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The prevalence and distribution of soil-inhabitingFusarium species in the soil of vegetable crops grown under custom-made plastic tunnels were studied at three geographical locations on the island of Bahrain. Six species ofFusarium representing a total of 1154 isolates were isolated on modified Komada medium. All species reported in this survey are recorded for the first time from the hot, arid desert of Bahrain.Fusarium solani andF. oxysporum were among the most frequently isolated fungi in all locations and crops. 相似文献
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Mandeel QA 《Mycopathologia》2007,163(1):9-20
By use of plane and solid geometry and probability models, efficiencies of infection and competition for nutrients and infection
sites by a nonpathogenic strain of Fusarium oxysporum (C14) with F. oxysporum f. sp. cucumerinum on the rhizoplane of cucumber were calculated. The model is derived from previously published data. Efficiencies for successful
infection were 0.04 chlamydospores per infection site for both pathogen and nonpathogen. Observed successful infections by
the pathogen in competition with the nonpathogen were close in values to the competition ratio (CR) calculated as the number
of chlamydospores on the infection court of the pathogen divided by the total number of both pathogen and nonpathogen at relatively
low densities. When total chlamydospores were, on average, closer than 175 μm apart, however, competition for nutrients/mutual
inhibition occurred. At such densities there was an overestimation of the effect of competition for infection sites. These
relationships were modeled at inoculum densities of pathogen and/or nonpathogen of 5000 chlamydospores per g soil and above,
however, in the field, maximum densities of 1000 colony forming units/g (cfu) were observed. Most likely models of competition
for infection sites at this density of the pathogen revealed that infection efficiency was only approximately halved, even
when 0.98 of the possible 30 infection sites were occupied by the nonpathogen. It is conclude that competition for nutrients
and/or infection sites is an insignificant factor in biocontrol of Fusarium wilt diseases by nonpathogenic fusaria. 相似文献
3.
A rarely collected myxomycete, Comatricha mirabilis, developed on five collections of bark of large shrubs from the desert in the Kingdom of Bahrain. The distinctive morphology of this specimen is identical or very similar to that of specimens previously known from goat droppings in the USA (Illinois, Holotype), straw (England) and an unreported substrate in France. The spore and capillitium of the new specimens are compared to those from USA and England with light and scanning electron micrographs. The new collections are considered in the light of the previously known distribution of this taxon and other species. Comatricha mirabilis is suggested to be a myxomycete that is more common in certain arid habitats than previously recognized. 相似文献
4.
Mandeel QA 《Mycopathologia》2006,161(3):173-182
In earlier studies, biological control of Fusarium wilt of cucumber induced by Fusarium oxysporum f. sp. cucumerinum was demonstrated using nonpathogenic strains C5 and C14 of Fusarium oxysporum. Strain C14 induced resistance and competed for infection sites whether roots were wounded or intact, whereas strain C5 required
wounds to achieve biocontrol. In the current work, additional attributes involved in enhanced resistance by nonpathogenic
biocontrol agents strains to Fusarium wilt of cucumber and pea were further investigated. In pre-penetration assays, pathogenic
formae specials exhibited a significantly higher percentage of spore germination in 4-day-old root exudates of cucumber and
pea than nonpathogens. Also, strain C5 exhibited the lowest significant reduction in spore germination in contrast to strain
C14 or control. One-day-old cucumber roots injected with strain C14 resulted in significant reduction in germ tube orientation
towards the root surface, 48–96 h after inoculation with F. o. cucumerinum spores, whereas strain C5 induced significantly lower spore orientation of the pathogen and only at 72 and 96 h after inoculation.
In post-penetration tests, passive transport of microconidia of pathogenic and nonpathogens in stems from base to apex were
examined when severed plant roots were immersed in spore suspension. In repeated trials, strain C5, F. o. cucumerinum and F. o. pisi were consistently isolated from stem tissues of both cucumber and pea at increasing heights over a 17 days incubation period.
Strain C14 however, was recovered at a maximum translocation distance of 4.6 cm at day 6 and later height of isolation significantly
declined thereafter to 1.2 cm at day 17. In pea stem, the decline was even less. Significant induction of resistance to challenge
inoculation by the pathogen in cucumber occurred 72 and 96 h after pre-inoculation with biocontrol agents. Nonetheless, strain
C14 induced protection as early as 48 h and the maximum resistance was reached at 96 h. The presented data confirm the previous
findings that attributes important for nonpathogenic fusaria to induce resistant are: rapid spore germination and orientation
in response to root exudate; active root penetration and passive conidia transport in stem to initiate defence reaction without
pathogenicity and enough lag period between induction and challenge inoculation. Strain C14 possesses all these qualifications
and hence its ability to enhance host resistance is superior than strain C5. 相似文献
5.
SDS — dissociated proteins from eight isolates belonging to threeFusarium species were assessed and compared using polyacrylamide gel electrophoresis. Intra and inter specific variation in banding patterns were analyzed both qualitatively and quantitatively. Special emphasis was placed on variability of protein banding pattern between two nonpathogenic strains ofF. oxysporum (C5 and C14). Protein profiles from host-associated isolates were distinct, and each isolate showed a uniquely characteristic profile. Attempts were made to provide information on the genetic system controlling pathogenicity, compared to nonpathogenicity, at the protein level. The data obtained from electrophoresis support the potential use of this experimental approach to help distinguish between differentFusarium isolates. 相似文献
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