Long‐term survival of Acidovorax citrulli in citron melon (Citrullus lanatus var. citroides) seeds

Long‐term survival of Acidovorax citrulli in citron melon (Citrullus lanatus var. citroides) seeds was investigated. Citron melon seed lots infected with A. citrulli were generated in the field by inoculating either the pistils (stigma) or pericarps (ovary wall) of the female blossoms. Seventeen A. citrulli isolates from 14 different haplotypes belonging to two different groups (group I and II) were used for inoculation. After confirming that 100% of seed lots were infected, they were stored at 4°C and 50% RH for 7 years. After storage, the viability of A. citrulli cells from individual lots was determined by plating macerated seeds on semiselective medium as well as growing seeds for 14 days and scoring for bacterial fruit blotch symptoms. The type of A. citrulli isolate (group I or group II) used did not significantly influence bacterial survival. However, A. citrulli survival was significantly greater in seed lots generated via pistil inoculation (52·9 and 29·4%) than via pericarp inoculation (23·5 and 17·6%). Repetitive extragenic palindrome (rep)‐PCR on A. citrulli isolated from citron melon seed lots after storage displayed similar fingerprinting patterns to those of the reference strains originally used for blossom inoculation, indicating that cross‐contamination did not occur. The results indicate that A. citrulli may survive/overwinter in citron melon seeds for at least 7 years and bacterial survival in seed was influenced more by method of blossom inoculation than by the type of bacterial isolate.     

Effects of sulphur on yield and malting quality of barley

Eight field experiments were conducted at four sites in the UK in 2003 and 2004 to investigate the effects of sulphur (S) application on yield and malting quality of barley. Significant yield responses to S additions were obtained in five out of the eight experiments, with yield increases ranging from 0.2 to 1.2 t/ha (4.7–22.5%). At the two most S-deficient sites, S application significantly increased malt diastatic power, alpha-amylase activity, friability and homogeneity, and decreased (1→3,1→4)-β-glucan concentration in the wort, indicating an improved endosperm modification during malting. Sulphur applications also significantly increased the concentration of S-methylmethionine (the precursor of dimethylsulphide) in kilned malt, which could impact on beer flavour. When the supply of N was limiting, S applications decreased grain N concentration due to a dilution effect as a result of increased grain yield. In some cases, S applications resulted in decreased grain size. At sites non-deficient or marginally deficient in S, applications of S had little effect on grain or malting quality parameters. The need to maintain an adequate S supply to barley for both yield and malting quality was demonstrated.     

The value of species rarity in biodiversity recreation: A birdwatching example

Wildlife viewing recreation offers conservationists opportunities for education and generating revenue but can also have detrimental ecological impacts. To manage these opportunities and impacts effectively, a better understanding is needed of what people value in wildlife viewing events. We examine the relationship between species rarity and value for wildlife viewing recreation. We undertook visitor counts of birdwatchers attending rare (vagrant) bird sightings and collected home postcodes to assess the distances these individuals travelled to achieve these sightings. We also undertook visitor counts at common bird viewing locations for comparison. We regressed birdwatcher numbers against rarity, site protection status, time the bird had been on site and day of the week when the count took place. We undertook these analyses for rare bird sightings only, using a continuous measure of rarity, and for both rare and common species combined, using a categorical rarity index. Species rarity was the clearest predictor of visitor numbers in both the analyses. When studying rare birds only, we found the functional form of the relationship between rarity and visitor numbers to be inverse and asymptotic. Individuals also travelled further to see rarer species. However, while exceptional numbers of visitors attended exceptionally rare bird sightings, the marginal value of rarity appeared to be relatively low. Despite the opportunity for revenue raising and education provided by rare bird sightings, a comparison of visitor numbers at sightings inside and outside protected areas showed no evidence that managers of protected areas capitalise on these opportunities.     

Myzus persicae (Sulzer) in diffuse light and dark rustic storages and resultant PLRV transmission

Population levels ofMyzus persicae (Sulzer) were studied on potato tubers in diffuse light and dark rustic storage houses in Peru. No differences in numbers of aphids/sprouted eye on potatoes infested naturally during storage in diffuse light or darkness were observed. Significantly more alate aphids were observed on tubers stored in darkness than in diffuse light storage houses. Viral transmission was occurring during the storage period. The incidence of viral transmission was not significantly influenced by storing tubers in diffuse light or dark storages. There were significantly more plants infected with virus from tubers that had not been sprayed for aphid control than from tubers that had been sprayed     

Climatology of Acacia mearnsii. 1. Characteristics of natural sites and exotic plantations

Climatic variation in the natural distribution of Acacia mearnsii in Australia was analysed. Data from sites where the species has been successfully grown in plantations and trials in Africa, Asia and South America were used to determine the species' climatic adaptability. Annual mean temperatures at these plantations and trial sites ranged from 13.9 to 23.9°C, whilst annual mean precipitation ranged from 693 to 2263 mm. The coldest month minimum temperature at these sites was –0.6°C. This information, along with other details of climatic requirements presented in the paper, will assist in selecting sites for future trials at new locations.     

The effect of stocking density and repeated handling on the growth of juvenile mulloway, Argyrosomus japonicus (Temminck & Schlegel 1843)

The effect of stocking density on the growth of mulloway, Argyrosomus japonicus, was tested with 17 g fish stocked at 4.08, 8.16, or 16.32 kg m⁻³ in 50 l aquaria. Weight checks were carried out every 2 weeks to track performance. Each density treatment was also compared to a nonhandled control group to establish if handling during weight checks influenced the growth of mulloway. Mulloway performed poorly at the lowest density and, under the current experiment conditions, growth did not appear to be negatively affected by regular handling.