Comparison of Spray and Point Inoculation with &amp;lt;i&amp;gt;Fusarium graminearum&amp;lt;/i&amp;gt; to Evaluate FHB Disease in Two Winter Wheat Genotypes Under Temperature Stress

Victor Chijioke Okereke

doi:10.11648/j.cbb.20170501.11

Abstract

Two near isogenic lines of wheat; Mercia 1 (Rht-B1b) and Mercia 2 (Rht-D1b) were evaluated for Type I and Type II resistance using point or spray inoculation and incubated under controlled environment. The experiment was a complete factorial combination of 2 x 4 x 2 x 4 {2 genotypes, 4 inoculation treatments (spray + Fusarium, spray + SDW, point + Fusarium, point + SDW) x 2 temperatures} and 4 randomised replicates. Wheat spikes were sprayed with a single spore isolate of F. graminearum 4 days after the start of flowering and transferred to controlled environment cabinets set at either 23/15°C or 28/20°C for 14 days and then taken outside to mature. Results reveals that genotype showed no difference in FHB severity in both spray inoculation and point inoculation but the temperature main effect only approached significance (P=0.071) with low temperature increasing FHB severity following point inoculation. High temperature significantly (P<0.001) increased DON concentration in spray inoculation, contrasted the effect in point inoculation. However, the amount of DON per grain showed no significant (P>0.05) effect. Grains per spike was significantly (P<0.011) reduced by 25% following spray when compared with point inoculation, but showed no significant (P>0.05) effect of temperature. On average, Fusarium infection significantly (P<0.001) reduced wheat grain weight by 28% when compared with uninoculated control.

Highlights

Two major dwarfing alleles Rht-B1b and Rht-D1b formerly known as Rht1 and Rht2 respectively, derived from Norin 10 have been used in over half the World’s wheat crop [1]
Results obtained showed that genotype did not defer in disease severity in both spray and point inoculation but the temperature main effect approached significance (P=0.071) (Fig. 1) only in point inoculation; with low temperature increasing FHB severity
Low temperature increased DON concentration in point inoculation while the DON concentration in spray pots was higher at high temperature

Summary

Introduction

Two major dwarfing alleles Rht-B1b and Rht-D1b formerly known as Rht and Rht respectively, derived from Norin 10 have been used in over half the World’s wheat crop [1]. In the UK, the majority of recommended wheat cultivars contain Rht-D1b after its first introduction in 1974 [2] and wheat cultivars carrying Rht-D1b have been linked to higher susceptibility to FHB. This is possibly due to the shortened distance from the spike to infected crop debris [3]. Of most importance in susceptible genotypes is the likelihood of mycotoxin production of which deoxynivalenol (DON) is of most concern and in highly resistant genotypes resistance is the major factor in suppressing disease development and DON accumulation. Point inoculation in FHB evaluation is a relatively stable method and is less affected by environment in terms of disease development [8]. Greenhouse evaluation has mostly employed the point inoculation methods whereas

Methods

Results

Discussion

Conclusion