieving cacao breeding programs.…”

Rainfall and temperature effects on flowering and pollen productions in cocoa

“…Although, all cultivated cocoas show great variability, it is generally agreed that they can be divided within the species, into three large groups: Criollos, Forastero Amazonians and Trinitarios (Cheesman, 1944;Gordon, 1976). Theobroma cacao, is a tropical understorey tree that is a major economic resource to several tropical countries (Browna et al, 2007;Lanaud et al, 2009;) The yields of Upper Amazon Cocoa have been militated by several factors since its introduction into Nigeria in 1874. All efforts toward its improvement had been limited partly by inadequate knowledge of the effects of climate on flowering pattern and pollination efficiency.…”