Department of Biosystems, Katholieke Universiteit Leuven, Willem de Croylaan 42, 3001, Leuven, Belgium.
Meise Botanic Garden, Nieuwelaan 38, 1860, Meise, Belgium.
BMC Plant Biol. 2021 Sep 9;21(1):415. doi: 10.1186/s12870-021-03142-y.
Conservation of plant genetic resources, including the wild relatives of crops, plays an important and well recognised role in addressing some of the key challenges faced by humanity and the planet including ending hunger and biodiversity loss. However, the genetic diversity and representativeness of ex situ collections, especially that contained in seed collections, is often unknown. This limits meaningful assessments against conservation targets, impairs targeting of future collecting and limits their use. We assessed genetic representation of seed collections compared to source populations for three wild relatives of bananas and plantains. Focal species and sampling regions were M. acuminata subsp. banksii (Papua New Guinea), M. balbisiana (Viet Nam) and M. maclayi s.l. (Bougainville, Papua New Guinea). We sequenced 445 samples using suites of 16-20 existing and newly developed taxon-specific polymorphic microsatellite markers. Samples of each species were from five populations in a region; 15 leaf samples from different individuals and 16 seed samples from one infructescence ('bunch') were analysed for each population.
Allelic richness of seeds compared to populations was 51, 81 and 93% (M. acuminata, M. balbisiana and M. maclayi respectively). Seed samples represented all common alleles in populations but omitted some rarer alleles. The number of collections required to achieve the 70% target of the Global Strategy for Plant Conservation was species dependent, relating to mating systems. Musa acuminata populations had low heterozygosity and diversity, indicating self-fertilization; many bunches were needed (> 15) to represent regional alleles to 70%; over 90% of the alleles from a bunch are included in only two seeds. Musa maclayi was characteristically cross-fertilizing; only three bunches were needed to represent regional alleles; within a bunch, 16 seeds represent alleles. Musa balbisiana, considered cross-fertilized, had low genetic diversity; seeds of four bunches are needed to represent regional alleles; only two seeds represent alleles in a bunch.
We demonstrate empirical measurement of representation of genetic material in seeds collections in ex situ conservation towards conservation targets. Species mating systems profoundly affected genetic representation in seed collections and therefore should be a primary consideration to maximize genetic representation. Results are applicable to sampling strategies for other wild species.
保护植物遗传资源，包括作物的野生近缘种，在应对人类和地球面临的一些关键挑战方面发挥着重要作用，这些挑战包括消除饥饿和生物多样性丧失。然而，居外收集物，特别是种子收集物的遗传多样性和代表性往往是未知的。这限制了对保护目标的有意义评估，损害了未来收集的目标定位，并限制了它们的使用。我们评估了三种香蕉和大蕉野生近缘种的种子收集物与源种群的遗传代表性。焦点物种和采样区域为 M. acuminata subsp. banksii（巴布亚新几内亚）、M. balbisiana（越南）和 M. maclayi s.l.（巴布亚新几内亚的布干维尔）。我们使用 16-20 个现有的和新开发的分类群特异性多态性微卫星标记套件对 445 个样本进行了测序。每个物种的样本均来自一个区域的五个种群；每个种群分析了 15 个来自不同个体的叶片样本和 16 个来自一个果穗的种子样本。
与种群相比，种子的等位基因丰富度分别为 51%、81%和 93%（分别为 M. acuminata、M. balbisiana 和 M. maclayi）。种子样本代表了种群中的所有常见等位基因，但省略了一些罕见的等位基因。达到《全球植物保护战略》70%目标所需的收藏数量取决于物种的交配系统。Musa acuminata 种群的杂合度和多样性较低，表明自交；需要许多果穗（>15 个）才能代表 70%的区域等位基因；一穗中包含的 90%以上的等位基因仅包含在两个种子中。Musa maclayi 是典型的异交种；只需三个果穗即可代表区域等位基因；在一穗中，16 个种子代表等位基因。Musa balbisiana 被认为是异交的，但其遗传多样性较低；需要四个果穗的种子才能代表区域等位基因；一穗中只有两个种子代表等位基因。
我们展示了通过在居外保护中对种子收集物的遗传物质进行实证测量来实现保护目标的代表性。物种的交配系统对种子收集物的遗传代表性有深远影响，因此应该是最大限度地提高遗传代表性的主要考虑因素。结果适用于其他野生物种的采样策略。
