Communications in agricultural and applied biological sciences最新文献

Powdery mildew has emerged on triticale in the early 2000s in many locations, probably due to a host range expansion of the wheat formae speciales, Blumeria graminis f.sp. tritici. Many triticale cultivars are highly susceptible to powdery mildew, mainly in seedling stage, revealing a probably narrow genetic basis for powdery mildew resistance genes (Pm). Moreover, as Blumeria graminis is an obligate biotrophic fungus, it is very time consuming and difficult to maintain powdery mildew isolates for a non-specialized laboratory and populations can evolve. In order to identify wheat Pm genes efficient against natural populations of powdery mildew, wheat differential hosts and triticale seedlings were inoculated below susceptible triticale crop naturally contaminated by mildew, in several locations and several years. Symptoms on seedlings were measured after approximately two weeks of incubation in favorable fungus growth conditions. According to these data, we classified the Pm genes presents in our wheat differential hosts set in 3 classes: Pm already overcame by triticale powdery mildew, Pm having variable effects and Pm still efficient against triticale mildew. Data on triticale seedlings allowed us to identify some few triticale cultivars resistant to Blumeria graminis in seedling stage. We will try to identify Pm genes present in those cultivars next year by testing them with the characterized isolates of powdery mildew from Gent University. Nevertheless, interspecific crossing of wheat, resistant to powdery mildew in seedling stage, and rye have been initiated to introduce potentially interesting genes for resistance in triticale.

Wheat production in African countries is a major challenge for their development, considering their increasing consumption of wheat flour products. In the Democratic Republic of Congo, wheat and wheat-based products are the important imported food products although there is a potential for the cultivation of small grain cereals such as durum wheat, wheat and triticale. Trials done in Lubumbashi in the Katanga Province have shown that Septoria Leaf Blotch, Septoria Glume Blotch and Fusarium head blight are the main constraints to the efficient development of these cultures. Some varieties of Elite Spring Wheat, High Rainfall Wheat, Triticale and Durum Wheat from CIMMYT were followed during 4 growing seasons and agronomic characteristics and their levels of disease resistance were recorded. Correlations of agronomic characteristics with yields showed that in most cases, thousand kernel weight is the parameter that has the most influence on the yield level (p < 0.0001). The analysis of variance for all diseases showed that there were significant effects related to the year, the species and the interaction years x species. Triticale varieties seem to have a better resistance against the two forms of Septoria compared to wheat varieties but, they seem to be more sensitive to Fusarium Head Blight than wheat varieties. However, the Fusarium Head Blight has a rather low incidence in Lubumbashi.

The causal agent of Septoria tritici blotch, Mycosphaerella graminicola, is currently the most frequently reported pathogen on wheat crops worldwide. The populations of this fungus were previously studied in Tunisia using microsatellite markers, but no information is available on the mitochondrial (mt) genetic structure of the fungus in this country. The objective of this study was thus to examine the genetic diversity and population structure of M. graminicola in Tunisia using mtDNA markers. A set 105 monoconidial isolates of the pathogen were sampled in 2012 from four geographical locations in Tunisia (Bizerte, Béja, Kef and Jendouba) and assessed for diversity and polymorphism of three mtDNA sequences (Mg1: 388 bp, Mg2: 570 bp, Mg3: 929 bp) using PCR-RFLP-SSCP. Mg2 and Mg3 were the more polymorphic sequences with 12 and 9 observed alleles, respectively, while Mg1 was the less polymorphic one with only two alleles. Data analyses revealed a moderate mt gene diversity and a low mt haplotype diversity within the population. Further analyses showed a low population differentiation (G(ST) = 0.16) and a moderate gene flow (Nm = 2.61) within the population. Both UPGMA and Bayesian clustering methods confirmed this lack of mt genetic structuration. Our study allowed us to characterize for the first time mt genetic structure of M. graminicola in Tunisia and to report a moderate mt gene diversity, a low mt genotype diversity and a lack of mt genetic structure of the parasite in this country.

Soil herbicides are applied around crop emergence and kill germinating weeds in the surface layer of the soil. These herbicides play an important role in the chemical management of weeds in major arable crops. From an environmental point of view there is a clear need for smarter application of these chemicals. This paper presents research done in The Netherlands on Variable Rate Application (VRA) of soil herbicides by taking into account spatial variation of the soil. Herbicides adsorbed to soil parameters such as clay or organic matter are not available for herbicidal activity. Decision Support Rules (DSR) describe the relation between the soil parameter and herbicide dosage needed for effectively controlling weeds. Research methods such as greenhouse trials, models and on farm research to develop DSR are discussed and results are presented. Another important ingredient for VRA of soil herbicides is an accurate soil map of the field. Sampling and subsequent interpolation is costly. Soil scans measuring a proxy that is subsequently translated into soil properties such as clay fraction and soil organic matter content offer a quicker way to achieve such maps but validation is needed. DSR is applied to the soil map to get the variable dosage map. The farmer combines this map with the routing, spray volume and spray boom width in the Farm Management Information System (FMIS), resulting in a task file. This task file can subsequently be read by the board computer resulting in a VRA spray map. Reduction in soil herbicide depends on the DSR, the spatial variation and pattern of the soil, the spatial configuration of the routing and the technical advances of the spray equipment. Recently, within the framework the Programma Precisie Landbouw, first steps were made to test and implement this in practice. Currently, theory and practice of VRA of soil herbicides is developed within the research program IJKakker in close cooperation with pioneering farmers in The Netherlands.

S. nodorum is an economically important necrotrophic pathogen of cereals and grasses worldwide. In past several years appeared in literature quite a number of reports on existence of proteinaceous effectors produced by the fungus which induce necrosis in cereal host tissue. These host specific toxins induce necrosis by interacting with specific, dominant host genes. Up to the present research on S. nodorum toxin resistance was conducted only with wheat. Because wheat chromosomes are present in triticale genome, it is highly likely that mechanism used by S. nodorum for necrosis induction in triticale is the same as in wheat. Simple pilot experiment conducted in our laboratory, confirms that mechanism of necrosis induction via proteinaceous toxins is similar for both, wheat and triticale.

Winter hexaploid triticale lines and cultivars were identified by protein (storage and enzyme) and DNA markers. The locus of B-Amy-2 and Adh-1 were characterized by two alleles, Mdh-1 by 3 alleles, B-Amy-1 and Mdh-2 by 4 alleles and the locus controlling cathodic peroxidase isozymes, a-amylase and esterase by 6, 9 and 12 alleles, respectively. Intra-and intervarietal variation, for the enzyme coding loci, gliadin and glutenine were found. According to the isoenzyme analysis and the grain quality lines 28 and 49 (softness, high amylose content: 28.9-25.6, protein: 11,6- 11,2% and albumin 50-43%) could be marked as genotypes suitable for brewing and were characterized by allele b-Amy-1-b. Genotypes 1420 and 1434 are good for bread making with a hardness index between 52 and 62 and a W value (alveograph) of 110- 120. Allele a-Amy-b is positively correlated with amylose content (r = 0.601) and negatively with protein content (r - 0.490), the correlation of the presence of allele 1-Amy-1-b and amylose content is r- 0.549. Three breeding lines had 40% amylose content in grain and flour. Furthermore, the presence of allele Mdh-1 was associated with a high content of glutenin (r = 0.568), and controlled by genes localized in a single linkage group. Also statistically significant correlations for Mdh-1 -a and Prx-D containing albumin to total protein (%) could observed. It was illustrated that the peroxidase activity and free proline content can be used as resistance markers to abiotic factors.

The use of micro-dams in potato furrows is an interesting technology to reduce erosion and runoff in hilly areas. These phenomena are major sources of surface water contamination by nutrients and plant protection products (Gillijns et al., 2005). In 2011 Bayer CropScience set up a trial in collaboration with the Walloon Agricultural Research Centre (CRA-W) and ULg-Gembloux Agro-Bio Tech in Huldenberg (Belgium) to demonstrate this technique in potatoes. Micro-dams create barriers between furrows in order to encourage rainwater to infiltrate in the soil rather than to run off. The results from the trial over this year confirm that the application of micro-dams is effective in reducing erosion and runoff significantly. The total loss of plant protection products (PPP) to surface water is dramatically reduced and also strongly depends on the physic-chemical characteristics of the active ingredients. In addition, the technique tends to produce a higher yield of potato tubers as an effect of an optimised utilisation of the available rainwater and nutrients.

Algeria started working on triticale since the late seventies, it was first as a scientific curiosity (1974-1980), the production of this crop began in the early eighties and expanded well for a decade (10.000ha) then decreased for another decade due to lack of subsidies and serious interest from decision makers putting all their effort in wheat production which is the predominant crop in the country. Since the 1990s up to date, it is developing again mainly based on feed market requirements (20.500ha in 2001) and a better consideration by stakeholders. Triticale is now developed by the informal seed system. Triticale is grown in Algeria under a wide range of soil and climatic conditions, including dryland and marginal soils. Under high input and rainfall environments, the best triticale cultivars have comparable grain yield with wheat but slightly lower to barley. This advantage is larger under dry conditions. Our study was dealing with an evaluation of the progress made in time since their introduction and selection of triticale varieties. The study was conducted on twenty five varieties and advanced lines, selected in the different phases of triticale development, during the three last seasons (2009 - 2012) in two contrasting regions (semi arid and high input environment) showed very interesting results and a linear improvement in grain yield and its components, and also in the feeding quality traits. The improvement was apparent in both sites; although result data was higher in number in the high input environment, the increase rate was larger in the semi arid area of study. In the favorable area, grain yield increased from 2.94t/ha for the varieties developed in the early phase (late 1970s), to 3.98t/ha for the varieties released in the second phase (1990s) up to 5.45t/ha for the latest varieties developed in the 2000s. Grain yield increased in the dry area from 2.42t/ha to 4.92t/ha. The trend is almost the same for all yield components and even for forage quality traits.

The extracts of stem and seeds of Piper ribesioides (Piperaceae) were prepared in hexane, dichloromethane, ethyl acetate and ethanol and evaluated for their efficacy against 3-day-old adult brown plant hoppers, Nilaparvata lugens Stal under laboratory conditions. The treatment was given topically and results suggest the dose dependent response related to exposure time. The ethyl acetate extract was the best with an LC50 = 738 ppm-, 24 h post-treatment. There was substantial increase in activity (LC50 = 27.298 ppm) with the increase in duration of exposure. This trend was observed in all treatments that suggests the potential of Piper ribesioides as an insecticide for N. lugens as an alternative control.

Efficacy of hexane, dichloromethane, ethyl acetate, and methanol crude extracts of stems and leaves of Tudehagi triquetrum (Legumin: Papilionaceae) and seeds of Phaseolus lathyroides (Leguminiale: Papilionaceae) was examined for the antifeedant activity against third instars larvae of Helicoverpa armigera using leaf disc no-choice method in the range of 0 to 2% concentrations for 6 and 12 hours. The ethyl acetate extract from T. triquetrum was the most effective at 6 hours with FI50 of 0.5346%, while the hexane extract from P. lathyroides only exhibited 0.7228% FI50 value at 6 hours. The antifeedant effect appeared to be time and concentration dependent, i.e. feeding deterrence depleted with increased exposure. Moreover, it is obvious from our study that both extracts could be used under short-term applications in an integrated pest management strategy of pest control.