Genetic variation for ergot (Claviceps purpurea) resistance and alkaloid concentrations in cytoplasmic-male sterile winter rye under pollen isolation

Abstract

Ergot caused by Claviceps purpurea results in the contamination of rye grain by sclerotia that contain alkaloids toxic to humans and other mammals. Ergot incidence and severity are affected by various factors including the availability of pollen during flowering. To test the presence of variation for ergot resistance due to anatomical and/or biochemical factors in rye, we studied cytoplasmic-male sterile (CMS) inbred lines of the Petkus gene pool (two sets each having 30 lines) and their testcrosses with maintainer tester lines (Set I crossed with two and Set II with a third tester line). Sixty-four CMS lines (60 lines, three testers in CMS form, one standard CMS line) and 90 CMS testcrosses were evaluated in four and three environments, respectively, for ergot severity measured as sclerotia weight per ear under pollen isolation and artificial spray inoculation. We also analysed the concentration of the six most important alkaloids and their isomeres in 25 lines. A very high ergot severity was achieved, and despite that genotypic variance among the 64 CMS lines was significant (P \ 0.01). In testcrosses, genotypic variance was smaller, even being not significant in testcrosses of one tester. Genotype 9 environment interaction variances and correlation coefficients between lines and their testcrosses were significant (r = 0.56-0.75, P \ 0.01) in all instances. Most prevalent alkaloids were ergosin, ergocristin, and ergotamin. There were no significant genotypic differences among lines for any alkaloid or isomer, but total alkaloid concentration showed genotypic variation with low significance level (P \ 0.1). In conclusion, we detected genotypic differences for resistance in CMS rye based on variable response of ovaries during infection process that can be exploited by multi-locational evaluation and selection to develop ergot resistant hybrids.

The effect of environmental factors and plant genotype on the severity of Claviceps purpurea in winter rye

“…Geiger & Bausback (1979) also found quantitative differences in susceptibility among artificially inoculated cytoplasmic male-sterile rye lines when grown in the absence of rye pollen. Therefore, good perspectives exist for developing hybrids achieving or even surpassing the resistance level of the best population varieties (Miedaner et al 2010a). Unfortunately, we were not able to find a fully resistant genotype so far.…”

“…In the absence of rye pollen, the ergot occurrence depended on cytoplasmic male-sterile rye genotypes which were weakly (ten) and strongly (four genotypes) affected. Such differences in host resistance most likely are caused by anatomical and/or biochemical mechanisms (Miedaner et al 2010a). Geiger & Bausback (1979) also found quantitative differences in susceptibility among artificially inoculated cytoplasmic male-sterile rye lines when grown in the absence of rye pollen.…”

“…In many studies on evaluation and selection of rye genotypes resistant to ergot, conidia received in pure cultures were used as a source of rye infection by C. purpurea (Miedaner et al 2010a;Mielke 2000;Mirdita et al 2008;Mirdita & Miedaner 2009). …”

“…In our study we proved that spraying rye plants at midday increased ergot occurrence twofold in comparison with rye plots not sprayed. Spraying with water decreases the availability of pollen for flowering and increases ergot incidence (Miedaner et al 2010a).…”

Genetic and transcriptional dissection of resistance to Claviceps purpurea in the durum wheat cultivar Greenshank

“…Husn. Ergot is a significant problem for hybrid production systems for rye, barley and wheat production systems, where male sterility is induced to allow crosspollination for F 1 hybrid seed formation (Mantle and Swan 1995;Miedaner et al 2010).…”