Musa balbisiana resists Xanthomonas wilt disease through interfering with the multiplication of Xanthomonas vasicola pv musacearum coupled with whole organ (leaf) death

Abstract

Xanthomonas wilt disease caused by Xanthomonas vasicola pv. musacearum (Xvm) is the most devastating disease of bananas, plantains and Enset in East and Central Africa. There is no known resistant banana to this disease among the cultivated varieties but here we confirm that one wild type, Musa balbisiana is resistant. Plants recovered from wilt symptoms and although it initially migrated beyond the point of inoculation, Xvm population did not build up and its presence was restricted to the inoculated and the immediate follower leaves which subsiquently wilted and died in some plants. The pathogen population within plant tissues was observed to drop in a 50 mg tissue from 3.06x107cfu at 18days after inoculation in the inoculated leaf to 1.5x104cfu by the 12th week after inoculation in the immediate follower leaf and later to 0 cfu by the 20th week after inoculation in other follower leaves. In contrust to the same size of tissue in the susceptible cv “Nakinyika” its population increased from 3.41x108 to 1.08x1011cfu within 3 weeks after inoculation. In addition, bacterial migration within M. balbisiana was slow, where it took up to 12 weeks to be detected as far as only the immediate follower leaves. In the susceptible cv “Nakinyika” Xvm migration was faster and it had spread to adjacent leaves within 2 weeks after inoculation. Consistent with the decreasing bacterial population and limited migration, initial symptom development was also delayed, only first observed in the inoculated leaf at 10 weeks after inoculation. In addition, the incidence and severity of wilt remained low at 33% and 20% respectively and with the exception of the individual wilted leaves that subsiquently died, the plants were never broken down but continued to grow without anymore symptoms.