陈山红心杉1.5代种子园遗传多样性和子代父本分析

【目的】陈山红心杉是江西特有的杉木优良种源,其近髓心的木质部为高比例的油亮栗褐色,是工艺建筑和室内装潢极为宝贵的天然材料。对陈山红心杉1.5代种子园进行遗传多样性和子代父本分析,为红心杉种子园的管理提供科学依据。【方法】以江西省青原区白云山林场陈山红心杉1.5代种子园及其子代测定林为研究材料,利用12对SSR引物,对种子园32个亲本及14个无性系的459个子代进行遗传多样性和父本分析。【结果】各引物在亲本群体中检测到等位基因数(N_a)为3~7,平均为4.41个;引物在子代群体中检测到的等位基因数(N_a)为4~11,平均为6.50个,较亲本群体高2.09个。亲本群体的平均有效等位基因数(N_e)为2.330,子代群体的平均有效等位基因数为2.306。子代群体包含亲本群体所有的等位基因,并检测到25个子代特有的等位基因。子代群体的Shannon’s信息指数(I)=1.004高于亲本群体的0.992,说明子代群体的遗传多样性略高于亲本群体。子代群体和亲本群体的观测杂合度(H_o)分别为0.525和 0.571,表明子代群体中杂合单株的比例较亲本有所下降。种子园的多位点异交率(t_m)是1.012,单位点异交率(t_s)为0.991,说明种子园异交率较高。双亲近交系数(t_m-t_s)为0.021,表明种子园无性系间近交水平比较低。种子园的有效花粉供体数目(N_ep)为7.81。种子园的多位点父本相关性R_p(m)]和单位点父本相关性R_p(s)]分别为0.128和-0.016,单位点和多位点父本相关性的差值R_p(s)-R_p(m)=-0.144<0,表明亲本间没有明显的近亲关系。家系间的多位点异交率(t_m)变化幅度为0.938~1.200,有10个家系的多位点异交率(t_m)大于0。家系间近交系数(t_m-t_s)变化幅度为-0.127~0.150,9个家系的近交系数大于零,说明这些家系存在近交现象。通过父本分析,在80%的置信水平下确定了325个子代的父本来源,占分析子代总数的70.8%。子代的亲本均不是同一无性系,说明种子园无自交现象。各家系子代确定父本的比率不一致,41号家系子代确定父本的比率最高,为93.9%,其余家系子代确定父本比率为54.3%~90.9%。8号家系确定父本的30个子代中,16个子代的父本为同一无性系,占家系子代总数的53.3%;12号家系确定父本的26个子代中,12个子代的父本为同一无性系,占家系子代总数的46.2%,说明无性系间授粉亲和性不同。种子园存在非随机交配现象,在32个潜在无性系中,有26个无性系提供了有效花粉,其中父本贡献率最高的是22号和29号无性系,各为33个子代提供了花粉,其贡献率均为10.2%,其他无性系的父本贡献率为0.3%~8.9%。父本贡献率最高的前11个无性系共计产生了70.2%的子代。【结论】陈山红心杉1.5代种子园遗传多样性丰富,子代保持了亲代的遗传多样性水平;种子园异交率较高,部分家系存在低水平的近交;子代父本分析表明,种子园无自交现象,无性系间授粉亲和性不同,父本贡献率不均等。

Genetic diversity and paternity analyses in a 1.5th generation seed orchard of Chenshan red-heart Chinese fir

【Objective】 Chinese fir Cunninghamia lanceolata (Lamb.) Hook] is an important, fast-growing timber species that is widely distributed in southern China. The Chenshan red-heart Chinese fir is derived from C. lanceolata originating in Jiangxi Province, and its high proportion of shiny, chestnut-brown xylem surrounding the pith is an extremely valuable raw material for craft, architecture and interior decoration. This study aimed to provide a scientific basis for the management of red-heart Chinese fir seed orchards. 【Method】 We investigated the genetic diversity and analyzed the paternity of a 1.5th generation seed orchard of red-heart Chinese fir in the Baiyunshan Mountain Forest Farm (Qingyuan District, Jiangxi Province, China). The genetic diversity of 32 parent trees and 459 open-pollinated progenies from 14 clones in a 1.5th generation clonal seed orchard was analyzed using 12 polymorphic SSR loci. We then conducted a paternity test of the progeny. 【Result】 We detected 3-7 and 4-11 alleles (N_a) at averages of 4.41 and 6.50 per SSR loci, respectively, in the parent and progeny populations. The average number of alleles in the progeny population was 2.09, which was higher than that in the parent population. The effective numbers of alleles (N_e) were 2.330 and 2.306 in the parent and progeny populations, respectively. The progeny population contained all alleles detected in the parent population. In addition, 25 alleles detected in the progeny population were undetectable in the parent population. The Shannon information index (I) was 1.004 and 0.992 in the parent and progeny populations, respectively, indicating slightly higher genetic diversity in the progeny than in the parent population. The observed heterozygosity (H_o) was smaller in the progeny, than in the parent population (0.525 vs. 0.571), indicating a slightly lower proportion of heterozygosity in the progeny than in the parents. The multilocus (t_m) and single-locus (t_s) outcrossing rates in the seed orchard were 1.012 and 0.991, respectively, and the inbreeding between parents was not significant (t_m-t_s = 0.021). The number of effective pollen donors (N_ep) was 7.81. The multilocus R_p(m)] and single locus R_p(s)] paternal correlations of the seed orchard were 0.128 and -0.016, respectively. The difference R_p(s)-R_p(m)] between them was -0.144 < 0, indicating the absence of close relationships among the parents. The multilocus outcrossing rate (t_m) among families ranged from 0.938 to 1.200, and the multilocus outcrossing rate (t_m) of 10 families was more than 0. The biparental inbreeding (t_m-t_s) among families ranged from -0.127 to 0.150, and the t_m-t_s of nine families was more than 0, indicating that these families were inbred. The male parents of 325 progeny were determined at an 80% confidence level, accounting for 70.8% of the total progeny analyzed. The male and female parents of all progeny were generated from different clones, indicating the absence of selfing in this seed orchard. The proportions of paternal identification among families differed. The proportion of paternal identification of family No. 41 was the highest (93.9%), whereas that of the other families ranged from 54.3% to 90.9%. Paternal parents of 30 offspring in family No. 8 were identified, the paternity of 16 offspring was the same clone, accounting for 53.3% of the total offspring of this family. Paternal parents of 26 offspring in family No. 12 were identified, the paternity of 12 offspring was the same clone, accounting for 46.2% of the total offspring of this family. These results indicated that pollination affinity differed among the clones. A non-random mating phenomenon was also identified in the seed orchard. Among 32 clones, 26 provided effective pollen. Clone numbers 22 and 29 provided pollen for 33 offspring with the highest male parent contribution rate of 10.2%, compared with the 0.3%-8.9% rate of other clones. Eleven clones with the highest paternal contribution produced 70.2% of the offspring. 【Conclusion】 The 1.5th generation clonal seed orchard of red-heart Chinese fir was found to have rich genetic diversity, which remained equally in the progeny and parent populations. The outcrossing rate of this seed orchard was high, and some families had a low level of inbreeding. Self-pollination was absent, pollination affinity differed among clones, and the paternal contribution of clones was not equal throughout this red-heart Chinese fir seed orchard.