Contamination Control and Disease Management of Banana 'Grand Nain' Plantlets

During the growth of micro-propagation of 1 million Grand nain plantlets to 10 million, from elite and infection-free mother rhizomes, sterilized by standard techniques in the laboratory, profiles of bacterial and fungal contamination were monitored in growth rooms (24 +/- 2 degrees C, 60% RH, 4000 Lux) as a function of rainy season, winter and summer. The incidence of contamination was correlated with air quality in the growth rooms as well as temperature, relative humidity and rainfall. Subsequently the 45 days matured plantlets were subjected to primary hardening (27 +/- 1 degrees C, 70% RH, 15000 Lux) for additional 45 days, during which mortality rate was monitored as a function of pest/disease attack, cold injury, heavy rain, sun shock, handling and accidents. This was followed by subjecting the plants to secondary hardening for another 45 days (ambient conditions) at 50% light cut off due to shade nets, during which similar profiles were monitored. It was observed that the incidence of contamination was highest (3.4%) during rainy season (June-September), reduced (1.9%) during winter and was lowest (1.0%) during summer, almost corroborated by quality of air inside and outside the laboratory. Similar profile was witnessed during primary hardening too, where mortality rate was 1.2% in rainy season, 1.1% in winter and 0.6% in summer. The mortality rate was 0.3% due to handling, 0.2% due to pest/disease attack and <0.1% due to other reasons. A slight deviation in mortality profile was observed during secondary hardening as a function of rainy season (3.1%), winter (0.9%) and summer (1.2%). During this period 1.0% mortality was due to pest/disease attack, 0.4% due sun shock, 0.2% due to handling and about 0.05% due to other reasons. While witnessing the growth of micro-propagation from 1 million plantlets in 1997 to 10 million in 2007, the overall incidence of fungal contamination rose from 0.6 to 1.1% and bacterial contamination from 0.3 to 0.9%. Measures taken to achieve the metamorphosis of micro-propagation business are discussed.