Recurrent selection for quantitative resistance to soil-borne diseases in beans in the Mixteca region, Mexico

Most of the bean breeding for disease resistance has been done considering it as a qualitative trait. This work reports on bean breeding for resistance as a quantitative trait. Recurrent mass selection was used in order to simultaneously increase the polygenically inherited resistance to all locally important bean pathogens but with emphasis on bean common mosaic virus (BCMV) and bacterial blight (BB) in the Mixteca Region, Mexico. Qualitative resistances against soil-borne diseases, induced mainly by facultative pathogens, possessing little parasitic specialization, are unlikely to occur, and although breeding against these kinds of diseases was not originally planned, it turned out to be part of collateral field screening. The accumulation of quantitative resistance against soil-borne diseases in advanced lines of this program is described and includes two field experiments, a cycle for seed augmentation in large plots and two greenhouse experiments. The majority of lines of the advanced breeding cycles produced consistently higher yields and higher survival rates, when compared with the original parents and commercial varieties. However, the regional land races still have higher survival rates but they have lower yields. Soil-borne diseases were present during all breeding cycles carried out under field conditions in the Mixteca Region. This work indicates that breeding for quantitative resistance involves all locally important pathogens. It is then feasible to accumulate high levels of quantitative resistance, in a relatively short time, even to these intermittently severe, soil-borne diseases that are otherwise so difficult to manage. This revised version was published online in July 2006 with corrections to the Cover Date.     

Population structure and genetic diversity in Colombian Simmental cattle

Tropical Animal Health and Production - A vital requirement to design and implement a breeding program is to know the structure and genetic diversity of a population. The aim of this study was to...     

Evidence of hybridization between Yaqui catfish Ictalurus pricei (Rutter, 1896) and channel catfish Ictalurus punctatus (Rafinesque, 1818) in north-west México revealed by analysis of mitochondrial and nuclear genes

1. The Yaqui catfish, Ictalurus pricei, is the only native ictalurid species described from north-west México and south-west USA. It is an endangered species owing to the decline and loss of most of its historical populations, mainly because of competition and hybridization with the non-native channel catfish, Ictalurus punctatus. The Arroyo Cajón Bonito is one of the few remnant populations of Yaqui catfish in the Yaqui River basin, and it is threatened by the presence of channel catfish that escaped from private culture facilities.
2. Phylogenetic analysis of two mitochondrial and two nuclear genes was used to detect evidence of hybridization with channel catfish in a collection of 20 catfish from Arroyo Cajón Bonito. Fourteen putatively pure Yaqui catfishes, five hybrids and one channel catfish were detected.
3. This study further highlights hybridization between channel and Yaqui catfish as the main threat to the remaining Yaqui catfish populations. We recommend urgent evaluation of the remnant populations of native catfish elsewhere and their current conservation status.

     

Growth and survival of the pearl oyster Pinctada imbricata (Röding 1758) in supended and bottom culture in the Golfo de Cariaco, Venezuela

We evaluated growth and survival rates of Pinctadaimbricata in relation to environmental changes during nine months insuspended and bottom culture in the Golfo de Cariaco, Venezuela. Juveniles,measuring 13 mm in length, were cultured using two methods, (1) inSpanish-type baskets suspended at 3–4 m in depth from a longline and (2) in baskets embedded on the seabed (7–8 m indepth). At monthly intervals, we quantified mortality and took a sample ofoysters to determine shell length (dorsal-ventral axis) and the dry mass of theshell, muscle and remaining tissues. We also quantified the dry mass of foulingon the shells (a potentially important environmental factor). Survival rateswere slightly higher in suspended culture (98–100%), although notsignificantly higher than on the bottom. The growth rate was higher in suspendedculture than on the bottom culture, and the difference between culture methodswas greater for tissue and shell biomass than for shell dimensions. At the endof the study, oysters measured 55 mm in shell length for oysters insuspension and 45 mm for those on the bottom. Although growth wasnot significantly correlated with any environmental factor, it tended toincrease with increases in chlorophyll a during periods ofupwelling, thus suggesting that phytoplankton abundance enhanced the growth ofPinctada imbricata. The pearl oyster Pinctadaimbricata should be an excellent species for aquaculture activities,given its high rates of growth and survival in suspended culture and itseconomic importance in the Caribbean region.     

A review of the environmental effects and alternative production strategies of marine aquaculture in Chile

In Chile, fish, mussel and seaweed cultivation has expanded significantly over the last decade. This review considers the accumulated knowledge on the environmental effects of aquaculture in Chilean coastal areas, analyses the capacity of the industry to treat its waste and also gives some insight into new culture technologies and strategies that are currently under research and discussion in Chile. Data relating to the environmental impact of aquaculture in Chile are scarce and much is subject to severe methodological restrictions with regard to sampling design. Results related to the environmental effects show that seaweed cultivation can have an impact on sedimentation processes, increase of invertebrate assemblages and algal epiphytic abundances. It has also been ascertained that mollusc farming causes biodeposition, faunal changes and possible effects related to the introduction of new species, as well as pathogens and other unforeseen species. It has been affirmed that fish cultivation, in particular that of salmon species, also has an environmental impact related to organic sedimentation and changes in the fauna. However, these results indicate that, in general, the current dynamics of bays and fjords seem to be an important factor for the environmental sustainability of the salmon culture areas. Salmon cultivation has also been associated with phytoplankton blooms, but this point was not supported by a monitoring programme in southern Chile. Furthermore, there is concern related to new pathogen introduction and therapeutical applications to the fish cultures, and further research is required in this field. Regulations to protect the environment from the consequences of aquaculture activities have been adopted during the last couple of years. The main regulations are provided by international market standards. Nevertheless, these regulations can only be effective if other human activities, such as urban discharge, intensive agriculture fertilisation and pesticide utilisation, are taken into consideration, in an integrated perspective. On the other hand, the Chilean salmon farming industry in particular, would be in a position to cover the costs involved in the treatment of waste waters, if feeding management were improved in the future. Finally, active research is currently being undertaken into new cultivation strategies, such as the use of integrated cultivation and the recycling of nutrient-rich waters, which should permit the diversification of this economic activity in Chile, while minimising the environmental impact.     

Regulation of lysine metabolism and endosperm protein synthesis by the opaque-5 and opaque-7 maize mutations

Two high lysine maize endosperm mutations, opaque-5 (o5) and opaque-7 (o7), were biochemically characterized for endosperm protein synthesis and lysine metabolism in immature seeds. Albumins, globulins, and glutelins, which have a high content of lysine, were shown to be increased in the mutants, whereas zeins, which contain trace concentrations of lysine, were reduced in relation to the wild-type lines B77xB79+ and B37+. These alterations in the storage protein fraction distribution possibly explain the increased concentration of lysine in the two mutants. Using two-dimensional polyacrylamide gel electrophoresis of proteins of mature grains, variable amounts of zein polypeptides were detected and considerable differences were noted between the four lines studied. The analysis of the enzymes involved in lysine metabolism indicated that both mutants have reduced lysine catabolism when compared to their respective wild types, thus allowing more lysine to be available for storage protein synthesis.     

A global stochastic index for water quality: The case of the river Turia in Spain

Which are applicable in all Member States. Those directives specify a set of physical and chemical characteristics, which depend on the use the water is intended for, the parameters to be regularly controlled in a network of sampling points, and the limiting values of those parameters for each quality level. Hence, an administrative quality classification for each sampling point is obtained. This article proposes a stochastic quality index that takes into account the uncertainty surrounding the quality classification still remaining after the data have been observed. This stochastic index is built with the probability classification vector of each parameter. In order to obtain those vectors, a mixed-lognormal model is introduced and its statistical analysis developed. The methodology proposed here is then applied to the data observed in the La Presa station, one of the sampling points of the Spanish surface water quality network. Located on the river Turia, near the city of Valencia, its aim is to control the quality of water intended for the abstraction of drinking water. Its stochastic quality classification is obtained and compared with the legally applicable administrative one.     

Technological classification of basque cider apple cultivars according to their polyphenolic profiles by pattern recognition analysis

The polyphenolic compositions of 31 Basque cider apple cultivars were determined in pulp, peel, and juice by high-performance liquid chromatography--diode array detection analysis of crude extracts and after thiolysis. Data sets, consisting of individual polyphenol concentrations, total procyanidin content, and the average degree of polymerization of procyanidins, were evaluated by multivariate chemometric techniques, to develop decision rules for classifying apple cultivars technologically into bitter and nonbitter categories. A preliminary study of the data structure was performed by cluster analysis and principal component analysis in each apple material. Bitter apple varieties presented higher contents of flavan-3-ols and/or dihydrochalcones than nonbitter cultivars. Different classification systems for the two categories on the basis of the chemical data were obtained applying several supervised pattern recognition procedures, such as linear discriminant analysis, K-nearest neighbors, soft independent modeling of class analogy, partial least-squares, and multilayer feed forward artificial neural networks. Excellent performance in terms of recognition and prediction abilities for both categories (100% of hits) was achieved in every case (pulp, peel, or juice). Polyphenolic profiles of apple pulp, peel, or juice provide enough information to develop classification criteria for establishing the technological group of apple cultivars (bitter or nonbitter).