Evaluation of different methods for isolating Phytophthora spp. from a Canterbury waterway

Phytophthora spp. pose a risk to New Zealand’s managed and natural ecosystems. As Phytophthora spp. are well adapted to aquatic environments, water surveillance can be used to identify their distribution. Seven bait species (Rhododendron arborescens, Pittosporum undulatum, Banksia attenuata, Camellia japonica, Pittosporum eugenioides, Pinus radiata, and Cedrus deodara) were evaluated for Phytophthora spp. isolation. Water was collected from 2 sites in the Suckling river (Tai Tapu) and half was membrane-filtered (3-μm pore size) to capture spores. Leaf baits were floated directly on unfiltered water at room temperature in the laboratory for 7 days. Baits were also placed in nylon-mesh bags and floated in the Suckling river sites (in situ) for 7 days. Leaf lesions and membrane filters were cultured on Phytophthora spp. selective media. Eighty-six Phytophthora spp. isolates representing 5 colony morphotypes were recovered, 6 (3 morphotypes) from membrane filters, 25 (4 morphotypes) from baits on collected river water, and 55 (5 morphotypes) from in situ baits. The highest numbers of isolates were recovered from R. arborescens (50.6%; 4 morphotypes), Pinus radiata (17.2%; 3 morphotypes) and Pittosporum undulatum (12.6%; 2 morphotypes). In situ baiting using Rhododendron arborescens and Pinus radiata was the most effective method of isolating Phytophthora species

Soil arbuscular mycorrhizal fungal communities differentially affect growth and nutrient uptake by grapevine rootstocks

Arbuscular mycorrhizal fungi (AMF) deliver potentially significant services in sustainable agricultural ecosystems, yet we still lack evidence showing how AMF abundance and/or community composition can benefit crops. In this study, we manipulated AMF communities in grapevine rootstock and measured plant growth and physiological responses. Glasshouse experiments were set up to determine the interaction between rootstock variety and different AMF communities, using AMF communities originating under their own (i.e., “home”) soil and other rootstocks’ (i.e., “away”) soil. The results revealed that specific AMF communities had differential effects on grapevine rootstock growth and nutrient uptake. It was demonstrated that a rootstock generally performed better in the presence of its own AMF community. This study also showed that AMF spore diversity and the relative abundance of certain species is an important factor as, when present in equal abundance, competition between species was indicated to occur, resulting in a reduction in the positive growth outcomes. Moreover, there was a significant difference between the communities with some AMF communities increasing plant growth and nutrient uptake compared with others. The outcomes also demonstrated that some AMF communities indirectly influenced the chlorophyll content in grapevine leaves through the increase of specific nutrients such as K, Mn, and Zn. The findings also indicated that some AMF species may deliver particular benefits to grapevine plants. This work has provided an improved understanding of community level AMF-grapevine interaction and delivered an increased knowledge of the ecosystem services they provide which will benefit the wine growers and the viticulture industry

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