Control of shoot necrosis and plant death during micro-propagation of banana and plantains (Musa spp.)

Abstract

Shoot necrosis and plant death occurred during large-scale propagation of Musa cultivars, viz. Grande Naine (AAA), Dwarf Cavendish (AAA), Nendran (AAB) and Quintal Nendran (AAB). The timing and frequency of necrosis was influenced by the cultivar. Grande Naine and Dwarf Cavendish showed necrosis after the 7th subculture at frequencies of 27 and 29%, whilst at the rooting stage (after seven transfers of shoot multiplication) the frequencies were 18 and 19% respectively. In Nendran and Quintal Nendran, necrosis occurred after the 5th subculture at frequencies of 38 and 40%, and at the rooting stage (after five transfers of shoot multiplication) the frequencies of necrosis were 26 and 27% respectively. Several methods were tested for alleviating shoot necrosis, including shortening the culture period, altering the media salt strength, use of various plant growth regulators, different levels of sucrose, fructose, silver nitrate, and increasing the concentration of calcium chloride. Only the addition of calcium chloride proved effective in reducing shoot necrosis. Transfer of shoots showing early signs of necrosis to Murashige and Skoog medium with an addition of 50–100 mg l-1 calcium chloride facilitated recovery of more than 90% of the shoots. The same addition to shoot multiplication medium for 2–4 transfers after the 6th and 4th subcultures respectively, for bananas and plantains alleviated shoot necrosis up to the 12th subculture in all cultivars. This also prevented necrosis during subsequent rooting. The prevention of loss of cultures by shoot necrosis by the addition of calcium chloride at the shoot multiplication stage, and thereby the reduction of production cost, will be beneficial to the banana micro-propagation industry.