Progress of Hybrid Breeding of Pinus caribaea and Strategy for Future Development

This paper reviews the hybrid breeding activities of Pinus caribaea that have been carried out in China up to date and proposes the strategy for future development of hybrid pine. Pinus caribaea, including 3 varieties of var. caribaea, var. hondurensis and var. bahamensis, is an important softwood species for pulp and timber in the tropics of China. Hybrid breeding of the species started in the later 1970s. Analysis of a 15 year old trial of Pcc×Pee hybrids established in 1981 showed that volume of the best hybrids was as large as 1.66-2.88 times of the parental species while the average basic wood density and fiber length were between the two parental species. In the early 1990s, more trials were established in Fujian, Guangdong, Guangxi and Hunan Provinces. The Australian hybrid used as control grew fastest but was more susceptive to wind break. A 2.5 year old trial established in Zhanjiang showed that the hybrids of P. elliottii×P. caribaea var. hondurensis and P.caribaea var. caribaea×P. caribaea var. bahamensis displayed superior growth over hybrid of P. elliottii×P. caribaea var. caribaea and P. caribaea var. hondurensis×P. caribaea var. caribaea. The germination rates (averaged less than 30%) of the hybrid seeds were low and variable among families. The results from a trial at Taishan showed that height and volume increases were 35.8% and 244.6% for Pee×Pch and 40.8% and 210.9% for Pee×Pcc respectively. Analysis of combining abilities was conducted. Australian hybrids of Pee×Pch including both F1 and F2 hybrid seeds were imported and introduced to Fujian, Guangdong, Guangxi and Jiangxi for pilot trials. Although the superiority of the F2 hybrid was not as high as that of the F1, the average growth was still better than that of the local seed sources. Studies of vegetative propagation by cuttings revealed that the rooting rates could reach above 85% although they were highly variable among families. More crosses of Pee×Pcb need to be tested in future.