Effect of crop rotation on native vesicular arbuscular mycorrhizal propagules in soil

The effect of crop rotation of native vesicular arbuscular mycorrhizal fungi was studied. Finger millet was grown as the first season crop in 15 plots. In the second season a mycorhizal host (cowpea) and a non-mycorrhizal host (mustard) were grown in 5 plots each, and the remaining 5 plots were left fallow. In the third season cowpea was grown in all the plots. Leaving the land fallow reduced the mycorrhizal propagules by 40% while growing a non-mycorrhizal host reduced it by 13%. Cowpea grown in the third season coincided with a slow build up of mycorrhizal propagules in soil. There was a slow build up of mycorrhizal propagules late in the season irrespective of the treatment in the preceding season.     

Pathways for Virus Assembly around Nucleic Acids

Understanding the pathways by which viral capsid proteins assemble around their genomes could identify key intermediates as potential drug targets. In this work, we use computer simulations to characterize assembly over a wide range of capsid protein–protein interaction strengths and solution ionic strengths. We find that assembly pathways can be categorized into two classes, in which intermediates are either predominantly ordered or disordered. Our results suggest that estimating the protein–protein and the protein–genome binding affinities may be sufficient to predict which pathway occurs. Furthermore, the calculated phase diagrams suggest that knowledge of the dominant assembly pathway and its relationship to control parameters could identify optimal strategies to thwart or redirect assembly to block infection. Finally, analysis of simulation trajectories suggests that the two classes of assembly pathways can be distinguished in single-molecule fluorescence correlation spectroscopy or bulk time-resolved small-angle X-ray scattering experiments.     

豇豆胰蛋白酶抑制剂基因转化芥菜及抗虫鉴定

用农杆菌介导将豇豆胰蛋白酶抑制剂 (CpTI)基因导入芥菜 ,获得了Kan抗性植株 .经PCR扩增、PCR Southern印迹和Northern印迹分析 ,转化再生植株大部分呈阳性 ,而非转化的再生植株均为阴性 ,证明CpTI基因已存在于芥菜基因组中 .在室内进行了喂虫试验 ,结果表明转基因芥菜抗虫性明显高于对照 ,转基因植株之间存在抗虫性差异     

Effects of Acibenzolar-S-Methyl Application to Rotylenchulus reniformis and Meloidogyne javanica

Effects of acibenzolar-s-methyl, an inducer of systemic acquired resistance in plants, on Rotylenchulus reniformis and Meloidogyne javanica in vitro and in vivo were determined. A single foliar application of acibenzolar at 50 mg/liter (5 ml of solution per plant) to 7-day-old cowpea or soybean seedlings decreased R. reniformis and M. javanica egg production by 50% 30 days after inoculation. The mechanism of acibenzolar on plant-parasitic nematodes was then investigated. Acibenzolar at 50 to 200 mg/liter did not affect movement of R. reniformis and M. javanica or penetration of second-stage juveniles (J2) of M. javanica on cowpea. However, M. javanica development was slowed and fecundity was reduced in plants treated with acibenzolar. On average, 50% of J2 that penetrated acibenzolar-treated cowpeas developed into mature females with eggs, whereas the other 50% exhibited arrested development. The number of eggs per egg mass was 450 in water-treated cowpeas, whereas the number declined to 250 in acibenzolar-treated plants. Acibenzolar may be responsible for stimulating the plants to express some resistance to the nematodes.     

Electronically monitored cowpea aphid feeding behavior on resistant and susceptible lupins

The feeding behavior of cowpea aphid, Aphis craccivora Koch (Homoptera: Aphididae) was examined on seedlings of narrow leafed lupin, Lupinus angustifolius L., and yellow lupin, L. luteus L., using electronic monitoring of insect feeding behavior (EMIF). Aphid feeding behavior was first compared between resistant (cv. Kalya) and susceptible (cv. Tallerack) varieties of narrow-leafed lupin. Aphids spent significantly more time in non- penetration and stylet pathway activities, and significantly less time in the sieve element phase on Kalya than on Tallerack, suggesting that feeding deterrence is an important component of aphid resistance in Kalya. Aphid feeding on a susceptible yellow lupin variety (cv. Wodjil) was then compared with that on two resistant lines, one (Teo) with high and the other (94D024-1) with low seed alkaloid content. There were no consistent differences in aphid feeding behavior between Wodjil and Teo. Total, mean and percentage sieve element phase times were significantly lower, and total and percentage times in non-phloem phase were greater on 94D024-1 than on Wodjil, suggesting the possibility of phloem-based deterrence in 94D024-1.     

一种简便、快捷的胰蛋白酶抑制剂基因的分离与克隆方法

从 3个豇豆品种幼嫩叶片中分离出核基因组 DNA,参照已知的几种 Bowman-Birk型胰蛋白酶抑制剂基因序列 ,设计合成了 2 7bp,且含有 Bam H I位点的寡核苷酸引物 ,分别以 3种豇豆核基因组 DNA为模板 ,PCR扩增 ,均得到长度约为 3 40 bp的 DNA片段。产物 DNA片段经 DNA序列分析 ,结果表明三者的碱基序列相同 ,与报道的胰蛋白酶抑制剂基因相比 ,同源性为 1 0 0 %和 99.7%。     

豇豆初生叶多胺氧化酶的催化特性

从豇豆幼苗 (6d苗龄 )初生叶提纯得到的多胺氧化酶 (EC 1 .4.3 .6 )属于二胺氧化酶 ,最有效的底物是 1 ,4 二胺丁烷 (腐胺 )、1 ,5 二胺戊烷 (尸胺 )、1 ,6 二胺己烷、1 ,1 0 二胺癸烷等α 二胺 ,其催化活性随二胺类底物碳链的增长而相应减弱。豇豆多胺氧化酶对亚精胺和精胺也具有较高的催化活性。另外 ,底物腐胺和尸胺的浓度超过 2mmol/L或亚精胺和精胺浓度超过 3mmol/L时会对酶活性有抑制效应。以腐胺和尸胺为底物时 ,酶的最适 pH约为7.0 ,而以亚精胺和精胺为底物时其最适pH为 6 .5。该酶的催化活性还随反应介质的离子强度增加而降低。K ,Ca2 和Mg2 (皆为 1 0mmol/L)对酶活性无明显抑制作用 ,而同样浓度的Mn2 ,Zn2 ,Fe2 ,Co2 和Cd2 则对酶活性有不同程度的抑制作用。金属螯合剂EDTA(1 0mmol/L)和腺苷蛋氨酸脱羧酶抑制剂甲基乙二醛 双脒腙 (0 .1mmol/L)可抑制酶活性约 80 % ,而铜结合剂KCN(1 .0mmol/L)、羰基试剂羟胺 (0 .1mmol/L)和氨基胍 (0 .1mmol/L)可导致该酶完全失活     

Molecular mechanisms of insect adaptation to plant defense： Lessons learned from a Bruchid beetle

Plants can accumulate, constitutively and/or after induction, a wide variety of defense compounds in their tissues that confer resistance to herbivorous insects. The naturally occurring plant resistance gene pool can serve as an arsenal in pest management via transgenic approaches. As insect-plant interaction research rapidly advances, it has gradually become clear that the effects of plant defense compounds are determined not only by their toxicity toward target sites, but also by how insects respond to the challenge. Insect digestive tracts are not passive targets of plant defense, but often can adapt to dietary challenge and successfully deal with various plant toxins and anti-metabolites. This adaptive response has posed an obstacle to biotechnology-based pest control approaches, which underscores the importance of understanding insect adaptive mechanisms. Molecular studies on the impact of protease inhibitors on insect digestion have contributed significantly to our understanding of insect adaptation to plant defense. This review will focus on exposing how the insect responds to protease inhibitors by both qualitative and quantitative remodeling of their digestive proteases using the cowpea bruchid-soybean cysteine protease inhibitor N system.     

A multi‐parent advanced generation inter‐cross (MAGIC) population for genetic analysis and improvement of cowpea (Vigna unguiculata L. Walp.)

Multi‐parent advanced generation inter‐cross (MAGIC) populations are an emerging type of resource for dissecting the genetic structure of traits and improving breeding populations. We developed a MAGIC population for cowpea (Vigna unguiculata L. Walp.) from eight founder parents. These founders were genetically diverse and carried many abiotic and biotic stress resistance, seed quality and agronomic traits relevant to cowpea improvement in the United States and sub‐Saharan Africa, where cowpea is vitally important in the human diet and local economies. The eight parents were inter‐crossed using structured matings to ensure that the population would have balanced representation from each parent, followed by single‐seed descent, resulting in 305 F₈ recombinant inbred lines each carrying a mosaic of genome blocks contributed by all founders. This was confirmed by single nucleotide polymorphism genotyping with the Illumina Cowpea Consortium Array. These lines were on average 99.74% homozygous but also diverse in agronomic traits across environments. Quantitative trait loci (QTLs) were identified for several parental traits. Loci with major effects on photoperiod sensitivity and seed size were also verified by biparental genetic mapping. The recombination events were concentrated in telomeric regions. Due to its broad genetic base, this cowpea MAGIC population promises breakthroughs in genetic gain, QTL and gene discovery, enhancement of breeding populations and, for some lines, direct releases as new varieties.     

The parasitic fly Nemorilla maculosa exploits host‐plant volatiles to locate the legume pod borer,Maruca vitrata

Nemorilla maculosa Meigen (Diptera: Tachinidae) is a solitary endoparasitoid of the legume pod borer, Maruca vitrata Fabricius (Lepidoptera: Crambidae), a key pest of cowpea, Vigna unguiculata (L.) Walp. (Fabaceae) in Africa. A colony of N. maculosa, introduced for experimental purposes from Taiwan to the laboratories of the International Institute of Tropical Agriculture (IITA) in Benin, was used for our studies. Olfactory reponses of N. maculosa to leaves of infested or uninfested cowpea and yellow peabush, Sesbania cannabina (Retz.) Pers. (Fabaceae), and to M. vitrata larvae were evaluated in a four‐arm olfactometer. For all combinations of odor sources, responses between naïve and oviposition‐experienced female flies did not differ. Nemorilla maculosa females were attracted by odors from uninfested leaves of yellow peabush and flowers of cowpea when compared with clean air, and they were attracted to plants damaged by M. vitrata with larvae removed. However, the female fly did not discriminate between odors from infested and uninfested plants. The parasitic fly N. maculosa proved well able to use volatile compounds from various host plants (peabush and cowpea) to locate its host, with a more pronounced attraction by the combination of host larvae and infested host plant parts. These findings are discussed in light of the prospective use of N. maculosa as a biological control agent against the legume pod borer.