Signal molecules in the peanut–bradyrhizobia interaction

Main nodulation signal molecules in the peanut–bradyrhizobia interaction were examined. Flavonoids exuded by Arachis hypogaea L. cultivar Tegua were genistein, daidzein and chrysin, the latest being released in lower quantities. Thin layer chromatography analysis from genistein-induced bacterial cultures of three peanut bradyrhizobia resulted in an identical Nod factor pattern, suggesting low variability in genes involved in the synthesis of these molecules. Structural study of Nod factor by mass spectrometry and NMR analysis revealed that it shares a variety of substituents with the broad-host-range Rhizobium sp. NGR234 and Bradyrhizobium spp. Nodulation assays in legumes nodulated by these rhizobia demonstrated differences between them and the three peanut bradyrhizobia. The three isolates were classified as Bradyrhizobium sp. Their fixation gene nifD and the common nodulation genes nodD and nodA were also analyzed. Accession numbers: AY427207, EF202193, EF158295 (16S rRNA gene of strains NLH25, NOD31 and NDEHE, respectively); DQ295199, DQ295200, DQ295201 (Partial nifD gene sequences of strains NLH25, NOD31 and NDEHE, respectively).     

Relationship between Meloidogyne arenaria and Aflatoxin Contamination in Peanut

Damaged and developing kernels of peanut (Arachis hypogaea) are susceptible to colonization by fungi in the Aspergillus flavus group which, under certain conditions, produces aflatoxins prior to harvest. Our objective was to determine whether infection of peanut roots and pods by Meloidogyne arenaria increases aflatoxin contamination of the kernels when peanut is subjected to drought stress. The experiment was a completely randomized 2-x-2 factorial with 6 replicates/treatment. The treatment factors were nematodes (plus and minus M. arenaria) and fungus (plus and minus A. flavus inoculum). The experiment was conducted in 2001 and 2002 in microplots under an automatic rain-out shelter. In treatments where A. flavus inoculum was added, aflatoxin concentrations were high (> 1,000 ppb) and not affected by nematode infection; in treatments without added fungal inoculum, aflatoxin concentrations were greater (P ≤ 0.05) in kernels from nematode-infected plants (1,190 ppb) than in kernels from uninfected plants (79 ppb). There was also an increase in aflatoxin contamination of kernels with increasing pod galling (r² = 0.83 in 2001, r² = 0.43 in 2002; P ≤ 0.04). Colonization of kernels by A. flavus increased with increasing pod galling (r² = 0.18; P = 0.04) in 2001 but not in 2002. Root-knot nematodes may have a greater role in enhancing aflatoxin contamination of peanut when conditions are not optimal for growth and aflatoxin production by fungi in the A. flavus group.     

Thansgenic peanut plants obtained by particle bombardment via somatic embryogenesis regeneration system

INTRODUCTIONArachiS hypogaea L., Peanut or groundnut, isan importal commercial crop worldwide. It provides an excellellt source of protein and other nutrients. Its production and quality can be severelyimpacted under stressful growing conditions such ascdriate factors, pests and diseajses. Genetic engineering provides a prospective way to reduce certainproblems by transferring individual genes for pestresistance or other traits into elite germplasm of acultiVated species. Thansgenic pea…     

渗透胁迫对花生幼叶细胞性氧伤害的定量分析

在渗透胁迫条件下不同花生（Arachis hypogaea Linn．）品种的水势、质膜相对透性（RPMP）、超氧离子、丙二醛（MDA）含量和超氧化物歧化酶（SOD）活性两两之间都呈显著相关。而花生各品种的过氧化氢酶活性、过氧化物酶活性、谷胱甘肽含量和抗坏血酸含量与水势、RPMP、超氧离子、MDA含量和SOD活性等指标之间相关程度波动较大。水势对RPMP、MDA含量、超氧离子和SOD活性的弹性系数处于负效应阶段。SOD活性对RPMP、MDA含量和超氧离了的弹性系数的效应处于递减阶段。超氧离了对RPMP和MDA含量的生系数的效应处于递减阶段。各指标的弹性系数和相应的边际量因花生品种的抗旱能力不同而异。     

花生成熟花粉的超微结构

花生（Arachis hypogaea L．）成熟花粉为二细胞型,具3个萌发沟,少数有4个。外壁呈蜂窝状。花粉壁由覆盖层、基粒棒、外壁内层及内壁构成。线粒体嵴密集、相互平行,脂体被粗面内质网包围。粗面内质网与外核膜相连,亦与线粒体相连。高尔基体甚少。营养核无核仁及染色质,与生殖细胞相连形成雄性生殖单位（male germ unit）。生殖细胞锤形、有壁,见一末端延伸成长尾状（长8μm）。细胞质含核糖体、线粒体、微管,未见体。在有些生殖细胞核内观察到具双层膜、少量嵴及深色内含物的球形结构,其米来源及本质尚不知,有待进一步研究确定。     

Nucleotide-Dependent Isomerization of Glutamate Dehydrogenase in Relation to Total RNA Contents of Peanut

The physiological function of glutamate dehydrogenase (GDH) was investigated by treating germinating peanut (Arachis hypogaea L.) seeds with nucleoside triphosphate (NTP) solutions in order to alter the isoenzyme distribution patterns. The free nucleosides and nucleotides of the GTP-treated peanut were the highest [8.7 μmol g⁻¹(f.m.)], and they decreased through the ATP-treated peanut [5.8 μmol g⁻¹(f.m.)], and CTP-treated peanut [5.5 μmol g⁻¹(f.m.)], to the UTP-treated peanut [4.1 μmol g⁻¹(f.m.)]. The combination of 4 NTPs induced 20 % higher content of Pi [173 nmol g⁻¹(f.m.)] than in the control, but the combined ATP+UTP treatment induced the lowest (93.0 nmol g⁻¹(f.m.)] Pi. The 4 NTP treatment also induced the highest number of GDH isoenzymes (28) followed by the purine NTP treatments (15 to 20), but the pyrimidine NTP treatments and the combined purine + pyrimidine NTP treatments induced the lowest numbers (<15) of isoenzymes. The deamination/amination ratios were generally higher in the UTP (0.11), and CTP (0.06) treated peanuts than in the GTP (0.04), and ATP (0.07) treated peanuts. There were mutual relationships between higher numbers of GDH isoenzymes present in the GTP-, and ATP-treated peanuts and higher RNA (236.5 and 239.4 μg g⁻¹, respectively) contents on one hand, and between the lower numbers of isoenzymes in the CTP-, and UTP-treated peanuts and lower RNA (162.0 and 152.5 μg g⁻¹, respectively) contents. The recurrent relationships of the effects of the NTP treatments of peanut were UTP > ATP > CTP > GTP. This revised version was published online in July 2006 with corrections to the Cover Date.     

Diversity and compatibility of peanut (Arachis hypogaea L.) bradyrhizobia and their host plants

A high degree of genetic diversity among 125 peanut bradyrhizobial strains and among 32 peanut cultivars collected from different regions of China was revealed by using the amplified fragment length polymorphism (AFLP) technique. Eighteen different peanut bradyrhizobial genotypes and six peanut cultivars were selected for symbiotic cross-inoculation experiments. The genomic diversity was reflected in the symbiotic diversity. The peanut cultivars varied in their ability to nodulate with the strains used. Some cultivars had a more restricted host range than the others. Also the strains displayed a range of nodulation patterns. In yield formation there were clear differences between the plant cultivar/bradyrhizobium combinations. There was good compatibility between some peanut bradyrhizobial strains and selected cultivars, with inoculation resulting in well-nodulated, high-yielding symbiotic combinations, but no plant cultivar was compatible with all strains used. The strains displayed a varying degree of effectiveness, with some strains being fairly effective with all cultivars and others with selected ones. The AFLP genotypes of the strains did not explain the symbiotic behavior, whereas the yield formation of the plant cultivars was more related to the genotype. It is concluded that to obtain optimal nitrogen fixation efficiency of peanut in the field, compatible plant cultivar-bradyrhizobium combinations should be selected either by finding inoculant strains compatible with the plant cultivars used, or plant cultivars compatible with the indigenous bradyrhizobia.     

Effects of Peanut Genotypes on Meloidogyne Species Interactions

A 3-year microplot study was conducted to characterize the interaction between Meloidogyne arenaria race 1 (MA1) and M. hapla (MH), as affected by the five peanut genotypes: Florigiant, NC 7, NC 6, NC Ac 18416, and NC Ac 18016. The interactive effects on infection (total parasitic forms per root unit) and reproduction potentials of each nematode species and crop damage were determined. As a single population, MA1 had greater infection capacity and caused more crop damage than did MH, but both species had similar reproduction potentials. In mixed infestations, MA1 was more competitive than MH, as reflected by incidence of infection. Infection and reproduction potentials, and crop-damage capabilities of the mixed populations were similar to those of MA1 alone. All peanut genotypes were susceptible to infection by both nematodes. NC 6 was less susceptible to damage by MA1 and the mixed populations than other genotypes. A nematode treatment x genotype interaction was detected for root infection and crop damage, but not for population density or reproduction. With high preplant nematode levels (Pi), the populations reached their peak by midseason, whereas those with low Pi peaked after midseason. Crop damage in the second and third years was correlated with Pi level.     

Seasonal Population Dynamics of Selected Plant-Parasitic Nematodes on Four Monocultured Crops

Seasonal fluctuations in field populations of Meloidogyne incognita, Pratylenchus zeae, P. brachyurus, Criconemoides ornatus, Trichodorus christiei, and Helicotylenchus dihystera on monocultured corn, cotton, peanut, and soybean were determined monthly for 4 yr. Population densities of M. incognita were greater in corn and cotton plots than in peanut and soybean plots from July until January. Those of Pratylenchus spp. were greater on corn and soybean than on cotton and peanut during all months except May and June. C. ornatus populations were greater on corn and peanut than on cotton and soybean during all months. C. ornatus on corn and peanut was more numerous in July than in other months. There was no significant increase in populations of T. christiei, except on corn in June. H. dihystera was greater in cotton and soybean plots than in corn and peanut plots from August through December.     

Effect of mannose-binding lectin from peanut and pea on the stem borer Chilo partellus

A mannose-binding lectin found in vegetative tissues of peanut, Arachis hypogaea, was compared with mannose-binding lectin from pea, Pisum sativum, for toxic effects on larvae of the stem borer Chilo partellus (Swinhoe). After 10 days, the mortality of larvae fed on artificial diet containing 0.5% (m/m) peanut lectin was 46.2%. The mortality of larvae fed on 1.0% peanut lectin was similar (48.1%) but insects were significantly smaller than those of the 0.5% treatment. Larvae of both lectin treatments stopped feeding within three days. Larval size and mortality was not significantly reduced by 0.1% peanut lectin and 1% heat-treated lectin did not show toxic effects. The mannose-binding lectin from pea was not toxic to C. partellus at concentrations up to 1%. Peanut lectin bound to the apical membranes of columnar epithelial cells in the mid-gut of C. partellus. This suggests that peanut lectin has an antinutritive action and that it may protect vegetative tissues of peanut against insect pests.