Animal Production and Health Section, Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture, International Atomic Energy Agency, Vienna, Austria.
Faculty of Veterinary Medicine and Animal Science, University of Peradeniya, Peradeniya, Sri Lanka.
PLoS One. 2023 Aug 16;18(8):e0282761. doi: 10.1371/journal.pone.0282761. eCollection 2023.
The present study reports the population structure, genetic admixture and phylogeography of cattle breeds of Sri Lanka viz. Batu Harak, Thawalam and White cattle. Moderately high level of genetic diversity was observed in all the three Sri Lankan zebu cattle breeds. Estimates of inbreeding for Thawalam and White cattle breeds were relatively high with 6.1% and 7.2% respectively. Genetic differentiation of Sri Lankan Zebu (Batu Harak and White cattle) was lowest with Red Sindhi among Indus Valley Zebu while it was lowest with Hallikar among the South Indian cattle. Global F statistics showed 6.5% differences among all the investigated Zebu cattle breeds and 1.9% differences among Sri Lankan Zebu breeds. The Sri Lankan Zebu cattle breeds showed strong genetic relationships with Hallikar cattle, an ancient breed considered to be ancestor for most of the Mysore type draught cattle breeds of South India. Genetic admixture analysis revealed high levels of breed purity in Lanka White cattle with >97% Zebu ancestry. However, significant taurine admixture was observed in Batu Harak and Thawalam cattle. Two major Zebu haplogroups, I1 and I2 were observed in Sri Lankan Zebu with the former predominating the later in all the three breeds. A total of 112 haplotypes were observed in the studied breeds, of which 50 haplotypes were found in Sri Lankan Zebu cattle. Mismatch analysis revealed unimodal distribution in all the three breeds indicating population expansion. The sum of squared deviations (SSD) and raggedness index were non-significant in both the lineages of all the three breeds except for I1 lineage of Thawalam cattle (P<0.01) and I2 lineage of Batu Harak cattle (P<0.05). The results of neutrality tests revealed negative Tajima's D values for both the lineages of Batu Harak (P>0.05) and White cattle (P>0.05) indicating an excess of low frequency polymorphisms and demographic expansion. Genetic dilution of native Zebu cattle germplasm observed in the study is a cause for concern. Hence, it is imperative that national breeding organizations consider establishing conservation units for the three native cattle breeds to maintain breed purity and initiate genetic improvement programs.
本研究报告了斯里兰卡的三种牛品种，即 Batu Harak、Thawalam 和 White 牛的种群结构、遗传混合和系统地理学。所有三种斯里兰卡瘤牛品种均表现出中度高水平的遗传多样性。Thawalam 和 White 牛品种的近交估计值相对较高，分别为 6.1%和 7.2%。斯里兰卡瘤牛（Batu Harak 和 White 牛）与印度河流域瘤牛中的 Red Sindhi 相比遗传分化最低，与南印度牛中的 Hallikar 相比遗传分化最低。全球 F 统计数据显示，所有调查的瘤牛品种之间存在 6.5%的差异，斯里兰卡瘤牛品种之间存在 1.9%的差异。斯里兰卡瘤牛品种与 Hallikar 牛具有很强的遗传关系，Hallikar 牛是一种古老的品种，被认为是南印度大多数迈索尔型役用牛品种的祖先。遗传混合分析显示，Lanka White 牛的品种纯度很高，有超过 97%的 Zebu 血统。然而，在 Batu Harak 和 Thawalam 牛中观察到了显著的 Taurine 混合。在斯里兰卡瘤牛中观察到了两个主要的 Zebu 单倍群，I1 和 I2，前者在所有三个品种中均占主导地位。在所研究的品种中观察到了 112 个单倍型，其中 50 个单倍型存在于 Sri Lankan Zebu 牛中。错配分析显示，所有三个品种均呈单峰分布，表明种群扩张。除了 Thawalam 牛的 I1 谱系（P<0.01）和 Batu Harak 牛的 I2 谱系（P<0.05）外，所有三个品种的两个谱系的总和偏差（SSD）和不整齐指数均无显著差异。中性检验结果显示，Batu Harak（P>0.05）和 White 牛（P>0.05）的两个谱系的 Tajima's D 值均为负值，表明低频多态性过剩和种群扩张。本研究中观察到的本地 Zebu 牛遗传种质的稀释令人担忧。因此，国家育种组织必须考虑为这三个本地牛品种建立保护单位，以保持品种纯度并启动遗传改良计划。
