Studies on the Genetic Relationships of Sheep Populations from East and South of Central Asia

Hu sheep was sampled randomly from Huzhou city, Zhejiang province, China. Of the 11 genetic markers from the blood examined by starch-gel and cellulose acetate electrophoresis, polymorphisms in Hu sheep were found for 10 loci, i.e. post-albumin (Po), transferring (Tf), alkaline phosphatase (Alp), leucine aminopeptidase (Lap), arylesterase (Ary-Es), hemoglobin-β (Hb-β)、Xprotein(X-p), carbonic anhydrase (CA), catalase (Cat) and lysine (Ly). The same data except for Po locus were collected from another 14 sheep breeds from China and other countries, in order to ascertain their genetic relationships with one another and with the Hu sheep. The sheep populations from the east and south of Central Asia can be classified into three genetic groups: “Mongolian sheep”, “South Asian sheep” and “European sheep”. The Hu sheep belong to the “Mongolian sheep” group. (Asian-Aust. J. Anim. Sci. 2002. Vol 15, No. 10 : 1398-1402)


INTRODUCTION
The phylogenetic classification of domemestic animal populations is one of the bases for determining the scope of a breed, estimating the possibility of the potential distribution of special gene resources in a specific population, judging the possibility of identical genes (or gene groups) controlling similar body shapes in different populations, analysing the population characteristic of gene coadaptation, predicting heterosis, and devising breeding strategy (Chang et al., 1995).Hu sheep is the indigenous breed of Zhejiang province, China.It is distributed along the Taihu valley, and it is famous for its high fertility and beautiful lambskin.It is regarded as a "secret breed" in China (Zheng, 1980).
With regards to sheep, there are rich sheep resources in China.There were a few reports about some sheep populationsin in Asia (Tsunoda et al., 1988(Tsunoda et al., , 1990(Tsunoda et al., , 1992(Tsunoda et al., , 1995(Tsunoda et al., , 1998(Tsunoda et al., , 1999)), but apart from Yunnan sheep, no information is available about Chinese sheep breeds.The genetic relationships of sheep breeds from the east and south of Central Asia is not completely understood.
This paper attempts to describe the genetic constitution and origin of Hu sheep-a "secret breed" in China and the genetic relationships among the sheep breeds of the east and south of Central Asia, so as to provide a basis for the development of the sheep husbandry in this area.

Materials, sampling method
The Hu sheep studied were from Lianshi Town of Huzhou city in Zhejiang province of China.Blood sampling was performed by the "Random sampling in typical colonies of central area" method and we tried to avoid sampling two (or more) individuals that have traceable genetic relationship.Some external morphological characteristics of Hu sheep were also investigated.

Collecting and treatment of blood samples
8 ml of blood was taken from the cervical vein of each animal and put into a centrifuge tube using heparin as an anticoagulant.The blood serum is separated by centrifugation (3,000 rpm, 5-10 min) and transferred into a capped test tube.After that the same volume of 0.85% NaCl as the remaining blood cells was added and the tube was centrifuged for two or three times (3,000 rpm, 5-10 min).After the last centrifugation, the upper layer of serum was discarded and the same volume (or 1.5 times) distilled water was added into the remaining blood cells.After numbering, the tube was kept in a refrigerator (below -20°C).

Statistical analysis
Gene frequencies for the polymorphic traits were computed by the gene counting method for Al, Po, Tf, Hbβ, CA and Cat loci and by the square root method for Alp, Lap, Ary-Es, X-p and Ly loci.
The following two formulae were used to calculate the reliability that ensures the estimate not to deviate from the true value by more than 0.5 times (β) and the relative deviation when the reliability reaches 0.9545(η).
In the above formula, P and V(p) stand for gene frequency and gene variance, respectively; λ is the standard deviation of the estimate and is suitable for the first formula when its standard deviation is

Genetic relationship clustering
The population information and the gene frequencies for 10 loci in 15 populations (breeds) are shown in Tables 1 and 3.
These data were reported by other researchers who used the same techniques as we did for Hu sheep.Only 10 loci but not Po were included because these were the loci examined in all the other populations.Based on these data the genetic distance was computed by Ward's method and clustering was done by the Hierarchy Clustering Method (Chang, 1995).

RESULTS
The accuracy and reliability of the estimates of gene frequencies of Hu sheep are shown in Table 2.
Of the 11 loci tested, 10 showed polymorphisms.It can be seen from table 2 that the reliability of the estimates of gene frequencies for 25 alleles reached 0.95 except that for Po F , Tf A , Tf F , Hb-β A and CA F , and their reliabilities were 0.5222, 0.7478, 0.5222, 0.6212 and 0.899, respectively.

Genetic relationships
Figure 1 shows the genetic relationships among the 15 sheep populations.
From Figure 1 we can see that the 15 sheep populations from the east and south of Central Asia are clearly classified into three groups: one group consists of the Mongolian sheep (Ub, Kh), Yunnan sheep and Hu sheep, which can be described as "Mongolian sheep"; the other group consists of the Nepalese native sheep (Bar, Kag), Bangladeshi native sheep (Ban) and Vietnamese sheep (Viet), which can be described as "South Asian sheep"; another group consists of five European sheep (breeds in Japan) and a Nepalese sheep breed (Bhy), which can be described as "European sheep".We also find that the Hu sheep clusters closely with the Mongolian sheep.Chang et al. (1988) have discussed the method of genetic resources inspection.The accuracy depends on the sample and loci tested.In this study we adopted the "Random sampling in typical colonies of central area" method.The higher reliability and precision obtained for gene frequency estimates for 11 loci of Hu sheep proved that this method is effective.

Sampling method
The breeds in the east and south of Central Asia can be divided into three groups "Mongolian sheep", "South Asian sheep" and "European sheep" Tsunoda et al. (1999) divided the Asian sheep into three groups: Mongolian group, Indo-Pakistani group and Tibetan group.Our study is only limited to the 15 populations breeding in east and south of Central Asia.Whether the two results are identical or not needs further studies.

The dendrogram of genetic relationships indicates that Hu sheep clusters closely with Mongolian sheep and this can also be supported by the known history of sheep breeding
Mongolian sheep were brought into the Taihu valley when the Nan-Song Dynasty left their former capital-Bianjing (i.e., Kaifeng) to Linan (i.e., Hangzhou) (Editorial Committee of the "Breeds of Domestic Animal and Poultry in China" et al., 1989).Thus this study confirms the origin of the Hu sheep.

Table 1 .
Information on the 15 populations studied

Table 2 .
Estimates of gene frequencies and their reliabilities and precision

Table 3 .
The gene frequencies in the 15 populations used in this study