The occurrence and inheritance of a brittle rachis phenotype in Italian durum wheat cultivars

Italian and Tunisian durum wheats from different eras of breeding were assessed for the presence of a gene for brittle rachis. Nine of 15 Italian durum landraces had brittle rachides. Strampellis achievement was the release of the well-known variety, Senatore Cappelli, which was derived from a Tunisian landrace, Jenah Rhettifah, which has a brittle rachis. Rachides of two Tunisian landraces were also brittle. Since the 1950s, 16 accessions were released as selections from crosses or mutagenesis involving Senatore Cappelli. Seven of these accessions have brittle rachides. F₂ segregation in intercrosses of Senatore Cappelli with other durum accessions with brittle rachides indicated a common allele for brittle rachis. Segregation of the F₂ from Senatore Cappelli/ANW 10A and the F₂ of Senatore Cappelli/ANW 10B showed that the gene for brittle rachis of Senatore Cappelli was allelic to the brittle allele of the Br-B1 locus on chromosome 3B. Senatore Cappelli was presumably the only source of brittle rachis used in Italian breeding programmes. The genes for brittle rachis have been retained in the gene pool of durum wheat, suggesting that the brittle rachis character is not associated with an appreciable yield loss in modern farming systems in Mediterranean environments.