THE OESTROGEN RECEPTOR GENE ( ESR ) PVU II poLYMoRphISM GENoTYpE AND ALLELE FREQUENCIES IN CZECH LARGE WHITE AND LANDRACE

GOLIÁšOVÁ, E. , DVOŘÁK, J.: The oestrogen receptor gene (ESR) PvuII polymorphism allele frequencies in Czech Large White and Landrace. Acta univ. agric. et silvic. Mendel. Brun. , 2005, LIII, No. 2, pp. 33-38 Genotype and allele frequencies of the oestrogen receptor gene (ESR) PvuII restriction site were investigated in populations of the main Czech maternal breeds. 1253 sows and gilts and 396 boars in Large White and 334 sows and gilts and 318 boars in Landrace were genotyped from blood samples by the modified PCR-RFLP procedure as described in Short et al. (1997). In Large White, the frequency of allele B was about 0.51. In Landrace, the frequency of allele B reached from 0.02 for boars to 0.03 for sows. No significant deviations of the observed genotype frequencies from the frequencies expected according to Hardy-Weinberg equilibrium were found in both breed. Opposite trends in allele frequencies development could be assumed for analysed sows and boars of both breeds. In Large White sows the frequency of allele B raised probably due prefering sows with BB genotype, whereas in Landrace population the frequency of allele B decreased from yet unknown reasons. pig, litter size, candidate gene, ESR, allele frequencies Ročník LIII 3 Číslo 2, 2005 33 Efficiency of livestock production is highly influenced by reproductive success (Short et al., 1997). The genetic progress obtained in large national purebred populations is often much less than supposed (van der Lende et al., 2002) due to the nature of reproduction traits (low heritability, sex-limited, performance late in life etc.). Information about the identification of individual genes or anonymous genetic markers associated with litter size could contribute to an increased rate of genetic gain achieved in pig populations. Association between polymorphisms at several candidate genes and reproductive performance have been reported (Kirkpatrick, 2002). The PvuII polymorphism of the oestrogen receptor (ESR) gene has been shown to influence sow prolificacy in USA and European Meishan synthetics (Rothschild et al., 1995; Southwood et al., 1995). These results were confirmed for Large White populations as well (Rothschild et al., 1995; Short et al., 1997). Estimates of the ESR polymorphism effect in the first parities varied from 1.43 piglets per litter in Meishan synthetics to 0.42 piglets per litter in Large White lines, both per copy of allele B. In other studies no clear association between the ESR polymorphism and litter size traits was shown (Southwood et al., 1995; Rothschild et al., 1996; Legault et al., 1996). PvuII polymorphism of ESR gene was detected in the Czech Republic in 34 E. Goliášová, J. Dvořák Large White and Landrace populations (Kolaříková et al., 2000; Putnová et al., 2001; Vrtková and Dvořák, 2001) and in Prestice Black Spotted population as well (Nováková, 2003). The aim of the present paper was to investigate ESR-PvuII genotype and allele frequencies and their development in both main Czech maternal pig breed populations. MATERIAL AND METhoDS Genotype and allele frequencies of the oestrogen receptor gene (ESR) PvuII restriction site were investigated for a data set including 1253 gilts and sows and 396 boars of Large White and 334 gilts and sows and 318 boars of Landrace breed. Large White gilts and sows (next sows) originated from 34 nucleus herds and Landrace sows from 8 nucleus herds. Sow’s genotype data gathering was connected with the creation of Large White and Landrace hyperprolific lines. All animals were genotyped for the porcine oestrogen receptor gene (ESR). The PvuII polymorphism was analysed by the PCR–RFLP procedure from blood samples. The PCR with primer sequences as described in Short et al. (1997) was used to amplify DNA samples. The 120 bp long PCR product was in the presence of allele B cut into fragments of length 55 bp and 65 bp, whereas in the presence of allele A the PCR product remained intact. In the Czech Republic were for allele marking used letters C and D, in the present study are used letters according to original method: A and B for C and D, respectively. Allele and genotype frequencies were calculated within each breed. The Chi-square test was used to determine the presence of Hardy-Weinberg equilibrium for the ESR locus in each population. RESULTS AND DISCUSSIoN Genotype and allele frequencies in both main Czech maternal pig populations are very different (Tab. I and II). Whereas for Large White the frequency of the B allele reached values of about 0.51, in the Landrace population were observed frequencies of 0.02 for boars and 0.03 for sows. In contrast to the presence of all genotypes in Large White, in Landrace only AA and AB genotyped animals were found. Both Large White and Landrace populations were in HardyWeinberg equilibrium for the analysed locus. These results are in accordance with findings in other populations in the world. Whereas the frequency of allele B ranged from 0.38 to 0.72 in Large White or Large White based populations (Rothschild et al., 1995; Southwood et al., 1995; Short et al., 1997; Leeds et al., 2002; Vrtková and Dvořák, 2001), in Landrace based populations allele B disappeared or its frequency is very law (Tab. III). Although values of allele B frequencies were in various Landrace populations similar, sows with BB genotype were observed only in two studies (Noguera et al., 2003; Vrtková and Dvořák, 2001). The absence of sows with BB genotype in some studies could be explained by the low freqency of allele B together with small number of genotyped animals. But further possible explanation (the impact of selection pressure on traits in breeding objective, relation between BB genotype and fitness) cannot be clearly excluded. Trends in the development of allele frequencies in both investigated maternal breeds are presented in Tab. I. and II. Whereas for Large White boars the allele frequencies between years of birth are stable, for sows the frequency of allele B raises. The frequency of allele B for sows born before 1999 achieved 0.37. This value is in accordance with outcomes found by Vrtková and Dvořák (2001). The frequency of allele B in following years raises and in sows born in 2002 achieved almost 0.58. The increasing of the allele B frequency in Large White sows was probably made by preferring sows with genotype BB. Although only small number of AB genotyped animals was observed, the opposite trend in allele frequency development could be assumed in Landrace breed. This trend is confirmed by comparisson of the overall allele B frequency 0.03 with higher frequency 0.09 found in the year 2001 by Vrtková and Dvořák (2001). Rothschild et al. (1996) suggested that the ESR-PvuII polymorphism is mainly restricted to commercial lines with Large White due to interbreeding of Chinese pigs with Large White ancestors in England prior to the 1800s. Noguera et al. (2003) assumed that similarly as in Large White populations, the allele B found in Spanish Landrace originated from Chinese breeds. ESR-PvuII polymorphism was found in the most of analysed Landrace populations. Only sows of German Landrace breed were for this restriction site AA monomorphic. Then consider the number of genotyped sows, the absence of ESR-PvuII polymorphism was not probably made by error in way of data gathering. From study of Steinheuer et al. (2002) could be deduced, that analysed polymorphism in German Landrace exist (at least in past). These authors did not find any polymorphism for sows involved in the study, but small fraction of analysed litters descended from boars with genotype AB. In selected populations, a deviation from the Hardy-Weinberg equilibrium should be expected for genes, which have significant impact on the traits under selection. Although in Large White data set the performance of AA genotyped sows was about 0.5 piglets per litter greater (P < 0.01) than the litter size of BB genotyped sows (Goliášová and Wolf, 2004), any deviation from Hardy-Weinberg equilibrium was not detected. Similarly to our result, in INRA hyperprolific and control lines no significant deviation The oestrogen receptor gene PvuII polymorphism allele frequencies in Czech Large White and Landrace 35 I: Development of ESR-PvuII genotype and allele frequencies in Large White females and boars Year of birth N Genotype frequencies (%) Allele frequencies χ2 AA AB BB A B