Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


This study was conducted to identify those plant growth regulators that cause the greatest increase in shoot number of basic genotypes of the genus Saccharum and at the same time identify those genotypes that exhibit a high degree of response to certain growth regulators which have been proposed as tillering agents. A series of three factorial experiments was conducted under controlled conditions in the greenhouse utilizing fourteen cultivars representing the spectrum of the genus Saccharum along with five synthetic growth regulators proposed as tillering agents. Treatments were applied to the plants one month after germination. Shoot number and shoot height measurements were taken every two weeks, beginning two weeks after planting, for a period of eight weeks. Plants treated with (2-chloroethyl) phosphonic acid (ethephon) produced the highest number of shoots and showed increased growth rate. The (2-chloroethyl) trimethylammonium chloride (chlormequat) and poly oxyethylene(dimethylimino)ethylene (dimethylimino) ethylene-dichloride (bualta) treatments resulted in an increase in shoot production with no effect on plant vigor. One-napthaleneacetic acid (NAA) and 2,4-dichlorophenoxyacetic acid (2,4-D) increased shoot number but plant vigor was decreased. Certain combinations of S. spontaneum or S. sinense cultivars with ethephon, chlormequat or bualta, resulted in an increase in shoot number over the check, with no effect on plant vigor. A genetic study was also conducted to determine if the characteristic of response to ethephon by progenies of cultivars of S. spontaneum and CP65-357 crosses was under genetic control. Unfortunately, differences in response of the half-sib families and their respective parents were not detected in the genetic study. However, the rather large differences in shoot number and growth rate among genotypes in response to ethephon in both plant and ratoon cane evaluated in part one of this study, suggest that this characteristic of response is under genetic control. Total shoot number and growth rate were increased in the parental cultivars and their progenies through the use of ethephon as a tillering agent.