丛枝菌根真菌对不同番茄品种抗根结线虫病的影响

【背景】根结线虫病害严重制约我国设施蔬菜的生产。丛枝菌根真菌(Arbuscular Mycorrhizal Fungi,AMF)作为土壤中最重要的有益真菌之一,可以促进植物生长,提高植物抗病性,减轻土传真菌和线虫病害的发生。在蔬菜保护地栽培中,AMF对于植物线虫病防治作用的研究受到了广泛关注。【目的】针对番茄生产中危害最严重的南方根结线虫(Meliodogyne incognita)病害问题,研究AMF和番茄品种不同组合的抗线虫效应,以期为菌根真菌作为生物防治剂和生物菌肥应用于实际生产提供技术基础。【方法】在灭菌土壤中,人工接种根结线虫,比较不同菌种Rhizophagus intraradices(Ri)、Acaulosporamellea(Am)及菌种组合Rhizophagusintraradices+Acaulosporamellea(Ri+Am)在不同番茄品种(感病品种蒙特卡罗和抗线虫品种仙客1号)上对南方根结线虫侵染和繁殖的影响,研究AMF对根结线虫的拮抗效应。另外,采用南方根结线虫连作发病的土壤,在感病品种蒙特卡洛上接种AMF混合菌种Ri+Am,番茄苗移栽入连作土壤中,测定各生长指标和调查根结和卵块数量,评价接种AMF处理对根结线虫病的防治效果。【结果】在灭菌土壤中,普通番茄品种蒙特卡罗的菌根效应显著优于抗线虫番茄品种仙客1号,表现为前者单位根重的根结和卵块的数量均比对照显著降低,而后者仅降低了卵块数量;蒙特卡罗上接种Ri+Am混合菌种的效果优于接种单一菌种Am和Ri;而仙客1号上接种Ri的效果更好。接种线虫也显著影响了AMF的侵染,而且对抗性品种仙客1号的影响更为明显。但除了接种Am的处理,大多数处理收获时菌根侵染率仍维持较高的水平(70%以上)。在连作土壤中,感病品种蒙特卡罗接种混合菌种Ri+Am具有较好的抗/耐线虫效应,主要表现为促进植株生长,显著降低根结和卵块数量,但菌根侵染率较灭菌土壤低,约为40%。【结论】综合以上结果,表明菌根化苗能够在一定程度上减轻根结线虫病的危害。土壤灭菌条件下,在感病和抗线虫番茄品种上接种AMF能够减轻线虫的侵染和繁殖,而且在感病品种上的防治效果更加显著。在连作土壤中,在番茄感病品种上接种AMF也表现较好的抗线虫效果。     

Response of subterranean clover cultivars to root rot fungi

Twelve widely grown cultivars of subterranean clover (Trifolium subterraneum) were screened both under controlled environment conditions for their resistance to five fungi commonly associated with root rot and under field conditions for their resistance to natural root infections. All cultivars showed decreased seedling survival (particularly from Pythium irregulare and Rhizoctonia solani), tap and lateral root rot (particularly from Fusarium avenaceum, P. irregulare, and R. solani) and reduced plant size (particularly from R. solani and P. irregulare). Individual cultivars generally differed in their response to the five pathogens and for any one pathogen there was generally a range of cultivar susceptibilities. Cultivars with the best resistance to individual root pathogens were identified. The results for the five individual pathogens under controlled conditions only showed correlation with field data for some of the parameters compared.     

Pathogenicity of root knot nematode Meloidogyne incognita on okra and its management through botanicals

An investigation was carried out to study the pathogenicity of root knot nematode Meloidogyne incognita on okra and its management through various organic amendments. The inoculum level of 1000 juveniles per plant showed significant reduction in various plant growth parameters, which reveals that M. incognita is a potential pathogen of okra. With the increase in inoculums level of M. incognita (J₂), there was a progressive decrease in various plant growth parameters. The maximum reduction in plant growth parameters was observed at an inoculum level of 4000 juveniles per plant. The efficacy of five organic amendments viz. groundnut cake, castor cake, sunflower cake, linseed cake and sawdust was tested against root knot nematode M. incognita. Amending the soil with different oil cakes was found to be effective in reducing the nematode soil population, number of females, number of egg masses as well as root gall formation in okra. The highest increase in plant growth (13%) and maximum reduction in number of galls (54%), number of females (57%) and number of egg masses (55%) was recorded on application of groundnut cake.     

丛枝菌根真菌和根瘤菌对白三叶氮同化的影响

为揭示丛枝菌根真菌(AMF)和根瘤菌在白三叶氮(N)同化中的作用,该研究对白三叶进行单一或联合接种隐类球囊霉(Paraglomus occultum)和三叶草根瘤菌(Rhizobium trifolii),分析其对白三叶的生长、光合作用、叶片N和氨基酸含量以及N同化相关酶活性的影响。结果表明:(1)单一接种AMF或根瘤菌以及联合接种AMF和根瘤菌均显著增加了白三叶的株高、匍匐茎长度、叶片数、地上部生物量、总生物量、叶绿素b和总叶绿素含量、稳态光量子效率和叶片N含量,这种增强效应是联合接种>单一AMF>单一根瘤菌>未接种处理。(2)联合接种AMF和根瘤菌显著增加了白三叶叶片中丙氨酸、精氨酸、天冬酰胺、天冬氨酸、谷氨酰胺、谷氨酸和组氨酸的含量,显著提升了叶片N同化相关酶如硝酸还原酶、亚硝酸还原酶、谷氨酰胺合成酶、谷氨酸合成酶、谷氨酸脱氢酶、天冬酰胺合成酶和天冬氨酸转氨酶的活性,显著促进AMF对白三叶根系的侵染。综上认为,联合接种AMF和根瘤菌通过激活N同化相关酶活性有效促进N同化,产生更多氨基酸,进一步促进白三叶植株生长; 联合接种AMF和根瘤菌具有协同作用,有效促进了白三叶的N同化。     

丛枝菌根真菌群落对白三叶草生长的影响

不同施肥处理影响AMF(Arbuscular mycorrhizal fungi)群体结构,然而不同AMF群体结构对植物的生长以及养分吸收的影响尚未见报道,试验利用盆栽实验研究了7种不同来源的丛枝菌根真菌(AMF)群落对白三叶草生长和N、P、K以及微量元素Cu、Zn、Mn的吸收的影响。7种AMF群落分离自长期定位施肥试验地,分别为NPK、OM、CK、1/2OM、NP、NK和PK。每年施肥量是300kg N/hm2,135kg P2O5/hm2,300kg K2O/hm2。有机肥处理的N、P、K养分量与试验地NPK处理含量相同,原料以粉碎的麦秆为主,加上适量的大豆饼和棉仁饼,有机肥经堆制发酵后施用。试验土壤采用封丘试验地土壤,经灭菌处理。试验结果表明,接种不同AMF群落均能促进三叶草的生长,对养分吸收则表现不同。分离自CK试验地的AMF群落对三叶草侵染率显著低于其它6种AMF群落。分离自1/2OM和OM试验地的AMF群落较分离自NPK、CK、NP和NK的AMF群落显著促进了三叶草对P的吸收;各种AMF群落都促进了对N和K的吸收;分离自OM、CK、1/2OM、NP、NK试验地的降低了三叶草植株N含量;分离自NPK试验地的AMF群落提高了三叶草植物K含量;对于Cu、Zn、Mn元素的吸收,不同处理存在较大的差异。AMF群落对三叶草生长以及养分吸收贡献不同,这与不同施肥管理下不同AMF群落的优势种属的侵染率、养分转化以及菌丝发育及分布有关。     

Interaction of vascular plants and vesicular-arbuscular mycorrhizal fungi across a soil moisture-nutrient gradient

Summary Abundance and distribution of vascular plants and vesicular-arbuscular mycorrhizal (VAM) fungi across a soil moisture-nutrient gradient were studied at a single site. Vegetation on the site varied from a dry mesic paririe dominated by little bluestem (Schizachyrium scoparium) to emergent aquatic vegetation dominated by cattail (Typha latifolia) and water smartweed (Polygonum hydropiperoides). Plant cover, VAM spore abundance, plant species richness, and number of VAM fungi represented as spores, had significant positive correlations with each other and with percent organic matter. The plant and VAM spore variables had significant negative correlations with soil pH and available Ca, Mg, P and gravimetric soil moisture. Using stepwise multiple regression, Ca was found to be the best predictor of spore abundance. Test for association between plant species and VAM fungal spores indicated that the spores of Glomus caledonium are associated with plants from dry, nutrient poor sites and spores of gigaspora gigantea are positively associated with plants occurring on the wet, relatively nutrient rich sites. Glomus fasciculatum was the most abundant and widely distributed VAM fungus and it had more positive associations with endophyte hosts than the other VAM fungi. We found no relationship between beta niche breadth of plant species and the presence or absence of mycorrhizal infection. However, our data suggest that some plant species may vary with respect to their infection status depending upon soil moisture conditions that may fluctuate seasonally or annually to favor or hinder VAM associations.     

RFLP markers linked to the root knot nematode resistance gene Mi in tomato

Summary The Mi gene originating from the wild tomato species Lycopersicon peruvianum confers resistance to all major root knot nematodes (Meloidogyne spp.). This single dominant gene is located on chromosome 6 and is very closely linked to the acid phosphatase-1 (Aps-1) locus. Resistance to nematodes has been introgressed into various cultivars of the cultivated tomato (L. esculentum), in many cultivars along with the linked L. peruvianum Aps-1 ¹ allele. By using a pair of nearly isogenic lines differing in a small chromosomal region containing the Mi and Aps-1 loci, we have identified two RFLP markers, GP79 and H6A2c2, which are located in the introgressed L. peruvianum region. Analysis of a test panel of 51 L. esculentum genotypes of various origins indicated that GP79 is very tightly linked to the Mi gene and allows both homozygous and heterozygous nematode-resistant genotypes to be distinguished from susceptible genotypes, irrespective of their Aps-1 alleles. Marker H6A2c2 is linked to the Aps-1 locus and is capable of discriminating between the L. peruvianum Aps-1 ¹ allele and the L. esculentum Aps-1 ³ and Aps-1 ⁺ alleles. In combination, these RFLP markers may provide a powerful tool in breeding tomatoes for nematode resistance.     

Interaction of soil microbes with mycorrhizal fungi in tomato

In this study, the interaction of soil microbes with mycorrhizal fungi (MF) was performed to understand the effect on tomato. A pot and a field experiment were employed to investigate the impact of soil microbes i.e. Fusarium oxysporum f. sp. lycopersici, Trichoderma harzianum, Aspergillus niger and Rhizobium leguminosarum, on AM fungi in pots and field studies. The soils without microbes which treated controls with or without mycorrhizal inoculation were also included. Plant growth and root colonisation were measured 36, 75 and 120?days post inoculation (dpi) in the both pot experiment and field study. Soil microbes’ effects on the growth behaviour of the tomato plant were determined via the shoot and root weight. R. leguminosarum and A. niger did not affect the colonisation ability much, but F. oxysporum f. sp. lycopersici and T. harzianum resulted in the inhibition of AM fungal colonisation in both pot and field studies. Our study provides evidence for the effects of soil microbes on the diversity of AM fungi and their effect on the tomato plants. The higher concentrations of phosphorus and of proteins in the root tissues, previously colonised with AM fungi, point out their effect as biofertilizers, according to the concept of sustainable agriculture.     

Effect of 28-homobrassinolide on susceptible and resistant cultivars of tomato after nematode inoculation

In vitro effects of 28-homobrassinolide (HBl) were evaluated on morphological and biochemical parameters of susceptible (Pusa Ruby) and resistant (PNR-7) cultivars of tomato, 5 days after nematode inoculation. In susceptible cultivar, nematode invasion reduced the plant growth while growth was enhanced after brassinosteroid treatment. In case of resistant plants, nematodes were not able to invade the roots and here also, pre-sowing treatment of seeds with HBl further enhanced the growth of plants. An increase in specific activities of antioxidative enzymes (catalase, ascorbate peroxidase, guaiacol peroxidase, glutathione reductase, glutathione peroxidase and superoxide dismutase) was observed in susceptible plants treated with HBl. In resistant cultivar, nematode inoculation increased the specific activities which were further enhanced with HBl treatment. The results obtained in the present study indicated the ameliorative effects on tomato varieties treated with HBl even after nematode stress. Thus, suggesting a possible role of HBl in lessening the oxidative stress generated during nematode invasion and boosting the resistance capacity of plants.     

Dual axenic culture of sheared-root inocula of vesicular-arbuscular mycorrhizal fungi associated with tomato roots

Surface-sterilized sheared-root inocula of two vesicular-arbuscular mycorrhizal (VAM) fungi (Glomus intraradices and G. versiforme) from pot cultures associated with excised tomato roots showed significant sporulation and the production of an extensive hyphal biomass. As many as 10²–10³ axenic mature spores were recovered in Petri dishes during 3 months incubation in the dark. Propagules of both species were able to complete their vegetative life cycle in vitro and efficiently colonize Acacia albida roots after 1 month under greenhouse conditions. The effectiveness of 0.5 cm pieces of VAM roots as starter inocula indicates the high inoculum potential of intravesicle propagules.     

Interaction of a root-knot nematode (Meloidogyne hapla) and plant intraspecific diversity in clover-grass communities

AimsSoil organisms can influence the plant diversity-productivity relationship at species level; however, little is known about their role in the relationship at an intraspecific level. This study aimed to investigate the interaction between the effects of plant intraspecific diversity and a root-knot nematode on primary production and community evenness.     

Monoxenic maintenance and reproduction of root-knot nematode (Meloidogyne hapla) on multiple-species in vitro root culture systems

The ability of tomato root tips transformed with Agrobacterium rhizogenes and non-transformed onion and dandelion root tips to regenerate and provide suitable monoxenic hosts for the maintenance of root-knot nematode (Meloidogyne hapla) was investigated. Populations of M. hapla were successfully established on all root culture systems examined, but the onion root culture was overall the most effective method for long-term maintenance and reproduction of M. hapla. The use of a pre-induction medium containing the hormone !-naphthaleneacetic acid was necessary for the production of onion root culture systems but was not required for the establishment of tomato or dandelion root cultures. Differences in nematode reproduction were observed on tomato when multiple populations of M. hapla were used for inoculations.     

Effect of vesicular-arbuscular mycorrhizal and phosphatase-producing fungal inoculation on growth and nutrition of white clover supplied with organic phosphorus

In a pot experiment white clover was grown for 50 d in two sterilized low phosphorus soils supplied with organic phosphorus as sodium phytate. Seed inoculation withAspergillus fumigatus, a phosphatase-producing fungus (PPF), and soil inoculation withGlomus mossece, a vesicular-arbuscular mycorrhizal (VAM) fungus resulted in increased shoot and root dry mass and root length, phosphatase activity in soil and shoot concentrations of P and to a lesser extent of Mg. The effects on these parameters were most distinct upon combined inoculation treatment (PPF+VAM). A significant increase in hyphal length density and decrease in Mn concentration was observed only upon PPF+VAM treatment. Shoot concentrations of Cu and Zn were highly enhanced by VAM but not by PPF. Of the total P uptake the PPF contribution accounted for 39–41 %, VAM contributed 41–50 % and their combination resulted in 55–58 %, in comparison to only 38–40 % contribution due to soil microorganisms under unsterilized conditions. The depletion of organic phosphorus in the rhizosphere soil increased in the order (PPF+VAM)>VAM>PPF> unsterilized soil>sterilized soil. The results demonstrate the efficient use of phytate phosphorus byA. fumigatus andG. mosseœ and suggest that dual inoculation is superior to a single one.     

施氮量和土壤灭菌对根结线虫侵染番茄根系的影响

设施蔬菜生产中,根结线虫病害频繁发生,严重威胁了设施蔬菜生产的安全性和可持续性.为了探究氮肥施用量和土壤灭菌对根结线虫侵染番茄根系的影响,采用二因素(施氮量和土壤是否灭菌)二水平完全随机区组设计,进行盆栽试验.施氮量分别为100和300 mg·kg-1,采用γ射线对土壤灭菌或不灭菌.结果表明:未灭菌条件下,与高氮处理相比,低氮处理单位根长和单位根干重的根结数分别减少了42.5%和30.4%,地上部干重和根干重分别增加了43.9%和31.4%,氮素农学利用效率提高4.3倍;对土壤进行γ射线灭菌,有效地消除了根结线虫对番茄根系的侵染,地上部干重增加了31.8%;适当减少氮肥施用量能显著降低根结线虫对设施番茄根系的侵染,促进番茄生长,提高氮素农学利用效率.     

Plant life span and response to inoculation with vesicular-arbuscular mycorrhizal fungi

Summary This study sought to investigate the relationships among residual soil phosphorus (P) pools, plant life span, successional persistence and responsiveness to vesicular-arbuscular mycorrhizal (VAM) infection. Plants of five species which varied in life span, persistence, and VAM responsiveness were grown in nutrientpoor soils in a glasshouse for 8 weeks and given weekly feedings with either high- or low-P solutions. There was little effect of plant life span or VAM status on changes in residual available (1 M KCl extractable) P. In contrast, there were strong correlations between VAM responsiveness and changes in the exchangeable P pool (1 M NH₄C₂H₃O₂ extractable). Plants with greater VAM responsiveness and greater persistence through succession were able to reduce this potentially available P pool by as much as 50% in 8 weeks. In contrast, plants with poor or negative responsiveness to mycorrhizal infection and little successional persistence exhibited little control over potentially available P pools. These data confirm other studies which demonstrate that VA mycorrhizae access insoluble forms of P, thereby controlling potential supply rate over the longer term. Such control over soil P pools may contribute to successional persistence via either inhibition or tolerance mechanisms, and should be considered in any comprehensive theory of the mechanisms underlying succession.     

Interaction of vesicular arbuscular mycorrhiza with root knot nematodes in tomato

Summary The interaction between the VA mycorrhizal fungus,Glomus fasciculatus and the root-knot nematodes,Meloidogyne incognita andM. javanica, and their effects on the growth and phosphorus nutrition of tomato was studied in a red sandy loam soil of pH 6.0. Inoculation of tomato roots with root-knot nematodes enhanced infection and spore production byG. fasciculatus. Inoculation of tomato plants withG. fasciculatus significantly reduced the number and size of the root-knot galls produced byM. incognita andM. javanica. Inoculation withG. fasciculatus although improved plant growth and its total phosphorus content compared to the uninoculated plants, the difference were not statistically significant.     

Flavonoids exclusively present in mycorrhizal roots of white clover exhibit a different effect on arbuscular mycorrhizal fungi than flavonoids exclusively present in non-mycorrhizal roots of white clover

Abstract

The flavonoids 5,6,7,8,9-hydroxy chalcone, 3,7-hydroxy-4′methoxy flavone, 5,6,7,8-hydroxy-4′-methoxy flavone and 3,5,6,7,4′-hydroxy flavone can be detected only in non-mycorrhizal roots of white clover, but not in mycorrhizal roots, whereas the flavonoids acacetin, quercetin and rhamnetin are only present in mycorrhizal roots. We tested the effect of several concentrations of these compounds on spore germination, hyphal growth, hyphal branching, formation of clusters of auxiliary cells and of secondary spores of the arbuscular mycorrhizal fungi Gigaspora rosea, Gigaspora margarita, Glomus mosseae and Glomus intraradices. Our results indicate that depending on the flavonoid, the tested compounds are involved at different stages in the regulation of mycorrhization. This hypothesis is strengthened by their differing effect on several AM fungal growth parameters. Furthermore, our study provides more data on the AM fungus genus/species specificity of flavonoids.     

Screening of tomato cultivars in the presence of the root-knot nematode,Meloidogyne javanica

In the present study, 12 varieties of tomato, viz., Arka Vikas, Damayanti, F-hybrid, Hybrid Padmarag, Hybrid Tripti, Marudam, Punjab chhoara, Pusa early dwarf, Punjab kesari, P.K.M.I, Roma and Pusa Ruby were screened for the presence of the root-knot nematode, M. javanica to obtain information on the varying degrees of resistances to tomato cultivars. All the cultivars of tomato tested were found to be infected with the root-knot nematode, M. javanica, however, to a varying extent. Consequently, there was a reduction in the growth parameters of cultivars leading to have an impact on the yield and quality of fruits. The cultivar, Marudam was found resistant while the cultivar the Pusa early dwarf was moderately resistant and rest of the 10 cultivars was highly susceptible.     

Effect of vesicular-arbuscular mycorrhizal fungi on verticillium wilt of cotton

The development of vesicular-arbuscular mycorrhizal fungi (VAMF): Glomus mosseae (Nicol and Gerd.) Gerdemann and Trappe, Glomus versiforme (Karsten) Berch, Sclerocystis sinuosa Gerdemann and Bakhi and Verticillium dahliae and the effects of the VAMF on the verticillium wilt of cotton (Gossypium hirsutum L. and Gossypium barbadense L.) were studied with paper pots, black plastic tubes and clay pots under natural growth conditions. All of the tested VAMF were able to infect all the cotton varieties used in the present experiment and typical vesicles and arbuscules were formed in the cortical cells of the cotton roots after inoculation. The cap cells, meristem, differentiating and elongating zones of the root tip were found to be colonized by the VAMF. In the case of most V. dahliae infection, the colonization occurred mostly from the root tip up to 2 cm. VAMF and V. dahliae mutually reduced their percentage of infection when inoculated simultaneously. VAMF inoculation reduced the numbers of germinable microsclerotia in the soil of the mycorrhizosphere, while the quantity of VAM fungal spores in the soil was not influenced by infection of with V. dahliae. The % of arbuscule colonization in roots was negatively correlated with the disease grades, while the numbers of vesicles in roots were not. These results suggest that certain vital competition and antagonistic reactions exist between VAMF and V. dahliae. VAMF reduced the incidence and disease indices of verticillium wilt of cotton during the whole growth phase. It is evident that cotton seedling growth was promoted, flowering was advanced, the numbers of flowers and bolls were increased, and this resulted in an increase in the yield of seed cotton. Among the VAMF species, Glomus versiforme was the most effective, and Sclerocystis sinuosa was inferior. So far as the author is aware, such an effect of VAMF on the increase of cotton wilt tolerance/resistance is reported here far the first time.     

Effect of liming on spore germination,germ tube growth and root colonization by vesicular-arbuscular mycorrhizal fungi

Summary The effect of soil acidity on spore germination, germ tube growth and root colonization of vesicular-arbuscular mycorrhizal (VAM) fungi was examined using a Florida Ultisol. Soil samples were treated with 0, 4, 8 and 12 meq Ca/MgCO₃/100 g soil and each lime level received 0, 240, and 720 ppm P as superphosphate. Corn (Zea mays L.) was planted in the soil treatments, inoculated with eitherGlomus mosseae orGigaspora margarita spores and grown for 31 days. Acid soil inhibits mycorrhizal formation byG. mosseae through its strong fungistatic effect against the spores. The dolomitic lime increased mycorrhizal formation by both fungal species.G. margarita is much less sensitive to acidic conditions thanG. mosseae. Al ions are a very important component of the fungistatic property against the VAM symbiosis. VAM fungus adaptation may be important for plants growing on infertile acid soils if soil inoculation with these fungi is to contribute significantly to low-input technology for tropical agricultural systems.