Periderm and lenticel characterization in relation to potato cultivar, soil moisture and tuber maturity

Summary Using the fluorescent lipid stain fluorol yellow 088 to detect suberin in tubers, the numbers of layers and the thickness of the suberized cells in the periderm and within the lenticels showed changes after the early stage of tuber formation. These changes as tubers matured were affected by cultivar and soil moisture conditions. Penetration of the surface tissues of tubers by the water soluble stain safranin O was confined to the lenticles. Although the zone of suberized cells in lenticels acted to some extent as a barrier to penetration, there was not a clear relationship between permeability and suberization. Stored tubers showed thicker suberin berriers in lenticels than freshly harvested tubers. When lenticels of stored tubers proliferated the suberin barrier was disrupted but a further thick suberin barrier formed after exposure to air for two weeks. The findings are discussed in relation to biological control ofErwinia by antagonistic bacteria.     

Solvent-free oxidation of primary carbon-hydrogen bonds in toluene using Au-Pd alloy nanoparticles

Selective oxidation of primary carbon-hydrogen bonds with oxygen is of crucial importance for the sustainable exploitation of available feedstocks. To date, heterogeneous catalysts have either shown low activity and/or selectivity or have required activated oxygen donors. We report here that supported gold-palladium (Au-Pd) nanoparticles on carbon or TiO(2) are active for the oxidation of the primary carbon-hydrogen bonds in toluene and related molecules, giving high selectivities to benzyl benzoate under mild solvent-free conditions. Differences between the catalytic activity of the Au-Pd nanoparticles on carbon and TiO(2) supports are rationalized in terms of the particle/support wetting behavior and the availability of exposed corner/edge sites.     

Effect of extraction time and acid concentration on the separation of proglycogen and macroglycogen in horse muscle samples

The objective of this study was to determine whether the concentrations of proglycogen (PG) and macroglycogen (MG) in biopsy samples of horse muscle are influenced by extraction time or perchloric acid (PCA) concentration. In study 1, individual muscle-biopsy samples from 10 horses were divided into 4 parts each and then randomly subjected to 4 periods of extraction (10, 20, 60, or 120 min) with 1.5 M PCA. In study 2, individual muscle-biopsy samples from 6 horses were divided into 24 pieces each and then randomly subjected to 12 combinations of extraction time (10, 20, 30, or 40 min) and PCA concentration (0.5, 1.5, or 3.0 M). The results from study 1 indicated that PG and MG concentrations are affected only after extraction for 120 min; the PG concentration decreased significantly (P < 0.05), and the MG concentration increased (not significantly). In study 2, extraction in 3.0 M PCA yielded significantly lower PG and higher MG concentrations (P < 0.05) than extraction in 0.5 or 1.5 M PCA with each of the extraction times. The results of this study further support the existence of 2 glycogen pools and demonstrate that they are not an extraction artifact. The study also suggests that the 2 pools are stable during extraction over a range of extraction times and acid concentrations. However, if the exposure to acid is very long and, or, the acid concentration is high, some of the insoluble PG appears to be hydrolyzed and to enter the MG pool.     

Update on the diagnosis and treatment of disorders of calcium regulation.

The availability of PTH, iCa, PTHrP, and 25OHD assays for evaluation of calcium abnormalities in companion animals has been well received [table: see text] by clinicians and diagnosticians. Use of these assays has heightened awareness that some of these disorders are more common than originally thought. Also, there is added insight of alterations of calcium homeostasis as a consequence of other illness or environmental factors such as diet. Animal counterparts of other disorders of calcium metabolism in people are likely to be identified, and use of these assays should play a significant role. As already emphasized, the foundation of using [table: see text] these assays is first assessing whether the calcium abnormality is of a parathyroid-dependent or parathyroid-independent classification.     

Farmers’ participation and breeding for durable disease resistance in the Andean region

In the Andean region, the Preduza project and its partners combined breeding for durable disease resistance using locally adapted cultivars and farmer participatory methods. The approach taken resembles participatory variety selection (PVS). Farmers participated in the selection of advanced materials, rather than finished cultivars. This paper describes this approach and reports experiences with farmers–breeders collaboration. As breeders involved farmers as participants, they learned more about the most important criteria of male and female farmers for preferred cultivars in the marginal environments of Andean cropping systems. This approach encouraged the use of locally adapted cultivars (often landraces), made the breeders less dependent on foreign materials, and has resulted in selection and development of new wheat, barley, common bean, quinoa, potato and maize cultivars. Breeding programmes based on crossing locally adapted cultivars followed by selection by the breeders in the early phases of the breeding programmes and by participatory selection with the farmers in the more advanced stages of the breeding programmes appeared successful. It became clear that breeders must be well acquainted with the farmer preferences such as the requirements for specific agronomic, storage, processing and marketing traits. Over a period of five years the centralized formal breeding approach predominantly based on material produced by the international institutes was replaced by decentralized breeding approaches based largely on local germplasm with extensive farmer participation.     

Inheritance of resistance to Phytophthora infestans in two diploid Mexican solanum species

Inheritance of resistance to Phytophthora infestans in the diploid Mexican species S. bulbocastanum and S. verrucosum appears to be quantitative. In these species there seems to be no clear distinction between a hypersensitive reaction to infection and one indicating a high degree of partial resistance. Sibbing or selfing apparently improves the degree of resistance in the progeny over that of the parents. S. verrucosum, a self-compatible species which shows little or no inbreeding depression after selfing, has especial advantages as a genetic tool and as a source of blight resistance, over S. bulbocastanum and other diploids.Contribution No. 119, Canada Dept. of Agriculture Research Station, Fredericton, New Brunswick, Canada     

Using multiple objective linear programming to evaluate multi-participant agroforestry systems

Multiple objective linear programming is used to evaluate a simulated two-participant maize/cassava/leucaena/teak agroforestry system. Examples using two different price ratios are presented along with possible methods to optimize the system with regard to the interests of the two profit seeking participants. A third example examines possible solutions to a system involving a profit seeking forester and a non-monetary subsistence farmer.

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Progmación Usando progmacion lineal con objectivos multiples se estudia un sistema agroforestal simulado de maiz, yuca, leucaena y teca, considerando dos participantes. Se presentan ejemplos usando dos niveles de pricios con metodos posibles paraq optimizar el sistema con respcto a intereses monetarios de los dos participantes. En un tercer ejemplo se examinan las soluciones posibles para el sistema, involucrando un silvicultor interesado en beneficios monetarios y un agricultor de subsistencia con interes no monetarios.