BUDS STERILIZATION AND PLANT GROWTH REGULATORS for IN VITRO REGENERATION OF „BUBU‟ POTATO (solanum tuberosum L.) VARIETY

Abstract

Potato is one of the important crops in Ethiopia and there is a favourable condition to produce than other African countries. but the production is low because of long dormancy periods which leads to delayed planting, poor crop emergence and vigour and limited availability of planting materials. Thus, this research was conducted to estimate the effect of tuber sizes, GA3 concentration and soaking time on dormancy breaking and sprouting characteristics. Additionally, the effect of Bavistin and mercuric chloride sterilant chemicals with soaking duration, and different concentrations of PGRs (BAP, KIN, NAA and IBA) for in vitro shoot regeneration of the „Bubu‟ potato variety were evaluated using lateral bud as explants. The experiments were laid out in a factorial arrangement Complete Randomized Design with three replications at Plant Biotechnology Laboratory, Haramaya University. The Results of study showed that three-way interaction (tuber size, GA3 concentration and soaking time) showed the presence of significant differences in sprout length and sprout vigour traits. Whereas, the interaction of GA3 and tuber size had a significant effect on dormancy period and sprout thickness. A number of sprout/ tuber traits showed significant differences only by tuber sizes. While the percentage of tuber sprouted was not affected by any factors. The main factor of soaking time had a significant effect on dormancy period and sprout thickness traits. The result showed that large-size tubers with treatment of GA3 at concentrations of 50 ppm & medium with 100 ppm produce short (36.4 days) dormancy period. The large tuber size had a significantly better (2.3) number of sprouts per tuber than the other tuber sizes without difference with (1.9) medium size. The longest sprout (17.7- and 17.3-mm) were recorded from small tuber size soaked with 50 and 100 ppm for 15 min and medium soaked with 100 ppm for 45 min produced sprout lengths respectively. While the shortest (<5 mm) sprouts were from all sizes of untreated tubers. The best sprout vigour (4.7 scores) from medium tuber size soaked with 25 ppm of GA3 for 15 minutes was commendable for dormancy breaking and attaining high sprouting quality of the “Bubu” potato variety. Results revealed that when lateral bud explants were sterilized with the treatment of 70% Ethanol for 1 min + 0.3% Bavistin for 10 minutes + 0.05% HgCl2 for 3 min) the explant produced the highest (80%) healthy disinfected survival, least (6.6%) contamination and least (20%) mortality rate. The Ms Medium containing 2 µg/ml of KIN were significantly reduced (3 day) the days to shoot initiation, produced the highest (93%) percentages of the shoot, highest number of leaves (6.3 leaves), most shoot number (7.0 shoots) and the longest shoot (11.7 mm). Generally, overall the results revealed that using medium tuber sizes treated with 25 ppm GA3 for 15 minutes were reduced the Dormancy period and make the best sprout qualities and increasing the concentration and soaking time reduce the quality of sprout. Lateral buds sterilized without combination (apply alone) were not produce survived explant, also both cytokinin (BAP and KIN) alone reduced the days to shoot initiation and obtained highest shoot multiplication, whereas both Auxin (NAA and IBA) alone and in combination with cytokinin produce higher days to shoot initiation and lowest multiplication. The further study expanded by investigating including more potato varieties and more explant sources that the factors affect acclimatization to ex vitro conditions and microtuberization in micro propagated potato variety plantlets.