---

Bacterial leaf streak (BLS) is one of the most important seed borne diseases of cereals, especially in wheat and barley. This disease can cause yield loss of up to 40% by producing dark brown spots on the glumes, called black chaff. Although this disease has spread widely in Iran recently, a quick and economical method for molecular and accurate detection of the disease agent, Xanthomonas translucene, has not been identified in the country. Quick and accurate detection of the bacteria in seed masses plays an important role in disease management. In this research, the development of a diagnostic kit for the causal agent of wheat bacterial leaf streak disease based on LAMP (Loop Mediated Isothermal Amplification) was performed by designing specific primers based on two new housekeeping genes rpoD and dnaK, which have not been used as LAMP targets previously). The serial dilution method of the bacterium was used to determine the sensitivity of the designed primers. The efficiency of the diagnostic kit was evaluated by collecting commercial wheat seed masses from different regions of the country and using the pure culture of the bacteria. The results showed that the primers designed based on the rpoD gene were the most effective. These primers detected up to 3.5 x 10² bacteria cells in one milliliter. The specificity of the primers was proved by performing the LAMP reaction on different genera of wheat pathogenic bacteria. The results of this project can be used for the rapid detection of X. translucense in wheat seeds and can be used as one of the management strategies for preparing healthy seeds.


 

---

Bacterial leaf streak (BLS) caused by Xanthomonas translucens pv. cerealis (Xtc) is an important disease of wheat (Triticum aestivum L.) worldwide. The management methods presently in practice are insufficient to meet current safety and/or efficacy standards. Therefore, use of resistant genotypes is the best approach to manage BLS. The present study was undertaken to identify possible sources of resistance to Xtc in cereal cultivars and germplasm. Twelve strains of Xtc were isolated from symptomatic leaves in several regions in Kerman province. Out of twelve, nine strains produced the expected Xtc-specific 120 bp fragment using PCR and the primer pairs PABr/PBf. Six strains produced water-soaked streaks covered with exudates on wheat cultivars, whereas the three remaining strains incited only chlorotic streaks with no water-soaking on leaves. A highly virulent strain that caused conspicuous water-soaking and necrosis was used for inoculation of 645 winter and spring wheat, barley, and rye accessions to identify possible sources of resistance to BLS. The fourth leaves of test plants were infiltrated with bacterial suspension and scored after seven to ten days. Among all the accessions evaluated, only two rye accessions, namely, 4538 and 4794, were resistant to BLS. These two rye accessions can potentially be used in breeding rye and triticale cultivars for resistance to BLS.