Potential of Hydroxamic Acids in Breeding for Aphid Resistance in Wheat

Abstract

Swedish wheats were analysed at the seedling stage for hydroxamic acids (Hx), a family of natural aphid resistance factors. Analysis comprised the historical development from old landraces to modern cultivars, and included cultivars in the Swedish National List of Cultivars for 1992–93. Spring and winter wheats contained similar average Hx concentrations, 2.12 ± 0.801 (n = 26) and 2.37 ± 0.816 (n = 49) mmol/kg fr. wt, respectively. Cultivars recommended for 1992–93 showed lower levels of Hx, 1.14 ± 0.574 (n = 7) and 1.97 ± 0.751 (n = 8), respectively. Breeding wheat for higher Hx levels as a means of obtaining increased aphid resistance is discussed.     

Clinico-chemical blood parameters in foals in the first two months of life]

Eighteen healthy foals were studied from birth until 2 months of age. Blood samples were obtained at the following times: presuckle, 30 hours, 1, 3, 5, 7 and 9 weeks of age. Changes in serum P, Mg, Ca, Na, K, Cl, iron, AP, ASAT, ALAT, GGT, GLDH, CK, lipase, urea, creatinine, cholesterol, triglyceride, uric acid, protein and fibrinogen and in plasma total solids were examined and the values compared to reference values of adult horses. There were characteristic age related changes in several parameters. Single measurements should be interpreted cautiously to allow for individual variations.     

A comparison of morphology,pathogenicity and restriction fragment patterns of mitochondrial DNA among isolates of Phytophthora porri Foister

Thirteen strains ofPhytophthora porri from five different hosts were compared with respect to their morphology, cardinal temperatures for growth, pathogenicity to leek and cabbage and restriction fragment patterns of mitochondrial DNA. Morphology of vegetative growth was rather similar in most isolates. Those characters which differed among isolates showed overlapping variability and could not be used to distinguish groups, with the exception of production of oogonia and sporangia and the antheridium type. Considerable differences were found in restriction patterns of mitochondrial DNA, isolates from the same host mostly showing identical patterns. Isolates from differentAllium species showed relatively similar restriction patterns if compared to the other isolates. Isolates fromBrassica oleracea proved to be a homogeneous group, quite different from the others with respect to restriction patterns, production of sporangia, production of oogonia, antheridium type and pathogenicity. One isolate, CBS 366.59, isolated from and pathogenic toA. porrum, deviated in many characters from the other isolates. It showed the restriction patterns ofPhytophthora nicotianae and also the high cardinal temperatures for growth typical for this species. The sporangia, however, were distinctly non-papillate and the majority of antheridia was of the paragynous type.     

Plant water stress and K starvation reduce absorption of foliar applied K by olive leaves

Three-month-old mist-rooted ‘Picual’ olive cuttings were transplanted into 2-l plastics pots containing perlite as substrate and fertigated with a complete nutrient solution containing 0.05, 0.1 or 2.5 mM KCl depending on the experiment. In the first experiment, plants were sprayed with RbCl (Rb⁺ is a K⁺ analog) at a rate of 4% at 63 days after transplanting (DAT). Foliar Rb⁺ uptake through leaves increased with K⁺ concentration in the nutrient solution, indicating that foliar Rb⁺ uptake was lower when plants were K⁺ deficient than when they were adequate. On the contrary, it was observed that translocation of Rb⁺ from leaves to other organs of the plant was higher under K⁺ deficiency conditions. In the second and third experiments, when differences appeared on shoot length due to K⁺ nutritional status (0.05 or 2.5 mM KCl) at 63 DAT, a group of plants were subjected to water stress during 7 weeks. On the other hand, another group of plants (control plants) did not receive any water stress treatment during the experiments. After this period of 7 weeks, all plants were sprayed with RbCl at 4%. Leaf K⁺ concentration diminished in water-stressed plants independently of plants nutritional status. Foliar Rb⁺ uptake through leaves was restricted by water stress either in plants with low K⁺ (0.05 mM KCl) or plants with high K⁺ (2.5 mM KCl). Translocation of Rb⁺ from leaves was greater under water stress conditions in both K⁺ nutritional statuses. In conclusion, the results obtained could explain the irregular response in olive trees to foliar K⁺ sprays, particularly, when they grow in rainfed orchards.