We have designed two taxon-selective primers for the internal transcribed spacer (ITS) region in the nuclear ribosomal repeat unit. These primers, ITS1-F and ITS4-B, were intended to be specific to fungi and basidiomycetes, respectively. We have tested the specificity of these primers against 13 species of ascomycetes, 14 of basidiomycetes, and 15 of plants. Our results showed that ITS4-B, when paired with either a 'universal' primer ITS1 or the fungal-specific primer ITS1-F, efficiently amplified DNA from all basidiomycetes and discriminated against ascomycete DNAs. The results with plants were not as clearcut. The ITS1-F/ITS4-B primer pair produced a small amount of PCR product for certain plant species, but the quantity was in most cases less than that produced by the 'universal' ITS primers. However, under conditions where both plant and fungal DNAs were present, the fungal DNA was amplified to the apparent exclusion of plant DNA. ITS1-F/ITS4-B preferential amplification was shown to be particularly useful for detection and analysis of the basidiomycete component in ectomycorrhizae and in rust-infected tissues. These primers can be used to study the structure of ectomycorrhizal communities or the distribution of rusts on alternate hosts.

ITS primers with enhanced specificity for basidiomycetes--application to the identification of mycorrhizae and rusts.

Changes in agricultural practices with time have led to a decline in soil structure and with it, an increase in soil-borne plant diseases. Agricultural practices such as incorporating organic amendments and managing the type and quantity of crop residue, have a direct impact on plant health and crop productivity. Soil management practices involving tillage, rotation, and burning will impact the amount and quality of organic matter that is returned to the soil. These practices influence pathogen viability and distribution, nutrient availability, and the release of biologically active substances from both crop residues and soil microorganisms as illustrated by the model system of Cochliobolus sativus on the development of common root rot in cereals. The application of organic amendments, manures and composts that are rich in nitrogen, may reduce soil-borne diseases by releasing allelochemicals generated during product storage or by subsequent microbial decomposition. The modes of action for disease suppression are elucidated for a number of diseases including verticillium wilt and common scab of potato. Developing disease suppressive soils by introducing organic amendments and crop residue management takes time, but the benefits accumulate across successive years improving soil health and structure.

Suppressing soil-borne diseases with residue management and organic amendments

We used the polymerase chain reaction (PCR) to amplify specific regions of the nuclear and mitochondrial genomes of fungi using DNA extracted from pure cultures as well as that directly from ectomy...

Identification of indigenous and introduced symbiotic fungi in ectomycorrhizae by amplification of nuclear and mitochondrial ribosomal DNA

Numerous container-based studies in greenhouses or growth rooms have consistently demonstrated a suppressive effect of composts on soil-borne diseases such as damping-off and root rots (Pythium ultimum, Rhizoctonia solani, Phytophthora spp.), and wilts (Fusarium oxysporum and Verticillium dahliae). Composts have also been shown to suppress several diseases in the field, although the effects have been generally smaller and more variable than in container experiments. Several diseases of turf grass were suppressed by top-dressing with compost. These diseases are Fusarium patch (Microdochium nivale), red thread (Laetisaria fuciformis), damping-off (Pythium graminicola), brown patch (Rhizoctonia solani), dollar spot (Sclerotinia homoeocarpa) and snow mould (Typhula ishikariensis). The disease suppressive effect of compost generally increased with rate of application. Compost inclusion rates of at least 20% (v/v) were normally required to consistently obtain a disease suppressive effect, particularly in peat-b...

Suppression of soil-borne plant diseases with composts: A review

1 Pisolithus.- 2 Suillus.- 3 Laccaria.- 4 Hebeloma.- 5 Rhizopogon.- 6 Tuber.- 7 Scleroderma.- 8 Amanita.- 9 Paxillus.- 10 Cantharellus.- 11 Lactarius.- 12 Cenococcum.- 13 Hysterangium.- 14 Thelephora.- 15 Resupinate Ectomycorrhizal Fungal Genera.

Ectomycorrhizal fungi : key genera in profile

Species-specific polymorphisms in transcribed ribosomal DNA of fivePythium species

Registration of 'LCP 85-384' sugarcane

‘L 79-1002’ (Reg. No. CV-132, PI 651501) sugarcane (a complex hybrid of Saccharum offi cinarum L., S. spontaneum L., S. barberi Jeswiet, and S. sinense Roxb. amend. Jeswiet) was released on 26 Apr. 2007 by the Louisiana State University Agricultural Center in cooperation with the USDA-ARS and the American Sugarcane League, Inc. The cross for L 79-1002, a F 1 hybrid, was made in 1974 using ‘CP 52-68’ as the female parent and Tainan, a S. spontaneum clone, as the male parent. Initial clonal selection was done in single stools. Testing was done from 1976 through 1983 in yield trials conducted in the traditional sugarcane growing area in south Louisiana and in the colder, non-sugarcane growing regions of north Louisiana. Yield testing was resumed in 2002 through 2005 as interest in biofuels research renewed. L 79-1002 was released for an emerging biofuels industry because of its high fi ber content and biomass (cane yield) potential. Average fi ber content for L 79-1002 is approximately 257 g kg –1 . The new cultivar also has excellent vigor and ratooning ability. Experiments conducted at Bossier City, Louisiana (32.1° N lat) indicated a broader range of adaptability than sugarcane cultivars grown for the production of sucrose.

Registration of 'L 79-1002' sugarcane.

Clonal propagation of sugarcane(interspecific hybrids of Saccharum)is conducive to spread of systemicdiseases, such as ratoon stunting disease,caused by Leifsonia xyli subsp. xyli. This important disease iscontrolled by obtaining and plantinghealthy seed-cane. In Louisiana, commercialseed-cane initially produced through tissueculture is available to sugarcane farmersand is being widely planted. Long-termacceptability of this seed-cane productionmethod depends on the production of healthyplants that do not differ significantly inphenotypic and yield characteristics fromthe clones originally selected and releasedas commercial cultivars. To determinewhether tissue culture affects yield or itscomponents, three cultivars, CP 70-321, LCP85-384, and HoCP 85-845, were compared inthree successive crops initially plantedwith stalks from three sources: plantsderived from callus culture of the leafroll above the apical meristem, directregeneration from the apical meristem, andconventional bud propagation. Stalks ofplants derived from both explant sourceswere typical of seed-cane farmers wouldpurchase for planting that had beenpreviously rogued for phenotypic variantsand increased by bud propagation.Differences in yield components amongtissue culture explant sources and budpropagated cane only occurred in CP 70-321.Stalk diameter and stalk weight were lowerand stalk population was higher for plantsderived from leaf roll callus compared tobud propagated cane. Yield components weresimilar for plants derived from an apicalmeristem and bud propagation. Individualplant phenotypic variants resulting fromsomaclonal variation were not observed inany of the cultivars derived from eitherexplant source. In summary, genotype andexplant source affected persistent, uniformphenotypic variation resulting from tissueculture that changed some yield components. However, apical meristem culture wassuitable for production of seed-cane, assugarcane derived by meristem culture ofthree cultivars did not differsignificantly from the original germplasmfor any measured yield trait.

Effect of tissue culture explant source on sugarcane yield components

Soil amendment with different organic materials was evaluated in greenhouse experiments for effects on root rot and growth of sugarcane. Materials included composts prepared from cotton gin trash, cottonwood bark, mixed hardwood bark, municipal solid waste, and municipal yard waste; municipal biosolids; and a sugar mill by-product, filterpress cake. Field soil, steam-treated field soil, and steam-treated soil infested with Pythium arrhenomanes were amended with nonsterile or steam-treated organic materials. A metalaxyl fungicide treatment was included for comparison. When added in nonsterile form, cotton gin trash compost, filterpress cake, and biosolids suppressed disease and increased plant growth in field soil and soil infested with P. arrhenomanes, but this ability was reduced after steam treatment. Bark composts were capable of suppressing root rot and increasing plant growth in field soil and Pythium-infested soil when added in either nonsterile or steam-treated forms. Plant growth in steam...

https://apsjournals.apsnet.org/doi/pdfplus/10.1094/PDIS.1999.83.11.1039

Jeffrey W. Hoy

Papers

Species-specific polymorphisms in transcribed ribosomal DNA of fivePythium species

Registration of 'LCP 85-384' sugarcane

Registration of 'L 79-1002' sugarcane.

Effect of tissue culture explant source on sugarcane yield components

Organic Material Soil Amendment Effects on Root Rot and Sugarcane Growth and Characterization of the Materials.