Genetic Analysis of Cryotolerance in Cotton During the Overwintering Period Using Mixed Model of Major Gene and Polygene

The joint analysis of the mixed genetic model of major gene and polygene was conducted to study the inheritance of cryotolerance in cotton during the overwintering period.H077（G.hirsutum L.,weak cryotolerance） and H113（G.barbadence L.,strong cryotolerance） were used as parents.Cryotolerance of six generation populations including P1,P2,F1,B1,B2,and F2,from each of the two reciprocal crosses H077×H113 and H113×H077 were all investigated.The results showed that cryotolerance in cotton during the overwintering period was accorded with two additive major genes and additivedominance polygene genetic model.For cross H077×H113,the heritabilities of major genes in B1,B2,and F2 were 83.62,76.84,and 90.56%,respectively;and the heritability of polygene could only be detected in B2,which was 7.76%.For cross H113×H077,the heritabilities of major genes in B1,B2,and F2 were 67.42,68.95,and 83.40%,respectively;and the heritability of polygene was only detected in F2,which was 6.51%.In addition,the whole heritability in F2 was always higher than that in B1 and B2 in each cross.Therefore,for the cryotolerance breeding of perennial cotton,the method of single cross recombination or single backcross should be adopted to transfer major genes,and the selection in F2 would be more efficient than that in other generations.

Development and quality of bovine embryos produced in vitro using growth factor supplemented serum-free system

The influence of a growth factor supplemented serum-free system on the development, gene expression, and cryotolerance of in vitro pro- duced bovine embryos was investigated. To assess the embryo development and gene ex- pression in blastocysts, abattoir-derived oo- cytes (obtained from 3 - 10 or <3 mm follicles) were matured and fertilized in serum-free media and cultured in synthetic oviductal fluid sup- plemented with fetal bovine serum (FBS, 4%), epidermal growth factor (EGF, 10 ng/mL), insulin like growth factor-1 (IGF-1, 100 ng/mL), stem cell factor (SCF, 50 ng/mL) or combinations of the growth factors. Expressions of selected gene transcripts were relatively quantified in the d 8 blastocysts. To assess the cryotolerance, d 4 morulae (derived from 3 - 10 mm follicles and cultured with the supplementation of FBS or combinations of the growth factors) were vitri- fied, thawed and cultured (with respective sup- plementations). Total cell number and DNA frag- mentation in blastocysts derived from the vitri- fied morulae were assessed through TUNEL assay. The rate (%) of cleavage, blastocyst and expanded/hatched blastocyst did not differ among the culture medium supplementations within the follicle size of 3 - 10 mm (range 65.1 ± 4.3 - 75.4 ± 3.9;22.4 ± 3.9 - 36.4 ± 3.6;and 11.2 ± 2.9 - 23.3 ± 3.2, respectively) or <3 mm (range 59.3 ± 4.2 - 74.5 ± 3.7;15.0 ± 3.5 - 28.7 ± 4.5;and 9.3 ± 2.8 - 17.3 ± 2.7, respectively). Nevertheless, significantly lower (P < 0.05) cleavage and blastocyst rates with FBS and lower blastocyst rate with SCF supplementations were observed for the oocytes derived from <3 compared to 3 - 10 mm follicles. The expression patterns of BCL-2, BAX, HSP1A1, GJA1 and BIRC5 tran- scripts varied significantly (P < 0.05) in all cases, except for BIRC5 in the blastocysts derived from 3 - 10 mm follicles. Following thaw and culture, the development (%) of vitrified morulae into expanded/hatched blastocysts was lower (P < 0.01) with the supplementation of growth fac- tors compared to FBS. In contrast, total number of cells and DNA fragmentation index in blas- tocysts were not different among the treatments. In conclusion, the growth factor supplemented serum-free system was satisfactory for in vitro bovine embryo production. Nevertheless, the system was not efficient when embryos were derived from <3 mm follicles and cultured with SCF. Additionally, gene expression patterns and cryotolerance of the embryos were affected with the treatments of growth factors compared to serum.