Mkize Lwamkelekile Sitshilelo, Zishiri Oliver Tendayi
School of Life Sciences, University of KwaZulu-Natal, Private Bag X54001, Durban, 4000, South Africa.
Trop Anim Health Prod. 2020 Jul;52(4):2079-2089. doi: 10.1007/s11250-020-02231-8. Epub 2020 Feb 11.
The Nguni cattle breed predominates South Africa and is endowed with traits favourable against environmental stressors such as heat stress and resistance to diseases. Interventions to improve production have led to the erosion of the genetic integrity of local breeds and the introduction of exotic breeds has proved ineffective as they fail to perform well due to different climatic conditions and production systems. In this study, the genetic structure and genetic lineage of Nguni crossbreds from 6 populations were assessed using the mitochondrial cytochrome b gene. Twelve polymorphic sites were detected resulting in 11 haplotypes with haplotype and nucleotide diversities of 0.550 ± 0.135 and 0.0019 ± 0.0011, respectively. Only 2 of the 6 populations displayed recent population expansion events, whereas the majority adhered to neutral evolution. The basal haplotype contained approximately 60% of the studied populations and there were four unique haplotypes that were revealed. A possible Nguni descript haplotype was uncovered, and this haplotype was found in all populations but was however devoid of individuals from around the world. The genetic structure of the populations was rather low (average pairwise F = 0.066 and Slatkins F = 0.094), and approximately 96% of the total genetic variation was accounted for by differences within populations. Phylogenetic analyses supported the clustering of all the samples within the Bos taurus clade and no Bos indicus haplotype was detected. Furthermore, no intermediate haplotype of taurine and indicine was detected. Overall, the maternal lineage of the crossbreds points to a taurine origin and the low genetic diversity depicts the retention of the Nguni genetic pool and possibly its superior adaptive traits.
恩古尼牛品种在南非占主导地位，具有抵御热应激等环境压力源以及抗病的有利性状。旨在提高产量的干预措施导致当地品种的遗传完整性受到侵蚀，而引入外来品种已被证明效果不佳，因为它们由于不同的气候条件和生产系统而表现不佳。在本研究中，使用线粒体细胞色素b基因评估了来自6个种群的恩古尼杂交种的遗传结构和遗传谱系。检测到12个多态性位点，产生了11个单倍型，单倍型多样性和核苷酸多样性分别为0.550±0.135和0.0019±0.0011。6个种群中只有2个显示出近期的种群扩张事件，而大多数种群遵循中性进化。基础单倍型包含约60%的研究种群，并且揭示了4个独特的单倍型。发现了一种可能的恩古尼描述性单倍型，该单倍型在所有种群中都有发现，但没有来自世界各地的个体。种群的遗传结构相当低（平均成对F = 0.066，斯莱特金F = 0.094），并且大约96%的总遗传变异是由种群内部的差异造成的。系统发育分析支持所有样本在牛属进化枝内的聚类，未检测到瘤牛单倍型。此外，未检测到瘤牛和印度牛的中间单倍型。总体而言，杂交种的母系谱系指向瘤牛起源，低遗传多样性描绘了恩古尼基因库的保留以及可能其优越的适应性状。
