Brown Roots Research Articles

Involvement of Olpidium bornovanus and O. virulentus in the occurrence of melon root rot and vine decline caused by Monosporascus cannonballus in central Italy

Monosporascus root rot and vine decline (MRRVD), caused by Monosporascus cannonballus , has become one of the most important diseases of melon worldwide. Recent evidences suggest that M. cannonballus is not the sole cause of MRRVD, but other pathogens, Olpidium spp. and Melon necrotic spot virus (MNSV) are also involved. The aim of this study was to ascertain the potential concomitant involvement of these pathogens in the development MRRVD of melon in Central Italy analyzing a soil sampled from a greenhouse with a known history of this disease. O. bornovanus and O. virulentus along with M. cannonballus were identified from the sampled soil. Bait melon plants grown in the contaminated soil were colonized by both Olpidium species and by M. cannonballus, showing roots browning and foliage wilt. No infection by MNSV was detected in bait plants. In the tripartite pathogenicity test, O. bornovanus alone was found to be a virulent pathogen, capable of colonizing roots with a high percentage of colonization intensity, resulting in root browning and foliage wilting. Both disease severity and intensity of Olpidium colonization determined by the co-inoculation of ascospores of M. cannonballus and Olpidium spp. were statistically similar to that resulted by Olpidium or by ascospores separately inoculated. Root symptoms were accompanied by a gradual vine decline and foliage wilting. Root rot and vine decline, which was previously attributed in Central Italy primarily to M. cannonballus, needs to be reattributed, since O. bornovanus and O. virulentus are also involved without apparent synergistic effect among the pathogens.

ДОСЛІДЖЕННЯ АНАТОМІЧНОЇ БУДОВИ НАДЗЕМНИХ ОРГАНІВ PRIMULA JULIAE KUSN

Вперше здійснено дослідження особливостей анатомічної будови надземних органів первоцвіту (примули) Юлії родини первоцвіті, в результаті якого виявлено їх характерні мікроскопічні діагностичні ознаки. Встановлені мікродіагностичні ознаки дають можливість ідентифікувати лікарську рослинну сировину і можуть бути використані для розробки проекту АНД.

The effect of different temperatures on browning incidence and phenol compound metabolism in fresh-cut lotus (Nelumbo nucifera G.) root

Lotus root (Nelumbo nucifera G.) is an important aquatic vegetable in China. Browning easily during the processing and storage reduces the value of lotus root. Therefore, browning is an important issue for the lotus root industry. PAL, PPO and POD genes were reported as being involved in fruit and vegetable tissue browning, and PAL, PPO and POD enzymes have long been associated with lotus root browning. However, the molecular mechanism of PAL, PPO and POD involved in fresh-cut lotus root browning is poorly understood. This paper analyses the effect of different temperatures on the phenolic content, browning, PPO, PAL and POD enzyme activity and the expression pattern of PPO, PAL and POD genes in fresh-cut lotus root. The results show that the change of PAL, PPO and POD enzymatic activity occurs in parallel with the increase in browning degree in storage at different temperatures. Furthermore, the total phenol content and PAL enzyme activity changes are basically identical, suggesting that PAL might be the key genes involved in the synthesis of total phenol content. Two NnPAL, 2 NnPPO and 7 NnPOD genes were isolated using RNA-seq, and the upregulation of NnPAL1, NnPPOA, NnPOD1, NnPOD2, NnPOD3, NnPOD4, NnPOD5 and NnPOD6 by high temperature coincided with the increase in related enzyme activities and the browning degree of fresh-cut lotus root, which should be considered the most important candidates for fresh-cut lotus root browning.

Toxicity of Zinc on Growth of an Aquatic Macrophyte, Ipomoea Aquatica Forsk

The effects of different concentrations of Zn on growth of an aquatic macrophyte, Ipomoea aquatica Forsk. were studied. Fresh weight, dry weight, shoot length, root length, number of nodes, development of leaves, and chlorophyll and carotene contents were the different growth parameters considered. Toxicity symptoms like browning and decaying of roots could be observed in plants treated at 22.7 mg L-1 Zn as early as 3rd day of experiment while yellowing of older leaves appeared during the later period of exposure. High concentration of Zn (12.71 – 22.7 mg L-1) significantly inhibited the growth of plant while lower Zn concentrations up to 4.09 mg L-1 enhanced its growth. However, at 7.26 mg L-1 Zn the chlorophyll as well as total carotene content in leaf of I. aquatica were significantly reduced from that in control on 5th day of exposure and subsequently the reduction was observed in lower concentrations. Thus, I. aquatica can be employed in biomonitoring of Zn polluted aquatic ecosystems using root browning, root and shoot growth inhibition, and chlorophyll and total carotene contents as sensitive biomarkers.

Axillary bud and pericycle involved in the thickening process of the rhizophore nodes in Smilax species.

The species of the genus Smilax, popularly known as sarsaparilla, are widely used in folk medicine due to the antirheumatic properties of its underground structures. Smilax fluminensis and S. syphilitica occur in forested areas and form thickened stems called rhizophores from which adventitious roots grow. To provide information for more accurate identification of the commercialised product and for elucidating the process of stem thickening, a morphology and anatomy study of the underground organs of the two species was conducted. The adventitious roots differ in colour and diameter depending on the stage of development. They are white and have a larger diameter in the early stages of development, but as they grow, the adventitious roots become brown and have a smaller diameter due to the disintegration of the epidermis and virtually the entire cortex. In brown roots, the covering function is then performed by the lignified endodermis and the remaining walls of the cells from the last parenchyma cortical layer. These results are similar to those found in studies of other Smilax and suggest that the anatomy of the roots can be useful for identifying fraud in commercialised materials. The thickening process of the nodal regions of the rhizophores in both species involves the activity of axillary buds and pericyclic layers.

Marked differences in standing biomass, length density, anatomy and physiological activity between white and brown roots in Fraxinus mandshurica Rupr. plantation

Root browning is closely related to physiological function, but the dynamic and underlying mechanism are poorly understood. Our objective was to explore the interrelationship between root browning, in the context of root branch order, and standing biomass, root length density, and soil resources availability at the ecosystem level. We measured the standing biomass and length density of white, brown and black roots of the first three branch orders in Fraxinus mandshurica Rupr.. Root anatomy, morphology, physiological activity, as well as soil total available nitrogen, moisture, and temperature were also determined. White roots had longer specific root length, higher physiological activity, and intact cortex compared with brown roots. Grand means of biomass and length density in white roots were 5.6-fold and 4.4-fold higher than those in brown roots, respectively. Sampling time, soil depth, and branch order generally had significant effects on the biomass and length density of both white and brown roots. In addition, sampling time consistently had significant effects on the brown to white root ratio, whereas the ratio was only moderately correlated with soil temperature. Root browning has pronounced impacts on tree root resource acquisition and belowground carbon allocation in F. mandshurica at both individual root and ecosystem levels.

Effects of root restriction on nitrogen and gene expression levels in nitrogen metabolism in Jumeigui grapevines (Vitis vinifera L.×Vitis labrusca L.)

To decipher the relationship between the inhibited shoot growth and expression pattern of key enzymes in nitrogen metabolism under root restriction, the effects of root restriction on diurnal variation of expression of nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS1-1, GS1-2, GS2) and glutamate synthase (Fd-GOGAT, NADH-GOGAT) genes and nitrogen levels were evaluated in two-year-old Jumeigui grapevines (Vitis vinifera L.×Vitis labrusca L.) when significant differences in shoot growth were observed between treatments at expansion stage (22 days after anthesis). Grapevines were planted in root-restricting pits as root restriction and in an unrestricted field as the control. Results showed that root restriction significantly reduced shoot growth, but promoted the growth of white roots and fibrous brown roots and improved the fruit quality. (NO3−+NO2−)-N concentration in all plant parts, NH4+-N concentration in white roots and total N concentration in leaves and brown roots were significantly reduced under root restriction. Gene expression analysis revealed that mRNA levels of genes related to the GS1/NADH-GOGAT pathway were lower in root-restricted than in control petioles, whereas genes involved in the GS2/Fd-GOGAT pathway were up-regulated under root restriction. Root restriction also resulted in down-regulation of genes involved in nitrogen metabolism in leaves, especially at 10:00, while transcript levels of all these genes were enhanced in root-restricted white and brown roots at most time points. This organ-dependent response contributed to the alteration in NO3− reduction and NH4+ assimilation under root restriction, leading to less NO3− transported from roots and then assimilated in root-restricted leaves. Therefore, this study implied that shoot growth inhibition in grapevines under root restriction is closely associated with down-regulation of gene expression in nitrogen metabolism in leaves.

Histopathological changes and evaluation of resistance in Asian rice (Oryza sativaL.) against rice root-knot nematode,Meloidogyne graminicolaGolden & Birch.

The rice root-knot nematode, Meloidogyne graminicola is one of the major pest of the rice-wheat cropping system, and is responsible for considerable yield reductions. Resistance against M. graminicola in rice could be most valuable in alleviating this problem. In the present study, 64 rice cvs./landraces were evaluated for resistance against rice root-knot nematode on the basis of root-knot index. Our study showed a large variation in susceptibility and sensitivity to M. graminicola infection among the rice cvs./landraces examined. Out of the total 64 rice cvs., seven (Abhishek, Khaja, Super Sugandhamati, Kishori Dehraduni, Gaudeshwari, Tuniaslet, Chima Kamin) had less than 10 galls/plant and of these, Abhishek exhibited a strong resistance response with least number of galls (2 galls/plant) and necrotic browning of roots. The nematode females in the roots of cv. Abhishek were smaller in size compared to those on the highly susceptible cv. Bangla Patni. The histopathological studies showed that the giant cells collapsed and degenerated before the J2s developed into adults. The resistant trait exhibiting rice cultivar, Abhishek, holds promise for resistance breeding and also for identifying resistance gene/s against M. graminicola.

Effects of the endophyte Epichloë festucae var. lolii of perennial ryegrass (Lolium perenne) on indicators of oxidative stress from pathogenic fungi during seed germination and seedling growth

To determine whether infection by a fungal endophyte of the genus Epichloe has a modifying influence on pathogenic fungal stress, endophyte-infected (E+) and endophyte-free (E-) seeds of perennial ryegrass (Lolium perenne), inoculated with the ryegrass pathogens Alternaria alternata, Ascochyta leptospora, Bipolaris sorokiniana, Curvularia lunata and Fusarium avenaceum were used for germination experiments and quantification of oxidative stress. Four measures of oxidative stress were used: malonaldehyde (MDA) content, peroxidases (POD) and superoxide dismutase (SOD) activity, and proline content. MDA content, an indicator of membrane lipid peroxidation damage, was significantly lower in E+ seedlings than in E- seedlings under stress from the test fungi. POD activity of E+ seedlings exposed to A. alternata, B. sorokiniana and C. lunata was significantly higher than similarly challenged E- seedlings. SOD activity of E+ seedlings was significantly higher than E- seedlings after exposure to A. alternata, B. sorokiniana, C. lunata and As. leptospora. Proline content of E+ seedlings exposed to the five pathogens was significantly higher than E- seedlings. Interestingly, these effects were present in the absence of disease symptoms apart from some root browning of E+ and E- seedlings exposed to B. sorokiniana. The results of this study showed that the seed-borne endophyte E. festucae var. lolii has potential to enhance establishment of perennial ryegrass by providing protection against pathogenic fungi during the critical early stages of seed germination and subsequent growth.

Effects of Reductants on Phytoextraction of Chromium (VI) by Ipomoea aquatica

Reductants are often used to reduce Cr(VI) in chemical treatments, yet the effects of the reductants on Cr(VI) phytoremediation are not fully understood. This study investigates the effects of different reductants on Cr(VI) phytoremediation by Ipomoea aquatica in simulated solution with 3 mg L−1 of Cr(VI), pH0 of 6, and an incubation time of 5 days. Results indicate that the applications of S2O32−, Fe0, and Fe2+ at low doses notably increased root Cr concentrations, which were obviously higher than that those in the control (Cr6+ alone). However, high reductant concentrations decreased bioaccumulation of Cr in the roots and shoots of the plant.Statistical results indicate that Cr concentrations were significantly and negatively correlated with Fe concentrations in the roots and shoots of the plant (p < 0.05). This suggest that Fe accumulation inhibited Cr accumulation in the plant. A Cr(VI) concentration of 3 mg L−1 caused short, brown lateral roots with tip necrosis, leaf chlorosis, and noticeable shoot wilting. The leaf necrosis and shoot wilting is caused by oxidative damage of lateral roots by Cr(VI) rather than by the reactive oxygen species generated by the oxidative stress. Addition of the reductants effectively reduced these plant injuries.

Characterization of the antifungal and plant growth-promoting effects of diffusible and volatile organic compounds produced by Pseudomonas fluorescens strains

We analyzed the antifungal and plant growth-promoting (PGP) effects of diffusible and volatile organic compounds (VOCs) produced by new rhizospheric isolates. The bacterial strains were identified as Pseudomonas fluorescens UM16, UM240, UM256, and UM270, based on their complete 16S ribosomal gene sequencing. These pseudomonads showed a high degree of antagonism against the phytopathogen Botrytis cinerea during confrontation assays. In addition, all strains significantly increased Medicago truncatula biomass and chlorophyll content. Interestingly, these activities were exerted by the emission of either diffusible organic compounds or VOCs. During biocontrol experiments, the four P. fluorescens strains were able to protect M. truncatula plants from B. cinerea infection by reducing stem disease symptoms and root browning. The potential presence of phenazines, cyanogens, and ACC (1-aminocyclopropane-1-carboxylate) deaminase, as well as the production of biofilm, siderophores, proteases, and indole-3-acetic acid were identified in most of the strains. The VOCs emitted by all four Pseudomonas strains were similar, and sulfur-containing compounds were among the most abundant, including dimethyl disulfide. Interestingly, the strain UM270 was the only one that produced dimethylhexadecylamine, a compound with antifungal and PGP activities. In conclusion, the Pseudomonas strains analyzed here exert multiple antagonistic and PGP mechanisms, and represent an excellent option to be used as either biocontrol or biopromoting agents in crops.

Potential use and mode of action of the new strain Bacillus thuringiensis UM96 for the biological control of the grey mould phytopathogen Botrytis cinerea

The potential use of Bacillus thuringiensis UM96 as a biocontrol agent for the grey mould phytopathogen Botrytis cinerea was evaluated. In order to dissect the mode of action of this UM96 strain, we also examined the role of lytic activities in the antagonism. First, B. thuringiensis UM96 was characterised based on 16S rRNA and gyrA gene sequencing and phenotypic traits. Petri dish biocontrol assays demonstrated that when strain UM96 was inoculated 24 h previous to B. cinerea, the mycelial growth was inhibited by up to 70%. Test for lytic enzymes activities of cellulase and glucanase was negative. Chitinase was the only positive enzyme activity in two different culture media. PCR detection of the chiB gene was also positive. Chitinolytic supernatants, obtained from rich and minimal media supplemented with colloidal chitin as the sole carbon source, from B. thuringiensis UM96 showed a strong inhibitory effect of B. cinerea that was not observed with heat-treated supernatant. Interestingly, when the supernatant was supplemented with 100 µM allosamidin, a chitinase specific inhibitor, the antagonistic activity was suppressed significantly. A lack of chitinase activity was also observed in allosamidin-treated supernatants. Our pathogenic B. cinerea strain also exhibited susceptibility to pure Streptomyces griseus chitinase. Finally, the chitinolytic strain B. thuringiensis UM96 was able to protect Medicago truncatula plants in vitro from B. cinerea infection and significantly reduced the necrotic zones and root browning of the plants. Together, these results suggest a potential use of B. thuringiensis UM96 for the biological control of B. cinerea and a role for chitinases during the antagonism displayed.

EFEITO DE ANTIOXIDANTES SOBRE O ESCURECIMENTO DE BATATAS BAROA MINIMAMENTE PROCESSADAS - DOI: 10.13083/1414-3984.v22n03a01

Objetivou-se com este trabalho avaliar o efeito de diferentes concentrações dos antioxidantes ácido ascórbico e ácido cítrico sobre o escurecimento de batatas baroa minimamente processadas. As raízes foram selecionadas, lavadas com detergente e enxaguadas em água corrente. Em seguida, foram sanitizadas, descascadas, cortadas em fatias de 1cm de espessura e novamente sanitizadas com posterior enxágue. Logo após, as rodelas foram imersas nos seguintes tratamentos: água gelada; solução de ácido ascórbico 1% + ácido cítrico 1%; solução de ácido ascórbico 2% + ácido cítrico 2% e solução de ácido ascórbico 3% + ácido cítrico 3%. As rodelas foram centrifugadas, acondicionadas em embalagens de polipropileno e mantidas a 5 ± 2 oC e 90 ± 5% de umidade relativa, durante um período de oito dias. Para a avaliação da perda de massa, o experimento foi instalado em esquema fatorial 4 x 9 (4 tratamentos aos 0, 1, 2, 3, 4, 5, 6, 7 e 8 dias) no delineamento inteiramente casualizado com quatro repetições. Para as análises de cor, pH e teor de sólidos solúveis foi utilizado um esquema fatorial 4 x 5 (4 tratamentos aos 0, 2, 4, 6 e 8 dias) com quatro repetições. Os dados foram submetidos à metodologia de superfície de resposta. As batatas apresentaram melhor qualidade com o tratamento 3% ácido ascórbico + 3% ácido cítrico, chegando ao final do armazenamento com menor perda da coloração amarela.

First Report of Root Rot Caused by Pythium aphanidermatum on Bell Pepper (Capsicum annuum L.) in Italy.

During July 2012, symptoms of root rot were observed on bell pepper (Capsicum annuum) grown in 2,000 m2 of commercial greenhouses near Cuneo in northern Italy. Symptoms first developed 30 to 40 days after transplanting, when greenhouse temperatures ranged from 25 to 30°C, and 10% of the plants were affected. Affected plants were stunted with leaf chlorosis, reduced growth, and sudden wilting. Roots were severely affected with a brown discoloration, water-soaking, and soft rot. Eventually, affected plants collapsed. Tissue fragments of 1 mm2 were excised from symptomatic roots, dipped in a 1% sodium hypochlorite solution, and placed on potato dextrose agar (PDA) and an agar medium selective for oomycetes (3). Plates were incubated under constant fluorescent light at 22 ± 1°C for 5 days. An isolate grown for 12 days on V8 agar medium (200 ml V8 Campbell Soup, 15 g agar, 0.5 g CaCO3, and 1 liter distilled water) showed aseptate hyphae that were 3.5 to 6.3 μm (avg. 5.2 μm) wide. Oogonia were globose, smooth, and 24.3 to 29.0 (avg. 25.1) μm in diameter. Antheridia were barrel-shaped, while oospores were globose, and 17.3 to 23.5 μm (avg. 21.2 μm) in diameter. These morphological characters identified the microorganism as a Pythium sp. (4). The ITS region of rDNA of a single isolate was amplified using the primers ITS1/ITS4 and sequenced. BLAST analysis (1) of the 781-bp segment (GenBank Accession KF840479) showed 100% homology with the ITS sequence of an isolate of Pythium aphanidermatum in GenBank (AY598622.2). Pathogenicity tests were performed twice on 30-day-old plants of C. annuum cv. Cuneo grown in 2-L pots (4 plants/pot), containing a steam-disinfested, organic peat substrate (70% black peat and 30% white peat, pH 5.5 to 6.0, N 110 to 190 mg/liter, P2O5 140 to 230 mg/liter, K2O 170 to 280 mg/liter) that was infested with wheat and hemp kernels colonized by the isolate of P. aphanidermatum, at a rate of 1 g colonized kernels/liter potting medium. The inoculum was prepared by autoclaving at 121°C for 30 min a mixture of wheat-hemp kernels (2:1 v/v) in a 1-liter flask, to which the bell pepper isolate of P. aphanidermatum was added in the form of colonized agar medium selective for oomycetes plugs. Before use, the inoculated flask was incubated for 10 days at 22°C in the dark. Four plants/pot were transplanted into each of four pots filled with the infested medium/growth chamber, while the same number of plants were grown in non-infested substrate in pots in each growth chamber. Plants were kept in two growth chambers, one set at 20°C and the other at 28°C. Symptoms first developed 7 days after inoculation. After 30 days, 50% of inoculated plants showed brown roots and died in the growth chamber set at 28°C, while only 10% of the plants were symptomatic at 20°C. Control plants remained asymptomatic at both temperatures. P. aphanidermatum was re-isolated consistently from the symptomatic roots of plants grown in the infested soil by using the same protocol as the original isolations, while no fungal colonies were obtained from asymptomatic roots of the non-inoculated control plants. To our knowledge, this is the first report of the presence of P. aphanidermatum on C. annuum in Italy. The same disease was reported in the United States (2). The importance of the disease, although limited in distribution at present to the greenhouses surveyed in northern Italy, could increase in areas where sweet pepper is grown intensively.

감초, 황기 추출물로 블랜칭 처리한 신선편이 연근의 갈변 억제

This study was conducted to inhibit the browning of fresh-cut lotus roots by blanching in a Glycyrrhiza glabra L. and Astragalus membranaceus Bunge extract solution (0.5%). Lotus roots were cut to 1 cm using a knife. The fresh-cut lotus roots were blanched at 50℃ in distilled water (DW, Cont), Glycyrrhiza glabra L. extract solution (GE), and Astragalus membranaceus Bunge extract solution (AE). After treatment, they were packaged with 0.04 mm PE bags and were stored at 10℃ for 12 days. Their color, hardness, DPPH radical scavenging activity, pH, and total soluble solids were then investigated. During storage, the samples treated with GE and AE had high L* values. They were also found to have higher values compared to the control group in the analysis of the browning index. No difference was found, however, in the hardness analysis. With regard to the DPPH radical scavenging activity, the sample treated with Glycyrrhiza glabra L. extract had the highest activity. In the pH analysis, all the groups were found to have a decrease tendency for all the storage periods. The total soluble solids decreased in the control group and slightly increased in the AE and GE groups. These results show that blanching in Glycyrrhiza glabra L. or Astragalus membranaceus Bunge extract is effective for preventing the browning of fresh-cut lotus roots.

棉花转基因体细胞胚胎的诱导及植株再生

以陆地棉种质系Coker 312为材料，探讨了三种氨基酸对棉花转基因胚性愈伤生长、胚状体诱导、萌发及NAA对转基因再生植株生根的影响，建立一个高效的转基因体细胞胚萌发系统。结果表明：单独使用Pro、Glu时能提高转基因胚性愈伤增长、胚状体诱导及萌发能力，但以综合使用效果更为显著，Ala的附加没有显著影响；当生根培养基NAA的浓度为0.3 mg/L，根的诱导数量及质量都优于对照。但NAA的浓度不宜过高，过高则加重了根的褐化程度。对得到的转基因再生植株进行Kan涂抹实验，Kan抗性苗获得率可达到11.53%；PCR检测约83.78%的Kan抗性苗呈阳性。 In this paper, the effect of three amino acids on the growth of embryonic calli, embryo germination after transformation and the effect of Naphthlcetic acid (NAA) on rooting in cotton (Gossypium hirsutum L.) were investigated. The results showed that: embryogenic callus growth and embryo germination ability were effectively improved on the medium with Glu and Pro, especially with 0.5 mg/LGlu and 0.5 mg/L Pro at the same time. However, the additional of Alahad no significant impact; Using 0.3 mg/L NAA in the rooting medium could produce more strong roots, but too high NAA concentration increased the level of root browning. The percentage of Kan-resistant regenerated plantlets reached 11.53% according to the Kanamycin smear experiments and about 83.78% of the Kan-resistant plantlets were proven to be PCR-positive. The successful transformation and regeneration protocol established in this study can be used to improve cotton cultivars by genetic engineering.

포장재질에 따른 열처리한 연근의 저장 중 품질변화

This study was investigated the changes in quality of heat treated fresh-cut lotus roots using various packaging materials. Lotus roots were purchased from Daegu, Korea. Lotus roots were washed, peeled and sliced with a sharp ceramic knife. The prepared peeled and sliced lotus roots were dipped for 45 sec in water at . After air-dried at room temperature, the slices were packaged with polyethylene films, polyethylene terephthalate tray+wrapping, vacuum packaging and then stored at . Changes in weight loss, color, firmness, microorganisms and sensory characteristics were measured. In general, the weight loss rate was increased slightly in vacuum packaged lotus roots. Application of heat treatment delayed browning of lotus roots, and especially vacuum packaged lotus roots were the most lowest value. However, L and value of PE film packaged lotus roots were increased highly during storage. The heat treated and vacuum packaging inhibited the growth of microorganisms effectively. The organoleptic quality of vacuum packaged lotus roots showed the best by sensory evaluation.

Effects of Agrobacterium rhizogenes strains and other parameters on production of isoflavonoids in hairy roots of Pueraria candollei Grah. ex Benth. var. candollei

Using several explants of Pueraria candollei Grah. ex Benth. var. candollei and two strains of Agrobacterium rhizogenes (ATCC 15834 and 43057), hairy root cultures were established. Including 100 μM acetosyringone in the culture medium enhanced frequency of hairy root induction by up to 58 %. Subsequently, effects of inoculum size (IS) and temperature on growth and production of isoflavonoids in hairy roots were determined. Conditions of 1 % IS and 32 °C promoted the highest accumulation of total isoflavonoid content, up to 31.0 ± 22.6 mg/g dry weight (DW), in hairy roots. Moreover, culture of hairy roots at 32 °C decreased browning of hairy roots. Furthermore, this temperature promoted accumulation of the secondary metabolite daidzein; whereas, hairy root cultures at the stationary phase accumulated higher amounts of the isoflavonoid puerarin rather than daidzein.

Effect of root restriction on nitrogen levels and glutamine synthetase activity in ‘Kyoho’ grapevines

To unravel the inhibition of root restriction on shoot growth, the changes of nitrogen levels and glutamine synthetase (GS, EC 6.3.1.2) activity were investigated in four-year-old root-restricted ‘Kyoho’ grapevines (Vitis vinifera×Vitis labrusca) in greenhouse from veraison up until 62 days after harvest. ‘Kyoho’ grapevines were planted in buried bed as root restriction and in raised bed (unrestricted rooting zone) as the control. Results showed that root restriction significantly decreased the total amount of N in leaves, berry flesh, white and brown roots, (NO3−+NO2−)–N content in leaves, white and brown roots, and NH4+–N content in brown roots. In addition, root restriction reduced not only N remobilization and recycling from leaves to roots after harvest, but also the total GS activity in both leaves and roots, suggesting that root restriction has a negative influence on glutamine synthesis in grapevines. However, soluble protein content in both leaves and white roots significantly increased under root restriction from 118 to 180 days after anthesis (DAA). It can be attributed to the increased synthesis of polypeptides and/or the enhanced de novo synthesis of proteins in root-restricted vines. In summary, the results illustrated less N reserve in root-restricted vines, which might be responsible for shoot growth inhibition under root restriction.

Quantitative relationships of Pseudomonas chlororaphis 63-28 to Pythium root rot and growth in hydroponic peppers

The ability of Pseudomonas chlororaphis 63-28 to suppress Pythium root rot (Pythium aphanidermatum) and promote plant growth was investigated in hydroponic peppers that were predisposed or not predisposed to the disease. The biocontrol agent was introduced into the nutrient solution 10 days before the roots were inoculated with the pathogen. The root zone was maintained at 23oC except when roots were exposed to 33oC for three days before inoculation to induce predisposition to root rot. At constant 23oC (no predisposition) application of P. chlororaphis at 107 CFU mL-1 nutrient solution delayed root browning more effectively than did higher or lower densities. In predisposed plants, densities of 106, 107 and 108 CFU mL-1 were equally superior. When applied at 107 CFU mL-1, the density of P. chlororaphis on roots of the two temperature regimes ranged from log10 5.88 to 6.45 CFU g-1 fresh roots at seven to 19 days after application. The agent delayed root browning, re-mediated predisposition to root rot, and increased growth of inoculated and non-inoculated plants. Leaf expansion was a sensitive marker of root rot and remediation by P. chlororaphis. We conclude that P. chlororaphis 63-28 has substantial potential for managing the disease regardless of predisposition.