QTL detection for growth traits in Pinus elliottii var. elliottii and P. caribaea var. hondurensis

Quantitative trait locus (QTL) detection was carried out for growth traits in 122 F1 progenies of Pinus elliottii var. elliottii (PEE) × P. caribaea var. hondurensis (PCH) hybrid. The PCH male parent linkage map contained 108 markers in 16 linkage groups, while the PEE female parent contained 93 markers in 19 linkage groups. Sequence-related amplified polymorphism (SRAP), microsatellite (SSR), expressed sequence tag polymorphism (ESTP) and inter-simple sequence repeat (ISSR) were selected from an existing linkage map. Growth traits investigated were height at age five (HT05) and six years (HT06), diameter at breast height at age five (DBH05) and six years (DBH06) and annual growth from age five to six years of height (AGHT) and diameter at breast height (AGDBH). Kruskal-Wallis and interval mapping approaches were used to estimate levels of significance, the number of QTLs, the percentage of the phenotypic variation explained by each of QTLs and their positions on the genetic linkage maps. Twenty six QTLs with significance levels p < 0.05 were detected on the parental maps for the six growth traits, which explained more than 15% of the phenotypic variation, suggesting an existence of major-effect genes. Several QTLs had the pleiotropy controlling more than one single growth trait. Overall, the proportion of phenotypic variation explained by QTLs ranged from 5.9% to 40.6% for HT05 and HT06, from 6.6% to 42.0% for DBH05 and DBH06 and from 5.8% to 22.3% for AGHT and AGDBH. The results from this study provide a basis for marker-aided selection (MAS) in PEE × PCH hybrids.