International Workshop: Plant Health: Challenges and Solutions

This workshop highlighted current developments in the field of plant protection against pests and pathogens. This included the current problems in the field, latest tools and developments in detection and diagnosis, smart biologics, emerging and re-emerging microbial pathogens and resistance breeding. The workshop aimed to bring together leading researchers, young scientists and industrialists from the plant protection sectors to exchange knowledge and share best practice in integrated pest management towards food security. Specifically, we aimed to: highlight the most recent pathogen detection and diagnostic tools; discuss the benefits of using smart biologics including beneficial microorganisms; discuss new technologies that could help to deliver faster pathogen and pest control strategies; consolidate existing and develop new connections between the plant protection research communities; enhance the application of molecular and immunochemical detection technologies within the plant health industry; explore different ways to translate laboratory-based research into application, especially in biological control and reduction of mycotoxins; increase the awareness of problems that the plant health industry faces; discuss the latest developments in the field and disseminate these cutting-edge scientific outcomes to a wider community; provide a platform for knowledge exchange between academics and industry; foster new research collaborations that are focused on delivering benefits for plant health improvement; and enable participants to develop links to assist their professional development. Presentations from experts in the field provided delegates with an understanding of the latest problems in plant health control. This provided an opportunity for delegates to identify and exploit key technologies across the plant protection industry

Identification of New Resistance Sources From Diploid Wild Strawberry Against Powdery Mildew Pathogen

Powdery mildew pathogen causes diseases in berries and resistance breeding is hampered by the lack of sufficient sources. While control of fungal pathogens relies on chemical fungicides. In either case, a reliable source of resistance for breeding purposes is imperative for efficient protection of the crop plants. A powdery mildew isolate designated GOU1 has been identified as Podosphaera aphanis var. aphanis using light microscopy and sequencing the ITS region. Pathogenicity tests on 3 diploid wild strawberry (Fragaria vesca L.) ecotypes with GOU1 revealed 3 distinctive interaction phenotypes; enhanced susceptible (ecotype 1), intermediate susceptible (ecotype 2) and resistant (ecotype 3). In vitro staining methods with diaminobenzidine and trypan blue showed massive mycelial web and conidiophore production on the susceptible ecotype, but there was no mycelia and conidiophore production on the resistant ecotype 3. In the ecotype 3 conidiospore penetration was associated with accumulation of hydrogen peroxide production on the host cells. These findings suggest that these ecotypes could be explored as resistant gene sources to powdery mildew fungus

Effect of light and darkness on the growth and development of downy mildew pathogen Hyaloperonospora arabidopsidis

Disease development in plants requires a susceptible host, a virulent pathogen, and a favourable environment. Oomycete pathogens cause many important diseases and have evolved sophisticated molecular mechanisms to manipulate their hosts. Day length has been shown to impact plant‐oomycete interactions but a need exists for a tractable reference system to understand the mechanistic interplay between light regulation, oomycete pathogen virulence, and plant host immunity. Here we present data demonstrating that light is a critical factor in the interaction between Arabidopsis thaliana and its naturally occurring downy mildew pathogen Hyaloperonospora arabidopsidis (Hpa). We investigated the role of light on spore germination, mycelium development, sporulation and oospore formation of Hpa, along with defence responses in the host. We observed abundant Hpa sporulation on compatible Arabidopsis under day lengths ranging from 10 to 14 hours. Contrastingly, exposure to constant light or constant dark suppressed sporulation. Exposure to constant dark suppressed spore germination, mycelial development and oospore formation. Interestingly, exposure to constant light stimulated spore germination, mycelial development and oospore formation. A biomarker of plant immune system activation was induced under both constant light and constant dark. Altogether, these findings demonstrate that Hpa has the molecular mechanisms to perceive and respond to light and that both the host and pathogen responses are influenced by the light regime. Therefore, this pathosystem can be used for investigations to understand the molecular mechanisms through which oomycete pathogens like Hpa perceive and integrate light signals, and how light influences pathogen virulence and host immunity during their interactions

Mapping of the gene in tomato conferring resistance to root-knot nematodes at high soil temperature

Root-knot nematodes (RKNs, Meloidogyne spp.) can cause severe yield losses in tomatoes. The Mi-1.2 gene in tomato confers resistance to the Meloidogyne species M. incognita, M. arenaria and M. javanica, which are prevalent in tomato growing areas. However, this resistance breaks down at high soil temperatures (>28°C). Therefore, it is imperative that new resistance sources are identified and incorporated into commercial breeding programmes. We identified a tomato line, MT12, that does not have Mi-1.2 but provides resistance to M. incognita at 32°C soil temperature. An F2 mapping population was generated by crossing the resistant line with a susceptible line, MT17; the segregation ratio showed that the resistance is conferred by a single dominant gene, designated RRKN1 (Resistance to Root-Knot Nematode 1). The RRKN1 gene was mapped using 111 Kompetitive Allele Specific PCR (KASP) markers and characterized. Linkage analysis showed that RRKN1 is located on chromosome 6 and flanking markers placed the locus within a 270 kb interval. These newly developed markers can help pyramiding R-genes and generating new tomato varieties resistant to RKNs at high soil temperature

ATR2Cala2 from Arabidopsis-infecting downy mildew requires 4 TIR-NLR immune receptors for full recognition

Arabidopsis Col-0 RPP2A and RPP2B confer recognition of Arabidopsis downy mildew (Hyaloperonospora arabidopsidis [Hpa]) isolate Cala2, but the identity of the recognized ATR2Cala2 effector was unknown. To reveal ATR2Cala2, an F2 population was generated from a cross between Hpa-Cala2 and Hpa-Noks1. We identified ATR2Cala2 as a non-canonical RxLR-type effector that carries a signal peptide, a dEER motif, and WY domains but no RxLR motif. Recognition of ATR2Cala2 and its effector function were verified by biolistic bombardment, ectopic expression and Hpa infection. ATR2Cala2 is recognized in accession Col-0 but not in Ler-0 in which RPP2A and RPP2B are absent. In ATR2Emoy2 and ATR2Noks1 alleles, a frameshift results in an early stop codon. RPP2A and RPP2B are essential for the recognition of ATR2Cala2. Stable and transient expression of ATR2Cala2 under 35S promoter in Arabidopsis and Nicotiana benthamiana enhances disease susceptibility. Two additional Col-0 TIR-NLR (TNL) genes (RPP2C and RPP2D) adjacent to RPP2A and RPP2B are quantitatively required for full resistance to Hpa-Cala2. We compared RPP2 haplotypes in multiple Arabidopsis accessions and showed that all four genes are present in all ATR2Cala2-recognizing accessions

Genome sequence of the plant-growth-promoting bacterium Bacillus velezensis EU07

Many Gram-positive spore-forming rhizobacteria of the genus Bacillus show potential as biocontrol biopesticides that promise improved sustainability and ecological safety in agriculture. Here we present a draft-quality genome sequence for Bacillus velezensis EU07, which shows growth-promotion in tomato plants and biocontrol against Fusarium head blight. We found that the genome of EU07 is almost identical to that of the commercially used strain QST713 but identified 46 single-nucleotide differences that distinguish these strains from each other. The availability of this genome sequence will facilitate future efforts to unravel the genetic and molecular basis for its beneficial properties