Prevalence of puroindoline grain hardness genotypes among historically significant North American spring and winter wheats

Grain hardness ("hard" or "soft" kernel texture) is the single most importa nt trait in determining the utilization and marketing of wheat (Triticum ae stivum L,), Puroindoline a and b proteins represent the molecular basis for this trait. This study surveyed the prevalence of puroindoline hardness mu tations (alleles) among North American spring and winter wheat varieties wi th emphasis on those that are historically important. Each variety was asse ssed for kernel texture using the Single Kernel Characterization System; Ha rdness alleles were defined by puroindoline gene sequence and the presence or absence of puroindoline a protein on polyacrylamide gels. A total of 90 spring wheats were examined: nine were soft and possessed wildtype ("soft") puroindoline sequences, 10 were mixed hardness, and the remaining 71 were uniformly hard. Of these hard spring wheats, 18 carried the Pina-D1b hardne ss allele (null for puroindoline a protein), 47 the Pinb-D1b allele (Gly-46 -Ser-46), and four the Pinb-D1c allele (Leu-60-Pro-60). Two hard spring whe ats possessed a new allele, designated Pinb-D1e, which involves a single nu cleotide change in Trp-39 to a "stop" codon, Lastly, among the spring wheat s, a new hardness allele was found in the hard component of the variety 'Ut ac' which was mixed, This allele, Pinb-D1f, also involved a single nucleoti de change such that Trp-44 became a "stop" codon, A total of 62 winter whea t varieties were examined, of which five were soft and three were of mixed hardness, Of interest, the three mixed hardness wheats were 'Turkey', 'Khar kof, and 'Weston'. The hard component of each carried the Pinb-D1b allele, Of the 54 remaining wheats, all of which were hard, all but two carried thi s same Pinb-D1b allele, 'Chiefkan' winter wheat carried the same Pinb-D1e a llele as 'Canadian Red' and 'Gehun' spring wheats. 'Andrews' hard red winte r wheat possessed a new allele, designated Pinb-D1g, which was a single nuc leotide change in Cys-56 to a "stop" codon, In conclusion, hard grain pheno type results from one of various mutations in either of the puroindoline pr oteins. To-date, seven hardness alleles have been discovered and characteri zed in hexapoid wheat. All but one occur in the puroindoline b gene coding sequence and result from single nucleotide changes, These molecular markers are useful in characterizing lineages and analyzing ancestral relationship s.