Effects of preharvest sprouting on the genetic structure of durum wheat 'landraces'

Preharvest sprouting that occurs in wheat might affect seed viability and c ause genetic erosion during periodical rejuvenation of durum wheat accessio ns in a gene bank. Two durum wheat landraces (MG 7723 and MG 7805) that had been rejuvenated for several years and did show a high percentage of presp routed seeds in the lot from the fourth rejuvenation cycle were identified. The frequency of durum and bread wheat genotypes and the distribution of t he two species in three seed classes (ungerminated seeds, seeds with swolle n embryo and germinated seeds) were studied. The modified phenol test was u sed to identify durum and bread wheat seeds and the genotypic frequencies w ithin each species were assessed on the basis of acid polyacrylamide gel el ectrophoretic patterns of gliadin storage proteins. In these two landraces, durum wheat was more susceptible to preharvest sprouting than bread wheat and the frequency of bread wheat seeds significantly increased over the thr ee rejuvenation cycles examined. Despite this, preharvest sprouting did not cause significant changes in the genotypic frequencies observed within spe cies or loss of some genotypes that could not be attributed to susceptibili ty to sprouting.