Manomohan Vandana, Ramasamy Saravanan, Pichler Rudolf, Nagarajan Murali, Karuppusamy Sivakumar, Krovvidi Sudhakar, Nachiappan Raja K, Peters Sunday O, Periasamy Kathiravan
Animal Production and Health Section, Joint FAO/IAEA Division, International Atomic Energy Agency, 1400 Vienna, Austria.
Veterinary College and Research Institute, Tamil Nadu Veterinary and Animal Sciences University, Chennai 600051, India.
Animals (Basel). 2022 Jul 19;12(14):1838. doi: 10.3390/ani12141838.
During the last few decades, the effective population size of indigenous zebu cattle breeds has declined drastically, resulting in the classification of some of them into the vulnerable, endangered, or critically endangered category. Drastic reductions in the effective size of a population may result in genetic bottlenecks and can affect within-breed genetic variability and its viability. The present study was undertaken with the objective of evaluating South Indian zebu cattle populations for mutation drift equilibrium and to detect the occurrence of recent genetic bottleneck events. A total of 293 cattle from eight indigenous breeds were genotyped at 27 FAO/ISAG-recommended microsatellite marker loci. Three different statistical tests, viz., the sign test, standardized differences test, and Wilcoxon sign rank test were performed using allele frequency data to detect loci with heterozygosity excess under the infinite alleles, stepwise, and two-phase mutation models. Under the infinite alleles model, the observed number of loci with heterozygosity excess (He > Heq) ranged between 10 and 19 among the investigated cattle breeds. However, the observed heterozygosity excess was not statistically significant (p > 0.05) in any of the studied breeds. Similarly, the standardized differences test and Wilcoxon sign rank test revealed no concrete evidence for the occurrence of a recent genetic bottleneck in South Indian zebu cattle breeds. The qualitative test for mode-shift distortion revealed a normal L-shaped distribution of allele frequencies, suggesting a lack of evidence for the loss of low-frequency alleles in all the investigated South Indian zebu cattle breeds.
在过去几十年里，印度本土瘤牛品种的有效种群数量急剧下降，导致其中一些品种被归类为易危、濒危或极度濒危类别。种群有效规模的急剧减少可能导致遗传瓶颈，并可能影响品种内的遗传变异性及其生存能力。本研究旨在评估南印度瘤牛种群的突变漂变平衡，并检测近期遗传瓶颈事件的发生情况。对来自八个本土品种的总共293头牛在27个粮农组织/国际动物遗传学会推荐的微卫星标记位点进行了基因分型。使用等位基因频率数据进行了三种不同的统计检验，即符号检验、标准化差异检验和威尔科克森符号秩检验，以检测在无限等位基因、逐步和两阶段突变模型下杂合度过剩的位点。在无限等位基因模型下，在所研究的牛品种中，观察到杂合度过剩（He > Heq）的位点数在10到19之间。然而，在任何一个研究品种中，观察到的杂合度过剩在统计学上都不显著（p > 0.05）。同样，标准化差异检验和威尔科克森符号秩检验也没有揭示南印度瘤牛品种近期发生遗传瓶颈的具体证据。模式转移畸变的定性检验显示等位基因频率呈正常的L形分布，这表明在所有研究的南印度瘤牛品种中缺乏低频等位基因丢失的证据。
