POWDERY MILDEW RESISTANCE: IS THERE A SINGLE GENE THAT CONFERS COMPLETE RESISTANCE?

  • gene family is encoded by a variable number of loci from which only one locus or, in some cases, multiple loci needs to be mutated to achieve complete immunity, meaning several MLO deletions are likely to increase resistance.
  • In the recent publication (2) several candidate gene families, including MLO genes, were associated with partial or quantitative resistance in cannabis, based on presence-absence (PAV) and copy number analyses (CNV), suggesting a multi locus nature for PM resistance in cannabis (2).
  • resistance is generally regarded as more durable (9), less likely to break (due to pathogen adaptation) and more likely to confer broad- spectrum resistance (resistance to multiple strains of the pathogen).
  • This approach allows not only to identify single-gene/single-locus effects, but also to identify multiple quantitative loci and generate genetic markers for them.
  • These can be used to efficiently screen large numbers of progeny in a short period of time at a low cost and select for individuals containing multiple desirable alleles (QTL stacking) leading to strong long-term, durable resistance to PM in cannabis.

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