Virus Free Clonal Propagation f Banana in Vitro

Abstract

Banana, one of the most important fruit crops of Pakistan is grown mainly in the Southern Province of Sindh. Until recently the crop has been growing very successfully. Plantings in 1988 were some 23,500 with annual production of around 210,000 tonnes, of which over 20,000 were in Sindh, mainly on the left bank of the river Indus. It was in 1988-89 when the bunchy top disease was first observed in Sindh and later on (1991) identified as “Banana Bunchy Top Disease” (BBTD) caused by Banana Bunchy Top Virus BBTV. According to the Agriculture Extension Department of Sindh, the planting was reduced to 8,000 ha (60 percent crop loss) by the end of 1992 causing huge losses of 90 percent in terms of per hectare annual yield. In Monetary terms, the income loss for 1992 amounts roughly to Rs. 915 million. The disease attained the form of epidemic and devastated the crop causing loss of up to 100% in some areas. Present research studies on the “virus free clonal propagation of banana” were conducted during a period of 3 years i.e., from June 1995 to May 1998. During this period a number of experiments/trials were carried out on two varieties of banana i.e., Basrai cv, w.hybrid cv. at Biotechnology Laboratory, Department of Biotechnology, Sindh Agriculture University, Tandojam. Our objective was to produce virus free banana plants, through in vitro micropropagation. The banana cultivars “Basrai and William hybrid’ were grown on the Latif Farm of Sindh Agriculture University, Tandojam to provide continuous supply of explant material for the laboratory trials. The shoot tips of the healthy-looking plants of these two varieties e.g., Basrai and w. hybrid were maintained as explant material. The meristem tips were isolated from the suckers measuring about 3mm and cultured on MS medium with supplement of 1AA and Cytokinin BAP. It was observed that maximum explants survived on the medium MS + 10 uM/L BAP + 5uM/LIAA and lowest number of plants survived on MS+2g/L IBA+2mg/LIAA. It shows that for obtaining maximum explant survival it is necessarily to have BAP and IAA in the medium. For multiplication of banana shoots, it was observed that high concentrations of cytokinin BAP shows the best results. At lower concentrations only one or two shoots were obtained. The higher concentrations i.e., MS+20 uM BAP/L showed best response and this concentration was most effective for the multiplication of shoots. Dissecting of shoot tips in subsequent culture stimulated shoot multiplication up to 7-10 shootlets in MS medium with 20 uM/L BAP splitting of shoot tips strongly induced multiple root formation. Three different media were used for shoot tip multiplication in banana. Two containing BAP one lack of BAP only those responded which contains BAP and the best effective was that in which BAP was in higher concentration. Results of root formation showed that formation could be induced in number of days in as few as 4 days. It was observed that ½ strength MS showed satisfactory results only for primary rooting system but when MS+ M/IBA was used it showed better results for primary, secondary and tertiary rooting system. More number of vigram roots with subsequent increase in length were observed in supplementation of IBA in MS medium. Plants with well-developed rooting system were transferred to pots containing sterilized sand and them to earthen pots. Pots were irrigated with distilled water daily and provided with liq MS medium twice a week and after 1-2 weeks they showed descending survival rate due to lack of proper humidity conditions. Few survived plants transferred in the field which do not show any symptoms of BBTV. It was observed that virus free banana plants could be produced successfully on commercial scale through micropropagation technique by using MS medium supplemented with different levels of growth regulators i.e., MS+IAA + BAP and MS + IAA + IBA and MS + BAP.