EFFICIENT SCREENING PROCEDURE FOR BLACK SIGATOKA DISEASE OF BANANA

Current methods for screening for reaction of Mycosphaerella fijiensis are mostly field based and subject to variability caused by weather conditions. The objective of this study was to develop an efficient screening procedure for black sigatoka disease in order to provide a reliable controlled environment screening method. A fragmented mycelia-based infection system was developed using weighed mycelia suspensions, in 0.18% water agar. Consistent and repeatable black sigatoka infection was achieved in cv. Gross Michel as a reference susceptible cultivar. The infection system developed was used to validate screenhouse reaction of banana genotypes to M. fijiensis. Three East African highland genotypes (AAA-EA), one plantain genotype (ABB), two dessert (AAB and AAA) and one hybrid genotype (AAAA) were tested. Inoculum of M. fijiensis was adjusted to 15 mg ml-1 fragmented mycelium and applied to the abaxial surfaces of the first two open leaves. Plants were evaluated for 6 weeks post inoculation (PI). Significant differences in the response of the different genotypes, to M. fijiensis infection were observed at 3, 4, 5 and 6 weeks PI. All East African highland and dessert genotypes were susceptible. M9 hybrid and Psang awak (ABB) expressed resistance, characterised by high disease incubation period and slow rate of symptom development, with Psanag awak being the most resistant. Artificial inoculation of in vitro plants with weighed fragmented mycelial suspension, was practicable for determining resistance to M. fijiensis. This is the first report demonstrating that use of weighed fragmented mycelial inoculum spread over the entire leaf surface, can be used to quantitatively assess reaction of banana genotypes to M. fijiensis under screenhouse conditions.Les m\ue9thodes actuelles de d\ue9pistage de Mycosphaerella fijiensis sont essentiellement bas\ue9es sur des \ue9valuations dans le champ et sont souvent sujets \ue0 des variabilit\ue9s climatiques. L\u2019objectif de cette \ue9tude \ue9tait de d\ue9velopper une proc\ue9dure efficace de d\ue9pistage de la maladie foliaire du bananier Sigatoka dans le but de proposer une m\ue9thode de d\ue9pistage non influenc\ue9e par l\u2019environnement. Un syst\ue8me d\u2019infection a \ue9t\ue9 d\ue9velopp\ue9 en se servant de myc\ue9lium en suspension dans 0,18% de solution agar. Des infections consistantes et r\ue9p\ue9t\ue9es ont \ue9t\ue9 r\ue9alis\ue9es in cv. La vari\ue9t\ue9 Gross Michel a \ue9t\ue9 utilis\ue9e comme r\ue9f\ue9rence susceptible. Le syst\ue8me d\u2019infection d\ue9velopp\ue9 a \ue9t\ue9 utilis\ue9 pour valider la r\ue9action des accessions de bananiers en serre \ue0 M. fijiensis. Trois g\ue9notypes de bananiers adapt\ue9s aux hautes altitudes en Afrique de l\u2019Est (AAA-EA), un g\ue9notype de type plantain (ABB), deux d\ue9serts (AAB and AAA) et un hybride (AAAA) ont \ue9t\ue9 test\ue9s. Des inocula de M. fijiensis ont \ue9t\ue9 doses \ue0 15 mg ml-1 et appliqu\ue9s sur la face dorsale des deux premi\ue8res feuilles ouvertes. Les plants ont \ue9t\ue9 \ue9valu\ue9s pendant 6 semaines apr\ue8s inoculation (PI). Des diff\ue9rences significatives ont \ue9t\ue9 observ\ue9es dans les r\ue9ponses des g\ue9notypes \ue0 l\u2019infection \ue0 diff\ue9rents stages apr\ue8s inoculation (3, 4,5 et 6 semaines) de M. fijiensis. Tous les g\ue9notypes de haute altitude et les d\ue9serts ont \ue9t\ue9 r\ue9v\ue9l\ue9s susceptibles. L\u2019hybride M9 et Psang awak (ABB) se sont montr\ue9s r\ue9sistants, ils sont caract\ue9ris\ue9s par une longue p\ue9riode d\u2019incubation et un taux bas de d\ue9veloppement de sympt\uf4mes, Psanag awak s\u2019est r\ue9v\ue9l\ue9 le plus r\ue9sistant. L\u2019inoculation artificielle in vitro des plants avec des suspensions de fragments myc\ue9liens, a \ue9t\ue9 pratique dans la d\ue9termination de la r\ue9sistance \ue0 M. fijiensis. Ceci est le premier r\ue9sultat d\u2019\ue9tude scientifique ayant d\ue9montr\ue9 que cette technique peut \ueatre utilis\ue9e pour l\u2019\ue9valuation de la r\ue9action des g\ue9notypes de bananiers \ue0 l\u2019infection de M. fijiensis dans des conditions d\u2019exp\ue9riences en serre.

Thermodynamics of RNA structures by Wang–Landau sampling

Motivation: Thermodynamics-based dynamic programming RNA secondary structure algorithms have been of immense importance in molecular biology, where applications range from the detection of novel selenoproteins using expressed sequence tag (EST) data, to the determination of microRNA genes and their targets. Dynamic programming algorithms have been developed to compute the minimum free energy secondary structure and partition function of a given RNA sequence, the minimum free-energy and partition function for the hybridization of two RNA molecules, etc. However, the applicability of dynamic programming methods depends on disallowing certain types of interactions (pseudoknots, zig-zags, etc.), as their inclusion renders structure prediction an nondeterministic polynomial time (NP)-complete problem. Nevertheless, such interactions have been observed in X-ray structures

Lead concentrations in blood from incubating common eiders (Somateria mollissima) in the Baltic Sea

Here we investigate if lead may be a contributing factor to the observed population decline in a Baltic colony of incubating eiders (Somateria mollissima). Body mass and blood samples were obtained from 50 incubating female eiders at the Baltic breeding colony on Christianso during spring 2017 (n = 27) and 2018 (n = 23). All the females were sampled twice during early (day 4) and late (day 24) incubation. The full blood was analysed for lead to investigate if the concentrations exceeded toxic thresholds or changed over the incubation period due to remobilisation from bones and liver tissue. Body mass, hatch date and number of chicks were also analysed with respect to lead concentrations. The body mass (mean +/- SD g) increased significantly in the order: day 24 in 2018 (1561 +/- 154 g) < day 24 in 2017 (1618 +/- 156 g) < day 4 in 2018 (2183 +/- 140 g) < day 4 in 2017 (2359 +/- 167 g) (all p < 0.001). The lead concentrations increased significantly in the opposite order i.e. day 4 in 2017 (41.7 +/- 67.1 mu g/L) < day 24 in 2017 (55.4 +/- 66.8 mu g/L) < day 4 in 2018 (177 +/- 196 mu g/L) < day 24 in 2018 (258 +/- 243) (all p < 0.001). From day 4 to 24, the eider females had a 1.33-fold increase in blood lead concentrations in 2017 and a 1.46-fold increase in 2018. Three of the birds (13%) sampled in 2018 had lead concentrations that exceeded concentrations of clinical poisoning (500 mu g/L) and eleven (48%) had concentrations that exceeded the threshold for subclinical poisoning (200 mu g/L). In 2017, none of the birds exceeded the high toxic threshold of clinical poisoning while only one (4%) exceeded the lower threshold for subclinical poisoning. Three of the birds (6%) sampled in 2018 had lead concentrations that exceeded those of clinical poisoning while 12 birds (24%) resampled in both years exceeded the threshold for subclinical poisoning. In addition, lead concentrations and body mass on day 4 affected hatch date positively in 2018 (both p < 0.03) but not in 2017. These results show that bioavailable lead in bone and liver tissue pose a threat to the health of about 25% of the incubating eiders sampled. This is particularly critical because eiders are largely capital breeding which means that incubating eiders are in an energetically stressed state. The origin of lead in incubating eiders in the Christianso colony is unknown and it remains an urgent priority to establish the source, prevalence and mechanism for uptake. The increase in lead from day 4 to day 24 is due to bone and liver remobilization; however, the additional lead source(s) on the breeding grounds needs to be identified. Continued investigations should determine the origin, uptake mechanisms and degree of exposure to lead for individual birds. Such research should include necropsies, x-ray, lead isotope and stable C and N isotope analyses to find the lead sources(s) in the course of the annual cycle and how it may affect the population dynamics of the Christianso colony which reflects the ecology of the Baltic eiders being suitable for biomonitoring the overall flyway

Incubation Behaviour of Common Eiders Somateria Mollissima in the Central Baltic: Nest Attendance and Loss in Body Mass

Here we present the recording of body mass change and weight loss during incubation in a Common Eider Somateria mollissima colony at Christiansø in the Central Baltic (55°19'N 15°11'E). The study was conducted during April and May 2015 and a total number of four birds were followed (two were lost due to predation and three due to power outages). Body mass and nesting behaviour was recorded electronically over a period of 26-27 days using automatic poultry scales and a surveillance video camera. During incubation, the eiders underwent a 28-37% loss in body mass and left the nest on average 13 times (range: 7-17 times) for a period of 7-70 min. In general, birds with high initial body mass left their nest for a shorter total time than birds with lower initial body mass. The recorded daily changes in body mass indicate that the eiders foraged during the incubation period, not just leaving the nest for rehydration or in response to disturbance, which improve our current understanding of eider incubation behaviour. Such information is important to fully understanding of eider breeding biology in order to better conserve and manage the species during its breeding seasons where individual birds undergo extreme stress that may affect reproductive outcome and adult survival

Northern Bullfinch Pyrrhula p. pyrrhula irruptive behaviour linked to rowanberry Sorbus aucuparia abundance

Autumn Northern Bullfinch abundance at bird observatories around the Baltic Sea confirmed periodic irruptive behaviour outside of its normal wintering range, but age-ratio data suggested dispersal was not linked to reproductive success. Rowan berries are important food of Fennoscandian Northern Bullfinches and show synchronised masting in annual fruit production over large spatial scales. Norwegian and Finnish annual berry abundance indices from 1972-2004 were used to test the hypothesis that poor rowanberry production in normal wintering areas was responsible for efflux of birds to other areas. Annual Finnish wintering bird surveys and catches at local bird observatories correlated with rowanberry abundance indices, supporting the prediction that highest Bullfinch abundance would occur in normal wintering areas in years with heavy rowanberry crops. Northern Bullfinch autumn abundance at Danish and Swedish bird observatories (outside the normal winter range) showed inverse correlations with Norwegian rowanberry crops, supporting the prediction of highest irruptions in years of lowest rowanberry abundance from the normal wintering range. These data suggest that at large spatial scales, berry masting can have profound effects on the annual distribution and migratory behaviour of birds consuming the crop