Pierce's disease of grapevines: isolation of the causal bacterium

A Gram-negative, rod-shaped bacterium has been consistently isolated from grapevines with Pierce's disease. Grapevines inoculated with the bacterium developed Pierce's disease, and the bacterium was reisolated from the plants. The bacterium was serologically and ultrastructurallv indistinguishable from the one in naturally infected plants, and also indistinguishable from a bacterium isolated from almonds with almond leaf scorch disease.     

Development of salt tolerant IR64 near isogenic lines through marker-assisted breeding

Salt stress causes considerable damage to rice with a consequent reduction in grain yield, however, conventional breeding for this stress is time-consuming and costly. Recently, marker-assisted breeding has shown enormous potential to accelerate breeding of stress tolerant varieties because of its precision, time saving, and cost effectiveness. The present study was carried out to transfer Saltol, a major QTL on chromosome 1 associated with salinity tolerance, from FL478, a tolerant genotype, into IR64, a popular lowland variety through marker-assisted backcrossing (MABC). This technique considerably enhanced the recovery rate of the recurrent parent genome within three backcross generations, which could have saved several backcrosses compared with conventional schemes to achieve the same results. By using this technique, up to 99.7% of the recurrent parent genome was recovered at BC₃F₂ generation, saving at least three backcrosses compared with conventional breeding schemes. Salinity tolerance of IR64-Saltol lines was evaluated using saline culture solution adjusted to electrical conductivity of 12 dS m^-1 using NaCl. Based on selected physiological and growth parameters, the new Saltol introgression lines showed a significantly higher tolerance of salinity than their recurrent parent IR64. The results of this study confirm the benefits of using molecular markers in plant breeding to enhance tolerance of abiotic stresses.     

Effects of the okra leaf,nectariless, frego bract and glabrous conditions on yield and quality of cotton lines

Summary Effects on yield and quality associated with the glabrous leaf, frego bract, okra leaf and nectariless genes (singly and combined) were studied under two insecticide spray regimes (heavy and light) in field experiments repeated over three seasons. Under the heavy spray regime there were few consistent differences between mutant genotypes and the normal except for low yields associated with the glabrous leaf, nectariless, frego bract genotype and the okra leaf genotype. Under the light spray regime, genotypes containing the okra leaf gene and/or the nectariless genes were associated with higher yields than the normal and genotypes containing glabrous leaf and/or frego bract genes were associated with lower yields. Positive epistatic interactions occurred in a number of instances including the okra leaf gene in the glabrous hair, normal bract background under heavy spraying, and with all backgrounds under light spraying, and for glabrous leaf in both the okra normal and okra frego backgrounds under heavy spraying. Nectariless also interacted positively with the normal leaf, normal hair, normal bract background under light spraying. Pronounced negative epistatic interactions only occurred in the light spray regime, and included glabrous leaf in all backgrounds, and frego bract in all backgrounds except the normal leaf, normal hair. The mutant genes had only minor effects on lint quality. The implications of the results for breeding and pest management are diseussed.     

Rock-type discrimination from ratioed infrared scanner images of pisgah crater, california

The radiances in two thermal infrared channels of an airborne scanner system were ratioed to produce images that recorded compositionally diagnostic emittance variations for several silicate rock types near Pisgah Crater, California.     

A geomorphological framework for river characterization and habitat assessment

1. Methods to assess the physical habitat available to aquatic organisms provide important tools for many aspects of river management, including river health monitoring, determination of river restoration/rehabilitation strategies, setting and evaluating environmental flows and as surrogates for biodiversity assessment. 2. Procedures used to assess physical habitat need to be ecologically and geomorphologically meaningful, as well as practicable. A conceptual methodological procedure is presented that evaluates and links instream habitat and geomorphology. 3. The heterogeneity of habitat potential is determined within geomorphic units (such as pools, runs, riffles) by assessing flow hydraulics and substrate character. These two variables are integrated as hydraulic units — patches of uniform flow and substrate. 4. This methodology forms a logical extension of the River Styles framework that characterizes river form and behaviour at four inter‐related scales: catchments, landscape units, River Styles (reaches) and geomorphic units. As geomorphic units constitute the basis to assess aquatic habitat availability, and they form the building blocks of river and floodplain systems, intact reaches of a particular River Style should have similar assemblages of instream and floodplain habitat. 5. An application of the hydraulic unit procedure is demonstrated in gorge, partly‐confined and alluvial River Styles from the Manning catchment in northern New South Wales, Australia. Copyright © 2001 John Wiley & Sons, Ltd.     

Temperature and dissolved oxygen influence growth and digestive enzyme activities of yellowtail kingfish Seriola lalandi (Valenciennes, 1833)

A 5 week experiment was carried out with juvenile yellowtail kingfish Seriola lalandi to investigate the interactive effects of water temperature (21, 24, or 27°C) and dissolved oxygen regime (normoxic vs. hypoxic) on the growth rate, feed intake and digestive enzyme activity of this species. Specific growth rate (SGR) was highest at 24°C, regardless of oxygen regime, but the SGRs of the fish exposed to hypoxia at 21, 24 and 27°C were 13%, 20% and 17% lower, respectively, than the SGRs recorded for the fish reared under normoxic conditions. The digestive enzyme activities (i.e. trypsin, lipase and α‐amylase) were influenced by temperature but did not appear to be affected by dissolved oxygen concentration. Information about the effects of water temperature and dissolved oxygen on feeding, growth and digestive capacity of juvenile yellowtail kingfish could contribute to improving feed management decisions for production of this fish species under different environmental conditions.