NLR- and mlo-Based Resistance Mechanisms against Powdery Mildew in Cannabis sativa

Abstract

Powdery mildew (PM) is one of the most common Cannabis sativa diseases. In spite of this, very few documented studies have characterized the resistance genes involved in PM defense mechanisms, or sources of natural genetic resistance in cannabis. The focus of the present work is on the two primary mechanisms for qualitative resistance against PM. The first is based on resistance (R) genes characterized by conserved nucleotide-binding site and/or leucine-rich repeat domains (NLRs). The second one involves susceptibility (S) genes, and particularly mildew resistance locus o (MLO) genes, whose loss-of-function mutations seem to be a reliable way to protect plants from PM infection. Cannabis defenses against PM are thus discussed, mainly detailing the strategies based on these two mechanisms. Emerging studies about this research topic are also reported and, based on the most significant results, a potential PM resistance model in cannabis plant–pathogen interactions is proposed. Finally, innovative approaches, based on the pyramiding of multiple R genes, as well as on genetic engineering and genome editing methods knocking out S genes, are discussed, to obtain durable PM-resistant cannabis cultivars with a broad-spectrum resistance range.

Identification and Transfer of a New Powdery Mildew Resistance Gene PmCAHM from Landrace Changanhongmai into Common Wheat

“…Full exploration and utilization of beneficial genetic resources in wheat local varieties and farm-grown varieties are of great significance for modern wheat disease-resistant breeding and genetic improvement. However, in actual wheat breeding, the utilization efficiency of local varieties is very low due to their inferior agronomic traits (such as low grain yield, lodging), long breeding time, and difficulty in breaking the genetic balance of unfavorable genes [40][41][42][43]. Most studies of powdery mildew resistance in local varieties are based on gene localization [44,45].…”

Integrated Management of Pathogens and Microbes on <em>Cannabis sativa</em> L. (Cannabis) under Greenhouse Conditions

“…The utility of disease-tolerant genotypes that may have been developed through selective breeding and genotype screening is an important aspect of IDM for stock plants. Disease-tolerant genotypes of cannabis have been identified for a number of pathogens, including root rot (Fusarium oxysporum) [23], powdery mildew (Golovinomyces ambrosiae) [10][11][12]32], leaf blight (Neofusicoccum parvum) [33], and bud rot (B. cinerea) [34,35] (Figure 8). Recent research suggests that specific defense genes may play a role in certain hostpathogen interactions, leading to a resistant phenotype [11][12][13]36].…”

Integrated Management of Pathogens and Microbes in Cannabis sativa L. (Cannabis) under Greenhouse Conditions

“…The utility of disease-tolerant genotypes that may have been developed through selective breeding and genotype screening is an important aspect of IDM for stock plants. Disease-tolerant genotypes of cannabis have been identified for a number of pathogens, including root rot ( Fusarium oxysporum ) [ 23 ], powdery mildew ( Golovinomyces ambrosiae ) [ 10 , 11 , 12 , 32 ], leaf blight ( Neofusicoccum parvum ) [ 33 ], and bud rot ( B. cinerea ) [ 34 , 35 ] ( Figure 8 ). Recent research suggests that specific defense genes may play a role in certain host–pathogen interactions, leading to a resistant phenotype [ 11 , 12 , 13 , 36 ].…”