Mildew-resistant mutants induced in North American two- and six-rowed malting barley cultivars

Mildew-resistant mutants were induced with sodium azide in three North American malting barley cultivars, two in the six-rowed Ursula (URS1 and URS2), one in the six-rowed Gertrud (GER1), and one in the two-rowed Prudentia (PRU1). Two of the mutants, URS1 and PRU1, showed complete resistance and were shown to have two new alleles at the mlo locus; these were designated, respectively, mlo31 and mlo32. Mutant URS2, showing partial resistance, was inherited as a dominant gene, but was not an allele at the Mla locus. The mean yield of each mutant was higher than that of its parental line, but yield levels varied across environments, although this was independent of the severity of the mildew attack. Other reasons, for example, the severity of the necrotic lesions in the mutants, may account for yield variations. The malting quality of the GER1 mutant proved similar to that of Gertrud, but both URS1 and URS2 showed lower malt extract than Ursula. This lower extract might be due to the smaller grain size of the mutants that could, in turn, result from necrotic lesions in the leaves, as implied by the effects on grain yield.Communicated by G. Wenzel     

Population structure and cryptic genetic variation in the mango fruit fly,Ceratitis cosyra (Diptera,Tephritidae)

The fruit fly Ceratitis cosyra is an important agricultural pest negatively affecting the mango crop production throughout Africa and also feeding on a variety of other wild and cultivated hosts. The occurrence of deeply divergent haplotypes, as well as extensive morphological variability, previously suggested possible cryptic speciation within Ceratitis cosyra. Here we provide the first large-scale characterisation of the population structure of Ceratitis cosyra with the main objective of verifying cryptic genetic variation. A total of 348 specimens from 13 populations were genotyped at 16 polymorphic microsatellite loci. Hardy-Weinberg equilibrium (HWE) deviations were observed in 40.4% of locus-population combinations and suggested the occurrence of genetic substructuring within populations. Discriminant Analysis of Principal Components (DAPC) showed genetic divergence between the vast majority of vouchers from Burundi and Tanzania (plus a few outliers from other African countries) and all other specimens sampled. Individual Bayesian assignments confirmed the existence of two main genotypic groups also occurring in sympatry. These data provided further support to the hypothesis that Ceratitis cosyra might include cryptic species. However, additional integrative taxonomy, possibly combining morphological, ecological and physiological approaches, is required to provide the necessary experimental support to this model.     

Chemoenzymatic synthesis of modified maltooligosaccharides from cyclodextrin derivatives.

Methyl and p-nitrophenyl alpha-maltooligosaccharides with a 3,6-anhydro ring on the fourth glucosyl residue, starting from the reducing end, were prepared. Enzymatic coupling catalyzed by CGTase, between 3A,6A-anhydrocyclomaltohexaose and methyl or p-nitrophenyl alpha-D-glucosides led to maltohepatosides. When miglitol, a nojirimycin analogue was used, maltooligosaccharides with miglitol at the reducing end were also obtained. After glucoamylase digestion, maltopentaosides with a 3,6-anhydro glucose as antepenultimate unit were produced in good yield. The same methyl maltopentaoside was also obtained when 3A,6A-anhydrocyclomaltoheptaose was incubated with methyl alpha-D-glucoside and CGTase, glucoamylase, glucose oxidase and catalase. These results provided new information about the specificity of the subsites of CGTase.     

Péétration et migration d'éléments minéraux appliqués sur les feuilles en présence de diméthylsulfoxyde

The aim of this work was to determine the effect of DMSO on the uptake and translocation of potassium and phosphorus applied on corn and bean leaves. Radioactive isotopes ⁴²K and ³²P were used in most of the experiments. The results obtained reveal that DMSO (0.5% and above) increases the penetration of potassium applied as nitrate or chloride, but seems to have no effect on the penetration of ³²P when applied as different phosphates.