Pistil late flower differentiation in English walnut (Juglans regia L.): A developmental basis for heterodichogamy

We have investigated the phenology of pistillate flower differentiation in several protogynous and protandrous clones of English walnut (Juglans regia), a heterodichogamous species. Results indicate that initiation of pistillate flowers begins within 6–8 weeks following pistillate anthesis. By 8–10 weeks, organogenesis stops and does not resume until shortly before bloom the following spring. Cessation of organogenesis corresponds to the time that the growing fruits attain full size and begin a series of developmental events that include shell lignification, rapid embryo growth, and ultimately, accumulation of sugars and lipids in the embryo. Termination of pistillate flower organogenesis was noted in each of the clones examined regardless of the mode of dichogamy characteristic for that clone. In each of the protogynous clones, however, perianth initiation occurred before cessation of organ initiation in the spring. By contrast, in protandrous clones, tepals did not form until growth resumed the following year. Thus, the protandrous cultivars require more organogenetic activity during the weeks prior to anthesis, as perianth parts must be initiated in addition to the gynoecium.     

English walnut fruit growth and development

Samples of the ‘Ashley’, ‘Hartley’ and ‘Franquette’ cultivars of English walnut (Juglans regia L.) were collected at weekly intervals from bloom to harvest, and development of the fruit, embryo and surrounding tissue was followed. The first division of the zygote occurred approximately one week after pollination, by which time the endosperm, nucellus and integument had shown considerable growth. The endosperm first formed cell walls at the 8-celled embryo stage and was completely cellular by the time the embryo contained approximately 64 cells. Rapid growth of the cotyledons started as the shell began to harden at Week 7. Measurement of fruit growth indicated that fresh weight gain in ‘Ashley’ and ‘Hartley’ fruits followed a double sigmoid pattern, characterized by a 3-week period of slowed growth that began approximately 7 weeks after bloom. Rate of increase in total length and diameter also slowed greatly at Week 7. Fresh weight gain in ‘Franquette’ appeared to follow a single sigmoid curve, with no prolonged period of slowed growth corresponding to that in the other cultivars. Kernel growth also described a double sigmoid curve, with its initial, rapid phase nearly coincident with the beginning of Stage III of the whole-fruit, fresh-weight curve at Week 10.     

A survey of peach viruses in Lebanon

Field surveys were carried out in the main peach-growing areas of Lebanon to assess the presence and distribution of viruses and viroids in commercial orchards. Field inspections were made in spring and summer 2000 to observe symptoms of virus and viroid diseases respectively. In total, 950 trees in 95 commercial plantings from three different regions of Lebanon (Bekaa Valley, Mount Lebanon and north Lebanon) were surveyed and sampled. Immunoenzymatic tests (DAS-ELISA) were used to ascertain the presence of the following: Prunus necrotic ring spot ilarvirus (PNRSV), Prune dwarf ilarvirus (PDV), Apple mosaic ilarvirus (ApMV), Apple chlorotic leaf spot trichovirus (ACLSV), Plum pox potyvirus (PPV), Tomato ringspot nepovirus (ToRSV) and Strawberry latent ringspot nepovirus (SLRSV). Peach latent mosaic pelamoviroid (PLMVd) and Hop stunt hostuviroid (HSVd) were identified by molecular hybridization. About 25% of the tested samples were infected by one or more viruses. In particular, the prevailing virus was PNRSV (61.2% of infection), followed by ACLSV (27.1%), PDV (22.4%) and ApMV (2.1%). Mixed infections were about 13%. ToRSV, SLRSV and PPV were not found. HSVd was apparently absent, whereas PLMVd was identified in 34% of the samples examined. This viroid prevailed in certain areas of Mount Lebanon in both native and foreign cultivars.     

The genome of Brucella melitensis

The genome of Brucella melitensis strain 16M was sequenced and contained 3,294,931 bp distributed over two circular chromosomes. Chromosome I was composed of 2,117,144 bp and chromosome II has 1,177,787 bp. A total of 3198 ORFs were predicted. The origins of replication of the chromosomes are similar to each other and to those of other -proteobacteria. Housekeeping genes such as those that encode for DNA replication, protein synthesis, core metabolism, and cell-wall biosynthesis were found on both chromosomes. Genes encoding adhesins, invasins, and hemolysins were also identified.     

Canine adenoviruses and herpesvirus.

Canine adenoviruses (CAVs) and canine herpesvirus (CHV) are pathogens of dogs that have been known for several decades. The two distinct types of CAVs, type 1 and type 2, are responsible for infectious canine hepatitis and infectious tracheobronchitis, respectively. In the present article, the currently available literature on CAVs and CHV is reviewed, providing a meaningful update on the epidemiologic, pathogenetic, clinical, diagnostic, and prophylactic aspects of the infections caused by these important pathogens.     

A preliminary account of the sanitary status of stone-fruit trees in Morocco

Field surveys were carried out in the main stone-fruit growing areas of Morocco to evaluate the sanitary status of commercial orchards, varietal collections and nurseries. The presence of virus and virus-like diseases was checked by ELISA, sap transmission to herbaceous hosts, testing on woody indicators and molecular hybridization (dot-blot and tissue-printing). 1211 samples (382 almond, 339 peach, 291 plum, 150 apricot and 49 cherry) were tested by ELISA for the presence of Prunus necrotic ring spot virus (PNRSV), Prune dwarf virus (PDV), Apple chlorotic leaf spot virus (ACLSV), Apple mosaic virus (ApMV) and Plum pox virus (PPV). The overall average of virus infection rate was 16.4%, whereas that of single species was: 22.6% for almond, 17.8% for plum, 15% for peach, 10.2% for cherry, and 2.7% for apricot. The following viruses were detected: PNRSV, PDV, ACLSV and ApMV. 565 samples were tested by dot-blot and tissue-printing hybridization for the presence of Peach latent mosaic viroid (PLMVd) and Hop stunt viroid (HSVd). 48 samples were infected, 41 by PLMVd and 7 by HSVd. In addition, nested-PCR tests identified Plum bark necrosis and stem-pitting associated virus (PBNSPaV) in a few almond trees affected by stem pitting.     

Host–parasite relationships of Meloidogyne incognita on spinach

Host–parasite relationships in root-knot disease of spinach caused by Meloidogyne incognita race 1 were studied under glasshouse conditions. Nematode-induced mature galls were large and usually contained one or more females and egg masses with eggs. Feeding sites were characterized by the development of giant cells containing granular cytoplasm and many hypertrophied nuclei. The cytoplasm in these giant cells was aggregated alongside the thickened cell walls. Stelar tissues within galls appeared disorganized. The relationship between initial nematode population density ( P _i) in a series from 0–128 eggs and second-stage juveniles per cm³ soil and growth of spinach cv. Symphony F₁ seedlings was tested under glasshouse conditions. A Seinhorst model [ y = m  + (1 −  m ) z ^P–T ] was fitted to fresh top- and total plant-weight data for inoculated and control plants. Tolerance limits ( T ) of spinach cv. Symphony F₁ to M. incognita race 1 for fresh top and total plant weights were 0·25 and 0·5 eggs and second-stage juveniles per cm³ soil, respectively. The minimum relative values for fresh top and total plant weights were zero in both cases at P _i ≥ 32 eggs and second-stage juveniles per cm³ soil. Root galling was least at low initial population densities and greatest at 16 eggs and second-stage juveniles per cm³ soil. Maximum nematode reproduction rate was 33·1-fold at the lowest P _i.     

Serological and molecular evidence that canine respiratory coronavirus is circulating in Italy

Canine respiratory coronavirus (CRCoV) is a group II coronavirus that was firstly identified in lung samples of dogs with canine infectious respiratory disease (CIRD) in UK in 2003. We report for the first time the identification of CRCoV in Italy, together with serological evidence that the virus has been circulating in the Italian dog population as from 2005. Serological investigations on 216 dog sera, carried out by an ELISA test using the strictly related bovine coronavirus (BCoV) as antigen, revealed an overall CRCoV seroprevalence of 32.06% in the last 2 years. RT-PCR targeting the S-gene of CRCoV was carried out on 109 lung samples collected from carcasses of dogs submitted for diagnostic investigations. Positive results were obtained from the lungs of a dog of the Apulia region that was co-infected with canine parvovirus type 2. Sequence analysis of the S-gene fragment amplified by RT-PCR (595bp) showed similarity to group II coronaviruses, with the highest nucleotide identity (98%) to the only CRCoV strain currently available in the GenBank database (strain T101). The results of the present study show that CRCoV is present also in continental Europe, although further studies are required to determine the real pathogenic potential of the virus.     

In vitro fermentative capacity of swine large intestine: comparison between native Lantang and commercial Duroc breeds

Native Lantang and commercial Duroc pigs were used as animal models to evaluate the differences existing in dietary fiber utilization ability between breeds. Animals were fed the same diet from weaning (4 weeks) to 4 months of age. Neutral detergent fiber (NDF) from wheat bran (as substrate) and fecal samples from the two breeds (as inoculum) were used in an in vitro gas production trial. Results showed that cumulative and maximum gas productions were higher in inocula from Lantang than those from the Duroc breed (P < 0.05). The degradation capacity of NDF for microbiome from Lantang fecal samples were significantly higher compared to Duroc (P < 0.01). The total quantity of short‐chain fatty acids and its constituents from the fermentation liquors were different between breeds, suggesting that the dynamic characteristics of fermentation differed between the two breeds. The PCR denaturing gradient gel electrophoresis fingerprint and cluster analysis demonstrated that microbial communities of the two breeds were separated into two clusters and the bacterial community structure of large intestine among the two breed of pigs was different. Our results concluded that Lantang had higher dietary fiber degradation capacity than Duroc pigs, and the higher degradation capacity for the former breed was due to differences in the inherent microbial community in their respective large intestines.