Studies On Genetic Variation Of Neolamarckia Cadamba And Superior Provenance And Family Early Selection

Neolamarckia cadamba belongs to the family Rubiaceae, is a valuable economic timber species with fast-growing hardwood, which has straight stem form, yellow-white wood, straight texture and uniform structure. However, the study about its genetic variation and selection has been reported rarely. In this study, germplasm resources were collected from Yunnan, Guangxi, Guangdong and Indonesia. The genetic variation between and within provenances was studied through provenance trial and an family genetic testing, respectively. On this basis, the superior provenances and families were selected. The main results are as follows:1. On each test site, The differences in growth characteristics reached significant level between provenances, it is suggested that there was a great potential for selection among them. The provenance repeatability of diameter at breast height(DBH), height(H) and volume index(V) between 0.5 to 0.77. On all sites, except that the differences between interaction of site and provenance about the crown diameter and the differences between provenances about the ratio of crown diameter to diameter at breast height were insignificant, the other growth characteristics between sites, provenances, the blocks within the sites, the interaction of site and provenance and the interaction of provenances and the block within the sites respectively were all significantly different. The 11 provenances in test could be divided into three groups. The first group was high-yield stable type, only including the No.10 provenance; The second group was slow-yield stable type, including the No.1, No.5, No.6, No.7, No.8 and No.11 provenances; The third group was slow-yield unstable type, including the No.3, No.4, No.9 and No.13 provenances. The neighbour-jioning clustering analysis indicated that 11 provenances were divided into three groups: the provenance No.1, No.3, No.4, No.7, No.8, No.9, No.10 and No.11; the provenance No.13; and the provenance No.5 and No.6 were assigned as group ?, group ? and group ?, respectively. The results indicated that significant genetic differences existed in growth characteristics from the different provenances and that the tendency of geographic variations were was obvious.2. The growth characteristics of N.cadamba were significantly different among families. On all sites, All growth characteristics among blocks, families and the interaction of block and family respectively are significantly different, except interaction of block and family about the ratio of crown diameter to diameter at breast height(RCDD) at Dongfang. The range of family heritability about each growth characteristics were shown as follows: diameter at breast height(0.44~0.63), height(0.42~0.52), height under branch(0.33~0.64), crown diameter(0.46~0.69), the ratio of crown diameter to diameter at breast height(0.18~0.50), the ratio of height to height under branch(0.3~0.51) and volume index(0.45~0.57). The family heritability about each growth characteristics were around 0.5, showing that each growth characteristics were under genetic control nearly at the moderate level. All individual heritability about each growth characteristics were less than family heriterbility, suggesting that there was a greater potential for selection between family. The 35 families in the test can be divided into four groups. The first group including No.401, No.808, No.919, No.922, No.928 and No.1001 families, was assigned as high-yield stable type,; The second group including No.103, No.301, No.501, No.503, No.601, No.705, No.706, No.803, No.809, No.811, No.917, No.945, No.1110, and No.1122 families, was assigned as slow-yield stable type,; The third group including No.402, No.703, No.802 No.807, No.913, No.914, No.924, No.931, No.950, No.1105, and No.1301 families was assigned as high-yield unstable type,; and the fourth group was assigned as slow-yield unstable type, including No.702, No.704, and No.946 families.3. On the sites both in Leizhou and Dongfang, Yunnan Dehong provenance and Yunnan Jinghong provenance fitted better, nevertheless, on the site in Haikou, Guangxi Nanning provenance, Yunnan Jinghong provenance and Indonesia provenance fitted better. The genetic gain of volume index about superior provenance selected reached 14.95%. On the site in Leizhou, No.924, No.1001, No.1002 and No.1122 families fitted better; on the site in Haikou, No.402, No.901, No.924, No.931, No.944, No.954 and No.1102 families fitted better; and on the site in Dongfang, No.401, No.808, No.901, No.922, No.928, No.1001 and No.1120 families fitted better. The genetic gain of volume index about superior families selected reached 15.54%.