Effect of the inoculum dose of three grapevine trunk pathogens on the infection of artificially inoculated pruning wounds

This study assessed the infection rates of different spore inoculum doses of the grapevine trunk pathogens Diplodia seriata, Phaeomoniella chlamydospora and Eutypa lata following artificial inoculation of pruning wounds. Potted vines of cv. Tempranillo were inoculated with doses ranging from 10 to 4000 conidia per wound of D. seriata and P. chlamydospora and led to recovery percentages of 10–100% for D. seriata and 16–94% for P. chlamydospora. Eutypa lata, when inoculated onto wounds of vines in a mature vineyard (cv. Shiraz) and on detached canes (cv. Cabernet Sauvignon) with a dose range of 10 to 1000 ascospores per wound, led to recovery percentages of 17–95%. In the field assay, there was no difference in recovery from wounds that were exposed to single or double inoculations with the same total spore dose, or between canes that were harvested 7 or 11 months after inoculation. The results obtained in this study showed significant variability in pathogen recovery between trials, comparable with that reported previously, which suggests that factors such as pathogen virulence, environmental parameters and experimental conditions may influence the infection process. According to this study, in order to obtain optimal recovery percentages of 50–70% for robust evaluation of pruning wound treatments, dose ranges of 100-1000 conidia of D. seriata, 100–2000 conidia of P. chlamydospora, and 100–500 ascospores of E. lata per wound would be required.Georgina Elena, Mark R. Sosnowski, Matthew R. Ayres, Pascal Lecomte, Celine Benetreau, Francesc Garcia-Figueres, Jordi Luqu

Alternative strawberry production using solarization, metham sodium and beneficial soil microbes as plant protection methods

High-impact chemical biocides are no longer used in crop production systems due to environmental concerns and sustainable agricultural practices must involve the use of environmentally friendlier alternatives for controlling pests and diseases. We compared the effect of two disinfestation treatments, solarization and metham sodium, combined with the arbuscular mycorrhizal fungus Glomus intraradices, the saprophytic fungus Trichoderma aureoviride and the plant growth-promoting rhizobacteria Bacillus subtilis, in strawberry crop production. Also, the effects of high temperatures achieved during the solarization process on the viability of mycorrhizal inocula were evaluated under controlled conditions in a laboratory study. Moist inocula of the arbuscular mycorrhizal fungus G. intraradices were maintained for three hours for five consecutive days at 35, 40, 45, 50 and 55 °C, respectively. Our results show that soil solarization and metham-sodium disinfestation improved strawberry yield by 24% and 18%, respectively, compared with the fruit yield obtained in untreated soil, whereas application of T. aureoviride and B. subtilis did not affect plant production in the absence of a pathological agent. Solarization and metham-sodium application did not eliminate the natural populations of arbuscular mycorrhizal fungi and at the end of the experiment all plants, independently of the treatments, were mycorrhizal. After the heating treatments, under controlled conditions, the inoculum of G. intraradices submitted to 50 °C completely lost its mycorrhizal potential

Studies on the effect of water and temperature stress on grapevines inoculated with Eutypa lata

Three independent studies were conducted in Australia and Spain to examine the effect of water and temperature stress on the development of Eutypa dieback of grapevines. In Adelaide, South Australia, ‘Red Grenache’ vines in pots were inoculated with Eutypa lata and subjected to various temperature and soil water regimes, then assessed for foliar symptoms, wood staining and colonization by the fungus. Vines subjected to a combination of heat or cold plus low or high soil moisture displayed more severe foliar symptoms, the most severe occurring on vines subjected to the hottest (30°C) and wettest (20–40 % soil water content) conditions. Wood staining was not related to foliar symptom severity or to the temperature and moisture combination. Furthermore, there was no relationship between staining and mycelial growth, indicating that staining may not be an accurate reflection of the spread of E. lata. In Cabrils, Spain, ‘Tempranillo’ vines were subjected to water stress in pots and showed a significant reduction in shoot diameter growth, stomatal conductance and leaf water potential. Inoculation with E. lata also decreased the leaf water potential of stressed vines. Wood staining in inoculated vines was similar irrespective of watering treatment. Further investigations are needed to elucidate the relationship between stress and growth of E. lata in infected vines. Field experiments in two climatically different regions (Barossa Valley and Riverland) of South Australia suggested that water-stressed vines in a warm, dry environment may be more susceptible to infection of pruning wounds by E. lata than vines receiving standard watering.Mark R. Sosnowski, Jordi Luque, Adrian P. Loschiavo, Soledad Martos, Francesc Garcia-Figueres, Trevor J. Wicks and Eileen S. Scot