Potato tubers form the world’s fourth largest staple food crop. Potato is also an important crop in the UK which stores 60% of its harvest for year round consumption. Large losses of tubers occur during storage: the principle cause is premature dormancy break, a process tightly regulated by plant hormones as well as other signals. Recently the expression of a strigolactone (SL) biosynthesis gene was knocked down in potato resulting in tubers with significantly reduced dormancy times; suggesting SL as a key regulator of potato tuber dormancy.
Detection of endogenous SL concentrations and SL synthesis, perception and signalling gene expression assays were optimised. Nutrient stressed potato plants synthesised more SL in the roots and the SL biosynthesis gene StMAX1 increased in expression.
A CRISPR-Cas9 vector optimised for use in potato was modified to target the SL perception gene StD14. Large deletions in the StD14 gene were induced resulting in plants that were significantly shorter and more branched than wild type (WT) plants. SL concentrations as well as SL biosynthesis, perception and signal gene expression in the roots of putative Std14 KO plants were not significantly dissimilar to WT plants. Std14 KO plants terminated tuberisation earlier than WT and Std14 KO tubers broke dormancy significantly earlier than EV but not WT. Std14 KO plants produced multiple aerial tubers from the base of shoot nodes.
Exogenous applications of SL to excised tuber buds significantly delayed dormancy break. RNAi constructs targeting the StD53 gene delayed dormancy break significantly and did so in a StD53 expression dependent manner.
The mechanism by which the potato species S.stenotomum maintains a long dormancy phenotype is SL independent but may be related to control of CKs metabolism.
In conclusion, SLs are a significant positive regulator of potato tuber dormancy and are a key target for future breeding to delay tuber dormancy break and reduce waste.