Utilization Of Genetic Diversity Research Articles

Biotechnology and Crop Improvement

Plant biotechnology, a major component of agricultural biotechnology, deals with various aspects of plant tissue culture, genetic transformation, and molecular biology techniques. Tissue culture methods offer a rich scope for creation, conservation, and utilization of genetic variability for the improvement of field, fruit, vegetable, and forest crops, and medicinal/aromatic plants. Micropropagation technology ensures true to type, rapid and mass multiplication of plants that possesses special significance in vegetatively propagated plant species. This technology has witnessed a huge expansion globally, with an estimated global market of 15 billion US$/annum for tissue-culture products. Some basic techniques of tissue culture, such as anther/microspore culture, somaclonal variation, embryo culture, and somatic hybridization, are being exploited to generate useful genetic variability for obtaining incremental improvement in commercial cultivars. Production of secondary metabolites, such as food flavors, food colors, dyes, perfumes, drugs, and scented oils used in aromatherapy, through cell cultures and hairy root cultures, are leading examples of molecular farming. Cryopreservation of germplasm at the cell/tissue/organ levels, in liquid nitrogen at −196°C, is highly rewarding for establishing germplasm banks, especially for vegetatively propagated crops and rare, endangered plant species. During the past 15 years, remarkable achievements have been made in the production, characterization, field evaluation, and release of transgenic varieties/hybrids in several crops. Transgenic varieties/hybrids of maize, cotton, soybean, potato, tomato, and papaya are now being commercially grown on about 134 million hectares spread across 25 countries. Research in genomics allows high-resolution genetic analysis for physical mapping and positional gene cloning of useful genes for crop improvement. Molecular (DNA) markers help in precise characterization of germplasm, construction of saturated linkage maps, and DNA fingerprinting of crop varieties. Molecular markers are now increasingly being used for marker-assisted gene pyramiding and alien gene introgression. Current research, involving large-scale DNA sequencing, microarrays, and robotics, is heading towards gene revolution and nanobiotechnology.

Analysis of Genetic Variation of Abalone (Haliotis discus hannai) Populations with Microsatellite Markers

Microsatellite markers were used to access the genetic variation in three populations of abalone Haliotis discus hannai. Two wild populations were collected from the sea areas in Changdao, Shandong and Dalian, Liaoning respectively. A cultivated population originated from the sea area in Kongdongdao, Shangdong. Six microsatellite loci were screened for genetic polymorphism. Polymorphic information content (PIC) value per loci was greater than 0.5 and can be used to analysis of genetic structure of the three abalone populations. Fifty-seven alleles were amplified from the three populations in six microsatellite loci. The average number of alleles (A) was 9.50 and the effective number of alleles (Ne) was 5.8572. The mean observed heterozygosity (Ho) and the mean expected heterozygosity (He) were 0.6925 and 0.7966, respectively. The Ho and He of two wild abalone populations were higher than that of cultured population. All these results provide a basis for conservation and utilization of genetic diversity of Haliotis discus hannai.

Mating system and DNA polymorphism of monokaryons with different mating type of Stropharia rugoso-annulata

The mating system of Stropharia rugoso-annulata Farlow apud Murrill was studied by pairing single spore isolates from the same fruitbody, and the genetic diversity of monokaryotic strains with different mating types was evaluated by the RAPD technique. Basidiospores could germinate normally on PGP (potato/glucose/peptone) medium at 30 °C. Analysis of self- and cross-pairings revealed that Stropharia rugoso-annulata was heterothallic and tetrapolar. RAPD analysis detected polymorphism among monokaryotic strains, with more genetic variation within monokaryotic strains with non-parental mating type compared to monokaryotic strains with parental mating type. These results were in general agreement with the existing knowledge, confirming the validity and usefulness of the RAPD technique. Therefore, the RAPD technique will provide an exciting and valuable tool for a large-scale study on identification and genetic resources of monokaryotic strains, and should lead to a more efficient understanding and utilization of genetic diversity of monokaryotic strains in cross breeding by breeders.

The origin of the domestic pig: independent domestication and subsequent introgression.

The domestic pig originates from the Eurasian wild boar (Sus scrofa). We have sequenced mitochondrial DNA and nuclear genes from wild and domestic pigs from Asia and Europe. Clear evidence was obtained for domestication to have occurred independently from wild boar subspecies in Europe and Asia. The time since divergence of the ancestral forms was estimated at approximately 500,000 years, well before domestication approximately 9,000 years ago. Historical records indicate that Asian pigs were introduced into Europe during the 18th and early 19th centuries. We found molecular evidence for this introgression and the data indicated a hybrid origin of some major "European" pig breeds. The study is an advance in pig genetics and has important implications for the maintenance and utilization of genetic diversity in this livestock species.

Conservation, Creation, and Utilization of Genetic Variation

Animal breeding aims at transforming genetic variability into the greatest possible genetic progress. Several factors have to be considered to achieve this goal. Efficient conservation of genetic variance by keeping large effective population size, and efficient utilization of newly arising variation by having an appropriate balance between selection pressure and effective size are important. There seem to be real possibilities now to artificially increase the amount of new variation generated above the level of spontaneous mutation. Induced mutation, transformation, and insertion may be used with advantage in future breeding schemes supplementing but not replacing the methods of today. The kind of utilization of the genetic variance also merits attention. Different selection strategies can lead to vastly different long-term results and also the direction of selection, indirect or direct, is important in schemes lasting several generations.

Sire effect on fatty acid composition of ovine adipose tissue.

The fatty acid composition of perirenal adipose tissue from 255 purebred and crossbred sheep was examined to determine the genetic effects of sire on each of five fatty acids. The sheep, all rams, were the progeny of 30 Dorset Horn sires. The animals were grazed on pasture and slaughtered at an average age of 21 months, when their mean carcass weight was 30 kilograms. The fatty acids studied and their mean percentage compositions were: stearic, 38%; oleic, 31%; palmitic, 20%; palmitoleic, 2%, and linoleic, 2%. These amounted to over 90% by weight of the tissue sample fatty acids. In addition, numerical functions were constructed as ratios for two pairs of fatty acids, ratio 1 (palmitoleic to palmitic) and ratio 2 (oleic to stearic), for estimation of the desaturase enzyme activity in the tissue samples studied. A Softness Index, expressed as a ratio between monounsaturated and saturated acids, was also included in the analysis. Significant birth year and maternal breed effects were found for all the traits studied. This was in contrast to the regression on slaughter age, which with two exceptions was not a significant source of variation in the data. The sire effect, based on 27 degrees of freedom, was highly significant or significant for all traits except stearic or linoleic acid and ratio 2. These results are discussed with reference to utilization of genetic variation between sites in selective breeding programs to modify fatty acid composition of ovine adipose tissue.

Problems in the estimation and utilization of genetic variability.

Problems in the estimation and utilization of genetic variability.