The success of a long-term breeding program for outcrossing tree species depends not only on genetic gains through selection but also on the maintenance of genetic diversity over consecutive generations of plant breeding. To inform future breeding and deployment of Melaleuca alternifolia, this study benchmarked genetic variation in 114 selected individuals from a third-generation breeding population with 18 microsatellite markers. Five loci were used to compare diversity measures in the breeding population to values of genetic variation for natural populations in Australia. The expected heterozygosity in the breeding population was high (H_E = 0.823) and comparable to the average heterozygosity for 427 individuals from 36 natural populations (H_E = 0.844). The inbreeding coefficient F_IS was 0.044 and 0.151 in breeding and natural populations, respectively. These favourable findings confirmed that objectives of past breeding practices were successful in maintaining diversity and preventing inbreeding. Sample size effects were evident, nonetheless, and the average number of alleles per locus (N_A) was markedly reduced, especially those of low frequency. To study the impact deploying clones would have on genetic diversity, simulated populations of clones were created by repeatedly sampling the breeding population for subsets of 10, 15 or 20 individuals and generating diversity parameters for all 18 loci. Results for each number of individuals were compared to the diversity in the entire breeding population. Sample size had no effect on H_E, but N_A was significantly and progressively reduced with smaller sample size.

异种树种的长期育种计划的成功不仅取决于通过选择获得的遗传增益，还取决于连续几代植物育种中遗传多样性的维持。为了为互花白千层的未来育种和部署提供信息，该研究对来自第三代育种种群中具有18个微卫星标记的114个选定个体的遗传变异进行了基准测试。使用五个基因座将育种种群的多样性测度与澳大利亚自然种群的遗传变异值进行比较。繁殖种群的预期杂合度很高（H _E  = 0.823），可与36个自然种群的427个个体的平均杂合度（H _E = 0.844）。繁殖种群和自然种群的近交系数F _IS分别为0.044和0.151。这些有利的发现证实了过去育种实践的目标在维持多样性和防止近交方面取得了成功。尽管如此，样本量的影响还是很明显的，而且每个基因座的平均等位基因数（N _A）明显减少，尤其是低频的。为了研究部署克隆对遗传多样性的影响，通过对10、15或20个个体的子集重复采样繁殖种群并生成所有18个基因座的多样性参数，来创建克隆模拟种群。将每个个体的结果与整个繁殖种群的多样性进行比较。样品量对H _E无影响，但N _A随着样品量的减少而显着并逐渐降低。