Conserving Vicia faba germplasm as a pure line collection requires reliable information of the selfing process. Previous knowledge about the effects of selfing was elaborated on the context of new data. In our study we increased the number of entries, 95 entries from the major, equina and minor groups were studied. The selfing process has been quantified by means of univariate as well as multivariate techniques. Effects of selfing on floral, yield and yield distribution traits were investigated by comparing two levels of selfing in open pollination conditions and in cages to exclude insects. Univariate analysis shows that selfing process results in plants with lower seeds per plant, seeds and ovules per pod and pod length. As selfing progressed there was change in yield distribution traits, the number of the lowest pod bearing node, the number of nodes between the first flower and the first pod increase and the number of nodes with pods decreases. Multivariate analysis indicates that: a) self-pollination profoundly influences plants performance and the three levels of selfing studied are clearly different; b) There is continuum pattern of change from one level of selfing to the another; c) The main characteristics that contributed to the separation among the levels of selfing varies with the botanical group. d) There was no significant contribution to the discrimination among levels of selfing of number of seeds per plant in the major group. Our results are relevant to the management of faba bean germplasm collections and enhance the formulation of integrated strategies of faba bean germplasm multiplication. 相似文献
The effect of selection for scrapie resistance on genetic variability in the rare Xalda sheep breed was studied. Pedigree information comprised 1851 animals (1444 alive) at the moment of sampling. A total of 304 reproductive (or selected for reproduction) Xalda individuals were sampled and genotyped for 14 microsatellites. Genetic variability was assessed using: gene diversity (1 − average kinship, GD), mean average relatedness (AR) and self-coancestry (ci) at the genealogical level; and expected heterozygosity (He), molecular mean kinship (Mk), molecular self-coancestry (si) and rarefacted average number of alleles per locus (A) at the molecular level. Two breeding strategies were evaluated: a) use of only young rams with genotype ARR/ARR and young ewes with low to moderate risk (risk groups R1 to R3); b) breeding without selection for PrP genotypes. The major cause of losses of genetic variability in the Xalda breed is the drift that occurs when a new group of reproductive individuals is selected. The loss of genetic variability is small in females compared to the males, where it is considerable. However, losses at the molecular level for young females with respect to adult females were above 5%. Young male individuals also retained most of the genetic variability assessed in adult rams. Selection against susceptibility to scrapie produced additional losses of more than 2% for He and A when rYF individuals are considered. As regards males, the situation becomes critical because of the scant number of available ARR/ARR young rams. The consequences for the management of the Xalda breed are discussed. 相似文献
Manchega is a local Spanish sheep breed located in the region of Castilla la Mancha, Actually there are 0.8 million of milked ewes. The selection scheme of Manchega breed (ESROM) started in 1988, involving a selection nucleus composed by 103,887 ewes distributed in 106 flocks. Results obtained from the ESROM has been moderate in comparison with other similar European schemes. By this and other reasons, to develop a specific tool to study the ESROM system seems to be necessary.
The objectives of this work were to develop a genetic simulation model based on the ESROM real system and to study the effects on genetic progress and inbreeding level achieved from different rates of AI used, the progeny test system and the selection nucleus size.
An additive infinitesimal model was assumed for the trait 120 days Total Milk Yield (TMY). Five alternatives selection criteria (two per each group of animals to be selected), differentiated on their selection intensities, were associated to the selection of lambs for future artificial insemination rams, natural mating rams and ewes. All selection decisions were based on periodical genetic evaluations (BLUP), using an animal model with repeated measures. 60 specific cases were studied, each one with 20 replicates.
An average true genetic progress per year ranging from 1.04% to 2.10% in AI rams and 0.59% to 2.11% in ewes were observed. Results of phenotypic progress varied from 0.44% to 1.83% per year. True inbreeding levels of ewes at year 17 were between 0.218% and 1.879%.
The model used had the expected behavior. In general, the studied selection scheme had its better results (maximum genetic progress), when AI rate was equal or greater than 50%, a greater number of new rams were tested per year (75 and 44) and a selection nucleus size equal or greater than 9000 ewes (30 flocks). Selection intensity of natural mating rams had a great impact on the genetic progress, especially when the use of AI was low. The greater the nucleus size, the higher the genetic progress, but an operative scheme from around 9000 initial ewes could be established.
Results observed demonstrate the existence of some critical areas, which could be verified on the real system in order to improve their effectiveness. In this framework, the ESROM could develop two complementary strategies: to improve the selection system of Natural Mating Rams (selecting only sons of AI rams) and/or to increase the levels of AI until 50%. 相似文献
Polish Arabian horses are a good example of a small population derived from a finite number of founders. Pedigree analysis showed significant reduction in the genetic diversity of the population. However, taking into account some circumstances suggesting the presence of balancing selection favouring heterozygotes in Polish breeding, it seems that this referred to pedigree uniformity rather than to a real decrease in genetic variability. The aim of the current study was to verify the hypothesis that balancing selection affects the population. The mare selection process was examined in detail regarding the polymorphism of 10 protein markers. The findings confirmed the tendency to favour the more heterozygous mares with regard to average heterozygosity in total and in relation to particular loci, studs, fathers and inbreeding ranges. The results were discussed in consideration of selection criteria, inbreeding level of Polish Arabs and heterozygosity in other populations. 相似文献
