Mycosphaerella Musicola - Life Cycle

Life Cycle

When spores of M. musicola are deposited on a susceptible banana leaf they germinate within three hours if there is a film of water present or if the humidity is very high. The optimal temperature for germination of the conidia is between 25-29ºC and for the ascospores, 25-26ºC. The germ tube grows epiphytically over the epidermis for about five days before penetrating the leaf via a stoma. Once inside the leaf the invasive hypha forms a vesicle and fine hyphae grow through the mesophyll layers into an air chamber. More hyphae then grow into the palisade tissue and continue on into other air chambers, eventually emerging through stomata in the streak that has developed. Further epiphytic growth occurs before the re-entry of the hypha into the leaf through another stoma repeats the process.

Both conidia and ascospores are important for dispersal of M. musicola with the ascospores being involved in the movement of the pathogen over longer distances than the conidia. The deposition of ascospores by wind currents is generally near the tips of the leaves resulting in a distinctive pattern of infection on the leaf extremities. When conidia are the source of the inoculum and these are dislodged by rain, a distinctive line of streaks is produced as water trickles down the leaf blade.