Effects of Gibberellic Acid and Benzyladenine on Dormancy Release, Growth and Multiplication of Oriental Lily Bulbs (Lilium spp.)

Abstract

One of the major challenges facing lily cut flower production and marketing is high cost of production of the lily bulbs which undergo a dormancy period in their growth cycle as do other bulbous plants and for the growth to continue this dormancy has to be released. To mitigate this problem commercial growers apply artificial dormancy breaking using low temperatures (4~5“ C) for 6-8 weeks. Low temperature treatments / cold storage of bulbs is expensive hence low cost dormancy breaking alternatives have to be sought. Studies done earlier have shown that Plant growth regulators can be used to break dormancy. Two trials were conducted at James Finlay Flower Company (Lemotit farm, Londiani), .to evaluate the effects of gihberellic acid (GA;) and benzyl adenine (BA) as alternative treatments for breaking dormancy in Oriental lily bulbs. The first trial was conducted from September 2009 to January 2010 while the second trial was conducted from January 2010 to April 2010. The factors were BA and GA; each at (0, 25, 50, 100, and 150) mg/l. Lily bulbs were soaked in different solution concentrations of BA and GA; at (0, 25, 50, 100, and 150)mg/l , singlyand in combinations for Z4 hours before planting. These treatments were compared with the conventional chilling treatment. Experiments were laid out in an unbalanced factorial design with three replications of l0 bulbs each and repeated in two trials. All data were subjected to analysis of variance (ANOVA) using the SAS statistical package. Significant means were separated using the Duncan’s Multiples Range Test (DMRT). In both trials 50mg/l of BA and GA; singly significantly promoted higher sprout emergence, reduced the number of days to opening of the first leaf whorl, long stem lengths, long rachis, and reduced the number of days to flowering. BA at l00mg/l significantly accelerated the number of days to 50% sprout emergence, and promoted high numbers of leaves, florets, and bulblets. Significant combined effects of BA 100mg/l and GA; 50mg/l were observed on the number of days to 50% sprout emergence, days to first leaf whorl opening, leaf count, long stems, increase in bulb weight, earlier flowering and highest number of bulblets. Combinations of the highest levels of the PGRs had adverse effects on all growth parameters resulting in dwarfed plants with poor quality flowers. BA and GA; both at 50mg/l singly and BA l00 mg/l plus GA; 50 mg/l in combination proved to be the best treatments to replace chilling treatment for the growth 'antl flowering of Oriental lily bulbs , lt was concluded that low concentrations of BA and GA; can be used as alternative treatments to chilling for breaking dormancy in Oriental lily bulbs and furthermore leads to high yields and low cost of production hence economically viable for small scale farmers.