Detection of Banana bunchy top virus and Banana streak Mysore virus by PCR: Impact of storing virus infected banana samples

Banana bunchy top virus (BBTV) and Banana streak Mysore virus (BSMyV) are economically important DNA viruses infecting of banana in India. A study was conducted to evaluate different methods of storage for BBTV and BSMyV infected banana leaf samples for detection by PCR. Virus infected leaves were stored at room temperature (28°C±2) as dried samples, which were processed by three methods viz., hot air oven at 55°C, calcium chloride (CaCl₂), and air drying (28 ± 2°C), at 4°C (in refrigerator) and at −86°C (in deep freezer) as wet samples. BBTV was detected in all samples stored at all conditions up to 15^th day of storage. On 30^th day of storage, the virus was consistently detected in samples dried in hot air oven and desiccated using CaCl₂ but not in samples dried at room temperature BSMyV was detected in symptomatic leaf samples dried in hot air oven and CaCl₂ desiccation on 45^th day of storage and even up to 60^th day of storage for samples stored at 4°C and −86°C. In case of asymptomatic samples, the virus was detected on 30^th day of storage for samples desiccated with CaCl₂ and at 4°C and −86°C. Drying the samples by CaCl₂ desiccation improved the detection of banana viruses by PCR. It is recommended that the tissue culture industries can dry the banana leaf samples by CaCl₂ desiccation before dispatching to accredited laboratories for testing BBTV and BSMyV.