Journal of Plant Biochemistry and Biotechnology

The genomic DNA isolation from mature leaf midrib is a tough job, because of the abundance of polysaccharides and secondary metabolites, which interferes with DNA isolation as well as polymerase chain reaction (PCR) studies. The leaf midrib of 3^rd leaf from 3-moths old, ex-vitro developing banana [AAA, Dwarf Cavendish-Basrai (Sindhri banana)] plants (healthy and BBTV infected) was grinded in liquid N₂. Exact 0.3 g of leaf midrib powder was washed with washing buffer (100 mM Tris-Cl, 5 mM EDTA, 0.35 M sorbitol, 1% 2-mercaptoethanol) then homogenized in 0.8 ml of three different pre-heated (60°C) DNA isolation buffers. Supernatant was extracted through phenol:chloroform:isoamyl alcohol (25:24, v/v), chloroform:isoamyl alcohol (24:1, v/v) and finally with chloroform (100%) one by one. Maximum yields were ranged from 49.33 and 27.73 μg mg⁻¹ DNA with impurities 5.67 and 5.87 μg mg⁻¹ through buffer I, while 45.77 and 25.53 μg mg⁻¹ DNA with 6.13 and 6.16 μg mg⁻¹ impurities through buffer III from healthy and infected plants respectively. Best one RAPD was observed in all the DNA samples isolated with different buffers, while viral amplification was good in DNA isolated with buffer I and II, when 10 (RAPD) and 25 ng DNA (C₁ gene) was used as a template in a reaction of 25 μl. Meanwhile, buffer II is limited for viral DNA isolation while buffer I (1M Tris-Cl, 5M NaCl, 2% cTAB, 50mM EDTA, 1% PVP, 0.2% 2-mercaptoethanol) has dual capacity for plant and virus DNA isolation. This described protocol is economic in terms of times, labor and cost.