The Molecular Line Opacity of MgH in Cool Stellar Atmospheres

A new, complete, theoretical rotational and vibrational line list for the A-X electronic transition in MgH is presented. The list includes transition energies and oscillator strengths for all possible allowed transitions and was computed using the best available theoretical potential energies and dipole transition moment function with the former adjusted to account for experimental data. The A-X line list, as well as new line lists for the B'-X and the X-X (pure rovibrational) transitions, were included in comprehensive stellar atmosphere models for M, L, and T dwarfs and solar-type stars. The resulting spectra, when compared to models lacking MgH, show that MgH provides significant opacity in the visible between 4400 and 5600 Angstrom. Further, comparison of the spectra obtained with the current line list to spectra obtained using the line list constructed by Kurucz (1993) show that the Kurucz list significantly overestimates the opacity due to MgH particularly for the bands near 5150 and 4800 Angstrom with the discrepancy increasing with decreasing effective temperature.Comment: 10 pages, 4 figures, 3 table

A worldwide perspective on the management and control of Dothistroma needle blight

Dothistroma needle blight (DNB) caused by Dothistroma septosporum and Dothistroma pini is a damaging disease of pine in many countries. The disease led to the abandonment of planting susceptible Pinus species in parts of Africa, Asia, Australasia, Europe and North America. Although the disease can be effectively controlled using copper fungicides, this chemical is only routinely applied in forests in New Zealand and Australia. Other management tactics aimed at making conditions less favourable for disease development, such as thinning or pruning, may be effective on some, but not all, sites. Disease avoidance, by planting non-susceptible species, is the most common form of management in Europe, along with deployment of hosts with strong disease resistance. Although D. septosporum is present almost everywhere Pinus is grown, it is important that an effort is maintained to exclude introductions of new haplotypes that could increase virulence or enable host resistance to be overcome. A global strategy to exclude new introductions of Dothistroma and other damaging forest pathogens, facilitated by collaborative programmes and legislation, is needed.This study was partially supported by the EU COST Action FP1102 DIAROD (Determining Invasiveness and Risk of Dothistroma, http:// www.cost.eu/COST_Actions/fps/FP1102)http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1439-03292017-10-31hb2017Forestry and Agricultural Biotechnology Institute (FABI)GeneticsPlant Scienc

Horizontal transmission of hypoviruses between vegetative compatibility types of Cryphonectria parasitica in Macedonia

Biological control of chestnut blight with hypovirulence depends on the successful transmission of hypoviruses between individuals of the chestnut blight fungus, Cryphonectria parasitica. Vegetative incompatibility inhibits horizontal virus transmission, but not completely. In an effort to assess the potential for the spread of hypoviruses in the Republic of Macedonia, we studied the transmission of Cryphonectria hypovirus 1 (CHV-1) among the five observed vegetative compatibility (vc) types of C. parasitica. One fungal isolate of each vc type was infected with CHV-1 and was paired in vitro with isolates of all other vc types for a total of 20 combinations of virus donors and recipients, and 250 replicate trials per combination. Virus transmission was scored after 7 days as successful if the recipient isolate took on an unpigmented culture phenotype typical of virus infection. Transmission occurred at high frequencies between some pairs of vc types, but in <1% of the trials for 10 of the 20 combinations of donors and recipients. Asymmetric transmission was observed between some vc types that had different alleles at vegetative incompatibility loci vic1 or vic7; i.e., transmission occurred at high frequencies in one direction, but very low frequencies between the same pair of isolates in the opposite direction. The expected virus transmission, calculated as the average transmission predicted for any two randomly chosen individuals from a population, was highly negatively correlated to vc type diversity. Results for isolates of C. parasitica from Macedonia were similar to those from Italy, but less transmission was generally observed. Differences in genetic background effects on transmission may vary among different populations even when isolates differ by the same vic alleles

Clonal population structure of the chestnut blight fungus in expanding ranges in southeastern Europe

Expanding populations are often less genetically diverse at their margins than at the centre of a species\u2019 range. Established, older populations of the chestnut blight fungus, Cryphonectria parasitica, are more variable for vegetative compatibility (vc) types than in expanding populations in southeastern Europe where C. parasitica has colonized relatively recently. To test whether vc types represent clones, we genotyped 373 isolates of C. parasitica from southern Italy, Romania, Bulgaria, Macedonia, Greece and Turkey using 11 sequencecharacterized amplified region (SCAR) markers. Ten SCAR loci and six vegetative incompatibility (vic) loci were polymorphic in these samples. These populations are clonal by all criteria tested: (i) among 373 isolates, we found only eight multilocus haplotypes, and the same haplotypes were found in multiple countries, sometimes separated in time by as much as 12 years; (ii) the number of haplotypes observed was significantly less than expected under random mating; (iii) populations are in linkage disequilibrium; (iv) the two sets of independent markers, SCARs and vc types, are highly correlated; and (v) sexual structures of C. parasitica were found only in Bulgaria and Romania. One mating type (MAT-1) was found in 98% of the isolates sampled. In contrast, a population in northern Italy, in the central part of the range in Europe, had 12 multilocus haplotypes among 19 isolates. The spread of a few clones could be the result either of founder effect and restricted migration, or these clones have greater fitness than others and spread because they are better adapted to conditions in southeastern Europe