Comparison trials between Oreochromis andersonii (Kafue Bream) and O. niloticus (imported species) under farm conditions in Zambia.

There has been much discussion for many years over the most suitable tilapia species to use in aquaculture. It has been thought for many years that Nile tilapia (Oreochromis niloticus) was the most productive, especially after it had been developed using the genetically improved farmed tilapia (GIFT) protocols, but no trials have taken place under standard farming conditions nor was there ever any consideration taken of the possible ecological side effects of the introduction of alien species into river systems. With the help of a small grant from the Food and Agricultural Organization of United Nations, Kalimba Farm, Zambia, undertook to carry out a direct comparison between the suitability of both O. niloticus and O. andersonii for fish culture under normal farm conditions. These trials took place over three years from 2004 to 2007. The overall results concluded that there were definite advantages for both species in different areas, but considering a genetically improved species was being compared with stock that had been genetically isolated for 25 years, the overall results were encouraging for the indigenous O. andersonii. In addition, taking into account the assumed damage to fragile river systems from the introduction of invasive O. niloticus it was felt that efforts should be made in future to encourage the use of O. andersonii as the preferred fish for aquaculture in areas of Zambia that are not already polluted with O. niloticus and, furthermore, an effort should be made to improve O. andersonii through an on-farm selective breeding programme using the GIFT protocols.

Will natural resistance result in populations of ash trees remaining in British woodlands after a century of ash dieback disease?

Novel pests and diseases are becoming increasingly common, and often cause additional mortality to host species in the newly contacted communities. This can alter the structure of the community up to, and including, the extinction of host species. In the last 20 years, ash dieback (ADB) disease has spread into Europe from East Asia. It has caused substantial mortality in ash tree ( Fraxinus excelsior L . ) populations. However, a proportion of the individuals in most populations appear to be less susceptible to ADB and resistance seems to have high heritability. These observations have led to suggestions that ash populations may be sustainable after the disease. In order to test this hypothesis, I modified an existing model of UK woodland (parametrized for Wytham Woods, Oxfordshire) to take into account the impact of ADB and allowed offspring to inherit resistance traits from their parent. The results suggest that ash populations would still exist in 100 years, but at lower levels than they are currently. For example, when the initial proportion of resistant individuals is about 10% and heritability of resistance is 0.5, then the population of ash falls to about one-third of present levels. The proportion of individuals initially resistant to ADB had a larger effect on population size after 100 years than the heritability of resistance. The fact that the initial size of the resistant population is important to achieve a high population size in the presence of ADB suggests that a selective breeding programme with the intention of augmenting the natural ash populations would be beneficial.

Marker-assisted Selection in Fish: A Review

The important economical traits like body growth, resistance to diseases, meat quality, etc. highly influence the profitability of food animals including fishes. The main target of every selective breeding programme is to produce improved traits offspring’s. However, improvement of performance traits through traditional phenotype-based selection needs several generations to optimise these characters. Marker-Assisted Selection (MAS) is a type of indirect method of selection of better performing breeding individuals. MAS is beneficial when the traits are difficult, expensive to measure and has both low heritability and recessive traits. MAS facilitates the exploitation of existing genetic diversity in breeding populations and can be used to improve desirable traits in livestock. MAS depends on identifying the link between a genetic marker and Quantitative Traits Loci (QTL). The distance between marker and target traits determines the association of the marker with the QTL. After identifying the markers linked to QTL, they can be used in the selective breeding programme to select the brooders having better genetic potential for the targeted trait. Improvement of performance traits through MAS is fast and more accurate and allows us to understand the genetic mechanism affecting performance traits.

Molecular evaluations of thirty one clones of poplar based on RAPD and SSR molecular markers

Poplar is an important tree species valued all over the world for its wood importance. Despite limited knowledge of the levels of genetic diversity and relatedness, their cultivation as a source of plywood is widespread. In order to facilitate reasoned scientific decisions on its management and conservation and prepare for selective breeding programme, genetic analysis of 31 genotypes was performed using RAPD and SSR molecular markers. Twenty six RAPD primers and 14 SSR primers amplified a total of 236 and 85 scoreable bands of which 86.44% and 86.02% were polymorphic. The mean coefficient of gene differentiation (Gst) was 0.388 and 0.341 indicating that 61.2% and 65.9% of the genetic variation resided within the populations. Analysis of molecular variance (AMOVA) indicated that majority of genetic variation (94.6% using RAPD and 89% using SSR) occurred among genotypes, while the variation between the three groups (categorized as tall, medium and small plants height) was 5.4% (using RAPD and 11% (using SSR). The dendrogram obtained from NJ and STRUCTURE analysis revealed splitting of genotypes into four clusters with clear distinction between short, medium and tall height genotypes, indicated that genetic differentiations measure with respect to RAPD and SSR. However, both the markers were equally useful in providing some understanding about the genetic relationship of different genotypes of poplar that are important in the conservation and exploitation of poplar genetic resources.

Selective breeding programme of common carp (Cyprinus carpio L.) in Serbia: Preliminary results

The aim of this study was to estimate heritability and genetic correlations between weight, length and height of common carp in Serbia (Cyprinus carpio L.) during 3-year growth period. The 50 families of common carp were produced in 2007 and used for the estimation of genetic parameters. The fish were measured at tagging for weight, length and height (W0, L0, H0), then during the first autumn (W1, L1, H1) and during the second autumn (W2, L2, H2). Based on univariate models heritability estimates were high for all traits (0.39, 0.34 and 0.45 for W1, L1 and H1, respectively) and also for the second production year (0.49, 0.47 and 0.44 for W2, L2 and H2, respectively). The genetic correlations were estimated using multivariate models and they were high between W1 and L1 and H1 (0.81 ? 0.06 and 0.91 ? 0.03 for L1 and H1, respectively), while between H1 and L1 were moderately correlated (0.54 ? 0.12). In the second production year genetic correlations were also high, between W2 and L2 and H2 (0.64 ? 0.09 and 0.74 ? 0.06, respectively), while between length and height they were lower (0.24 ? 0.15). Based on the current results improving growth rate of common carp through genetic selection is expected to be effective.

Immunogenetic correlates of susceptibility to infection with Heligmosomoides polygyrus in outbred mice

SUMMARYOutbred MF1 mice were characterized with respect to their susceptibility to infection with Heligmosomoides polygyrus (Nematoda) on the basis of faecal egg counts after 8 weeks of repeated infection (50 larvae/week). Selective breeding for resistance and susceptibility was carried out over 3 generations. The H-2 type of a sample of the mice was determined, and antigen recognition assessed on the basis of Western blots against adult and larval H. polygyrus homogenate. The selective breeding programme yielded very strong evidence for the heritability of susceptibility to infection. The results were consistent with a model of single gene control with resistance dominant over susceptibility. The presence of the H-2k haplotype was significantly associated with susceptibility, as was the recognition of a 17 kDa antigen in blots against both larval and adult worm homogenate. The proportion of mice phenotypically susceptible to infection, the proportion bearing the H-2k haplotype, and the proportion recognizing the 17 kDa antigen, were all approximately 0.25.