Species-specific responses to environmental stress on germination and juvenile growth of two Bolivian Andean agroforestry species

Integrating native trees in farmland can support soil, water and biodiversity conservation. This is particularly important in regions characterized by long periods of drought and soil erosion, such as the Bolivian Andes, where agroforestry with native woody species is rarely applied. Better knowledge on the effects of environmental stress on propagation and establishment of such native plants is needed to optimize their cultivation. In our study, we tested the effects of temperature and scarification on seed germination, and assessed seedling survival and juvenile growth of two potential agroforestry species (Prosopis laevigata var. andicola, Schinus molle) under diverse soil and water conditions. Temperatures above 30 °C accelerated germination, but they increased fungi infestation in the case of S. molle. The application of acid and mechanical scarification significantly improved the germination capacity of P. laevigata var. andicola. Medium to high moisture levels in sand provided the most favourable conditions for plant growth. S. molle was more sensitive to dry and P. laevigata var. andicola more vulnerable to water-saturated clay loam. Mulching enhanced the survival and growth of S. molle juveniles, but increased P. laevigata var. andicola’s growth in sand and dry soils only. Our results may facilitate guidance on improving propagation of these two potential agroforestry species under environmental stress conditions. More generally, our study shows that easily applicable treatments, such as mulching, can significantly improve the cultivation of native species, provided that their habitat requirements and limiting factors are well known. This highlights the relevance of identifying and closing such knowledge gaps for native trees and shrubs in order to promote their potential for use in agroforestry.     

Effects of milk replacer and starter diet provided as creep feed for suckling pigs on pre‐ and post‐weaning growth

This study was aimed at investigating the long‐term effects of provision of liquid milk replacer (MR) and solid starter diet (SD) during lactation on post‐weaning (PW) growth of pigs. In experiment 1, 33 cross‐bred litters were allotted to four treatments: no supplement (CON), MR ad libitum, SD ad libitum and 100 g SD/litter/day from lactation day 4 through weaning at day 21 during late fall. In experiment 2, 40 litters received MR or none in July. PW pigs received commercial diets to marketing. In experiment 1, weaning weight (WW), pre‐weaning average daily gain (ADG) and mortality (2.4%) were not influenced by creep‐feeding MR or SD. ADG was greater (P < 0.05) in the MR group versus CON during days 21–54, but did not differ across the treatments during days 54–162. In experiment 2, ADG during lactation and WW were greater in the MR group versus CON, with mortality lower in the former (5.6 vs. 10.3%). However, PW ADG to day 175 did not differ between the two groups. Results suggest that creep‐feeding MR or SD has no effect on PW growth. However, it remains possible that MR reduces PW mortality during the hot season.     

Innate immune homeostasis by the homeobox gene caudal and commensal-gut mutualism in Drosophila

Although commensalism with gut microbiota exists in all metazoans, the host factors that maintain this homeostatic relationship remain largely unknown. We show that the intestinal homeobox gene Caudal regulates the commensal-gut mutualism by repressing nuclear factor kappa B-dependent antimicrobial peptide genes. Inhibition of Caudal expression in flies via RNA interference led to overexpression of antimicrobial peptides, which in turn altered the commensal population within the intestine. In particular, the dominance of one gut microbe, Gluconobacter sp. strain EW707, eventually led to gut cell apoptosis and host mortality. However, restoration of a healthy microbiota community and normal host survival in the Caudal-RNAi flies was achieved by reintroduction of the Caudal gene. These results reveal that a specific genetic deficiency within a host can profoundly influence the gut commensal microbial community and host physiology.     

Effect of EDTA alone and in combination with polygodial on the growth of Saccharomyces cerevisiae

The antifungal activity of ethylenediaminetetraacetic acid (EDTA) against Saccharomyces cerevisiae was significantly affected by various conditions such as inoculum size, pH, and metal ions (Mg(2+), Ca(2+)). EDTA was found to be effective against this yeast at the inoculum size of 10(5) colony forming units (CFU)/mL with the minimum inhibitory concentration of 400 mug/mL and the minimum fungicidal concentration of 6400 mug/mL, but it was not effective at 10(7) CFU/mL up to 6400 mug/mL. The fungicidal activity of EDTA against S. cerevisiae was significantly enhanced in combination with polygodial. Isobolograms, fractional inhibitory concentration, and fractional fungicidal concentration indices were used for evaluating the interaction between combined compounds. This synergistic effect is likely due to polygodial's destructive action on the cellular membrane, which facilitates the transmembrane transport of foreign compounds (EDTA) into yeast cells. Once inside the cells, EDTA forms chelation with divalent metals such as Mg(2+) and Ca(2+), which are required by various essential enzymes.     

Single nucleotide polymorphism discovery and linkage mapping of lipoxygenase-2 gene (Lx 2) in soybean

Lipoxygenase-2 (Lx ₂) in soybean seed is mainly responsible for generation of grassy-beany and bitter flavors. Genetic elimination of this flavor can be accelerated by the development of single nucleotide polymorphism (SNP) markers linked to Lx ₂. A frame map based on simple sequence repeat (SSR) markers was constructed first using a recombinant inbred line (RIL) population of Pureunkong × Jinpumkong 2. Sixty-five SSR markers were incorporated into 13 linkage groups (LGs) spanning a total of 737 cM. Among five primer pairs designed from the Lx ₂ gene sequence, one produced an amplicon with sequence variations between Pureunkong and Jinpumkong 2. Three SNPs, T/C, G/A and C/A, were identified at 251,367 and 420 bp, respectively, in the intron region of the 804 bp amplified product. Using single base chain extension based on the capture probe sequence in the 5' region of the T/C SNP, the 90 RILs were genotyped for each allele of Lx ₂. The allelic segregation for the SNP linked toLx ₂ was in accordance with the expected ratio of 1:1 in the RIL population. Based on the results of linkage analysis between Lx ₂ and the SSR markers, Lx ₂ was found to be positioned on one end of LG F in the frame map, flanked by the SSR markers Satt522 and Sat074. This study demonstrates that SNP markers closely linked to Lx ₂can be developed to facilitate marker-assisted selection and fine mapping of the region around this locus. This revised version was published online in July 2006 with corrections to the Cover Date.     

新疆额敏县野果林苹果巢蛾主要寄生蜂调查

近年来,新疆塔城地区额敏县野果林遭受苹果巢蛾Yponomeuta padella Linnaeus的严重危害,造成重大经济损失.为寻找其有效天敌,保护这些珍贵的果树资源,2008-2009年,对额敏县野果林苹果巢蛾的寄生性天敌资源展开了调查.通过野外采集及室内饲养,发现了寄生于该害虫卵、幼虫及蛹的3种寄生蜂,即:卵-幼虫跨期寄生蜂--巢蛾多胚跳小蜂Ageniaspis fuscicollis(Dalman),蛹期寄生蜂-黄柄齿腿长尾小蜂Monodontomerusdentipes(Dalman)和幼虫-蛹跨期寄生蜂--全北群瘤姬蜂指名亚种Iseropus stercorator stercorator(Fabricius);其中巢蛾多胚跳小蜂为优势种,寄生率可达95.98%.本研究为苹果巢蛾的生物防治奠定了基础.     

Biotransformation and impact of ferulic acid on phenylpropanoid and capsaicin levels in Capsicum annuum L. cv. P1482 cell suspension cultures

Cell suspension cultures of Capsicum annuum L. cv. P1482 were fed with exogenous ferulic acid to monitor their biotransformation abilities. A portion of the ferulic acid was biotransformed into vanillin, a major natural flavor, and capsaicin, a principle secondary metabolite characteristic of Capsicum species. The cellular vanillin concentrations were relatively higher than capsaicin levels and were maximal (2 mg/g DW) 4 days after 0.6 mM ferulic acid feeding. Maximal vanillin levels in the culture medium were 10 mg/L at 4 and 3 days after feeding with 1.25 and 2.5 mM ferulic acid, respectively. With regard to capsaicin levels, the cellular levels were slightly decreased by ferulic acid feeding, whereas the levels in the culture medium were increased. Ferulic acid feeding not only enhanced vanillin and capsaicin production but also increased the concentrations of other phenylpropanoid metabolites.