[Effects of balanced fertilization on growth and fruit quality of 'Huang-guan' pear on desert area.] / å¹³è¡¡æ–½è‚¥å¯¹è’æ¼ åŒºé»„å† æ¢¨ç”Ÿé•¿ä¸Žå“è´¨çš„å½±å“.

A field experiment was carried out to study the effects of balanced fertilization on growth and development, yield, fruit quality and mineral content in 'Huang-guan' pear to provide a theoretical basis for the reasonable level of fertilization in pear orchards. Four treatments were arranged with 12-year old 'Huang-guan' pear trees from the same orchard: conventional fertilization (CK), low levels of N, P2O5 and high level of S (T1), medium levels of N, P2O5 and S (T2), high levels of N, P2O5 and low level of S (T3). The results showed that different treatments had little effect on the growth and development of current-year branch and leaves in the first year. However, in the se-cond year, T1 treatment promoted the length and diameter of current-year branch by 16.2% and 11.4%, respectively. Continuous fertilization could increase the leaf mineral contents in different degrees. The contents of Cu, Fe, and Zn in leaves under T1 treatment, Mg and B in leaves under T2 treatment, and P and Mn in leaves under T3 treatment were highest. Different fertilization levels had no significant effect on yield but on fruit quality. The contents of soluble sugars and vitamin C (Vc) were significantly increased by T2 treatment, which was 4.2% and 7.1% higher than those in CK. However, T1 significantly decreased contents of total soluble solid, soluble sugars and Vc, while highest organic acid content presented in T3. Fruit Fe content was positively correlated with soluble sugar content and fruit shape index, but was negatively correlated with single fruit mass, organic acids and Vc. Fruit P content was positively correlated with fruit shape index and firmness, but was negatively correlated with contents of soluble sugars, organic acids and Vc. Accordingly, T2 could improve fruit quality and maintain the productivity, and thus should be the suitable fertilization strategy for the 'Huang-guan' pear management in desert area.

Histopathology combined with transcriptome analyses reveals the mechanism of resistance to Meloidogyne incognita in Cucumis metuliferus.

Root-knot nematodes (Meloidogyne spp.) cause serious threat to cucumber production. Cucumis metuliferus, a relative of cucumber, is reported to be resistant to Meloidogyne incognita, yet the underlying resistance mechanism remains unclear. In this study, the response of resistant C. metuliferus accession PI482443 following nematode infection was studied in comparison with susceptible C. sativus cv. Jinlv No.3. Roots of selected Cucumis seedings were analysed using histological and biochemical techniques. Transcriptome changes of the resistance reaction were investigated by RNA-seq. The results showed that penetration and development of the nematode in resistant plants were reduced when compared to susceptible plants. Infection of a resistant genotype with M. incognita resulted in a hypersensitive reaction. The induction of phenylalanine ammonia lyase and peroxidase activities after infection was greater in resistant than susceptible roots. Several of the most relevant genes for phenylpropanoid biosynthesis, plant hormone signal transduction, and the plant-pathogen interaction pathway that are involved in resistance to the nematode were significantly altered. The resistance in C. metuliferus PI482443 to M. incognita was associated with reduced nematode penetration, retardation of nematode development, and hypersensitive necrosis. The expression of genes resulting in the deposition of lignin, toxic compounds synthesis, cell wall reinforcement, suppression of nematode feeding and resistance protein accumulation, and activation of several transcription factors might all contribute to the resistance response to the pest. These results may lead to a better understanding of the resistance mechanism and aid in the identification of potential targets resistant to pests for cucumber improvement.

Inhibition of highly pathogenic porcine reproductive and respiratory syndrome virus replication by recombinant pseudorabies virus-mediated RNA interference in piglets.

Highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) is a variant of porcine reproductive and respiratory syndrome virus (PRRSV) which, in recent years, has caused heavy economic losses to swine-producing areas. Although current vaccines are somewhat prophylactic, they provide only limited protection. Furthermore, there are currently no effective anti-HP-PRRSV drugs. Consequently, it is necessary to develop novel antiviral strategies. In the present study, three recombinant pseudorabies viruses (PRV) expressing siRNAs against the ORF7 of HP-PRRSV strain HN1 (PRV gG-/siRNAN1, PRV gG-/siRNAN2, and PRV gG-/siRNAN3) were evaluated for the inhibition of HP-PRRSV replication. The results indicated that recombinant PRV-mediated siRNA could significantly decrease the replication of traditional PRRSV strain H1 at mRNA and protein levels in Marc-145 cells. Moreover, one recombinant PRV (PRV gG-/siRNAN2) was found to be inhibit the multiplication of HP-PRRSV strain HN1 effectively in Marc-145 cells at both the protein and ORF7 mRNA level. Twenty 21-day-old healthy weaned piglets were divided into four groups of five piglets each. Groups 1 and 2 were injected i.m. with PRV gG-/siRNAN2 and PRV gG-/siRNANeg individually. The piglets in group 3 were challenged with the HP-PRRSV control. After 24h, the piglets in groups 1-3 were challenged i.m. with HP-PRRSV strain HN1, while those in group 4 were i.m. administered with PBS as a negative control. The results showed that HP-PRRSV in serum and lung samples from piglets was effectively inhibited by PRV gG-/siRNAN2. The clinical signs and gross lesions of piglets inoculated with PRV gG-/siRNAN2 were significantly less invasive than those of the PRV gG-/siRNANeg group and HP-PRRSV control group. These results showed that siRNAs mediated by recombinant PRV could effectively suppress HP-PRRSV replication in vitro as well as in vivo. RNAi mediated by recombinant PRV presents a potential novel method to prevent HP-PRRSV infections in swine. However, the protective efficiency of PRV gG-/siRNAN2 should be assessed in a larger number of piglets in future studies.

Cloning, in vitro expression and bioactivity of duck interleukin-18.

The encoding sequence for duck IL-18 was obtained, using reverse transcription-polymerase chain reaction, from mRNA harvested from Con A-stimulated Gushi (GS) duck splenic mononuclear cells. Recombinant duck IL-18 (rduIL-18) was produced in a prokaryotic expression system. In vitro bioactivity of rduIL-18 was determined in a lymphocyte proliferation assay and in vivo bioactivity of rduIL-18 was assessed by addition to a vaccine. Monoclonal antibody (mAb) and polyclonal antibodies (pAbs) specific for rduIL-18 were generated and subsequently characterized by ELISA, Western blot and neutralizing assays. Sequence analysis of GS duck IL-18 demonstrated an open reading frame (ORF) of 603 base pairs encoding for a 200 amino acid precursor protein. The duck encoding sequence shares 85.3% similarity to the chicken equivalent, at the nucleotide level. A His-duIL-18 fusion protein was recognized in Western blot by mAbs against duck and chicken IL-18 (chIL-18), but not by mAb against human IL-18. Recombinant duIL-18 induced in vitro proliferation of Con A-stimulated duck splenocytes and enhanced the immune response of ducks vaccinated with an inactivated oil emulsion vaccine against avian influenza virus. PAb and mAb 5B2 against rduIL-18 had neutralizing ability, inhibiting the biological activities of both recombinant duIL-18 and endogenous duIL-18. The results indicate that rduIL-18 has the potential to be used as an immunoadjuvant, and the mAb against rduIL-18 further facilitates basic immunobiological studies of the role of IL-18 in the avian immune system.