Influence of nitrate / ammonium ratio on the plant growth of banana and related wilt disease development

Hydroponics experiments were conducted to investigate the effects of nitrate/ammonium ratio on the growth of banana plants and invasion of banana Fusarium oxysporum f. sp. Cubense. The results showed that, 1) In comparison with the treatments of sole nitrogen source, under the treatment of 75% nitrate + 25% ammonium (75% N + 25% A), the biomass of banana plants and the content of N, P, K in plants were the highest amongst all the treatments. 2) The rhizospheric pH was decreased strongly under the 100% ammonium treatment, while the pH increased with the addition of nitrate in the root medium. 3) After inoculation of Fusarium oxysporum f. sp. Cubense, the population of pathogen in rhizosphere was increased by the application of ammonium nutrition, but the number of pathogen in root tissue was reduced especially when the ammonium ratio reached 100%, no pathogen was detected in the root. In conclusion, sole ammonium nutrition could depress the growth of banana plants, but it can inhibit Fusarium oxysporum f. sp. Cubense penetration into the root cells. In combination with our previous experiments in vitro, that 100% ammonium inhibited Fusarium oxysporum f. sp. Cubense penetration process through the host plant cell wall. Our results suggested that the high concentration of ammonium in root cytoplast and cytosol could play an important role in the inhibition of invasion of this pathogen.