Improving perennial ryegrass seed yields in take-all affected fields in Canterbury

Light seed and large seed dressing losses of perennial ryegrass seed crops were found to be associated with the presence of the root-rot pathogen Gaeumannomyces graminis var tritici (Ggt) which causes take-all in grasses and cereals. Preliminary pot experiments with a pasture bio-inoculant (PBI) comprising four isolates of Trichoderma atroviride demonstrated the potential for suppression of Ggt resulting in increased of perennial ryegrass dry matter and improved seed yield in prairie grass. During the 2019-20 and 2020-21 seed production seasons, large scale on-farm experiments with perennial ryegrass seed coated with PBI (new crop) or a prill formulation (drilled in an existing 2nd year crop) revealed good colonisation of the rhizosphere by Trichoderma and reduced Ggt root infection. PBI treatments increased perennial ryegrass dry matter and reproductive tiller number, resulting in a seed-yield increase of 4% (seed coat treatment) and 18% (prill formulation)

The impacts of take-all, drought and their interaction on Bromus wildenowii seed yield and the alleviation of these stresses by Trichoderma atroviride

Take-all, caused by the fungal pathogen Gaeumannomyces graminis var. tritici (Ggt) is an important root disease of cereals and grasses. An increasing occurrence of very light seeds in some New Zealand perennial ryegrass (Lolium perenne L.) seed crops may have been associated with Ggt, but any Ggt effects on grass seed yield were unknown. A glasshouse experiment, using prairie grass (Bromus wildenowii Kunth) as a model system was used to investigate the effect of Ggt on seed yield in the presence and absence of moisture stress (drought), and to determine whether strains of the fungal symbiont Trichoderma atroviride would allow the plant to better cope with both the biotic and abiotic stresses. Ggt significantly reduced seed yield by reducing the number of seeds per plant, while moisture stress significantly reduced all seed yield components. There was a significant interaction between Ggt and moisture stress because the moisture stress induced seed yield loss was greater in the presence of Ggt than in the absence of Ggt. In the absence of both abiotic and biotic stress, Trichoderma treatment had no effect on seed yield. However, Trichoderma significantly reduced Ggt root infection and this led to an increased seed yield. In the presence of Ggt and moisture stress, Trichoderma further increased seed yield by around double the increase for individual stress. Whether similar responses can be obtained in the field is currently being investigated

Urease producing microorganisms under dairy pasture management in soils across New Zealand

Urea, the most commonly used nitrogen fertiliser in New Zealand, can be quickly lost from the system via ammonia volatilisation or nitrate leaching following hydrolysis of urea by urease producing soil microorganisms (UPSMs). This study investigated UPSMs involved in urea degradation for upcoming research to reduce soil urease activity. Soils from under dairy pasture management across New Zealand, with a pasture species component of ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.) and aged between 9 months to 60 years old, were collected, and UPSMs were isolated and identified using both polymerase chain reaction (PCR)-based molecular and conventional methods. The fungal genera belonged to diverse taxonomical groups including the phylum Ascomycota: class: Dothideomycetes, Eurotiomycetes, Leotiomycetes and Sordariomycetes, the phylum Basidiomycota: class: Tremellomycetes and the phylum Zygomycota: order: Mucorales, all of which have a role in urea degradation in soil. Pasture soil-resident urease producing bacteria belonged to the Gammaproteobacteria and Betaproteobacteria. Cupriavidus sp. and Mucor hiemalis showed strong urease activity when cultured on urease medium. This is the first report on the urease activity of the pasture soil inhabitants Pochonia bulbillosa, Mariannaea elegans and Gliomastix sp. This study was part of a larger study underway to investigate control of UPSMs in soil to improve the efficiency of urea utilisation

Mechanisms of growth promotion by members of the rhizosphere fungal genus Trichoderma

Trichoderma spp. are best known for their biocontrol capabilities against a range of phytopathogenic microorganisms and increased plant drought tolerance. However, all the attributes of Trichoderma are also related to their ability to induce plant growth promotion by direct or indirect mechanisms. The activation of these mechanisms might be dependent on the ability of Trichoderma to respond to the environmental conditions and host plant.Our research work on Trichoderma has been supported by the Tertiary Education Commission, New Zealand through the Bio-Protection Research Centre, Marsden Fund, and Lincoln University Research Fund

Research priorities for harnessing plant microbiomes in sustainable agriculture

Feeding a growing world population amidst climate change requires optimizing the reliability, resource use, and environmental impacts of food production. One way to assist in achieving these goals is to integrate beneficial plant microbiomes-i.e., those enhancing plant growth, nutrient use efficiency, abiotic stress tolerance, and disease resistance-into agricultural production. This integration will require a large-scale effort among academic researchers, industry researchers, and farmers to understand and manage plant-microbiome interactions in the context of modern agricultural systems. Here, we identify priorities for research in this area: (1) develop model host-microbiome systems for crop plants and non-crop plants with associated microbial culture collections and reference genomes, (2) define core microbiomes and metagenomes in these model systems, (3) elucidate the rules of synthetic, functionally programmable microbiome assembly, (4) determine functional mechanisms of plant-microbiome interactions, and (5) characterize and refine plant genotype-by-environment-by-microbiome-by-management interactions. Meeting these goals should accelerate our ability to design and implement effective agricultural microbiome manipulations and management strategies, which, in turn, will pay dividends for both the consumers and producers of the world food supply