A novel mutant allele at the Cleistogamy 1 locus in barley.

KEY MESSAGE: A chasmogamous mutant was induced by exposing a cleistogamous cultivar to sodium azide. The altered cly1 sequence in the mutant was not in the miR172 binding site, as is the case in other known cleistogamous alleles, but rather in a region encoding one of the gene product's two AP2 domains. The genetic basis of cleistogamy (in which pollination occurs before the flower opens) in barley is centered on the Cleistogamy 1 locus (cly1). The sequence of the microRNA (miR172)-targeting site in the gene, which belongs to the APETALA2 family, differs between cleistogamous and chasmogamous cultivars at a single nucleotide position, resulting in the differential ability of the lodicules to swell. Here, mutagenesis of the barley cultivar 'Misato Golden' (which carries the cly1.b allele), achieved using sodium azide, was used to induce a change from cleistogamy to chasmogamy (non-cleistogamous flowering). The cly1 coding sequence in the selected mutant differed from that of cly1.b by two non-synonymous mutations, one of which was responsible for an altered residue in one of the AP2 domains present in the Cly1 protein. Although there was no difference in the miR172 targeting site between cly1.b and the novel allele (designated cly1.b3), the mutant's lodicules' ability to swell was indistinguishable from that observed in cultivars carrying the chasmogamous allele Cly1.a. The phenotype of cly1.b3/cly1.b, cly1.b3/cly1.b2 and cly1.b3/cly1.c heterozygotes indicated that cly1.b3 is recessive or incompletely dominant with respect to these alleles.

Isolation and identification of flavonoids accumulated in proanthocyanidin-free barley.

Flavonoids accumulated in proanthocyanidin-free near-isogenic lines iso ant 13, iso ant 17, and iso ant 22 of Nishinohoshi, developed by backcross breeding using a leading cultivar, Nishinohoshi, as a recurrent parent and a proanthocyanidin-free mutant as a nonrecurrent parent in Japan, were examined. A new flavanone, (2RS)-dihydrotricin 7-O-ß-D-glucopyranoside (1), known flavanones (2RS)-dihydrotricin (2) and (2RS)-homoeriodictyol (3), and known flavones chrysoeriol 7-O-[α-L-rhamnopyranosyl-(1→6)-ß-D-glucopyranoside] (4), chrysoeriol 7-O-ß-D-glucopyranoside (5), tricin (6), and chrysoeriol (7) were isolated from iso ant 17 of Nishinohoshi. The structures and stereochemistries of the isolated flavonoids (1-7) were elucidated on the basis of spectroscopic analyses. The concentrations of the isolated flavonoids (1-7) in iso ant 13, iso ant 17, and iso ant 22 of Nishinohoshi were similar to each other, whereas the flavonoids 1-5 and 7 were not detected in Nishinohoshi, an old Japanese cultivar, Amaginijo, and North American cultivar Harrington. The concentration of tricin (6) in Nishinohoshi was a half those in iso ant 13, iso ant 17, and iso ant 22 of Nishinohoshi. Except for iso ant 13, iso ant 17, and iso ant 22 of Nishinohoshi, the concentration of tricin (6) was highest in Nishinohoshi, followed by Amaginijo and Harrington. Thus, tricin (6), its precursor dihydrotricin (2), and its glucopyranoside, dihydrotricin 7-O-ß-D-glucopyranoside (1), as well as chrysoeriol (7) and homoeriodictyol (3) were accumulated in iso ant 13, iso ant 17, and iso ant 22 of Nishinohoshi probably by blocking at the step of flavanone 3-hydroxylase in the procyanidin biogenetic pathway, resulting in enhancement of the alternative biogenetic pathway.

Effect of infection timing on fusarium head blight and mycotoxin accumulation in open- and closed-flowering barley.

ABSTRACT Barley has two flowering types, chasmogamous (open-flowering) and cleistogamous (closed-flowering). We examined the effect of the timing of Fusarium graminearum infection on Fusarium head blight (FHB) and mycotoxin accumulation in barley cultivars with different flowering types using greenhouse experiments. In the first experiment, 13 cultivars were spray inoculated at two different developmental stages, and the severity of FHB was evaluated. The effect of the timing of infection differed among cultivars. Cleistogamous cultivars were resistant at anthesis but susceptible at 10 days after anthesis, whereas chasmogamous cultivars were already susceptible at anthesis. In the second experiment, five cultivars were inoculated at three different developmental stages and the concentrations of deoxynivalenol (DON) and nivalenol (NIV) in mature grain were analyzed. Cleistogamous cultivars accumulated more mycotoxins (DON and NIV) when inoculated 10 or 20 days after anthesis than when inoculated at anthesis, whereas chasmogamous cultivars accumulated more mycotoxins when inoculated at anthesis. Thus, the most critical time for F. graminearum infection and mycotoxin accumulation in barley differs with cultivar, and likely is associated with the flowering type. Late infection, even without accompanied FHB symptoms, was also significant in terms of the risk of mycotoxin contamination.