Solid Stem: A Radiation Induced Mutation inTriticum DurumDesf.

Abstract

SUMMARYData are presented on the inheritance and culm anatomy of a solid stem mutant, induced in durum wheat Cappelli by X-irradiation.F1 plants of the cross between the mutant and the mother line Cappelli had intermediate phenotype. Genetic analysis of F2 was particularly complicated as, in addition to parental types, many intermediate phenotypes were present. Completely hollow-stemmed plants reached 23.1% of the whole population, while the remaining individuals had at least the top internode below the spike filled with pith (3:1 segregation: 0.5>P>0.3). Two hypothesis might be considered to explain the data obtained, namely: 1) X-irradiation induced a semidominant mutation;2) X-irradiation neutralized the action of a gene for hollow stem, epistatic, only when homozygous, on one or more genes inducing stem solidness.Considering the cytogenetical information on solid stem in the genus Triticum, the second hypothesis seems most probable.A statistical analysis was carried on two anatomical parameters, namely: number of vascular bundles in the stem cross section and ratio between sclerenchymatic and total surface, both taken at the middle of each of the five uppermost internodes. The mean number of vascular bundles in the F, and in the mutant differed significantly from that of Cappelli; on the contrary, no significant differences were found in the mean ratios of sclerenchymatic to total stem area in Cappelli, the mutant and their F1.