Clonal Propagation of Guayule through Cuttings

Guayule (Parthenium argentatum Gray) is woody perennial, native to the Chihuahuan Desert of central Mexico and southwestern Texas.  Other relatives in the genus are used in landscaping, but guayule shows promise as a rubber/latex producing crop and potential bioenergy crop.  Guayule has a complex breeding system (facultative apomixis) often making it difficult to produce predictable progeny.  In order to advance uniform lines vegetative propagation techniques were explored.

A preliminary study was made to identify variables that needed further investigation in order to optimize cutting production.  Parent material consisted of approximately one-year-old field grown plants, originally from transplants produced from seed.  Terminal cuttings of varying lengths were made during cooler and more humid times of day with pruning shears.  Between one and six cuttings were made from around 500 plants, totally approximately 3,000 cuttings.

Cuttings were transferred from the field, on ice or in moist plastic bags, to a propagation house with mist benches and bottom heat.  Upon arrival they were either recut or not, and dipped into liquid Hormex (0.013% IBA and 0.24% NAA), powdered Rootone (0.2% NAA with thiram), or liquid naphthalene acetamide for 60 or 90 seconds, then placed into prepared trays of either a pre-wetted mixture of sand and Sunshine 1 mix or only sand.  

 After three weeks, approximately 70 percent of cuttings had rooted.  Cuttings that survived with callus, but no roots, were either recut and re-dipped, or just re-dipped, and placed back into trays.  The cuttings were reevaluated at four weeks. 

 Variables identified for further study were: (1) length of cuttings; (2) concentration of hormones; (3) time in hormone dip; (4) propagation media; and (5) environmental conditions.  Our preliminary results show that clonal propagation can be successfully used to propagate woody tissues of guayule plants.