BackgroundDespite wheat being a worldwide staple, it is still considered the most difficult to transform out of the main cereal crops. Therefore, for the wheat research community, a freely available and effective wheat transformation system is still greatly needed.ResultsWe have developed and optimised a reproducible Agrobacterium-mediated transformation system for the spring wheat cv ‘Fielder’ that yields transformation efficiencies of up to 25%. We report on some of the important factors that influence transformation efficiencies. In particular, these include donor plant health, stage of the donor material, pre-treatment by centrifugation, vector type and selection cassette. Transgene copy number data for independent plants regenerated from the same original immature embryo suggests that multiple transgenic events arise from single immature embryos, therefore, actual efficiencies might be even higher than those reported.ConclusionWe reported here a high-throughput, highly efficient and repeatable transformation system for wheat and this system has been used successfully to introduce genes of interest, for RNAi, over-expression and for CRISPR–Cas9 based genome editing.

rganic farming is characterized by management practices that promote soil biodiversity and beneficial ecological interactions to offset the need for synthetic inputs such as inorganic fertilizers and biocides. Pest and nutrient management in organic agriculture is largely accomplished through various diversification methods, including cover crops, crop rotations, trap crops and promotion of active soil microbial communities [1][2][3][4][5] . Although organic agriculture is often thought to be less productive in terms of yield as compared to conventional farming, it offers great potential to enhance ecosystem services and agricultural sustainability [5][6][7] .Accumulating evidence suggests that organic management practices also reduce pest populations and increase resilience to pest damage 8,9 . Decreased insect pests on long-term organic farms have largely been attributed to practices that limit pest build-up, increase predator biodiversity, and increase the numbers of beneficial insects [9][10][11][12][13] . The nitrogen contents of plants grown on organic farms are often lower than those of conventional systems 11,12 . Plants that are nitrogen-limited are often less attractive to herbivores, which could also explain the lower pest pressure observed in organic systems 12,14,15 . However, very little is known about the impact of organic management for plant defence capacity.Organic management strategies can increase microbial activity and biomass in soils 1,2,16 , alter microbial communities 17 and in some cases enhance plant associations with beneficial microbes in the rhizosphere 3,4 . Microorganisms that associate with plant roots play a critical role in resistance to abiotic and biotic stress [18][19][20] . Mycorrhizal fungi have been shown to induce plant systemic resistance 21,22 and can reduce susceptibility to pathogens 23 and herbivores 24 . Plant growth-promoting rhizobacteria commonly found in soil microbial pools, as well as commercial inoculants, induce defences and other physiological changes in the host plant that influence above-ground herbivores 19,[25][26][27][28] . Despite the known interactions between organic management, plant-microbe associations and changes in crop resistance, the potential of these interactions to reduce pest damage in agricultural systems remains largely untapped.In this study, we report that organic management influences pest populations through changes in plant resistance. We explore linkages between insect settling and performance, rhizosphere communities and phytohormones related to plant defence with tomato (Solanum lycopersicum) and the beet leafhopper (Circulifer tenellus), an important pest of California's processing tomato industry 29 . We demonstrate that tomatoes grown using conventional management are preferentially settled by leafhopper pests and have lower salicylic acid (SA) levels compared to tomatoes grown using organic management. Our results indicate that differences in insect preference were due at least partially to changes in SA accumulation and rhi...

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Genomic and cDNA clones of the anther-specific APG gene from Arabidopsis thaliana and Brassica napus, which encodes a novel proline-rich protein, were isolated and characterized. Southern blotting and Northern analysis of male fertile and cytoplasmic male sterile varieties of B. napus showed that the APG gene is present as a single copy in the Arabidopsis genome, and that the B. napus APG gene is a member of a small anther-specific gene family. Analysis of developmentally staged B. napus flower buds indicated that APG transcript is confined to the anther during the period of microspore development. Reporter gene fusions established that the APG promoter directs expression in a number of cell types in anthers of transformed plants. This expression is consistent with the temporal pattern of mRNA accumulation in B. napus buds and follows a complex developmental pattern. Most significantly, the promoter is active in both sporophytic and gametophytic cell types, with activity of the transgene in each cell type being delineated by various cytological markers.

Grapevine trunk diseases (GTDs) threaten the economic sustainability of viticulture, causing reductions of yield and quality of grapes. Biological control is a promising sustainable alternative to cultural and chemical methods to mitigate the effects of pathogens causing GTDs, including Botryosphaeria dieback, Eutypa dieback and Esca. This study aimed to identify naturally occurring potential biological control agents from grapevine sap, cane and pith tissues, and evaluate their in vitro antagonistic activity against selected fungal GTD pathogens. Bacterial and fungal isolates were preliminarily screened in dual culture assays to determine their antifungal activity against Neofusicoccum parvum and Eutypa lata. Among the fungal isolates, Trichoderma spp. inhibited mycelium growth of E. lata by up to 64% and of N. parvum by up to 73%, with overgrowth and growth cessation being the likely antagonistic mechanisms. Among the bacterial isolates, Bacillus spp. inhibited mycelium growth of E. lata by up to 20% and of N. parvum by up to 40%. Selected antagonistic isolates of Trichoderma, Bacillus and Aureobasidium spp. were subjected to further dual culture antifungal analyses against Diplodia seriata and Diaporthe ampelina, with Trichoderma isolates consistently causing the greatest inhibition. Volatile organic compound antifungal analyses showed that these Trichoderma isolates inhibited mycelium growth of N. parvum (20% inhibition), E. lata (61% inhibition) and Dia. ampelina (71% inhibition). Multilocus sequence analyses revealed that the Trichoderma isolates were most closely related to Trichoderma asperellum and Trichoderma hamatum. This study had identified grapevine sap as a novel source of potential biological control agents for control of GTDs. Further testing will be necessary to fully characterize modes of antagonism of these microorganisms, and assess their efficacy for pruning wound protection in planta.

No abstract

Genomic and cDNA clones of the anther-specific APG gene from Arabidopsis thaliana and Brassica napus, which encodes a novel proline-rich protein, were isolated and characterized. Southern blotting and Northern analysis of male fertile and cytoplasmic male sterile varieties of B. napus showed that the APG gene is present as a single copy in the Arabidopsis genome, and that the B. napus APG gene is a member of a small anther-specific gene family. Analysis of developmentally staged B. napus flower buds indicated that APG transcript is confined to the anther during the period of microspore development. Reporter gene fusions established that the APG promoter directs expression in a number of cell types in anthers of transformed plants. This expression is consistent with the temporal pattern of mRNA accumulation in B. napus buds and follows a complex developmental pattern. Most significantly, the promoter is active in both sporophytic and gametophytic cell types, with activity of the transgene in each cell type being delineated by various cytological markers.

1. Beneficial plant-associated soil microbes can promote plant tolerance to stress and promote nutrient uptake. Yet, the benefits of microbes for plant health can be altered by above-ground stressors like herbivores and pathogens. However, few studies have assessed reciprocal plant-mediated interactions between beneficial soil microbes and multiple above-ground stressors.2. We assessed if soil rhizobia influenced complex interactions among pea host plants, a vector herbivore (aphids) and a plant virus (Pea enation mosaic virus, PEMV). We also examined how aphids and PEMV affected the function of soil rhizobia.3. We show that plants attacked by PEMV produced fewer root nodules and had lower fresh root nodule biomass per g of fresh plant root biomass, and decreased expression of genes associated with nodulation, suggesting PEMV inhibited nitrogen fixation by rhizobia. However, soil rhizobia decreased aphid abundance and PEMV titre on host plants, such that rhizobia decreased the susceptibility of plants to herbivores and pathogens. 4. Assays of amino acids, and gene expression related to hormone signalling, show interactions among rhizobia, plants, aphids and PEMV were mediated by plant defence and nutrients. Viruliferous aphids induced salicylic acid in plants, and salicylic acid suppressed the function of rhizobia. Aphids feeding on plants grown in rhizobia-inoculated soil also obtained fewer essential amino acids than those feeding on plants grown in un-inoculated sterilized soil.5. Mutually antagonistic plant-mediated interactions between soil microbes and above-ground stressors affected plant susceptibility and herbivore nutrient uptake. This suggests ecological effects of soil microbes and above-ground stressors for plant health will likely vary based on multi-trophic plant-mediated interactions among herbivores, pathogens and soil microbes.