Differentiating individuals of Armillaria species in New Zealand forests

Background: Armillaria novae-zelandiae and A. limonea occur naturally as wood decay fungi in native forests in New Zealand. As pathogens they are responsible for significant root disease in trees and shrubs in plantations, crops and urban parks and gardens. A thorough understanding of their population dynamics entails knowledge of the spatial arrangement of their individual mycelia or genets. In previous work the distributions of vegetative compatibility groups (VCGs) of these fungi were mapped in an area of native forest prior to and after replacement by a young Pinus radiata plantation. With the advent of molecular technology, it has become possible to test species identities made earlier using culture techniques and to verify whether or not their VCGs, determined by incompatibility reactions between paired cultures, represent distinct individual genets. Methods: Stock subcultures of isolates representing each VCG were recovered from storage in order to obtain DNA. Extracted DNA was subjected to a polymerase chain reaction procedure (UP-PCR) using 11 universal primers to assess genetic variation between subcultures. Bands were scored as either present or absent for each primer-subculture combination and cluster analysis was undertaken by generating dendrogram trees to reveal genetic groupings among subcultures. Results: DNA cluster analysis divided subcultures of isolates into two species groups, A. novae-zelandiae and A. limonea, corresponding to identities determined through culture morphology. Within species, subcultures grouped into clusters that matched VCGs determined by earlier culture pairing. There was little indication of genetic variation within VCGs, except for one of A. limonea, which comprised two sub-clusters. Conclusions: The Armillaria species and VCGs identified by culture techniques in the laboratory were verified by independent molecular methodology. In general, the VCGs represent discrete individual genets or colonies in the field. Techniques that differentiate isolates based on differences in their DNA sequence provide a quick alternative to timeconsuming laboratory culture methods for resolving population spatial structure. However, some complementary isolate pairing may be necessary when rationalising the significance of groupings in dendrogram trees

The life cycle and field epidemiology of Uromycladium acaciae (Pucciniales) on Acacia mearnsii in South Africa

Uromycladium acaciae has damaged plantations of Acacia mearnsii in southern Africa since 2013. Uredinia of a species of Uromycladium have been known on A. mearnsii in South Africa since the 1980s. However, the recent damage is associated with telia and spermogonia. Uredinia and telia were previously treated as conspecific with a phylogenetic species concept. However, uredinia did not form after previous artificial inoculation experiments with teliospores. Controlled studies identified the optimum conditions for basidiospore infection, but the optimum conditions for sporulation and dispersal have not been identified. To investigate the life cycle and field epidemiology of Uromycladium on A. mearnsii, spores were trapped weekly and development of disease symptoms and plant phenology were monitored monthly at three plantations. Telia and spermogonia developed independently from uredinia, and nucleotide polymorphisms between rDNA of uredinia and telia were fixed based on high throughput sequencing and PCRs. All three weather variables measured had a significant effect on teliospore abundance at two of the three sites. Teliospore abundance was greatest during trapping periods when mean relative humidity was high, mean rainfall was 4–5 mm day−1 and mean temperature was 15–16°C. Teliospore counts peaked at the end of summer, potentially the result of epidemic build-up. Results support the hypothesis that despite sharing a most recent common ancestor, uredinia on A. mearnsii in southern Africa are independent to the life cycle of the telial rust, which likely constitutes a new introduction. Furthermore, teliospores of U. acaciae disperse under wet conditions, and the wet season between October and March is the optimal period for wattle rust development.Members of the Tree Protection Co-operative Programme (TPCP), the Department of Science and Technology (DST)/National Research Foundation (NRF) Centre of Excellence in Tree Health Biotechnology (CTHB) and the Wattle Rust Steering Committee funded by the Sector Innovation Fund (SIF) of the Department of Science and Technology (DST). The Genomics Research Institute of the University of Pretoria provided funding for high-throughput sequencing of Uromycladium acaciae. Stuart Fraser acknowledges Postdoctoral Fellowship funding from the University of Pretoria and New Zealand Ministry for Business Innovation and Employment through the Science Strategic Investment Fund.http://wileyonlinelibrary.com/journal/aabhj2022Forestry and Agricultural Biotechnology Institute (FABI)Plant Production and Soil Scienc

Progress Report: Evaluation of Spikey® for mitigating nitrogen leaching losses from a Bay of Plenty dairy farm: Results for monitoring undertaken from 2021 to 2023

A trial was setup in Spring 2020 on a commercial dairy farm in the Rotorua region to study the effects of Pastoral Robotics Limited’s Spikey® and NitroStopTM technology on pasture production and nitrogen (N) leaching. Pastoral Robotics is measuring pasture production while AgResearch are responsible for N leaching measurements. This report covers the AgResearch activities during the first three years of the trial.Report Number: RE450/2023/082</p

Deep soil coring for inorganic nitrogen as a method of predicting nitrogen loss due to leaching: Preliminary study results

Soil samples were collected from two paddocks on a commercial dairy farm near Methven in July 2023. The samples were analysed for ammonium and nitrate, the two main components of soil inorganic nitrogen (N). This report presents the data obtained from that sampling.Report no. RE450/2023/060</p

Progress Report: The effectiveness of Spikey® technology for reducing N leaching - Year 3, Dairy Trust Taranaki - Stratford farm

A grazing trial and associated lysimeter trial were setup in Spring 2020 on the Dairy Trust Taranaki farm in Stratford to study the effect of Pastoral Robotics Limited’s Spikey® technology and NitroStopTM product on pasture production and nitrogen (N) leaching. This report (Milestone 3.6) covers AgResearch activities during Year 1, Year 2 and the first 9 months of Year 3 of the four-year trial period.Report Number: RE450/2023/081</p

Translocation of Loline Alkaloids in <i>Epichloë</i>-Infected Cereal and Pasture Grasses: What the Insects Tell Us

Aphids are major pests of cereal and pasture grasses throughout the world, vectoring disease and reducing plant production. There are few control options other than insecticides. Epichloë endophytes that produce loline alkaloids in their hosts provide a possible mechanism of control, with both meadow fescue and tall fescue naturally infected with loline-producing endophytes showing a resistance to Rhopalosiphum padi. We screened Elymus spp. naturally infected with endophytes that produced loline alkaloids at concentrations known to affect aphids on fescue but found no effect on these insects infesting Elymus. A synthetic loline-producing endophyte association with rye also had no effect on the aphids. After hypothesizing that the lolines were being translocated in the xylem in Elymus and rye rather than the phloem, we tested the rye and meadow fescue infected with loline-producing endophytes against a xylem feeding spittlebug. The endophyte in rye inhibited the feeding of the insect and reduced its survival, whereas the endophyte-infected meadow fescue had no effect on the spittlebug but reduced the number of aphids. Lolines applied to the potting medium of endophyte-free and endophyte-infected rye, ryegrass, and tall fescue resulted in a decrease in the aphid populations on the endophyte-free pasture grasses relative to the untreated controls but had no effect on aphid numbers on the rye. We tentatively conclude that lolines, produced in both natural and synthetic association with Elymus and rye, are partitioned in the xylem rather than the phloem, where they are inaccessible to aphids

Fungi decaying the wood of fallen beech (Nothofagus) trees in the South Island of New Zealand.

In order to extend present knowledge of communities of wood decay fungi in native forests, basidiomycetes and ascomycetes were isolated from within 15 fallen stems in beech (Nothofagus, Nothofagaceae) forests in the South Island of New Zealand. Fungal species were identified as precisely as possible using traditional culturing and molecular approaches. The internal distribution of species within stems was determined. Common fungi that occupied significant portions of stems were Ganoderma applanatum sensu Wakefield, Australoporus tasmanicus, Inonotus nothofagi, Pleurotus purpureo-olivaceus and an unidentified hymenochaetaceous species. Richness and diversity of basidiomycete species were greater in stems of red beech (Nothofagus fusca) and silver beech (N. menziesii) than in those of matai (Prumnopitys taxifolia, Podocarpaceae) and tawa (Beilschmiedia tawa, Lauraceae), as determined from earlier studies in podocarp hardwood and beech indigenous forests. There was greater similarity in the species composition of basidiomycete fungi colonising the three beech species compared with those colonising rimu (Dacrydium cupressinum, Podocarpaceae), tawa and matai. Based on observations in this study and on international research on the effects of selective logging on basidiomycete biodiversity, the decision to restrict to 50% the extraction of wood following storm damage in beech forests on the South Island West Coast appears to have been appropriate.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

The life cycle and field epidemiology of Uromycladium acaciae (Pucciniales) on Acacia mearnsii in South Africa

Abstract Uromycladium acaciae has damaged plantations of Acacia mearnsii in southern Africa since 2013. Uredinia of a species of Uromycladium have been known on A. mearnsii in South Africa since the 1980s. However, the recent damage is associated with telia and spermogonia. Uredinia and telia were previously treated as conspecific with a phylogenetic species concept. However, uredinia did not form after previous artificial inoculation experiments with teliospores. Controlled studies identified the optimum conditions for basidiospore infection, but the optimum conditions for sporulation and dispersal have not been identified. To investigate the life cycle and field epidemiology of Uromycladium on A. mearnsii, spores were trapped weekly and development of disease symptoms and plant phenology were monitored monthly at three plantations. Telia and spermogonia developed independently from uredinia, and nucleotide polymorphisms between rDNA of uredinia and telia were fixed based on high throughput sequencing and PCRs. All three weather variables measured had a significant effect on teliospore abundance at two of the three sites. Teliospore abundance was greatest during trapping periods when mean relative humidity was high, mean rainfall was 4–5 mm day-1, and mean temperature was 15–16°C. Teliospore counts peaked at the end of summer, potentially the result of epidemic build-up. Results support the hypothesis that despite sharing a most recent common ancestor, uredinia on A. mearnsii in southern Africa are independent to the life cycle of the telial rust, which likely constitutes a new introduction. Furthermore, teliospores of U. acaciae disperse under wet conditions; and, the wet season between October and March is the optimal period for wattle rust development. This article is protected by copyright. All rights reserved

Susceptibility of native New Zealand Myrtaceae to the South African strain of Austropuccinia psidii: a biosecurity threat

Austropuccinia psidii, cause of myrtle rust, has spread globally where Myrtaceae occur. Multiple strains of A. psidii have been identified, including a unique strain found only in South Africa. The South African strain is a biosecurity concern for species of Myrtaceae worldwide. This is because preliminary testing of South African Myrtaceae suggests it could have a wide host range and thus, has the potential to be invasive. In this study, we assessed the ability of the South African strain to infect other species of Myrtaceae by testing the susceptibility of New Zealand provenance Myrtaceae. Seedlings of four native New Zealand Myrtaceae species (Metrosideros excelsa, Leptospermum scoparium, Kunzea robusta, and Kunzea linearis) were artificially inoculated in South Africa with a single-uredinium isolate of the South African strain. Fourteen days after inoculation, uredinia, and in many cases telia, had developed on the young leaves and stems of all four host species, which led to shoot tip dieback in the more severe cases. When comparisons were made between the species, K. robusta was the least susceptible to the South African strain of A. psidii, while L. scoparium and M. excelsa were the most susceptible. While only a limited number of seed families were tested, only a small proportion of the seedlings showed resistance to infection by the South African strain. This preliminary testing highlights the potential invasive risk the South African strain poses to global Myrtaceae communities, including New Zealand Myrtaceae