Basilaphelenchus gorganensis n. sp. (Aphelenchoidea,Tylaphelenchinae) from wood from northern Iran

Basilaphelenchus gorganensis n. sp. is described and illustrated from wood and bark of a dead tree from northern Iran. The new species is characterized by female body length (415–559 µm), three‐lined lateral fields, a sclerotized cephalic vestibule and cephalic framework, thin stylet with three elongate backwardly directed knobs, small spherical to oval metacorpus, with small and posteriorly located valve, simple vulva without any flap apparatus, 59‐ to 79‐µm‐long post‐vulval uterine sac, functional rectum and anus and dorsally convex, ventrally concave, usually ventrally bent conical female tail with a sharp tip. Males are common, apparently functional and characterized by well‐curved spicules, three pairs of small caudal papillae and no bursa at tail tip. Molecular phylogenetic inferences using partial sequences of small and large subunit ribosomal RNA genes (SSU and LSU rDNA) from different isolates of the new species revealed it differs from currently sequenced species and belongs to the Tylaphelenchinae clade.     

Brenneria spp. and Rahnella victoriana associated with acute oak decline symptoms on oak and hornbeam in Iran

Decline diseases of forest trees are complex syndromes not attributable to single causal factors. In Iran, symptoms of decline disease have been observed in a number of native forest species including Quercus castaneifolia (chestnut‐leaved oak), Q. brantii (Persian oak) and Carpinus betulus (hornbeam). The symptoms are prevalent in the northern forests and the Zagros mountain forests. There are parallels between the disease in Iran and acute oak decline (AOD) reported in the UK, specifically the presence of weeping cankers, which have been attributed to a polybacterial complex wherein Brenneria goodwinii is considered a key necrogen. Based on the AOD symptomatology, and as a first step towards discovering potential causal agents of the stem weeping symptoms of affected trees in Iran, necrotic tissues were tested primarily for the presence of B. goodwinii. Symptomatic Q. castaneifolia and C. betulus from the Mazandaran Province and symptomatic Q. brantii from Kohgiluyeh and Boyerahmad Province were sampled. Isolation and culture on a selective medium yielded uniform bacterial colonies. Isolates were characterized using phenotypic and genotypic (DNA sequencing) tests. The isolates were phenotypically identical to members of Pectobacteriaceae and Yersiniaceae, specifically Brenneria and Rahnella spp. The nucleotide sequences of the 16S rRNA and housekeeping genes gyrB, infB and atpD (MLSA) amplified via PCR demonstrated that the isolates from the trees in Iran were indeed B. goodwinii, B. roseae subsp. roseae, Rahnella victoriana and an unknown species of Brenneria. Most bacteria isolated from non‐symptomatic trees were Gram‐positive, and Pseudomonas spp. were dominant, but bacterial species isolated from the diseased trees were not detected in healthy trees. Hypersensitivity response tests were positive, but inoculation on saplings was more variable with internal necrosis developing only once in the test period. Therefore, further testing is required. This is the first report of the incidence of B. goodwinii, B. roseae subsp. roseae, R. victoriana and Brenneria sp. associated with acute oak decline‐like symptoms on Q. castaneifolia, Q. brantii and C. betulus across the western forests of Iran and in the world.     

Mechanisms and metabolomics of the host–pathogen interactions between Chestnut (Castanea species) and Chestnut blight (Cryphonectria parasitica)

Chestnut blight is a stem‐girdling disease of Castanea caused by the fungal pathogen Cryphonectria parasitica. Chestnut blight affects all Castanea species to some degree. In Asian species, chestnut blight is a commercially relevant disease which primarily affects nut production. In American and European species, chestnut blight has caused significant declines in wild populations and continues to negatively affect nut production in the European chestnut (C. sativa). Despite the profound effect of this disease in the Castanea genus, very little is known concerning the factors involved in the host–pathogen interaction between C. parasitica and its Castanea hosts. This review summarizes information on known mechanisms and metabolites involved in the host–pathogen interaction and contributes original information on the pathogen in relation to susceptible and putatively resistant genotypes with a view to furthering research that will promote a better understanding of this devastating disease and enable its control.     

Heterobasidion abietinum on Abies species in western Turkey

Forty‐five basidiocarp specimens of Heterobasidion were collected from native Abies species in three locations in western Turkey: A. nordmanniana ssp. bornmülleriana in Bolu province, A. nordmanniana ssp. equi‐trojani in Balikesir province and A. cilicica in Antalya province. Pure cultures were isolated from the basidiocarps and identified to the species level with the aid of mating tests. All the specimens proved to belong to the species Heterobasidion abietinum. This root rot fungus is common in the forests investigated and appears to be relatively virulent on Abies in Turkey. This is the first report of H. abietinum outside Europe.     

Characterization and application of recombinant β-glucosidase (BglH) from <Emphasis Type="Italic">Bacillus licheniformis</Emphasis> KCTC 1918

β-Glucosidase (β-1,4-D-glucoside glucohydrolase: EC.3.2.1.21) catalyzes the hydrolysis of β-glucosidic bonds between saccharides and aryl or alkyl groups. A gene encoding β-glucosidase from Bacillus licheniformis KCTC 1918, an anaerobic spore-forming soil bacterium, was cloned and characterized. The structural gene for the β-glucosidase consists of 1410 bp encoding 469 amino acid residues, and has a molecular weight of 53.4 kDa as estimated by sodium dodecyl sulfate polyacrylamide gel electrophoresis with 12% separating gel. The enzyme activity was determined against pNPG as a substrate. The enzyme was optimally active at pH 6.0 (citrate-phosphate buffer) and 47°C. β-Glucosidase retained 100% of its original activity for 24 h. The activity of the enzyme was stimulated by glycerol and urea and was decreased by Ca²⁺, Cu²⁺, Hg²⁺, Mg²⁺, and Mn²⁺. In particular, Cu²⁺ had the strongest negative effect on β-glucosidase activity. The purified β-glucosidase was active against pNPG and cellobiose. When the β-glucosidase was tested for cellulose hydrolysis, the supplement of β-glucosidase with cellulose increased the glucose yield from pine wood powder by 139.8%.     

PCR‐based identification of Erysiphe pulchra and Phyllactinia guttata from Cornus florida using ITS‐specific primers

The internal transcribed spacer (ITS) regions of rDNA and the intervening 5.8S rRNA gene for the powdery mildew fungi Erysiphe (sect. Microsphaera) pulchra and Phyllactinia guttata were amplified using standard polymerase chain reaction (PCR) protocols and the universal primer pairs, ITS₁ and ITS₄. PCR products for ITS were analysed by electrophoresis in a 1.5% agarose gel and sequenced. The size of the amplified ITS products (approximately 650 bp) were not sufficiently different to allow reliable differentiation of E. pulchra and P. guttata; however, their sequences were distinct. Specific primers for E. pulchra and P. guttata were developed and evaluated for use as diagnostic tools. The diagnostic band size from E. pulchra‐specific primer pair was 568 bp while the P. guttata band was 597 bp; the two primer pairs were highly specific to E. pulchra and P. guttata. Comparison of ITS sequences with information in the GenBank showed a very close similarity between sequences of E. pulchra isolates from Cornus florida in the USA and isolates collected on Cornus kousa in Japan. BLAST analysis of the sequence of the 650‐bp band from P. guttata revealed a close alignment with sequences of P. moricola (92%), P. kakicola (94%), and P. fraxini (92%). The sequence of P. guttata in C. florida also had a 98% identity with P. guttata in Calycanthus occidentalis and 94% identity with P. guttata in Corylus cornuta.     

Impact of weather variables and season on sporulation of Phytophthora pluvialis and Phytophthora kernoviae

Phytophthora pluvialis and Phytophthora kernoviae are the causal agents of important needle diseases on Pinus radiata in New Zealand. Little is known about the epidemiology of the diseases, making the development of control strategies challenging. To investigate the seasonality and climatic drivers of sporulation, inoculum traps, consisting of pine fascicles floating on water in plastic containers, were exchanged fortnightly at five sites in P. radiata plantations between February 2012 and December 2014. Sections of needle baits were plated onto selective media and growth of Phytophthora pluvialis and P. kernoviae recorded. To explore the generalizability of these data, they were compared to detection data for both pathogens from the New Zealand Forest Health Database (NZFHDB). Further, equivalent analyses on infection of Rhododendron ponticum by P. kernoviae in Cornwall, UK allowed the comparison of the epidemiology of P. kernoviae across different host systems and environments. In New Zealand, inoculum of P. pluvialis and P. kernoviae was detected between January–December and March–November, respectively. Inoculum of both species peaked in abundance in late winter. The probability of detecting P. pluvialis and P. kernoviae was greater at lower temperatures, while the probability of detecting P. pluvialis also increased during periods of wet weather. Similar patterns were observed in NZFHDB data. However, the seasonal pattern of infection by P. kernoviae in the UK was the opposite of that seen for sporulation in New Zealand. Phytophthora kernoviae was likely limited by warmer and drier summers in New Zealand, but by colder winter weather in the UK. These results emphasize the importance of considering both environmental drivers and thresholds in improving our understanding of pathogen epidemiology.     

Factors Affecting the Alkaline Cooking Performance of Selected Corn and Sorghum Hybrids

Dent corn (Zea mays L.) and sorghum (Sorghum bicolor L. Moench) sample sets representative of commonly grown hybrids and diverse physical attributes were analyzed for alkaline cooking performance. The influence of kernel characteristics including hardness, density, starch properties (thermal, pasting, and crystallinity), starch content, protein content, and prolamin content on alkaline cooking performance was also determined. Corn nixtamal moisture content was lower for hard, dense kernels with high protein contents; sorghum nixtamal moisture content was lower for kernels with low moisture contents and low starch relative crystallinities. Statistically significant (P < 0.05) regression equations showed that corn nixtamal moisture content was influenced by TADD (tangential abrasive dehulling device) index, kernel moisture content, starch content, and protein content; sorghum nixtamal moisture content was influenced by starch relative crystallinity, kernel moisture content, and abrasive hardness index. Pericarp removal was not strongly correlated with kernel characterization tests. Location (environmental) and hybrid (genetic) factors influenced most kernel characteristics and nixtamalization processing variables.