High Reserve in δ-Tocopherol of Peganum harmala Seeds Oil and Antifungal Activity of Oil against Ten Plant Pathogenic Fungi.

This investigation included the chemical analysis of Peganum harmala (P. harmala) seed oil and its antifungal properties against 10 fungal species. Seed oils of six populations were analyzed using high performance liquid chromatography (HPLC) and gas chromatograph/mass spectrometry (GC-MS). The HPLC analysis indicated that P. harmala seed oil exhibited a very high level of tocopherol contents, with values in the range of 2385.66-2722.68 mg/100 g. The most abundant tocopherol isomer was δ-tocopherol (90.39%), followed by γ-tocopherol (8.08%) and α-tocopherol (1.14%). We discovered for the first time the presence of tocotrenols in P. harmala seed oils of the six populations studied. The GC-MS analyses revealed that linoleic acid was the main fatty acid (65.17%), followed by oleic acid (23.12%), palmitic acid (5.36%) and stearic acid (3.08%). We also studied the antifungal activity of seed oil of the Medenine (MD) population on ten fungal pathogens. The antifungal effects differed among pathogens and depended on oil concentrations. Seed oil of the MD population caused a significant decrease in mycelial growth of all fungi tested, with values ranging 31.50-82.11%, except for Alternaria sp., which showed no inhibition. The antifungal activity against the 10 selected fungi can be explained by the richness in tocols of the extracted oil and make P. harmala a promising crop for biological control. Furthermore, the importance of fatty acids and the wide geographic spread in Tunisia of this species make this crop a potential source of renewable energy.

Relationship between epistasis and aggressiveness in resistance of pepper (Capsicum annuum L. ) to Phytophthora nicotianae

This study evaluated the types of gene action governing the inheritance of resistance to Phytophthora nicotianae necrosis in populations derived from two crosses involving two susceptible (Beldi and Nabeul II) and one resistant (CM334) cultivars of pepper (Capsicum annuum L.). Populations, composed of Pr, Ps, F1,F2,BC1Pr, and BC1Ps generations, were inoculated with six P. nicotianae isolates. Generation means analysis indicated that an additive-dominance model was appropriate for P. nicotianae isolates PnKo1,PnKo2 and PnKr1, which showed low aggressiveness in the two crosses. For the more aggressive isolates PnBz1,PnBz2 and PnKr2, epistasis was an integral component of resistance in the two crosses. The presence of epistasis in the resistance of pepper to P. nicotianae was dependent on the level of aggressiveness of the isolates. Selection in pepper with less aggressive isolates was efficient, but not with more aggressive isolates; on the other hand, selection with more aggressive isolates was more stable. The minimum number of genes controlling resistance was estimated at up to 2.71. In the majority of cases, the additive variance was significant and greater than the environmental and dominance variance.

Epistasis and genotype-by-environment interaction of grain protein content in durum wheat

Parental, F1, F2, BC1 and BC2 generations of four crosses involving four cultivars of durum wheat (Triticum durum Desf.) were evaluated at two sites in Tunisia. A three-parameter model was found inadequate for all cases except crosses Chili x Cocorit 71 at site Sidi Thabet and Inrat 69 x Karim at both sites. In most cases a digenic epistatic model was sufficient to explain variation in generation means. Dominance effects (h) and additive x additive epistasis (i) (when significant) were more important than additive (d) effects and other epistatic components. Considering the genotype-by-environment interaction, the non-interactive model (m, d, h, e) was found adequate. Additive variance was higher than environmental variance in three crosses at both sites. The estimated values of narrow-sense heritability were dependent upon the cross and the sites and were 0 percent-85 percent. The results indicate that appropriate choice of environment and selection in later generations would increase grain protein content in durum wheat.