Biomedical subjects
J K M Brown
Publications and source records attributed to J K M Brown.
Genetics of resistance to septoria tritici blotch in the Portuguese wheat breeding line TE 9111.
We report the genetics of resistance of the Portuguese wheat breeding line TE 9111 to septoria tritici blotch (STB), which is caused by Mycosphaerella graminicola. TE 9111 is the most resistant line known in Europe and combines isolate-non-specific, partial resistance with several isolate-specific resistances. We show that, in addition to high levels of partial resistance to STB, TE 9111 has a new gene for resistance to M. graminicola isolate IPO90012, named Stb11, that maps on chromosome 1BS, the Stb6 gene for resistance to isolate IPO323 and, probably, the Stb7 gene for resistance to isolate IPO87019. All of these genes are closely linked to microsatellite markers, which can be used for marker-assisted selection. TE 9111 may therefore be a valuable source of resistance to STB for wheat breeding, especially in Mediterranean environments.
Sequence variation in the CYP51 gene of Blumeria graminis associated with resistance to sterol demethylase inhibiting fungicides.
Resistance to sterol 14alpha-demethylase inhibiting fungicides (DMIs) has been correlated with mutations in the CYP51 gene, which encodes the target enzyme eburicol 14alpha-demethylase. To test the hypothesis that variation in the CYP51 gene explains variation for DMI sensitivity in barley and wheat powdery mildew species, this gene was sequenced from isolates of Blumeria graminis f.sp. hordei (Bgh) and f.sp. tritici (Bgt), respectively, which differed in their responses to DMIs in agricultural populations in the UK. Two single-nucleotide mutations in the CYP51 gene, which resulted in the amino acid substitutions Y136F and K147Q, were detected. K147Q is a novel mutation present only in Bgh isolates expressing very high levels of resistance. Sequence analysis of the CYP51 gene from the progeny of a cross between DMI-sensitive and resistant Bgh isolates showed that both mutations segregate with resistance, which is consistent with CYP51 controlling a major portion of DMI resistance. However, genetic analysis of resistance to the DMI triadimenol indicates that mutation of the CYP51 gene is not the only mechanism of resistance operating in B. graminis.
Evolution. Little else but parasites.
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Isogamous, hermaphroditic inheritance of mitochondrion-encoded resistance to Qo inhibitor fungicides in Blumeria graminis f. sp. tritici.
A mutation of glycine to alanine at position 143 in the mitochondrial cytochrome b amino acid sequence of Blumeria graminis f. sp. tritici cosegregated with the QoI-resistant phenotype in a ratio of 1:1 in a cross between a sensitive and a resistant isolate. This mutation was used as a mitochondrial marker to determine whether mitochondrial inheritance in B. graminis was anisogamous, as in heterothallic Neurospora sp., or isogamous and hermaphroditic, as in Aspergillus nidulans. Segregation of mitochondrial genotypes in B. graminis f. sp. tritici was consistent with inheritance of mitochondria being hermaphroditic and isogamous, in that all ascospores from an individual cleistothecium had the same mitochondrial genotype and that either parent could act as the maternal parent of a cleistothecium. Within each cleistothecium, nuclear segregation occurred independently of mitochondrial inheritance, as shown by segregation of resistance to the fungicide triadimenol and by segregation of avirulences to the wheat cultivars Galahad (Pm2), Armada (Pm4b), and Holger (Pm6).