Ondabu Naftali, Maina Solomon, Kimani Wilson, Njarui Donald, Djikeng Appolinaire, Ghimire Sita
Biosciences Eastern and Central Africa-International Livestock Research Institute (BecA-ILRI) Hub, P.O. Box 30709, Nairobi 00100, Kenya;
Kenya Agricultural and Livestock Research Organization (KALRO), P.O. Box 57811, Nairobi 00200, Kenya;
Agronomy (Basel). 2017 Feb 9;7(1):8. doi: 10.3390/agronomy7010008.
Brachiaria grass is an emerging forage option for livestock production in Kenya. Kenya lies within the center of diversity for species, thus a high genetic variation in natural populations of is expected. Overgrazing and clearing of natural vegetation for crop production and nonagricultural uses and climate change continue to threaten the natural biodiversity. In this study, we collected 79 ecotypes from different parts of Kenya and examined them for genetic variations and their relatedness with 8 commercial varieties. A total of 120 different alleles were detected by 22 markers in the 79 ecotypes. Markers were highly informative in differentiating ecotypes with average diversity and polymorphic information content of 0.623 and 0.583, respectively. Five subpopulations: International Livestock Research Institute (ILRI), Kitui, Kisii, Alupe, and Kiminini differed in sample size, number of alleles, number of private alleles, diversity index, and percentage polymorphic loci. The contribution of within-the-individual difference to total genetic variation of Kenyan ecotype population was 81%, and the fixation index ( = 0.021) and number of migrant per generation (m = 11.58) showed low genetic differentiation among the populations. The genetic distance was highest between Alupe and Kisii populations (0.510) and the lowest between ILRI and Kiminini populations (0.307). The unweighted neighbor-joining (NJ) tree showed test ecotypes grouped into three major clusters: ILRI ecotypes were present in all clusters; Kisii and Alupe ecotypes and improved varieties grouped in clusters I and II; and ecotypes from Kitui and Kiminini grouped in cluster I. This study confirms higher genetic diversity in Kenyan ecotypes than eight commercial varieties (Basilisk, Humidicola, Llanero, Marandú, MG4, Mulato II, Piatá and Xaraés) that represent three species and one three-way cross-hybrid Mulato II. There is a need for further collection of local ecotypes and their morphological, agronomical, and genetic characterizations to support Brachiaria grass breeding and conservation programs.
臂形草是肯尼亚畜牧业中一种新兴的饲料选择。肯尼亚位于该物种的多样性中心，因此预计其天然种群具有高度的遗传变异。过度放牧、为作物生产和非农业用途而清除天然植被以及气候变化继续威胁着自然生物多样性。在本研究中，我们从肯尼亚不同地区收集了79个生态型，并对它们进行了遗传变异检测以及它们与8个商业品种的亲缘关系分析。通过22个标记在79个生态型中总共检测到120个不同的等位基因。这些标记在区分生态型方面具有很高的信息量，平均多样性和多态信息含量分别为0.623和0.583。五个亚种群：国际家畜研究所（ILRI）、基图伊、基西、阿鲁佩和基米尼尼在样本大小、等位基因数量、私有等位基因数量、多样性指数和多态位点百分比方面存在差异。个体内部差异对肯尼亚生态型种群总遗传变异的贡献为81%，固定指数（F = 0.021）和每代迁移个体数（m = 11.58）表明种群间遗传分化较低。阿鲁佩和基西种群之间的遗传距离最高（0.510），ILRI和基米尼尼种群之间的遗传距离最低（0.307）。非加权邻接法（NJ）树显示，测试的生态型分为三个主要聚类：ILRI生态型存在于所有聚类中；基西和阿鲁佩生态型以及改良品种聚集在聚类I和II中；来自基图伊和基米尼尼的生态型聚集在聚类I中。本研究证实，肯尼亚生态型的遗传多样性高于代表三个物种和一个三交杂种穆拉托二号的八个商业品种（巴西利斯克、湿地臂形草、利亚内罗、马兰杜、MG4、穆拉托二号、皮亚塔和哈拉埃斯）。需要进一步收集当地生态型并对其进行形态学、农艺学和遗传学特征分析，以支持臂形草的育种和保护计划。
