Hyphal Growth Rate Research Articles

Mutants of Aspergillus nidulans deficient in nuclear migration during hyphal growth and conidiation

Anucleate primary sterigmata (aps) mutants of Aspergillus nidulans are partially blocked in conidiation (asexual sporulation) due to failure of the organized migration of nuclei into the conidiophore metulae. The mutants also have a slightly reduced hyphal growth rate and irregular distribution of nuclei in vegetative hyphae; the hyphal phenotype appears somewhat more variable than the conidiation defect. The mutants fall into two complementation groups, apsA and apsB, mapping on chromosomes IV and VI, respectively. apsB mutants are also partially defective in sexual reproduction.

Status of nuclear division in arbuscular mycorrhizal fungi during in vitro development

The number of nuclei in spores and along hyphae of an arbuscular mycorrhizal fungiGigaspora margarita was measured in digital images of fluorescence arising from mithramycin stained cultures. Typical dormant spores (250 μm diameter) contained 2000 nuclei. Eight hundred nuclei were mobilized during the first 3 days of germination. The number of nuclei in the spores nearly returned to the initial number after 22 days of hyphal growth. The average relative DNA content in the nuclei of dormant spores and in the nuclei of spores incubated for 22 days was comparable, as judged from fluorescence intensity. Hyphal elongation occurred with 460 nuclei per cm under a special set of in vitro conditions that promote extensive hyphal growth of arbuscular mycorrhizal fungi. We found an average total of 26000 hyphal nuclei per germinating spore after 22 days. The specific DNA polymerase α inhibitor aphidicolin did not inhibit spore germination but it rapidly reduced the rate of hyphal growth and arrested growth after 4 days. No nuclei were produced de novo during this time. These results demonstrate thatG. margarita replicates nuclear DNA and undergoes nuclear division when grown in vitro even in the absence of a plant host.

Quantification of mycoparasitism by the nematode-trapping fungusArthrobotrys oligosporaonRhizoctonia solaniand the influence of nutrient levels

The influence of nutrient level, type of carbon source and nitrogen concentration on the parasitism of Arthrobotrys oligospora on Rhizoctonia solani were investigated by quantification of coiling frequency. Changes in coiling frequency were also compared with changes in hyphal density and colony radial growth rate. Increasing concentrations of corn meal agar gave increasing coiling frequency up to a concentration of half the recomended strength. At higher concentrations the coiling frequency was constant, although the hyphal density of both fungi increased over the whole concentration range. Coiling frequency was positively correlated with the probability of hyphal encounter, calculated as the product of the hyphal densities of the two fungi, except at high CMA concentrations. Amongst several carbohydrates tested, glucose resulted in the highest, and sucrose the lowest, coiling frequency. The effect of the different carbohydrates on coiling frequency was not correlated with the hyphal densities of the fungi. Addition of a nitrogen source, NaNO3, removed the differences in coiling frequency between glucose and sucrose and increased coiling frequencies on both sugars.

Direction of hyphal growth: a relevant parameter in the development of filamentous fungi

Macroscopic and microscopic measurements of the growth of Trichoderma viride and Rhizopus oligosporus were compared at different values of water activity of the solid medium. The relationship between radial extension rate and hyphal growth rate was found to be dependent on water activity. The observed difference between these two parameters was explained by the distribution of apical directions. The validity of the radial extension rate as a growth criterion could be discussed. The angular distribution of apical axes of growth in the front of the colony was observed at different water activity levels of the solid medium, and a model which links radial growth rate to hyphal growth rate and direction of apex growth was proposed and experimentally validated.

The Effect of Temperature and Nematode Species On Interactions Between the Nematophagous Fungus Verticillium Chlamydosporium and Root-Knot Nematodes (Meloidogyne Spp.)

Optimal growth and sporulation on agar of an isolate of Verticillium chlamydosporium occurred at 32°C and 22°C, respectively. Differences in the numbers of colony-forming units isolated from the root surface of tomato plants grown at different temperatures reflected the rate of hyphal growth on agar. However, the numbers of colony-forming units in soil at different temperatures was related to the effect of temperature on sporulation in vitro; the fungus was most abundant in soil at 22°C, which was the optimal temperature for sporulation. After one nematode generation the most extensive root colonisation occurred at 20°C followed by 25 and 30°C. As a result, egg-masses exposed on the root surface were most extensively colonised at 20°C followed by 25 and 30°C. Total egg and juvenile counts showed that greatest control of Meloidogyne was achieved at 25°C (c 90%), while control at 20 and 30°C was usually 60-70%. The lower level of control by V. chlamydosporium at 20°C may result from a reduced proportion of nematode egg-masses exposed on the root surface at this temperature. Eggs of M. arenaria, M. incognita and M. javanica were equally susceptible to parasitism by V. chlamydosporium. Of these three species, M. arenaria induced large galls and formed large egg-masses while M. incognita and M. javanica induced small galls and formed small egg-masses at 20°C. The end result was that control with V. chlamydosporium was approximately the same for the three nematode species.

Populationsänderungen von Pseudocercosporella herpotrichoides mit und ohne Fungizidselektion

Abstract Population changes in Pseudocercosporella herpotrichoides with and without fungicide selection A conidium mixture of W (wheat‐type) and R (rye‐type) strains of Pseudocercosporella herpotrichoides (W:R = 1:1) was incubated on PD‐agar without fungicide or amended with the imidazole prochloraz or the triazole cyproconazole. The W:R ratio was assessed over four generations using the different benomyl sensitivity of the strains as marker. In untreated mixtures, the R strain completely dominated the population already after two generations. Similarly, in cyproconazole‐treated mixtures, the R strain increased to 100% after the second generation, whereas in prochloraz‐treated mixtures the R strain either followed the same pattern as in untreated mixtures or fluctuated around the initial proportion of 50% over four generations. The W and R strains displayed different fitness properties. The average hyphal growth rate was 8.5 mm/10 d and 4.5 mm/10 d for the W and the R strains, respectively; the sporulation capacity was 80 and 400 conidia/colony, respectively, for the two strains. The different fitness resulted in a strong dominance of the R strains both in vitro and in field populations towards the end of the vegetation period. This shift towards R‐dominance occurred about equally fast with or without fungicide selection.

Stomata as an Infection Court forPhytophthora megaspermaf. sp.medicaginisin Chickpea and a Histological Study of Infection

Stomata located beneath the cotyledons of 7-day-old chickpea seedlings were the preferential infection court for zoos pores of Phytophthora megasperma f. sp. medicaginis. Zoospores also accumulated preferentially in the root-hair zone. Penetration usually was intercellular between anticlinal epidermal cell walls, but intracellular penetration did occur via infection pegs produced from swollen germ-tube tips. Although no differences in prepenetration or penetration events were found between a field resistant (CPl56564} and a susceptible cuhivar (ICC6334} of chickpea, hyphal growth rate of the fungus was greater through wounded roots of the susceptible cultivar than in the resistant cultivar. There was no significant difference between hyphal growth rates through wounded epicotyl tissue of the resistant and susceptible cultivars. Stomata located at or below the soil line could act as an infection court for zoospores present in surface water, and cultivars that express resistance in the root tissue would appear susceptible if the resistance was not also expressed in the hypocotyl and the lower epicotyl. A soil-line infection court also could be involved in spreading the disease via zoospores present in surface water in the field.

The haustorial interface in a resistant interaction of Erysiphe pisi with Pisum sativum

The interface between Erysiphe pisi and pea cv. JI 1049 was studied at the ultrastructural and cytochemical levels and compared with those in two susceptible cultivars. Haustorial efficiencies, as indexed by the length of mycelium associated with each haustorium, and growth rates on the resistant and one susceptible cultivar were also compared. The interaction in the resistant cultivar differed from those in the susceptible cultivars in the following ways: (i) there was no contact between the host plasmalemma and the A neckband region; (ii) papillae were contiguous with the surface of the neck and thus were probably formed before haustoria and (iii) there appeared to be less polysaccharide in the extrahaustorial membrane. The extrahaustorial membrane in the resistant cultivar lacked ATPase activity, whereas the rest of the host plasmamembrane had normal activity. Each haustorium supported a significantly greater total hyphal length in the resistant than in the susceptible cultivars. Growth rates of superficial hyphae were very similar on the susceptible and resistant cultivars but there was a delay in the onset on hyphal growth on the resistant cultivar which correlated with the previously reported delay in formation of the first haustorium. In contrast to hyphal growth rates, the rate of haustorium production was significantly less in the resistant cultivar. It is proposed that resistance in cv. JI 1049 operates at the stages prior to haustorium formation, similarly to that in some non-host and partial resistance systems. Once formed, however, the function of the haustorium seems to be unimpaired, despite the observed interfacial differences.

建築空間における空中浮遊微生物粒子の評価方法に関する研究(第3報) : 真菌のコロニー形成メカニズムと温度条件

For the purpose of deciding the temperature and length of time for the incubation of the airborne fungal particles collected by biological particle samplers, the hyphal growth of Cladosporium cladosporioides var. and radial growth rate of colonies of 12 genuses of fungi acutully collected in ordinal indoor environments were experimentally analyzed. The hyphal growth rate was determind under microscopical conditions at 25℃ and the colony growth rate was by the direct measurement, at the temperature conditions of 4℃, 10℃, 15℃, 20℃, 25℃, 30℃, and 37℃. The colony growth rate were high in the range of 20〜30℃ and hyphal and colony growth rate at 25℃ coincided for the Cladosporium species. The conclusion is that the incubation at 25℃ in temperature and 72 hour for length of time is desirable though proper judgement is required in growing state.

Colony growth ofStreptomyces coelicolorA3(2) under conditions of continuous nutrient supply

Colony growth of Streptomyces coelicolor A3(2) was studied on a cellophane membrane beneath which was passed a continuous supply of liquid medium. Colony development and differentiation occurred normally but hyphal extension rates and colony radial growth rates were reduced and branch formation was increased in comparison with colonies grown on the same medium solidified with agar. These changes are thought to result from continuous removal of staling compounds which would otherwise suppress branching at the colony margin. Glucose concentrations in the range of 0–1 g · l−1 had little effect on radial growth and branching except at a concentration of 1 g glucose · l−1, at which branching at the colony margin was suppressed. This concentration of glucose did not permit continued growth on solid medium.

Regulation of hyphal growth rate of Hypoxylon mammatum by amino acids: Stimulation by proline

Variation among isolates of Hypoxylon mammatum caused by amino acids added as sole nitrogen sources demonstrated genetic heterogeneity among the population in the mechanisms regulating hyphal growth rates. Isolates were obtained by a random sample consisting of 22 single ascospore isolates from a local population of hypoxylon cankers on P. tremuloides. Hyphal growth rates were determined from colony diameter measurements on defined media containing either alanine, asparagine, glycine, leucine, lysine, or proline. All isolates but two grew faster on proline than the other amino acids tested. The mean growth rate of the population sample was 3.9 mm day −1 on proline compared to 1.96 mm day −1 on asparagine, the second fastest mean growth rate. Growth rates of the 22 isolates on these six amino acids were largely uncorrelated, indicating independent mechanisms of regulation. Only asparagine gave significant correlations with more than two other amino acids. A more detailed examination of selected isolates representing a range of growth rates on proline showed that the rapid growth rates were also dependent on other materials present in Difco Bacto-Agar. Growth of the proline stimulated isolates was considerably slower on media gelled with Noble agar. Other nitrogen sources, especially glutamate, added with proline stimulated the growth of these isolates. Isolate dependent variation in the stimulatory effect of the N source added with proline was demonstrated. Stimulation of growth rate by proline may be related to drought stress-enhanced canker elongation in vivo, since drought stress caused proline accumulation in the host, Populus tremuloides.

Pythium species causing damping-off of spinach seedlings under plastic-house cropping.

A high correlation was found between the incidence of damping-off and the isolation frequency of Pythium species for spinach in pot experiments with spinach-field soils. Pythium species isolated from diseased spinach were classified into two groups according to their hyphal growth rates at 10 and 35 C. Based on their morphological characteristics, they were identified as Pythium paroecandrum, heretofore not reported as a cause of spinach damping-off, and P. aphanidermatum, previously reported as a cause of damping-off of spinach in the USA and Japan. Both species caused severe pre- and post-emergence damping-off of spinach in pathogenicity tests, and both were pathogenic to cucumber, pumpkin, watermelon, kidney bean and soybean.

Oscillatory growth of fungal hyphae in wood cell walls

Longitudinal sections of birch and Scots pine sapwood maintained in microscope chambers under continuous culture conditions were inoculated with Phialophora fastigiata and Phialophora hoffmannii . Hyphal growth resulting in soft rot decay of wood cell walls was studied continuously using time-lapse cinemicrography. Each stage in the infection of wood cell walls was recorded on film and rates of hyphal growth were determined. Hyphal growth in the chamber was linear but about five times faster than growth within wood cell walls. The formation of soft rot cavities within wood cell walls is oscillatory and determined by successive phases of apical growth of fine hyphae. Chains of soft rot cavities within wood cell walls are formed by the activities of lignolytic enzymes released along the hyphal surface. The chemical composition of the cell wall of the wood species investigated affects the rate of cavity widening.

Biological properties of procymidone-resistant field isolates of Botrytis cinerea.

Botrytis cinerea resistant to procymidone was isolated from the vegetables grown in greenhouses. All of them showed low level of resistance (ED50 values were approximately 10 times), and no isolate with high level of resistance was found. Although the resistant isolates were indistinguishable from the sensitive strain in growth rate of hypha, ability to sporulate and spore germination on a nutrient agar, some of them did not grow after incubation at a high temperature of 32C. When the resistant strain was inoculated to tomato fruits together with the sensitive strain, the resistant strain rapidly decreased in a population and often disappeared during successive inoculations to other fresh fruits. In cases that procymidone was treated preventively or curatively against the resistant strain on the leaves of cucumber, the controlling efficacy was inferior to that against the sensitive strain. On the other hand, when the resistant and sensitive strains were mixedly inoculated to the plants, curative application of procymidone was more effective in controlling the disease than when the resistant strain was singly inoculated. The fungicide sensitivity of B. cinerea isolates from 7 greenhouses in Kochi Prefecture, where the resistant strain was extremely dominant in a population in March of 1982, was examined in December of 1982. The resistant strain was still dominant in 1 greenhouse, but no resistant B. cinerea was detected in 5 greenhouses and only a few in 1 greenhouse. These results suggest that the population of procymidone-resistant B. cinerea would be unstable in the concomitant presence of the sensitive strain.

Temperature relations of spore germination and hyphal growth of vesicular-arbuscular mycorrhizal fungi in soil

Spores of Glomus caledonium, Gigaspora calospora and Acaulospora laevis from the same source and grown under the same conditions had different temperature limits for germination. Within these limits, temperature affected the duration of the period between imbibition and the onset of germination. Over most of the range, for each fungus, temperature caused no change in either the proportion of the spores which germinated, the time (after onset of germination) taken for the maximum proportion to germinate or the rate and extent of hyphal growth. At temperatures close to the limits, the rate of both spore germination and hyphal extension were decreased. The upper temperature limits for germination were less than those in moist soils in the natural habitat of the fungi, a feature which may have an ecological role.

Morphological and Physiological Studies of the Genus Radiomyces

The range of morphological and physiological variation of ten isolates of Radiomyces embreei and four of R. spectabilis was examined. Scanning electron microscopy revealed that a single R. embreei isolate (1186) produced significantly smaller sporangiospores than nine other R. embreei isolates grown under four different culture conditions. The effect of temperature on hyphal growth and sporangiospore germination revealed that R. spectabilis isolates grew from 15 to 40 C, and two of the four isolates grew at 45 C, whereas nine of the 10 R. embreei isolates grew from 15 to 45 C, and five of these nine grew at 50 C. The unusual R. embreei isolate (1186) grew only at temperatures between 15 and 35 C. Sporangiospore germination occurred in eight of 10 isolates of R. embreei at temperatures between 25 and 50 C, and nine of the 10 isolates germinated between 25 and 45 C, whereas germination did not occur with isolate 1186 at 40 C or above. Sporangiospore germination of R. embreei isolates usually was 90% or greater in as few as 4 to 6 h, while only 1 to 5% of 1186 sporangiospores germinated in up to 24 h. Slow sporangiospore germination also was seen with R. spectabilis isolates, with two reaching only I to 3% germination in 16 to 24 h, and one strain attaining 31% germination in 10 h. Spore germination of R. spectabilis isolates and R. embreei 1186 continued over the period of up to one wk. The genus Radiomyces contains two species, Radiomyces spectabilis Embree (1959) and Radiomyces embreei Benjamin (1960). These fungi are Zygomycetes, members of the Mucorales, and were placed in the family Radiomycetaceae by Ellis and Hesseltine (1974). Both species have been isolated from dung of rodents and lizards collected from the southwestern United States and Mexico, and R. embreei also has been isolated from soil in Arizona (Ranzoni, 1968). Recently, an isolate of R. spectabilis was obtained from India. Both species of Radiomyces are homothallic, produce smooth-walled zygospores (FIG. 1), and sporangiophores bearing either multispored sporangioles (R. spectabilis, FIG. 2), or singlespored sporangioles (R. embreei, FIG. 3). The ultrastructure of R. embreei sporangioles was demonstrated by Dykstra (1974), who reported that each sporangiospore is surrounded by a distinct outer sporangiole wall which fragments at the time of germination. Embree (1964) determined the rate of asexual spore germination and hyphal growth in relation to temperature with the type isolates of the genus. He reported both species to be thermotolerant, and capable of growth at 45 C or greater. Since the ability to

Direct studies of dikaryotization in Schizophyllum commune. I. Live inter-cellular nuclear migration patterns.

Compatible matings of Schizophyllum commune were performed on glucose-peptone-yeast extract medium appended with gelatin (18%) and studied by phase contrast microscopy during nuclear migration. Three categories of nuclear migration were observed. Type I involved a pulsatile jerking of the entire cytoplasmic contents of the hypha, changed direction periodically, and, during periods of cytoplasmic tranquility, the nucleus continued to migrate. Type II A migration of nuclei occurred in the absence of visible cytoplasmic flow. Both Type I and Type II A nuclear movements exceeded the hyphal growth rate by 10--20-fold. Type II B nuclear migration also occurred in the absence of visible cytoplasmic flow and the velocity was within the range of the hyphal growth rate. No specific organelles that were detected either directed or facilitated Type II A or Type II B nuclear movements. The nucleolus could either lead or trail relative to the direction of nuclear movement. Nuclear migration can be attributed to both cytoplasmic flow and self motility, depending upon the particular regions of the migration hypha in which it occurs.

Direct studies of dikaryotization in Schizophyllum commune. II. Behavior and fate of multikaryotic hyphase.

The growth, duplication and fate of multikaryotic hyphae bearing true clamp connections, as derived from compatible matings of Schizophyllum commune, were studied by phase contrast microscopy. The nuclei (N) of multikaryotic apices maintained a near central position during hyphal growth. True clamp connection formation occurred with near synchronous mitosis followed by septal synthesis across the clamp neck and main hyphal axis. Nuclear progeny after mitosis in a hexakaryon included 6 N in the apex, 1 N in the clamp and 5 N in the penultimate cell; the solitary nucleus in the clamp later entered the penultimate cell. Similar events occurred for clamp connection formation and mitosis in the trikaryon, quadrikaryon or pentakaryon, whether in the apex or primary branches. Nuclear content of the multikaryotic apex (2 N through 10 N) had no apparent effect on the rate of individual hyphal growth. Reduction of the nuclear number in a trikaryon occurred by long-term entrapment of a solitary nucleus in the clamp and subsequent outgrowth of the dikaryotic penultimate cell. Occasionally, more than one nucleus became entrapped in the clamp cell. The ephemeral nature of the multikaryon was indicated by the fact that older cultures appeared to be exclusively dikaryotic hyphae at the colony periphery.

Colonization of lateral, seminal and adventitious roots of wheat by the take-all fungus, Gaeumannomyces graminis var. tritici

SummaryProgressive colonization of adventitious, seminal and lateral roots of wheat by Gaeumannomyces graminis var. triticiwas monitored for 18 days after direct inoculation of roots. Adventitious roots supported greater colonization by superficial runner hyphae above and below inoculation sites than did seminal roots due to more rapid establishment of colonization. Subsequent rates of superficial runner hyphal growth along the two types of root were not significantly different. In contrast with seminal and lateral roots, adventitious roots did not show any dark stelar discoloration during the period of observation. Both the rate of growth of superficial runner hyphae and of advance of dark stelar discoloration were substantially slower on lateral roots than on seminal roots. After an initial period of equal growth above and below inoculation sites, superficial runner hyphae grew more slowly below than above these sites on all three types of root.

Evidence for Production of Inhibitor by the Vesicular-Arbuscular-Mycorrhizal FungusGigaspora Margarita

Incubation of spores of Gigaspora margarita on agar medium containing activated charcoal resulted in an increased rate of hyphal growth. Circular patterns simulated by hyphal growth from groups of ...