International Symposium on Cereal Leaf Blights 2019 | University College Dublin, Ireland | 22-24 May 2019


Patrick Seed*
University of Nottingham

Ruth Bryant
RAGT Seeds Ltd

Rumiana Ray
University of Nottingham

Poster Presentation
Host Genetics and Resistance Breeding

Atrium, UCD O'Brien centre for Science
Poster 39

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Breeding novel genes for resistance to Zymoseptoria tritici causing Septoria tritici blotch (STB) in wheat is essential for the future sustainable management of the disease. Phenotyping tools measuring chlorophyll fluorescence (CF), in addition to traditional disease assessments, can be deployed to screen plant populations for the early detection and characterisation of novel resistance. The aim of this study was to characterise and differentiate the effects of a novel resistance gene (RG) identified in the cv. Cougar by RAGT from the known resistance gene, Stb6.  Sixteen genotypes from a population, cross between the winter wheat cv. Cougar and cv. Scout, containing all possible combinations of the novel RG and Stb6 were spray-inoculated at GS 27 with Z.  tritici (IPO323) and grown under controlled environment. The effect of the RG and Stb6 on the efficiency of photosystem (PS) II was quantified by measuring CF parameters with two different instruments, MultispeQ (PhotosynQ) and Fluorpen (PSI). Pycnidia production, necrosis latency and disease progression were visually assessed from 7 days post inoculation. During the asymptomatic phase of the disease, at 4 hours post by inoculation, RG lines exhibited reduced excitation energy flux trapped per active reaction centres and increased non-photochemical quenching (NPQt) compared to Stb6 lines. Once symptoms were visible, NPQt in RG lines decreased significantly whilst quantum yield of PS II increased. RG lines were also characterised by reduced disease symptoms progression (AUDPC) and delayed development of pycnidia and necrosis. The results show that the resistance gene is highly effective against STB as early as GS27 (early tillering) and differ from Stb6. CF can be used to characterise the effects of the RG on the early photochemical reactions of photosynthesis consistent with reduced symptom expression. Future work will use NILs to investigate the physiological and molecular mechanism of this novel resistance gene.