Inheritance of fatty acid composition was studied in an Fl diallel cross in Sinapis alba. Crosses were made among accessions having contrasting amounts of oleic (C18 :1) and erucic (C22 :1) acid . Concentrations of oleic, linoleic (C18 :2), eicosenoic (C20 :1) and erucic (C22:1) acids were determined by gas-chromatography for each mating combination . Genetic analysis confirmed that the composition of the fatty acids was controlled mainly by the nuclear genes of the embryo . Additive gene action with partial dominance for the reducing alleles was noted for oleic and linoleic acids, while erucic acid showed an additive mode of inheritance with partial dominance for the enhancing alleles . Positive heterosis was demonstrated for eicosenoic acid content . Erucic acid content was strongly negatively correlated with oleic acid, suggesting a genetic interdependence between the two fatty acids . Broad-sense and narrow-sense heritability estimates for each of oleic, linoleic and erucic acids were very high, due to low between-plants non-genetic component of variance .

The inheritance of resistance in common wheat {Tnticum aeitnum E.) to Septoria glume blotch, caused by the pathogen Septoria nodorum Berk., v.'as studied. Four quantitative parameters of resistance were measured: infection efficiency (IE) and disease seventy (DS) on intact young plants together with le.sion size (LS) and length of latent period (LP) on detached leaves. The method of testing the disease reaction of wheat to S. nodorum on detached leave.s was refined and standardised to minimize the nonpathological sources of variation. Pour wheat cultivars were tested for their reaction to 11 Septoria nodorum isolates. Two of the cultivars were crossed lor studies on the genetics of host resistance, using a single S. nodorum isolate tor inoculation; parental, F:, F; and F, populations were analysed.Interaction between wheat cultivars and S nodorum isolates was significant, but its variance component was Cjuue small compared with the main effects of cultivars and isolates. The inheritance of resistance was mainly additive, with low to moderate heritability, apparently controlled by 3 to 4 quantitative genes, with indications of gene lnteractiO'ns. LS and LP were highly correlated, suggesting pleiotropy for these two parameters of resistance, IE and DS (on mtact plants) \sTre moderately correlated to LS and LP (on detached leaves), apparently due to a partial pieiotropy or linkage.

No abstract

No abstract

The inheritance of resistanee in the wild wheat species Ae. speltoides L. to Septoria glume blotch {Septoria nodorum Berk.) was investigated. It was characterized by two parameters measured on detached leaves, namely lesion size (LS) and length of latent period (LP), and by the severity of the disease under field conditions (DS). The genetic analysis was based on the P, and F2 generations of a 4 X 4 diallel cross between four Ae. speltoides accessions showing differential resistance to the pathogen. The three parameters of resistance were highly correlated. Considerable heterosis for resistance was found for each of the parameters in most of the diallel combinations. The estimates of broad-sense heritability were moderately high (0.50 -LS, 0.60 -LP, 0.52 -DS), while the estimates of narrow-sense heritability were low (0.16 for LS, 0.20 for LP, 0.25 for DS). There were no indications for genic interaction. It is suggested that the resistanee is controlled by at least two genes with over-dominance of the alleles for higher resistance. Highly resistant Ae. speltoides accessions are a potential source of germplasm for improving the resistance of cultivated wheats to Septoria glume blotch. The possibility of using dominant alleles for resistance in hybrid cultivars is discussed.