A. Adam, M.I.E. Arabi, I. Idris and E. Al-Shehadah
The effect of Pseudomonas putida BTP1, Bacillus subtilis Bs2500, Bs2504, and Bs2508 strains on the incidence (I) and severity (S) of barley leaf stripe disease caused by Pyrenophora graminea was evaluated under field conditions. Three barley cultivars varying in resistance level were used. The resistance achieved in our study was long-lasting. P. putida BTP1 and Bs2508 were in general the most effective strains in reducing significantly both I and S of barley leaf stripe disease vis-a-vis three cultivars in two growing seasons 2013/2014. The disease was reduced up to 66% in Arabi Abiad treated with P. putida BTP1. The susceptible landrace cultivar Arabi Abiad exhibited a significant induction of resistance by Bs2508 and BTP1. However, the resistant cultivar Banteng did not exhibit significant further increase in resistance by these bacterial strains. The grain yield of bacterized plants artificially inoculated with P. graminea was not affected, except that of the cultivar Arabi Abiad treated with Bs2508 and Bs2504. Triggering of resistance by treating seeds with the bacterial strains would be of great value in agriculture, especially in case of barley infection by P. graminea at an early stage of plant development.
The yield response of widely grown cultivars and landraces of Syrian wheat challenged with common root rot (CRR: Cochliobolus sativus) was measured by comparing plots with and without artificial inoculation under experimental conditions in two consecutive seasons. The results showed that response to CRR differed depending on the susceptibility levels of the wheat cultivars, and that the disease significantly (P<0.05) reduced grain yield, number of tillers and kernel weight. The diseased plants had fewer tillers which consequently reduced grain yield per plant. Yield losses of Triticum durum cultivars were higher than those of Triticum aestivum. In addition, the T. durum landrace Horani exhibited the best level of resistance to the disease, which indicates that this landrace might be a candidate donor for resistance in future breeding programmes. As CRR can dramatically reduce wheat grain yields under favorable conditions, management practices that reduce disease severity are highly recommended.
A. Al-Daoude, M. Jawhar, E. Al-Shehadah, A. Shoaib, M. Orfi and M.I.E Arabi
Net blotch (NB), caused by the necrotrophic fungal pathogen Pyrenophora teres f. teres, substantially reduces barley grain yield and quality worldwide. The role of salicylic acid (SA) signaling in NB resistance has been poorly documented. In this study, SA levels as well as the expression of the SA-responsive gene PR2 were monitored in infected leaves of two barley genotypes, Banteng (resistant) and WI2291 (susceptible), at different time points of infection. SA signaling was activated in bothgenotypes 24 hours post infection (hpi) as compared with non-inoculated plants. However, with or without pathogen pretreatment, SA signifi cantly increased (P=0.001) in Banteng comparing with WI2291. RT-PCR analysis revealed that PR2 expression increases in the resistant and susceptible genotypes over the inoculation time points, with maximum expression (6.4 and 1.99-fold, respectively) observed 6 dpi. PR2 expression was paralleled by an increase in leaf SA content as shown by the test coincidence (F3, 32 = 4.74, P = 0.001). Based on barley genotype resistance levels, our data strengthen the idea that SA signaling and PR2 play a role in barley NB reduction