Parasitic specialization ofGeotrichum candidum citrus race

Parasitic specialization ofGeotrichum candidum citrus race, the causal agent of citrus sour rot, was investigated. Of seven isolates tested for pathogenecity, all could infect ten species of citrus fruits and edible parts of five species of noncitrus crops. Only one isolate (Ap2), isolated from soil of an apple orchard, could infect apple fruit.     

Distribution ofGeotrichum candidum citrus race in citrus groves and non-citrus fields in Japan

The presence ofGeotrichum candidum citrus race, the citrus sour rot pathogen, was examined in soils of citrus groves and non-citrus fields of Japan. Soil samples were collected from 223 sites (118 sites in citrus groves, and 105 sites in fields cultivated with 33 species of non-citrus plants and in evergreen broad-leaved forest) in 11 main citrus-growing prefectures, and Hokkaido, a non-citrus-growing area. Of 236 soil samples from citrus groves, 95.76% containedG. candidum citrus race and 0.42% contained the non-citrus race; while of 210 samples from non-citrus fields, 62.85% and 4.76% contained the citrus race and the non-citrus race respectively. All of the citrus race isolates obtained either from citrus groves or non-citrus fields were pathogenic on lemon (Citrus limon) and satsuma mandarin (Citrus unshiu), but some of these isolates failed to infect orange (Citrus sinensis). The non-citrus races were pathogenic on ripe tomato fruit (Lycopersicon esculentum) and ripe muskmelon fruit (Cucumis melo var.reticulatus). Results indicated that citrus sour rot pathogen is widely distributed in citrus groves and non-citrus fields of diverse plant species in Japan.     

Some physiological properties of citrus and noncitrus races ofGeotrichum candidum isolated from soil in Japan

Some physiological properties of citrus and noncitrus races ofGeotrichum candidum isolated from soils of citrus groves and noncitrus fields in Japan were studied. Of 358 isolated of citrus race, 260 isolates required pyridoxine for growth on asparagine-glucose agar, while 98 isolates could grow in the absence of pyridoxine. On the other hand, of 11 isolates of noncitrus race, 10 isolates could grow without pyridoxine, while 1 isolate absolutely required pyridoxine for growth. The citrus race grew well in autoclaved lemon juice at pH 2.2, while the noncitrus race failed to grow. The radial growth rate of the citrus race on potato-dextrose agar was higher than that of the noncitrus race. The two races grew well within the same range of temperature and pH, the optimal temperature ranging between 25 and 30°C, and optimal pH being 6.0. Both races utilized glucose, galactose, xylose, sorbose, sorbitol and mannitol as carbon sources, but could not utilize arabinose, lactose, maltose, rhamnose and sucrose. Arginine and asparaghine were the best nitrogen sources for both races, but KNO₃ could not be utilized.     

Effect of spent cotton stalks on color removal and chemical oxygen demand lowering in olive oil mill wastewater by white rot fungi

Wastewater from olive oil mill was decolorized (and its chemical oxygen demand reduced in static cultivation) using the fungiCoriolus versicolor, Funalia trogii, Phanerochœte chrysosporium andPleurotus sajor-caju. The effect of cotton stalk on decolorizing and COD removing capability was demonstrated.P. chrysosporium (in 20% medium with cotton stalk) reduced the COD by 48% and color by 58%,F. trogii (in 30% medium with cotton stalk) by 51 and 55%, respectively.     

Life table analysis of the green rice leafhopper,Nephotettix virescens (distant) (Hemiptera: Cicadellidae), and efficient vector of rice tungro disease in asynchronous rice fields in Indonesia

Population dynamics of Nephotettix virescens was studied in 17 paddy fields transplanted at intervals of about 1 month in 1988–1990. The adult density was highest either in the immigrant or the 1st generation and sharply decreased to the 2nd generation. The survival rate of the 1st generation was lowest in the transition season when areal population density increased. Key factor analysis revealed that the nymphal and adult mortality of the 1st generation (kn) was the principal source of population fluctuations. No significant correaltion was found between kn and natural enemy density, natural enemy density/healthy egg density, or the precipitation during the nymphal period. On these bases adult emigration was suspected to be the key factor. Areal population build-up of N. virescens in the transition season was considered to occur as a result of increasing immigration to young stages of rice.     

Genomic signatures of host‐associated divergence and adaptation in a coral‐eating snail,Coralliophila violacea (Kiener, 1836)

The fluid nature of the ocean, combined with planktonic dispersal of marine larvae, lowers physical barriers to gene flow. However, divergence can still occur despite gene flow if strong selection acts on populations occupying different ecological niches. Here, we examined the population genomics of an ectoparasitic snail, Coralliophila violacea (Kiener 1836), that specializes on Porites corals in the Indo‐Pacific. Previous genetic analyses revealed two sympatric lineages associated with different coral hosts. In this study, we examined the mechanisms promoting and maintaining the snails’ adaptation to their coral hosts. Genome‐wide single nucleotide polymorphism (SNP) data from type II restriction site‐associated DNA (2b‐RAD) sequencing revealed two differentiated clusters of C. violacea that were largely concordant with coral host, consistent with previous genetic results. However, the presence of some admixed genotypes indicates gene flow from one lineage to the other. Combined, these results suggest that differentiation between host‐associated lineages of C. violacea is occurring in the face of ongoing gene flow, requiring strong selection. Indeed, 2.7% of all SNP loci were outlier loci (73/2,718), indicative of divergence with gene flow, driven by adaptation of each C. violacea lineage to their specific coral hosts.     

Change in susceptibility of satsuma mandarin fruit to sour rot pathogen (Geotrichum candidum citrus race) with relation to biochemical changes during maturation and storage

Change in susceptibility of satsuma mandarin fruit (Citrus unshiu) cultivar “Miyagawawase” to sour rot pathogen was studied with relation to biochemical changes during maturation and storage. The susceptibility of the fruit decreased with the advancement of maturity and was relatively constant during storage at 25°C for 4 wk. The young, green fruit that contained less total soluble solid, sugars and polyphenol, but more citric acid and water contents than mature, yellow fruit was more susceptible to sour rot pathogen. The susceptibility was correlated with total soluble solid, citric acid, sugars and water contents, but not with polyphenol. The results suggested that the difference in susceptibility during maturation was influenced to some extent by several constituents of fruit, although they may not be the only factors involved in susceptibility.     

Serum selenium and gluthathione-peroxidase activities and their interaction with toxic metals in dialysis and renal transplantation patients

Selenium, aluminum, cadmium, and magnesium concentrations and gluthathione-peroxidase activities in sera of 35 healthy individuals, 30 renal transplants, and 30 hemodialysis patients were measured. Serum selenium, aluminum, and cadmium concentrations in both groups of patients were higher than the controls (p<0.001), whereas the serum gluthathione-peroxidase levels were lower (p<0.001). According to our results, it can be concluded that the patients receiving hemodialysis are subjected to more toxic elements than the transplantation patients. These findings imply that dietary selenium supplement may be suggested in renal failure for the detoxification of elements, such as cadmium and mercury. The essential trace element selenium takes part not only in the direct protection of endothelial cells against the accumulation of aggressive oxygen species, but also in the preventions of the toxic effects of cadmium or in the modulation of the active calcium transport.     

Effects of volatile compounds on arthrospore germination and mycelial growth ofGeotrichum candidum citrus race

Three groups of volatile compounds, i.e., alcohols, aldehydes and esters, were tested for their effects on arthrospore germination and mycelial growth ofGeotrichum candidum citrus race, the causal agent of citrus sour rot. Alcohols (heptanol, octanol, nonanol, decanol, geraniol, citronellol) at a concentration of 1.0 μl/ml showed 60% or more inhibitory effects on both germination and mycelial growth of this pathogen. Among aldehydes tested, only citral had an inhibitory effect of more than 50%, while esters had no effect. The chain length of straight-chain (C6–C12) alcohols correlated with inhibitory effect, and nonanol (C9) was most active. Treatment with alcohols or citral prior to inoculation reduced colonization and maceration of lemon peel by this pathogen by 70% or more. Results suggested that alcohols or citral can probably be used to prevent the development of citrus sour rot.