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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. 相似文献
2.
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. 相似文献
3.
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. 相似文献
4.
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. 相似文献
5.
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. 相似文献
6.
Pathogenic and nonpathogenic isolates of Geotrichum candidum sensu Suprapta et al. (1995) that affect citrus fruit are indistinguishable morphologically. In this work, differentiation
of the two pathogenicity types based on the internal transcribed spacer regions of ribosomal DNA (rDNA-ITS) and polygalacturonase
(PG) genes was attempted. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) of rDNA ITS and PCR
using specific primers to PG genes from each type could clearly differentiate the two pathogenicity types, and the profiles
by PCR-RFLP of rDNA ITS genes corresponded with those by type-specific PCR of PG genes. These results indicate that the two
pathogenic types can be differentiated at a molecular level and that PG genes are alternatively useful for distinguishing
between the two types. 相似文献
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