A playbook for developing disease-resistant crops through immune receptor identification and transfer

Plants are resistant to most pathogens because of an immune system that perceives invading microbes and activates defense. A large repertoire of innate immune receptors mediates specific direct or indirect recognition of pathogen-derived molecules. Disease is often a consequence of insufficient immune surveillance, and the transfer of immune receptor genes from resistant plants to susceptible crop varieties is an effective strategy for combating disease outbreaks. We discuss approaches for identifying intracellular and cell surface immune receptors, with particular focus on recently developed and emerging methodologies. We also review considerations for the transfer of immune receptor genes into crop species, including additional host factors that may be required for immune receptor function. Together, these concepts lay out a broadly applicable playbook for developing crop varieties with durable disease resistance.

High taxonomic diversity of cultivation-recalcitrant endophytic bacteria in grapevine field shoots, their in vitro introduction, and unsuspected persistence

Molecular and microscopic analyses reveal enormous non-cultivable endophytic bacteria in grapevine field shoots with functional significance. Diverse bacteria enter tissue cultures through surface-sterilized tissues and survive surreptitiously with varying taxonomic realignments. The study was envisaged to assess the extent of endophytic bacterial association with field shoot tissues of grapevine and the likelihood of introduction of such internally colonizing bacteria in vitro adopting molecular techniques targeting the non-cultivable bacterial community. PowerFood^®-kit derived DNA from surface-sterilized field shoot tips of grapevine Flame Seedless was employed in a preliminary bacterial class-specific PCR screening proving positive for major prokaryotic taxa including Archaea. Taxonomic and functional diversity were analyzed through whole metagenome profiling (WMG) which revealed predominantly phylum Actinobacteria, Proteobacteria, and minor shares of Firmicutes, Bacteroidetes, and Deinococcus-Thermus with varying functional roles ascribable to the whole bacterial community. Field shoot tip tissues and callus derived from stem segments were further employed in 16S rRNA V3-V4 amplicon taxonomic profiling. This revealed elevated taxonomic diversity in field shoots over WMG, predominantly Proteobacteria succeeded by Actinobacteria, Firmicutes, Bacteroidetes, and 15 other phyla including several candidate phyla (135 families, 179 genera). Callus stocks also displayed broad bacterial diversity (16 phyla; 96 families; 141 genera) bearing resemblance to field tissues with Proteobacterial dominance but a reduction in its share, enrichment of Actinobacteria and Firmicutes, disappearance of some field-associated phyla and detection of a few additional taxonomic groups over field community. Similar results were documented during 16S V3-V4 amplicon taxonomic profiling on Thompson Seedless field shoot tip and callus tissues. Video microscopy on tissue homogenates corroborated enormous endophytic bacteria. This study elucidates a vast diversity of cultivation-recalcitrant endophytic bacteria prevailing in grapevine field shoots, their in vitro introduction, and unsuspecting sustenance with possible silent participation in tissue culture processes.

Molecular phylogeny, diversity, community structure, and plant growth promoting properties of fungal endophytes associated with the corms of saffron plant: An insight into the microbiome of Crocus sativus Linn

A total of 294 fungal endophytes were isolated from the corms of Crocus sativus at two stages of crocus life cycle collected from 14 different saffron growing sites in Jammu and Kashmir (J & K) State, India. Molecular phylogeny assigned them into 36 distinct internal transcribed spacer (ITS) genotypes which spread over 19 genera. The diversity of endophytes was higher at the dormant than at the vegetative stage. The Saffron microbiome was dominated by Phialophora mustea and Cadophora malorum, both are dark septate endophytes (DSEs). Some endophytes were found to possess antimicrobial properties that could be helpful for the host in evading the pathogens. These endophytes generally produced significant quantities of indole acetic acid (IAA) as well. However, thirteen of the endophytic taxa were found to cause corm rot in the host with different levels of severity under in vitro as well as in vivo conditions. This is the first report of community structure and biological properties of fungal endophytes associated with C. sativus, which may eventually help us to develop agro-technologies, based on plant-endophyte interactions for sustainable cultivation of saffron. The endophytes preserved ex situ, in this study, may also yield bioactive natural products for pharmacological and industrial applications.