Interactive effects of fertilizer and inoculum concentration on subsequent development of xanthomonas wilt in banana

Abstract

Soil nutrient depletion and Xanthomonas wilt (Xanthomonas campestris pv. musacearum) are major causes of declining productivity in smallholder banana systems in East and Central Africa. This study examined the interactive effect of fertilizer and inoculum concentration on development of Xanthomonas wilt. Fertilization significantly (p<0.01) increased the plant height, plant girth and leaf area in banana compared to control without fertilizer. Despite this, between 9 and 21 days post inoculation (dpi) all inoculated plants had exhibited typical disease symptoms (that is, chlorosis, necrosis and wilting of leaves). No significant reduction (p>0.05) in disease incidence, wilt severity index or mortality could be associated with increasing fertilizer amounts. Interestingly, there was a highly significant (p<0.01) overriding effect of inoculum concentration on the ability of fertilizer to reduce wilt severity index and mortality in banana. Plants inoculated with 10 6 to 10 12 cfu mL-1 developed twice as much disease compared to 10 4 cfu mL-1 inoculations. Average mortality of 9.2% for 10 4 cfu mL-1 inoculated plants provides evidence of the potential to cause latent infections. Low bacterial loads are implicated in recent field resurgence of Xanthomonas wilt in banana orchards where disease had been successfully contained.

The soil fertility and leaf nutrient status in enset gardens in different altitude zones of the Gamo highlands, Ethiopia and inferences for Xanthomonas wilt prevalence

“…Hence, especially in view of the observed over-fertilisation, the potential of soil nutrients to amplify the current EXW epidemic may not be overlooked. Contrary to our findings, higher K, Ca and N levels reduced bacterial wilt incidence in banana (Atim et al, 2013) and NPK levels affected Xanthomonas wilt incidence and severity in banana (Ochola et al, 2014). Yet the effect of nutrients on a plant's response to disease is often species specific (Ghorbani et al, 2009;Spann et al, 2009) and results obtained in banana are not necessarily applicable to enset.…”

“…In general, environmental and edaphic conditions and play an important role in disease control in various crops (Agrios, 2005;Huber and Graham, 1999;Huber and Haneklaus, 2007;Huber et al, 2012;Mwebaze et al, 2006;Welde-Michael et al, 2008b). Also, recent studies on banana have indicated an effect of certain nutrients (N, P, K, Ca, and Si) in reducing bacterial wilt incidence (Atim et al, 2013;Mburu et al, 2016;Ochola et al, 2014). We therefore hypothesize that an insight into these interactions might yield a complementing path for disease control in enset systems as well.…”

Interactive effects of leaf age and inoculum concentration on downy mildew of cucumber plants and the implication of nutrients.

“…It was apparent that disease severity significantly increased with the increasing fungal load at the initial infection stages. Nevertheless, when downy mildew developed, no significant difference observed between two higher inoculum loads, as reported for other pathogens [24,25]. --------------------------------------------------…”

“…Therefore, the nutrients Fe, Zn and Ca of the leaves significantly influenced the total lesion area at P<0.05 in the day 11 post inoculation with P. cubensis ( Table 2). The important role that nutrients play with regard to inoculum concentration has also been reported for other diseases [24]. Besides, a study by Amand and Wehner about the effect of various factors such as leaf age, stomata opening on cucumber gummy stem blight stated that nutrients provided by guttation were more important in the infection process than other factors [16].…”

Bacterial Diseases of Bananas and Enset: Current State of Knowledge and Integrated Approaches Toward Sustainable Management

“…However, and in contrast, Ochola et al (2014) reported that increasing fertilizer amounts did not significantly reduce ( p > 0.05) disease incidence, wilt severity index or plant mortality for artificially inoculated banana plantlets in pot experiments.…”