Iragaba Paula, Kawuki Robert S, Bauchet Guillaume, Ramu Punna, Tufan Hale A, Earle Elizabeth D, Gore Michael A, Wolfe Marnin
Plant Breeding and Genetics Section, School of Integrative Plant Science Cornell Univ. Ithaca NY 14853 USA.
National Crops Resources Research Institute (NaCRRI) PO Box 7084 Kampala Uganda.
Crop Sci. 2020 May-Jun;60(3):1450-1461. doi: 10.1002/csc2.20152. Epub 2020 May 4.
Understanding the genetic relationships among farmer-preferred cassava ( Crantz) varieties is indispensable to genetic improvement efforts. In this study, we present a genetic analysis of 547 samples of cassava grown by 192 smallholder farmers, which were sampled at random within four districts in Uganda. We genotyped these samples at 287,952 single nucleotide polymorphisms using genotyping-by-sequencing and co-analyzed them with 349 cassava samples from the national breeding program in Uganda. The samples collected from smallholders consisted of 86 genetically unique varieties, as assessed using a genetic distance-based approach. Of these varieties, most were cultivated in only one district (30 in Kibaale, 19 in Masindi, 14 in Arua, and three in Apac), and only three were cultivated across all districts. The genetic differentiation we observed among farming districts in Uganda (mean fixation index [ ] = .003) is similar to divergence observed within other countries. Despite the fact that none of the breeding lines were directly observed in farmer fields, genetic divergence between the populations was low ( = .020). Interestingly, we detected the presence of introgressions from the wild relative Müll. Arg. on chromosomes 1 and 4, which implies ancestry with cassava breeding lines. Given the apparently similar pool of alleles in the breeding germplasm, it is likely that breeders have the raw genetic material they require to match the farmer-preferred trait combinations necessary for adoption. Our study highlights the importance of understanding the genetic makeup of cassava currently grown by smallholder farmers and relative to that of plant breeding germplasm.
了解农民偏爱的木薯（Crantz）品种之间的遗传关系对于遗传改良工作至关重要。在本研究中，我们对乌干达四个地区随机抽取的192位小农户种植的547份木薯样本进行了遗传分析。我们采用测序基因分型法对这些样本的287,952个单核苷酸多态性进行了基因分型，并将其与来自乌干达国家育种计划的349份木薯样本进行了联合分析。从小农户收集的样本包括86个基因独特的品种，这是通过基于遗传距离的方法评估得出的。在这些品种中，大多数仅在一个地区种植（基巴莱30个，马辛迪19个，阿鲁阿14个，阿帕克3个），只有三个品种在所有地区都有种植。我们在乌干达各种植区观察到的遗传分化（平均固定指数[] =.003）与在其他国家观察到的差异相似。尽管在农民田间没有直接观察到任何育种系，但群体之间的遗传差异很低（ =.020）。有趣的是，我们在1号和4号染色体上检测到了来自野生近缘种Müll. Arg.的渐渗，这意味着与木薯育种系有亲缘关系。鉴于育种种质中明显相似的等位基因库，育种者很可能拥有他们所需的原始遗传材料，以匹配采用所需的农民偏爱的性状组合。我们的研究强调了了解小农户目前种植的木薯的遗传组成以及相对于植物育种种质的遗传组成的重要性。
