| dc.description.abstract | Experiments were conducted between June 2005 and December 2006 at the Kenya
Agricultural Research Institute (KARl) National Potato Research Center (NPRC) - Tigoni,
to evaluate alternative methods of dormancy breaking and sprouting potato seed tubers.
Effects of four gibberellic acid (GA3) levels (0, 10, 20 and 30 mg kg" ) and five potato
genotypes (Tigonr, AsKnte, Dutch Robyjn, Kenya Karibu and Kenya Sifa varieties) were
evaluated in diffuse light storage (DLS), underground pit and polythene bags. In another
experiment, effects of four pre-storage treatments (pit, dark, cold and a control (DLS)) and four pre-storage treatment durations (1, 2, 3, and 4 weeks) followed by DLS storage were assessed. In all experiments, tubers were evaluated for sprouting (%), number of sprouts per tuber, sprout length, sprout vigor, potato tuber moth (PTM) incidence (%), and tuber rotting (%) for 12 weeks.
Higher scores of sprouting, number of sprouts per tuber sprout length and sprout
vigor score were observed in pit and polyethylene bags than in DLS. Dormancy period was reduced to three weeks in all genotypes except Kenya Sifa, which sprouted after five and seven weeks following GA3 treatments in polythene bags and DLS, respectively. GA3 increased sprouting (%), number of sprouts per tuber, sprout length and vigor score in all the experiments. Upon further storage of tubers in DLS after removal from the pit,
dormancy in all treatments ended in the fourth week. No significant differences were
observed amongst genotypes for all the parameters for the entire period of storage in DLS thereafter. Increase in GA3 concentration led to increase in rotting at 30 mg kg" for Tigoni, Kenya Sifa and Kenya Karibu under DLS. In the pit, potato seed tubers sprouted within the two weeks of storage. In polythene bags experiment, dormancy was terminated in four weeks in all genotypes and GA3 treatments in season 1 while in season 2, Kenya Sifa's control took 8 weeks to end dormancy. It is suggested that lower levels of GA3 of up to 20 mg kg-l should be adopted for promotion of sprouting of potato seed tubers. Further storage in DLS for 3 weeks before planting is suggested for potato seed tubers sprouted using GA3 under pit conditions to improve the quality.
Pit and dark pre-storage treatments led to increase in sprouting (%), number of
sprouts per tuber, sprout length and vigor score. 100% sprouting of potato seed tubers was attained under pit and dark storage by the fourth week at all pre-storage treatment durations while dormancy ended after 6 weeks of storage in the control. Sprouting was suppressed during cold pre-storage treatment. Tubers under pit and dark pre-storage treatment developed longer sprouts than those in DLS (Diffuse light storage) and cold treatments. Sprout length in pit and dark conditions increased with increasing pre-storage treatment duration. Pit pre-storage treatment led to highest vigor scores. In pit and dark pre-storage treatment, vigor scores increased with increasing duration of pre-storage treatment while in the cold, vigor scores were reduced with longer pre-storage treatment duration. Cold prestorage treatment suppressed the incidences of PTM and tuber rotting. Increased pre-storage treatment duration in darkness led to increased PTM damage. Long pit pre-storage treatment for 4 weeks led to increased rotting (%). Pit and dark pre-storage treatments are recommended to end dormancy and promote sprouting of good quality potato seed tubers. Short pre-storage treatment durations of up to 1 week in pit and dark respectively followed by 2 weeks of DLS storage is recommended. | en |
