Influence of soil impoverishment on the interaction between Glomus mosseae and saprobe fungi

 The effect of the saprobe fungi Wardomyces inflatus (Marchal) Hennebert, Paecilomyces farinosus (Holm & Gray) A. H. S. Brown & G. Sm., Gliocladium roseum Bain., Trichoderma pseudokoningii Rifai and T. harzianum Rifai, isolated from sporocarps of Glomus mosseae, on arbuscular mycorrhizal (AM) colonisation and plant dry matter of soybean was studied in 2/3 and 1/5 diluted soils in a greenhouse trial. Soil dilution to 1/5 had no effect on shoot dry matter of soybean but decreased AM colonisation and root dry weight of plants. CFU of saprobe fungi, except T. harzianum, were higher in 1/5 than in 2/3 diluted soils. W. inflatus and Gliocladium roseum decreased the shoot dry weight of soybean plant when inoculated together with Glomus mosseae. The saprobe fungi P. farinosus and T. pseudokoningii increased the shoot dry weights of plants grown in 1/5 diluted soil. The shoot dry weight and AM colonisation in 1/5 diluted soil were also increased when T. harzianum was inoculated together with Glomus mosseae. Thus, saprobe fungi increased AM colonisation of soybean plants by indigenous endophytes. The AM colonisation of plants at both soil dilutions was increased by Glomus mosseae. The highest level of AM colonisation was observed when P. farinosus and T. pseudokoningii were inoculated together Glomus mosseae. The dilution of soils influenced the interaction between inoculated microorganisms and their effect on plant growth. Accepted: 7 June 1999     

Bacterial associations with the mycorrhizosphere and hyphosphere of the arbuscular mycorrhizal fungus Glomus mosseae

Roots and mycorrhizal fungi may not associate with soil bacteria randomly, but rather in a hierarchical structure of mutual preferences. Elucidation of such structures would facilitate the management of the soil biota to enhance the stability of the plant-soil system. We conducted an experiment utilizing two isolates of soil bacteria to determine their persistence in distinct mycorrhizal regions of the root zone, and their effects on general rhizosphere populations of fluorescent pseudomonads (FP). Split-root sorghum (Sorghum bicolor L.) plants were grown in four-compartment containers, constructed so that the soils in individual compartments held either (1) roots colonized by the arbuscular-mycorrhizal (AM) fungus Glomus mosseae (M), (2) nonAM roots only (R), (3) hyphae of G. mosseae (H), or (4) no mycorrhizal structures (S). The soils were inoculated (10⁷ cells g^-1 dry soil) with antibiotic-resistant (rifampicin, rif; streptomycin, sm) strains of the soil bacteria, Alcaligenes eutrophus (rif^r50) or Arthrobacter globiformis (sm^r250), or were left uninoculated as control. A. eutrophus had been isolated from a specific source (hyphosphere soil of G. mosseae), and A. globiformis from mycorrhizosphere soils of two AM fungi. After 10 wk of growth, the presence of A. eutrophus was barely detectable (<10 cfu g^-1 dry soil) in nonAM (R and S) soils, but persisted well (10⁴ cfu g^-1 dry soil) in AM (H and M) soils. Numbers of A. globiformis were more evenly distributed between all soils, but were highest in the presence of AM roots (M soil). There were varied bacterial effects on root and AM-hyphal development: A. eutrophus decreased hyphal length in H soil, while A. globiformis stimulated root length in M soil. The two bacterial inoculants did not affect numbers of FP in H, R, and M soils, but the AM status of the soils did: the numbers of FP increased in the order M>R>H>S. There was a positive correlation of FP numbers with both bacterial inoculants in M and H soils. Numbers of FP changed with root or hyphal lengths, an effect that was related to changes in the numbers of the inoculated bacteria. The results indicate that the hyphosphere-specific A. eutrophus depended on the presence of G. mosseae, but that the nonspecific A. globiformis did not. The mycorrhizal status of soils may selectively influence persistence of bacterial inoculants as well as affecting the numbers of other native bacteria.     

Root colonization by the arbuscular mycorrhizal fungus Glomus mosseae and enhanced phosphorous levels in cucumber do not affect host acceptance and development of Frankliniella occidentalis

Abstract

We tested the effect of root colonization of cucumber (Cucumis sativus L.) by the arbuscular mycorrhizal fungus (AMF) Glomus mosseae on different parameters of a plant-thrips (Frankliniella occidentalis Pergande) interaction. In leaf disc bioassays, the feeding activity, the oviposition rate, the settling preference of adult females and the developmental time (first instar larva to adult) on leaves of mycorrhizal and non-mycorrhizal plants were studied. To distinguish between a nutritional effect through an improved phosphorous (P) status of the mycorrhizal plant and other effects caused by mycorrhization, non-mycorrhizal plants watered with a nutrient solution with (+P) or without P (?P) were included in the study. Mycorrhization did not affect any of the parameters on host acceptance tested, whereas on plants with a higher P-level the duration of the non-feeding stages (pronymphae, nymphae) of F. occidentalis was shortened, but all other developmental parameters were similar as in the control and the mycorrhizal plants. Our data indicate that the polyphagous thrips F. occidentalis is neither affected by mycorrhization of cucumber plants nor by enhanced P-levels.     

Genes involved in resistance to powdery mildew in barley differentially modulate root colonization by the mycorrhizal fungus Glomus mosseae

 Arbuscular mycorrhizal fungi (AMF) and Erysiphe graminis are obligate biotrophic fungi with different outcomes in their interaction with plants, different targeted host tissues, but similar patterns of development and infection processes. These similarities raise the question of whether the two types of biotrophic fungal infections have common features in their regulation. To investigate this question, we compared a number of Ror and Rar barley mutants susceptible to E.graminis f. sp. hordei, as well as their resistant progenitors, for susceptibility to infection by the AMF Glomus mosseae. The two powdery mildew-resistant lines BC Ingrid and Sultan presented a similar reduction in G. mosseae development within roots when compared to the wildtype cultivar Ingrid, indicating a systemic effect of the altered genes in the plant. Ror and Rar mutants, in which susceptibility to powdery mildew is restored, showed increased resistance to AM fungal development in their roots when compared to their progenitors, which suggests that corresponding mutations must have affected genes which differentially modulate symbiotic and pathogenic biotrophic plant-fungus interactions. Accepted: 16 September 1999     

VA菌根真菌Glomus mosseae对棉花根区微生物量和生物量的影响

ＶＡ菌根真菌Ｇｌｏｍｕｓｍｏｓｓｅａｅ对棉花根区微生物量和生物量的影响顾向阳,胡正嘉（华中农业大学土化系,武汉４３００７０）ＥｆｆｅｃｔｏｆＶＡＭＦｕｎｇｕｓＧｌｏｍｕｓｍｏｓｓｅａｅｏｎＭｉｃｒｏｂｉａｌＰｏｐｕｌａｔｉｏｎａｎｄＢｉｏｍａｓｓｉｎ...     

Interactions between Pseudomonas fluorescens biocontrol agents and Glomus mosseae, an arbuscular mycorrhizal fungus, within the rhizosphere

Interactions between Pseudomonas fluorescens biocontrol agents and Glomus mosseae , an arbuscular mycorrhizal fungus, were studied. The biocontrol agents included the genetically modified strains CHA96 and CHA0 pME3424 which produced enhanced levels of antifungal compounds. Tomato ( Lycopersicum esculentum ) and leek ( Allium porrum ) host plants were grown in sterile Terra-Green (calcined attapulgite clay) with limited nutrients. Mycorrhizal activity was indicated by shoot dry weight and phosphorus content. In all experiments, plants grown in the presence of G. mosseae had a significantly higher shoot dry weight than those grown in the absence of G. mosseae . Colonisation and activity of G. mosseae was unaltered in the presence of P. fluorescens isolates and presence of G. mosseae increased the population of P. fluorescens in the rhizosphere.     

In vitro antifungal activity of chitinolytic enzymes produced by bio-agents against root rot pathogenic fungi

A study was carried out using simple laboratory techniques to examine the influence of the antagonistic isolates of Trichoderma harzianum, T. viride, Bacillius subtilis and Pseudomons flourescence and their culture filtrates on selected soil-borne root rot pathogens Rhizoctonia solani and Fusarium solani. Testing procedures were standardised using two different methods. The experiments were based on the principle of dual culture and agar diffusion techniques. The experiment involved the recording of the percentage of reduction in growth and inhibition zones formed by various filtrates of antagonistic culture growth. The results showed that the antagonists tested had the ability to reduce the linear growth of fungal pathogens. Also, the cultures filtrates of antagonists had antifungal activities by forming inhibition zones. Culture filtrates have shown a strong clear inhibition zone which increases in diameter as the incubation period of antagonists increases. This observation was related to the increase in the activity of chitinolytic enzymes as secondary metabolic compounds produced in growth media by prolonging the period of incubation. The study has proved that such enzymes can be effectively used for suppression of soil-borne pathogens and that it can evolve as a potential biocide.     

Influence of bio-inoculants on the control of root rot and wilt disease of pyrethrum caused by Rhizoctonia solani

The effect of four bio-inoculants namely, Glomus aggregatum, Streptomyces sp., Bacillus subtilis and Trichoderma harzianum and a fungicide, Ridomil-mancozeb was evaluated on the biomass production and control of root rot and wilt disease under glasshouse conditions. Results showed that 21-day- prior inoculation with G. aggregatum was most effective where none of the treated plants produced disease symptoms and interestingly their growth was increased by 39.4%. The colonisation by G. aggregatum (>80%) also increased P concentration in shoot. While, similar treatment with Streptomyces sp., B. subtilis, T. harzianum and Ridomil-mancozeb individually failed to produce any significant effect over Rhizoctonia solani inoculated control, where all inoculated plant died, prematurely. The simultaneous and 3-day-post treatments of G. aggregatum were non-effective but simultaneous treatment with Streptomyces sp. produced 70% disease control, while B. subtilis and T. harzianum individually provided 50% control. Their effects were either better or at par when compared with the simultaneous treatment of Ridomil-mancozeb. In 3-day-post treatment, Streptomyces, B. subtilis and Ridomil-mancozeb individually provided 50% disease control, whereas T. harzianum was least effective as it could protect only 25% plants against infection. The results reveals that 15 days prior treatment of G. aggregatum can significantly controls the root rot and wilt disease of pyrethrum. Further, treatment of Streptomyces can also serve the next effective post infection control method.     

Eco-friendly approaches for the management of fenugreek root rot

To evolve eco-friendly management of fenugreek root rot caused by Rhizoctonia solani, a field trial was conducted during Kharif 2002 and Rabi seasons of 2002–2003 and 2003–2004. Experiments were conducted with eight treatments and three replications in RBD using the variety CO-2. The pooled analysis of the three season data showed that seed treatment with Trichoderma viride at 4g/kg of seed + soil application of Trichoderma viride at 5 kg/ha + soil application of neem cake at 150 kg/ha (T₃) recorded a percent disease index (PDI) of 23.1 versus 65.5 PDI in the control which accounted for a disease reduction of 64.7%. It was on par with seed treatment with Trichoderma viride at 4g/kg of seed + soil application of T. viride at 5 kg/ha (T₂) which reduced the disease incidence by 62.3% (24.7 PDI). The chemical treatment used for comparison, i.e. seed treatment with carbendazim + soil drenching at 0.1% + soil application of neem cake at 150 kg/ha recorded the lowest PDI of 16.8 with 74.4% disease reduction. Among the various treatments T₃ gave a seed yield of 572.7 kg/ha followed by T₂ (555.7 kg/ha). Treatment T₇ recorded the highest yield of 578.7 kg/ha. In the control plot the recorded yield was only 359.3 kg/ha. Though T₃ was more effective at reducing the disease incidence than T₂, the C:B ratio was higher (1:9.1) in respect of T₂ than T₃, which gave a C:B ratio of only 1:3.9. Hence, seed treatment with T. viride at 4g/kg + soil application of T. viride at 5kg/ha is a cost effective, eco-friendly management strategy for fenugreek root rot.     

甘肃大葱贮藏期镰孢菌腐烂病病原鉴定

【目的】大葱在贮藏期频繁发生镰孢菌腐烂病,损失严重。明确该病害病原种类对病害防治具有重要意义。【方法】利用组织分离法对采集自甘肃省兰州市(区)蔬菜市场的16份大葱贮藏期镰孢菌腐烂病病样进行病原物的分离、纯化培养,经单孢分离后根据形态学特征,再结合r DNA-ITS、EF-1a(tef)基因序列分析的方法进行鉴定。【结果】共分离得到80株镰孢菌,经鉴定分属3个种,即层出镰孢菌(Fusarium proliferatum)、尖孢镰孢菌(F.oxysporum)和燕麦镰孢菌(F.avenaceum),其中层出镰孢菌为大葱镰孢菌腐烂病的优势致病菌,分离频率为52.50%。对兰州白葱不同部位进行致病性测定,结果表明层出镰孢菌对大葱鳞茎的致病力最强,而燕麦镰孢菌对大葱鳞茎的致病力最弱。【结论】3种镰孢菌作为该病害的病原,属国内首次报道。     

Efficacy of antioxidants on incidence of Fusarium root and pod rot diseases in peanut

Several antioxidants namely ascorbic acid, salicylic acid, sodium benzoates, thiouria and catechol were used as seed treatment and foliar spraying to reduce the incidence of root and pod rot diseases of peanut caused by (Fusarium oxysporum, Fusarium solani and Fusarium moniliforme) as well as to determine of phenolic compounds and oxidative enzymes in the treated plants. Each antioxidant was used at different concentrations (2, 4, 6 and 8 mM) against tested pathogenic fungi in vitro. All antioxidants at 8 mM showed the greatest reduction of mycelial growth of the pathogens. In greenhouse experiments, treated seeds (Giza 5 cv.) or foliar spraying of peanut plants after 30 and 60 days from planting date with each antioxidant at 8 mM reduced severity of both diseases. The treated plants with antioxidants increased accumulation of phenolic compounds and activity levels of oxidative enzymes (catalase, peroxidase and polyphenoloxidase) in infected plants compared to healthy plants.

http://zoobank.org/urn:lsid:zoobank.org:pub:AF539C90-4B38-4BFE-B77B-5F2A5D764D7A     

Screening and biochemical characterisation of resistant and susceptible citrus species against dry root rot disease (Fusarium solani)

Fourteen citrus species were screened for their resistance against dry root rot under artificial inoculation conditions and classified as resistant (RHRL-122, RHRL-124, Australian sour, Sour dig, Balaji, Rangpurlime), moderately resistant (PKM-1, AL-Srirampur, Rough lemon), Susceptible (TAL 95/1, TAL 95/2, TAL 95/3, Nalgonda selection) and highly susceptible (TAL 94/13). The higher polyphenol oxidase (PPO) activity was observed in all infected leaves and roots of citrus species when compared to healthy leaves and roots at 15 and 30 days after inoculation (DAI). Higher PPO activity was observed in Balaji, Australian sour and Rangpurlime whereas lowest PPO activity was observed in TAL 94/13. In the case of leaf Peroxidase (PEO) isozyme profile an additional band which was darker and thicker was observed at an Em value of 0.24 in the case of Australia sour, Balaji and AL-Srirampur. In roots the PEO isozyme profile has the induction of single thick and darker additional band with an Em value of 0.47 was observed in Australian sour and Balaji. The banding profiles of estarase in leaves showed the induction of an extra band in the ase of Australian sour at Em 0.1, and at Em 0.53 in the case of Rangpurlime and Sourdig when compared to other species. The banding profile of esterase in roots was well expressed in Australian sour, PKM-1, Rough lemon, TAL-95/3, Rangpurlime and Sour dig. However, a minor band at Em 0.27 in Australian sour, TAL 95/1 and at Em 0.33 in Balaji was observed.     

The Glycine-Glomus-Bradyrhizobium symbiosis. IX. Nutritional, morphological and physiological responses of nodulated soybean to geographic isolates of the mycorrhizal fungus Glomus mosseae.

The objective of the work was to determine differences in plant response to geographic isolates of a vesicular-arbuscular mycorrhizal (VAM) fungus, and to demonstrate the need for such determinations in the selection of desirable host-endophyte combinations for practical applications. Soybean ( Glycine max (L.) Merr.) plants were inoculated with Bradyrhizobium japonicum and isolates of the VAM-fungal morphospecies Glomus mosseae (Nicol. & Gerd.) Gerd. and Trappe, collected from an arid (AR), semiarid (SA) or mesic (ME) area. Inoculum potentials of the VAM-fungal isolates were determined and the inocula equalized, achieving the same level of root colonization (41%, P >0.05) at harvest (50 days). Plants of the three VAM treatments (AR, SA and ME) were evaluated against von VAM controls. Significant differences in plant response to colonization were found in dry mass, leaf K, N and P concentrations, and in root/shoot, nodule/root, root length/leaf area and root length/root mass ratios. The differences were most pronounced and consistent between the AR and all other treatments. Photosynthesis and nodule activity were higher ( P <0.05) in all VAM treatments, but only the AR plants had higher ( P <0.05) photosynthetic water-use efficiency than the controls. Nodule activity, evaluated by H₂ evolution and C₂H₂ reduction, differed significantly between treatments. The results are discussed in terms of nutritional and non-nutritional effects of VAM colonization on the development and physiology of the tripartite soybean association in the light of intraspecific variability within the fungal endophyte.