Botrytis spp.: A Contemporary Perspective and Synthesis of Recent Scientific Developments of a Widespread Genus that Threatens Global Food Security

Abstract

This perspective presents a synopsis of the topics contained in the Phytopathology Pathogen Spotlight on Botrytis spp. causing gray mold, including pathogen biology and systematics, genomic characterization of new species, perspectives on genome editing, and fungicide resistance. A timely breakthrough to engineer host plant resistance against the gray mold fungus has been demonstrated in planta and may augment chemical controls in the near future. While B. cinerea has garnered much of the research attention, other economically important Botrytis spp. have been identified and characterized via morphological and genome-based approaches. Gray mold control is achieved primarily through fungicide applications but resistance to various chemical classes is a major concern that threatens global plant health and food security. In this issue, new information on molecular mechanism(s) of fungicide resistance and ways to manage control failures are presented. Finally, a significant leap in fundamental pathogen biology has been achieved via development of CRISPR/Cas9 to assess gene function in the fungus which likely will spawn new control mechanisms and facilitate gene discovery studies.

Genetic Diversity of Botrytis cinerea Revealed by Multilocus Sequencing, and Identification of B. cinerea Populations Showing Genetic Isolation and Distinct Host Adaptation

“…:Fr., a ubiquitous plant pathogen causing gray mold on more than 1000 plant species, including many economically important fruit, vegetable, and ornamental flower crops (Dean et al, 2012;Elad et al, 2016). Up to now, more than 30 species of Botrytis have been described, which are all necrotrophic pathogens except for Botrytis pyriformis which appears to be a saprophytic species (Hyde et al, 2014;Zhou et al, 2014;Zhang et al, 2016;Richards et al, 2020). A first comprehensive molecular classification of Botrytis spp.…”

The bud rot pathogens infecting cannabis (Cannabis sativa L., marijuana) inflorescences: symptomology, species identification, pathogenicity and biological control

“…Both crops are grown in Canada under guidelines established by Health Canada to ensure that producers meet specific requirements for safety and quality of the ensuing products derived from them. One of the greatest challenges for producers of both cannabis and hemp is the management of pathogens that infect the roots, leaves and inflorescences (Punja et al 2019). The inflorescences are clusters of flowers (without petals or sepals present in normal flowers) bunched together on compact terminal branches produced from a central stem (Small 2017;Spitzer-Rimon et al 2019).…”

“…These 'bud rot' pathogens are reported to include Botrytis cinerea Pers. Fr., a widespread and destructive pathogen of cannabis and hemp (Punja et al 2019;Garfinkel 2020), as well as several species of Fusarium and Penicillium that can cause pre-and postharvest bud rots (Punja 2021a(Punja , 2021b(Punja , 2021c. Infection by Hop latent viroid can also reduce the quality of cannabis inflorescences (Bektas et al 2019;Warren et al 2019).…”

“…flowers, fruits, stems and leaves, followed by prolific production of spores on the diseased tissues that give the appearance of grey fuzzy growth or 'grey mold'. The events occurring during host-pathogen interactions have been described elsewhere (Choquer et al 2007;Williamson et al 2007;Veloso and van Kan 2018;Richards et al 2021). Infection and disease development are both favoured by high humidity (>90%) or free moisture that are conducive for spore germination and mycelial growth, as well as the presence of wounds, which provide an entry point and source of nutrients (sugars, amino acids) for pathogen development (Carisse 2016;Bika et al 2021).…”

“…Symptoms of bud rot on cannabis and hemp plants include decay of a portion or of the entire inflorescence, followed by characteristic sporulation of the pathogen. Despite previously published reports that the causal agent of bud rot worldwide is B. cinerea (McPartland 1996;Punja et al 2019;Garfinkel 2020;Jerushalmi et al 2020), there have been no studies conducted to confirm whether there may be more than one species of Botrytis infecting cannabis or hemp plants in Canada or whether other pathogens can produce similar symptoms. The period of time when infection occurs or how disease symptoms progress on affected inflorescences has not been studied.…”