Differentiation of infectious laryngotracheitis virus isolates by restriction fragment length polymorphic analysis of polymerase chain reaction products amplified from multiple genes

Infectious laryngotracheitis (ILT) has been identified in most countries around the world and remains a threat to the intensive poultry industry. Outbreaks of mild to moderate forms of ILT are common in commercial layer flocks, while sporadic outbreaks of ILT in broiler flocks have also been recognized as an emerging problem in several countries. Examination of viral isolates using restriction fragment length polymorphism of polymerase chain reaction (PCR-RFLP) from individual ILTV genes has suggested that some of these outbreaks were caused by vaccine strains. In this study, PCR-RFLP of a number of ILTV genes/genomic regions including gE, gG, TK, ICP4, ICP18.5, and open reading frame (ORF) B-TK was used to examine a number of historical and contemporary Australian ILTV isolates and vaccine strains. PCR-RFLP of gE using restriction endonuclease EaeI failed to distinguish between any of the isolates including the vaccine strains. PCR-RFLP of gG, TK, and ORFB-TK using restriction endonucleases MspI and FokI, respectively, divided all the isolates into two groups. PCR-RFLP of ICP18.5 and ICP4 using restriction endonuclease HaeIII separated the isolates into three different groups with some field isolates only able to be distinguished from vaccine strains by PCR-RFLP of ICP18.5. A combination of groupings including gG, TK, ICP4, ICP18.5, and ORFB-TK PCR-RFLP classified the ILTV isolates under investigation into five different groups with most isolates distinguishable from vaccine strains. Results from this study reveal that to achieve reliable identification of strains of ILTV, the examination of multiple gene regions will be required, and that most of the recent ILT outbreaks in Australia are not being caused by vaccine strains.     

Runoff and sediment concentration of different parts of a road in Hyrcanian forests

Road prisms, such as cutslopes, fillslopes and road surfaces, can be important contributors of sediment to streams in forested watersheds. In this study rainfall simulations were carried out on cutslopes, fillslopes, road surfaces and forest grounds in hardwood forests of Lolet and Lat Talar, Iran. Water at intensity of 32.4 mm·h 1 was sprayed from a nozzle onto a square area of 0.48 m 2 . Runoff was collected by water gauge every 4 min and then runoff and sediment parameters were measured in each plot. Results indicated that on road surfaces, the runoff coefficient was 63.28%. On the cutslopes and fillslopes, the runoff coefficients were 35.14% and 10.23%, respectively. On the forest ground as a control, the runoff coefficient was 5.90%. Runoff volume was 2.73 mL·s-1 on the road surfaces and 1.52 mL·s-1 on cutslopes. On fillslopes the runoff volume was 0.44 mL·s-1 and on the forest ground 0.25 mL·s-1 . The greatest rate of soil loss was found on the cutslope (280.79 g·m-2·h-1). The total soil loss from the cutslopes was two times higher than that from the road surfaces and six times higher than that from the fillslopes. We conclude that cutslopes can be considered the main source of sediments in our study sites, but the function of road surface as a source of runoff generation is more important.     

Leaf macro- and micro-morphological altitudinal variability of Carpinus betulus in the Hyrcanian forest (Iran)

We investigated the altitudinal variation of Carpinus betulus L. in the Hyrcanian forest using leaf macro-morphological and micro-morphological traits. We collected a total of 1600 leaves from two locations. In each location, we sampled six populations along an altitudinal gradient ranging from 100 m to 1,150 m. We found that trees in the higher elevations have smaller leaf lamina than those in the lower elevations. In contrast, leaf mass per area was high at low altitudes and increased newly at the higher ones. Stomatal dimension was negatively correlated with elevation, while stomatal density was positively correlated with elevation. We also found that two transects showed the same plasticity trend. Leaf area showed the highest plasticity, while the number of veins showed the lowest plasticity. This study shows that altitude, and related temperature and rainfall, represents an important driving force in Carpinus betulus leaf morphological variation. Moreover, our results suggest that leaf area, leaf mass per area and stomatal density could influence the species responses to different ecological conditions.     

Response to selection for improved nitrogen fixation in common bean (<Emphasis Type="Italic">Phaseolus vulgaris</Emphasis> L.)

Breeding for high symbiotic nitrogen (N) fixation (SNF) in common bean (Phaseolus vulgaris L.) is expected to contribute to reduced application of chemical fertilizers in cropping systems involving common bean. The magnitude of variation and the genetic and phenotypic correlation among seed yield, SNF, estimated as the percentage of nitrogen derived from atmosphere, and related traits were studied in a population of 140 F₄-derived F₅ recombinant inbred lines, developed from a cross between low- and high-SNF bean genotypes ‘Sanilac’ and ‘Mist’, respectively. The experiment was conducted in a total of five location-years in Ontario, Canada, from 2011 to 2013. These location-years were grouped into stress- and optimum moisture test sites, based on the total precipitation during the growing season. In each test site two nitrogen supply management strategies, SNF-dependent and N fertilizer-dependent, were simulated separately in the field by inoculating the seed with a commercial Rhizobium leguminosarum bv. phaseoli and by application of N fertilizers at 100 kg ha^?1, respectively. The genetic variation was significant for seed yield, SNF and related traits. The heritability of the traits ranged from 14 to 71% and 4 to 25% in optimum moisture and in stress environments, respectively. No significant correlation between SNF and seed yield indicated that selection for high SNF does not necessarily lead to greater seed yield and that selection for both traits should be performed simultaneously.     

Estimation of salt tolerance in Andrographis paniculata accessions using multiple regression model

The complexity and polygenic nature of the salt tolerance trait in plants needs to develop a multiple indicator in the screening process. The mentioned issue led us to carry out an experiment to identify tolerant genotypes through multiple parameters in Andrographis paniculata. For this purpose, the 40-days seedlings were grown in different salinity levels (control, 4, 8, 12 and 16?dS?m^?1) on Hoagland??s medium. The results indicated that salinity had a significant effect on the morphological, physiological and biochemical traits. All measured morphological traits, and chlorophyll, K⁺ and Ca²⁺ content were significantly decreased with increasing salinity levels, while proline and Na⁺ content increased. The present exploration revealed that, salt tolerance index (STI), using the multiple regression model, demonstrated a more stable trend than the single variable assay (total dry weight). Furthermore, STI based on multiple regression analysis gives an accurate definition of salt-tolerant individuals. Under salt stress, tolerant accessions had high STI and produced higher proline, K⁺ and Ca²⁺, and lower Na⁺ content than sensitive accessions. Cluster analysis based on related traits to STI, indicated high similarity in each group. These outcomes can be utilized to evaluate the salt tolerance threshold in the species and may have a great advantage over conventional methods. Probably, our upshots can be applied in the next breeding programs to develop salt-tolerant varieties.     

Interaction of common bacterial blight quantitative trait loci in a resistant inter‐cross population of common bean

Common bacterial blight (CBB), caused by Xanthomonas axonopodis pv. phaseoli, is an important disease of common bean (Phaseolus vulgaris L.). Genetic resistance is the most economically efficient, environmentally friendly and socially acceptable approach to control plant diseases including CBB. To examine the main and interaction effects of the previously identified CBB resistance quantitative trait loci (QTL) associated with markers BC420 (B) on Pv06, SAP6 (S) on Pv10 and PVctt001 (P) on Pv04, in presence of the major QTL associated with the marker SU91 (S_u) on Pv08, a resistant F_4:5 recombinant inbred line population of the reciprocal crosses between OAC Rex (bb/ss/PP/S_uS_u) and HR45 (BB/SS/pp/S_uS_u) was evaluated under artificial field inoculation in disease nurseries in 2009 and 2010. While, in presence of the CBB QTL on Pv08, the QTL on Pv06 of HR45 accounted for 37–46% of phenotypic variation in the field, the effect of QTL on Pv04 and Pv10 were not significant under field conditions, even in the absence of the Pv06 QTL. Broad‐sense heritability estimates of CBB resistance and the QTL associated with BC420 were high for CBB severity and the area under the disease progress curve, promoting the continued efforts in pyramiding the QTL on Pv06 and Pv08 in common background, which provide high levels of resistance.     

Effect of canopy gap size and ecological factors on species diversity and beech seedlings in managed beech stands in Hyrcanian forests

We studied the species diversity of the herb layer and ecological factors in harvest-created gaps in beech stands under a single-tree selection system in Northern Iran. To determine diversity, the number of beech seedlings, and other ecological factors, 16 gaps were selected and subplots of 5 m2 were positioned at the centre and at the cardinal points of each gap. Species richness and Simpson diversity index increased with increasing gap area as did numbers of seedlings. With increasing humus layer thickness, species richness declined but the Hill evenness index increased. Species richness increased with increasing light availability. There was no relationship between crown radii of beech trees and diversity indices. Correlations between environmental factors and numbers ofindividuals of some species in the herb layer were not significant except in a few cases. The results help explain the effects of man-made gaps on the dynamics of managed beech stands and this benefits evaluation of silvicultural operating plans.     

Genetic analysis of yield and fruit traits in cantaloupe cultivars

The purpose of this research was to evaluate the combining ability of six local Iranian and one imported cantaloupe cultivar. Heritability of traits was estimated using a half‐diallel mating design. Seven parents and their crosses were evaluated in 2013 and 2014. The greatest general combining ability (GCA) for yield and fruit number was for “Rish‐baba” (0.53 kg/plant and 0.3, respectively). The cultivar “Ananasi” had the highest GCA for fruit weight and soluble solids content (SSC) (0.088 kg and 1.4, respectively). “Ananasi” presented the highest GCA values for fruit firmness, chlorophyll a and b and carotenoid content, as well as the highest total chlorophyll content. The cross Garmak × Rish‐baba showed the highest specific combining ability (SCA) for yield with heterosis value of 99%. High heritability estimates for SSC (0.52), flesh thickness (0.61) and concentration of chlorophyll a (0.7) were obtained. Although there were significant SCAs for yield, the parents are suggested to be improved prior to hybrid development. The parent “Ananasi” appears to be a suitable donor in breeding programmes.