Rice Isolates Research Articles

Studies on nitrogenase activity of diazotrophic isolates from different rice production systems

The present study was carried out to evaluate the nitrogen fixing ability of diazotrophs isolated from the rhizosphere soils of rice which were grown in three different rice growing systems. A total of hundred and ten isolates obtained were subjected to Acetylene Reduction Assay (ARA) and ninety eight isolates recorded significant amount of nitrogenase activity in a range of 185.73 to 3794.55 nmoles of ethylene mg of protein-1 h-1. The highest nitrogenase activity was recorded by Derxia (3794.55 nmoles of ethylene mg of protein-1 h-1) isolated from Trichy (lowland). Among the three different rice production systems, isolates obtained from lowland rice (Derxia – 3794.5 nmoles of ethylene mg of protein-1 h-1) recorded higher nitrogenase activity followed by Aerobic (Pseudomonas - 2194.89 nmoles of ethylene mg of protein-1 h-1) and SRI (Azotobacter - 1971.85 nmoles of ethylene mg of protein-1 h-1) rice isolates. The results revealed marked variation in the ARA of the diazotrophic isolates obtained from lowland, SRI and Aerobic rice. The nitrogenase activity of diazotrophs from rice fields have been reported earlier but the nitrogenase activity of diazotrophs from three different rice production systems from various parts of Tamil Nadu is reported for the first time from India.

Rice and soy protein isolate in pre-starter diets for broilers

Although most industries use a specific diet for the pre-starter phase, ingredients are used in the later phases, primarily corn and soybean meal, which at this stage do not have high digestibility. Three experiments ( Exp) were carried out to evaluate the substitution of corn by white or parboiled rice ( WR, PR) and the inclusion of 6% soy protein isolate ( SPI) in pre-starter diets (1 to 7 d). In Exp 1 (1 to 21 d), WR, PR, and SPI were added to the diets until the birds were 21-day-old, whereas in Exps 2 and 3 (1 to 33 d), only until birds were 7-day-old. Birds were fed a basal diet based on corn and soybean meal until the end of the experimental period. In Exp 1, the coefficients of total tract apparent retention ( CTTAR) of the pre-starter and the starter diets, ileal and jejunal digestibility of starch in the starter diets, and broiler performance were measured. Subsequently, the same pre-starter diets Exp 1 were evaluated in pellet (Exp 2) or mash (Exp 3) form and different oil percentage (Exp 2) or not (Exp 3). We hypothesized that the ingredients particle size (Exp 2) and fat content (Exp 3) could influence feed intake. There was no interaction among the evaluated factors (P > 0.05). Rice (WR or PR) promoted better results than corn in terms of CTTAR of dietary components, jejunal and ileal starch digestibility, and broiler performance (P < 0.01). In Exp 1, diets with 6% SPI presented better CTTAR, except Nitrogen (N), but lower feed intake, which negatively affected broiler performance (P < 0.01). In Exps 1, 2, and 3, the inclusion of SPI did not improve broiler performance (P > 0.05), so that SPI may not be the best choice for pre-starter diets. The study also suggests that better growth performance and nutrient digestibility can be obtained in broiler chickens if corn is replaced by rice in pre-starter diets.

Digestive enzymes reduce quality differences between plant and animal proteins: a double-blind crossover study

Background Whey protein is considered to be the optimal protein source to support muscle protein synthesis (MPS) with resistance training, based on its amino acid content (high in leucine), rapid digestibility, and high bioavailability within the muscle tissue [1]. Athletes can choose from different plant protein sources (e.g. soy, rice, pea, hemp), which differ in numerous ways, such as the presence of allergens (milk, soy), cholesterol, saturated fats, digestion rate (fast, intermediate, or slow absorption of amino acids), or the relative amount of individual amino acids. Rice protein has been shown to promote muscle hypertrophy with resistance training comparable to whey protein [2]. 48g of rice or whey protein isolate immediately post-exercise during an 8-week progressive, non-linear resistance-training protocol increased lean body mass, muscle thickness, and strength with no differences between groups. The findings are likely due to the high dose of protein used in the study, providing amounts of leucine greater than the 1.7 to 3.5g that has been proposed to be the range for optimal MPS. Rice protein, compared to whey (fast) and casein (slow), is an intermediate digesting protein and shows a 6.8% lower total amino acid appearance in the blood [3]. While dairy protein sources contain simple sugars, mainly lactose, plant proteins contain more complex carbohydrates, including fibers and glycoproteins. This study sought to investigate if co-ingestion of a plant protein specific digestive enzyme blend (Digest-All VP, a proprietary enzyme blend consisting of protease 6.0, protease 4.5, peptidase, bromelain and alpha-galactosidase, Chemi-Source, Inc., Oceanside, CA) can reduce the significant differences in amino acid appearance in the blood between plant and animal proteins.

The complete genome sequence of Dickeya zeae EC1 reveals substantial divergence from other Dickeya strains and species.

BackgroundDickeya zeae is a bacterial species that infects monocotyledons and dicotyledons. Two antibiotic-like phytotoxins named zeamine and zeamine II were reported to play an important role in rice seed germination, and two genes associated with zeamines production, i.e., zmsA and zmsK, have been thoroughly characterized. However, other virulence factors and its molecular mechanisms of host specificity and pathogenesis are hardly known.ResultsThe complete genome of D. zeae strain EC1 isolated from diseased rice plants was sequenced, annotated, and compared with the genomes of other Dickeya spp.. The pathogen contains a chromosome of 4,532,364 bp with 4,154 predicted protein-coding genes. Comparative genomics analysis indicates that D. zeae EC1 is most co-linear with D. chrysanthemi Ech1591, most conserved with D. zeae Ech586 and least similar to D. paradisiaca Ech703. Substantial genomic rearrangement was revealed by comparing EC1 with Ech586 and Ech703. Most virulence genes were well-conserved in Dickeya strains except Ech703. Significantly, the zms gene cluster involved in biosynthesis of zeamines, which were shown previously as key virulence determinants, is present in D. zeae strains isolated from rice, and some D. solani strains, but absent in other Dickeya species and the D. zeae strains isolated from other plants or sources. In addition, a DNA fragment containing 9 genes associated with fatty acid biosynthesis was found inserted in the fli gene cluster encoding flagellar biosynthesis of strain EC1 and other two rice isolates but not in other strains. This gene cluster shares a high protein similarity to the fatty acid genes from Pantoea ananatis.ConlusionOur findings delineate the genetic background of D. zeae EC1, which infects both dicotyledons and monocotyledons, and suggest that D. zeae strains isolated from rice could be grouped into a distinct pathovar, i.e., D. zeae subsp. oryzae. In addition, the results of this study also unveiled that the zms gene cluster presented in the genomes of D. zeae rice isolates and D. solani strains, and the fatty acid genes inserted in the fli gene cluster of strain EC1 were likely derived from horizontal gene transfer during later stage of bacterial evolution.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1545-x) contains supplementary material, which is available to authorized users.

Morphological and Molecular Variability of Rhizoctonia solani Isolates Causing Banded Leaf and Sheath Blight in Maize

Twenty seven isolates of Rhizoctonia solani causing Banded Leaf and Sheath Blight in maize were collected from different maize varieties and one from rice grown in various regions of Telengana State, India for easy breeding task. The isolates were analysed for their morphological and genetic characterization. The hyphal width varied from 5.00 (RS2, RS20) to 7.97 μm (RS10) of rice isolate (7.34 μm). The isolates RS7, RS 8, RS9 (Karimnagar), RS10, RS11, RS12 (Khammam) RS16 (Krishna) and RS26 (Kurnool) and one rice isolate RS28 produced barrel shaped monilioid cells. The clamp connection was present only in RS1 isolate from Pragnyapur mandal of Medak district. The three isolates RS16, RS17, RS18 from Krishna district and rice isolate RS28 recorded maximum colony growth of 90.00 mm within 48 h of incubation. The colour of most isolates varied from light grey to brown while the rice isolate showed a typical yellowish brown shade. The sclerotial number per 5.00 mm culture disc of test isolates ranged from between (7.00) to (17.67). Their size varied between 0.21 μm (RS 24) and 1.57 μm (RS11). The rice isolate RS28 recorded highest (19.00) sclerotial count compared to that of maize isolates. Sclerotial colour in all isolates except for RS 24 was yellowish brown to dark reddish brown whereas the rice isolate was dark yellowish brown. Molecular characterization of the test isolates using RAPD markers with UPGMA exhibited two major clusters with 66 to 90% genetic similarity. Art ic le History

Identification and utilization of actinobacteria for biocontrol of rice sheath blight pathogen, Rhizoctonia solani

Sheath blight of rice is an important soil-borne fungal disease caused by Rhizoctonia solani . Isolation and exploitation of bioagents associated with rice offers a great opportunity for sustainable management of rice diseases. Actinomycetes were isolated from rice rhizosphere and isolates were putatively selected based on characteristic colony morphology. 16S rDNA and ARDRA confirmed their identification as actinobacteria. Isolates belonged either to Streptomyces spp. or Actinopolymorpha spp. Under in vitro condition, isolates IABT-A1, IABTA2, IABT-A3, IABT-A6, IABT-A7, IABT-A8 and IABT-A9 showed 98-100 per cent inhibition of Rhizoctonia solani , rice sheath blight pathogen. Further, five isolates were evaluated under glass house condition and the potent actinobacteria against rice sheath blight was identified. Among these isolates, IABT-A7 ( Actinopoymorpha spp.) was most effective and application as seed treatment, soil and foliar spray was found most promising in terms of disease reduction and plant growth promotion. Actinopoymorpha spp. (IABT-A7) enhanced plant height, root length and root biomass in addition to reduced sheath blight infection in rice. This result indicates the role of actinobacteria isolate IABT-A7, as the probable stimulator of ISR (Induced Systemic Resistance) signaling pathway involved in plant disease resistance.

Mal-do-pé do arroz: hospedeiros e resistência varietal a Gaeumannomyces graminis var. graminis

Diversas gramíneas que ocorrem em lavouras de arroz apresentam sintomas do mal-do-pé, causado por Gaeumannomyces graminis var. graminis (Ggg), em condições naturais de infecção. Com o objetivo de obter informações sobre hospedeiros e resistência de genótipos de arroz ao mal-do-pé, foi estudada a patogenicidade do isolado Ggg-a 01, coletado de arroz, em sete espécies de capim e oito de cereais, em casa-de-vegetação. Os testes de inoculação mostraram que o isolado de arroz foi patogênico às plantas daninhas de capim arroz (Echinochloa crusgalli), avião (Pennisetum setosum), braquiária (Brachiaria sp.), digitária (Digitaria horizontalis), marmelada (Brachiaria plantaginea), pé-de-galinha (Eleusine indica) e timbete (Cenchrus echinatus) e que essas espécies constituem hospedeiros potenciais do patógeno. Cereais de inverno, como o trigo, aveia, centeio, cevada e triticale, bem como o sorgo, milho e milheto, apresentaram diferentes graus de suscetibilidade ao isolado Ggg-a 01. As diferenças foram significativas, quanto à altura da lesão e à produção de hifopódios e de peritécios nos colmos. Não foram observados peritécios em milheto, sorgo, timbete e milho. A resistência de 58 genótipos de arroz de terras altas ao isolado foi avaliada e os genótipos SCIA16 e SCIA08 apresentaram altura de lesão significativamente menor, sendo considerados resistentes, em relação ao genótipo CNAS10351, altamente suscetível.

Prezygotic Reproductive Isolation and Fertility in Crosses between &amp;lt;italic&amp;gt;Indica&amp;lt;/italic&amp;gt; and &amp;lt;italic&amp;gt;Japonica&amp;lt;/italic&amp;gt; Subspecies

Reproductive isolation is essential to the formation and maintenance of new species. Understanding the mechanism of reproductive isolation is fundamental in biological science. Reproductive isolation occurred between the indica and japonica subspecies in rice. However, mechanisms of prezygotic reproductive isolation in rice are poorly understood, which require further investigation. In this study, we have investigated the adherence and germination of the pollens using 17 crosses from a total of 12 varieties representative of indica , japonica , and wide-compatibility varieties. Prezygotic reproductive isolation was observed between the indica and japonica subspecies, which showed that the average pollen adhered was less than 5 per stigma in 2/3 inter-subspecific crosses. However, the average number of adherent pollen was more than 5 per stigma in 3/4 intra-subspecific crosses and all the crosses with the wide-compatibility varieties. Various abnormalities of pollen tube growth were observed in inter-subspecific crosses, but not in intra-subspecific crosses and crosses with the wide-compatibility varieties. The amount of the pollen adhered was irrelevant to the fertility in F1 hybrids, indicating that prezygotic and postzygotic reproductive isolation occurred independently. The reduced affinity between the pollens and stigma in indica and japonica subspecies prevents the formation of hybrid zygotes, which contributes to prezygotic reproductive isolation in rice. Our findings provide valuable insight in understanding the mechanism of reproductive isolation and have implications for utilization of heterosis.

Identification and functional analysis of AG1-IA specific genes of Rhizoctonia solani.

Rhizoctonia solani is an important necrotrophic fungal pathogen which causes disease on diverse plant species. It has been classified into 14 genetically distinct anastomosis groups (AGs), however, very little is known about their genomic diversity. AG1-IA causes sheath blight disease in rice and controlling this disease remains a challenge for sustainable rice cultivation. Recently the draft genome sequences of AG1-IA (rice isolate) and AG1-IB (lettuce isolate) had become publicly available. In this study, using comparative genomics, we report identification of 3,942 R. solani genes that are uniquely present in AG1-IA. Many of these genes encode important biological, molecular functions and exhibit dynamic expression during in-planta growth of the pathogen in rice. Based upon sequence similarity with genes that are required for plant and human/zoonotic diseases, we identified several putative virulence/pathogenicity determinants amongst AG1-IA specific genes. While studying the expression of 19 randomly selected genes, we identified three genes highly up-regulated during in-planta growth. The detailed in silico characterization of these genes and extent of their up-regulation in different rice genotypes, having variable degree of disease susceptibility, suggests their importance in rice-Rhizoctonia interactions. In summary, the present study reports identification, functional characterization of AG1-IA specific genes and predicts important virulence determinants that might enable the pathogen to grow inside hostile plant environment. Further characterization of these genes would shed useful insights about the pathogenicity mechanism of AG1-IA on rice.

Biochemical characterization of sunscreening mycosporine-like amino acids from two Nostoc species inhabiting diverse habitats.

We have screened two Nostoc species inhabiting diverse habitats for the presence of sunscreening mycosporine-like amino acid (MAA) compounds. The identification and characterization of one MAA (RT 3.1-3.8min, λmax -334nm) from both Nostoc species were performed using absorption spectroscopy, high-performance liquid chromatography (HPLC), electrospray ionization-mass spectrometry (ESI-MS), Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. Shinorine and porphyra-334 were commonly present in both Nostoc sp. strain HKAR-2 and Nostoc sp. strain HKAR-6. Nostoc sp. strain HKAR-2 also showed the presence of an unknown MAAs with retention time of 6.9min and a corresponding λmax of 334nm. Present investigation clearly demonstrated the presence of diverse profile of MAAs in the hot spring cyanobacterium in comparison to the rice field isolate. Thus, Nostoc sp. strain HKAR-2 would be a better source for the production of MAAs that can be used as a potent natural sunscreen against UV-B irradiation.

Cultural and morphological variability amongRhizoctonia solaniisolates from trans-gangetic plains of India

Banded leaf and sheath blight incited by Rhizoctonia solani f. sp. sasakii Khunn. (Teleomorph: Thanatephorus cucumeris) is gaining devastating potentials in India. The pathogen is reported to show variation in expression of symptoms on the same genotypes grown in different locations. Fifteen isolates from trans-gangetic plains of India were collected to examine the cultural and morphological variability and pathogenic behaviour on host Zea mays. The isolates were from maize and rice host origins. Considerable variability was found among the isolates. The isolates of maize origin were poor sclerotia producing in culture, formed compact dense/fluffy, pale white to yellowish growth on PDA, producing irregular to organized, smooth surfaced sclerotia, faster radial growth in culture, acute branching of hyphae and high pathogenicity. The rice isolates showed a contrasting behaviour in forming sub-central to scattered, pitted sclerotia lighter in weight than maize counterparts, compact sparse colony, slow to medium radial growth, light brown to dark brown colony. Aerial bearing was not recorded in most of these isolates. All the rice isolates were fast sclerotia initiating in culture; however, higher incubation period was recorded in pathogenicity tests. The lesions were also scattered and disease score ranged from 2.6–3.1. The cultural and morphological parameters used in this investigation may be used to examine the biology of R. solani isolates from other agro-climatic regions also.

Comparative Analysis of the Korean Population of Magnaporthe oryzae by Multilocus Microsatellite Typing.

Rice blast fungus, Magnaporthe oryzae, inflicts serious damage to global rice production. Due to high variability of this fungal pathogen, resistance of newly-released rice cultivars is easily broken down. To understand the population structure of M. oryzae, we analyzed the genetic diversity of the Korean population using multilocus microsatellite typing. Eleven microsatellite markers were applied to the population of 190 rice isolates which had been collected in Korea for two decades since the 1980’s. Average values of gene diversity and allele frequency were 0.412 and 6.5, respectively. Comparative analysis of the digitized allele information revealed that the Korean population exhibited a similar level of allele diversity to the integrated diversity of the world populations, suggesting a particularly high diversity of the Korean population. Therefore, these microsatellite markers and the comprehensive collection of field isolates will be useful genetic resources to identify the genetic diversity of M. oryzae population.

Development of Genomic SSR Markers and Molecular Characterization of Magnaporthe oryzae Isolates from Wheat in Brazil

Magnaporthe oryzae, the causal agent of wheat blast, was characterized on a molecular level with 38 newly isolated genomic SSR loci. Among the 31 wheat isolates analyzed, 15 polymorphic loci were detected, with an average of 1.7 alleles per locus, 28.9% of them being highly or reasonably informative. The number of polymorphic loci was higher in isolates from Londrina in the Brazilian state of Paraná and Coromandel in Minas Gerais compared with Goiânia in Goiás and São Borja in Rio Grande do Sul. The rice isolate was clearly different from the wheat isolates, and the size difference in polymorphic SSR loci between one isolate from wheat and one isolate from rice was associated with the number of repeats. Some isolates collected from different states and in different years demonstrated similarities of 100%. The markers developed here are useful for the genetic analysis of M. oryzae isolated from wheat, and isolates representing the variability detected in the field can be used to search for better wheat blast resistance.

Light affects fumonisin production in strains of Fusarium fujikuroi, Fusarium proliferatum, and Fusarium verticillioides isolated from rice

Three Fusarium species associated with bakanae disease of rice (Fusarium fujikuroi, Fusarium proliferatum, and Fusarium verticillioides) were investigated for their ability to produce fumonisins (FB1 and FB2) under different light conditions, and for pathogenicity. Compared to darkness, the conditions that highly stimulated fumonisin production were yellow and green light in F. verticillioides strains; white and blue light, and light/dark alternation in F. fujikuroi and F. proliferatum strains. In general, all light conditions positively influenced fumonisin production with respect to the dark. Expression of the FUM1 gene, which is necessary for the initiation of fumonisin production, was in accordance with the fumonisin biosynthetic profile. High and low fumonisin-producing F. fujikuroi strains showed typical symptoms of bakanae disease, abundant fumonisin-producing F. verticillioides strains exhibited chlorosis and stunting of rice plants, while fumonisin-producing F. proliferatum strains were asymptomatic on rice. We report that F. fujikuroi might be an abundant fumonisin producer with levels comparable to that of F. verticillioides and F. proliferatum, highlighting the need of deeper mycotoxicological analyses on rice isolates of F. fujikuroi. Our results showed for the first time the influence of light on fumonisin production in isolates of F. fujikuroi, F. proliferatum, and F. verticillioides from rice.

English

Potato dextrose and malt extract agar were found to be suitable for culturing different isolates of&nbsp;Pyricularia oryzae.&nbsp;Colonies of&nbsp;P. oryzae&nbsp;appeared as white on oat meal, rice polish and malt extract agar, grey on potato dextrose agar and whitish grey on rice agar. Spore induction was hastened on maize stem pieces than on rice and&nbsp;Panicum repens. Spore density on maize was 3420/ml of water as against 500/ml on&nbsp;P. repens.&nbsp;When spores of 11 isolates of&nbsp;P. oryzae&nbsp;were compared, conidia of the&nbsp;isolate from&nbsp;Pennisetum purpureum&nbsp;were significantly bigger than the other isolates.&nbsp;The spores of rice isolates from Erode and Gopichettipalayam were significantly smaller in length and width.Fingerprinting of 11 isolates of&nbsp;P. oryzae&nbsp;by retrotransposon - microsatellite amplified polymorphism (REMAP) showed a high level of variability and polymorphism among them. Phylogenetic analysis using REMAP markers grouped out one rice isolate from others. Two isolates of Tirunelveli region were grouped together like Erode and Gopichettipalayam isolates. Isolates causing leaf and neck blast showed 52.9% similarity. Isolates from Coimbatore and Gudalore were 32.7% similar; likewise two non-rice host isolates were grouped together with 27.6% similarity. &nbsp; Key words:&nbsp;Variability, culture media, rice blast,&nbsp;Pyricularia oryzae,&nbsp;retrotransposon, microsatellite.

The effects of 8 weeks of whey or rice protein supplementation on body composition and exercise performance

BackgroundConsumption of moderate amounts of animal-derived protein has been shown to differently influence skeletal muscle hypertrophy during resistance training when compared with nitrogenous and isoenergetic amounts of plant-based protein administered in small to moderate doses. Therefore, the purpose of the study was to determine if the post-exercise consumption of rice protein isolate could increase recovery and elicit adequate changes in body composition compared to equally dosed whey protein isolate if given in large, isocaloric doses.Methods24 college-aged, resistance trained males were recruited for this study. Subjects were randomly and equally divided into two groups, either consuming 48 g of rice or whey protein isolate (isocaloric and isonitrogenous) on training days. Subjects trained 3 days per week for 8 weeks as a part of a daily undulating periodized resistance-training program. The rice and whey protein supplements were consumed immediately following exercise. Ratings of perceived recovery, soreness, and readiness to train were recorded prior to and following the first training session. Ultrasonography determined muscle thickness, dual emission x-ray absorptiometry determined body composition, and bench press and leg press for upper and lower body strength were recorded during weeks 0, 4, and 8. An ANOVA model was used to measure group, time, and group by time interactions. If any main effects were observed, a Tukey post-hoc was employed to locate where differences occurred.ResultsNo detectable differences were present in psychometric scores of perceived recovery, soreness, or readiness to train (p > 0.05). Significant time effects were observed in which lean body mass, muscle mass, strength and power all increased and fat mass decreased; however, no condition by time interactions were observed (p > 0.05).ConclusionBoth whey and rice protein isolate administration post resistance exercise improved indices of body composition and exercise performance; however, there were no differences between the two groups.

Characterization of Magnaporthe grisea populations associated with rice and weeds in Iran

In this study, host-specific forms of the blast pathogen Magnaporthe grisea in Iran were characterized from distinct hosts using a combination of molecular and biological assays. A total of 106 isolates of M. grisea were obtained from north of Iran besides of seven international standards mating type (ISMT) tester isolates achieved from France. Population genetically analyzed with selected markers, such as complementation tests of nit mutants and rep-PCR to evaluate such events. Compatible isolates by complementation tests were assigned to the same vegetative compatibility group (VCG) detected as VCG1 to VCG9 among isolates from rice and weeds. During rep-PCR analysis a total of 42 polymorphic banding patterns were scored from 106 isolates which clustered by host with high bootstrap support (72 to 100 %). Genetic structure between rice and weeds isolates differed significantly. Eleven clonal lineages were identified with only two fingerprinting groups for ISMT isolates considering similarity coefficient of approximately 60 % with rice isolates. Additionally, the majority of the isolates from weeds (78.43 %) were gashed from rice isolates in 43 % similarity. Clear differences in cultivar compatibility within and between lineages suggest Distinctive patterns of genetic diversity of host-specific forms of M. grisea populations linked to crop domestication and agricultural intensification.

옥수수에 발생한 벼검은줄오갈병 바이러스 분절게놈 S8 및 S10 전 염기서열 분석

2011년에 고창 옥수수 재배지에서 RBSDV에 의한 벼 검은줄오갈병이 발생하였다. 병징은 키가 작아지고 잎에 줄무늬가 형성되면서 심하면 거의 수확이 되지 않는다. 이병주로부터 직접 dsRNA를 추출하여 RT-PCR에 의해 감염을 확인하였다. S8 및 S10 분절의 전 게놈에 특이적인 primer를 이용하여 유전자를 증폭하였다. 이것을 크로닝한 후 전 염기서열을 결정하였다. 염기서열 분석결과 S8 및 S10의 전염기서열은 각각 1,936 nt 및 1,801 nt로 구성되었다. 이는 벼에서 분리된 RBSDV와 같은 크기로 확인되었다. 벼에서 분리된 RBSDV와 상동성 분석결과 S8은 94.9-99.6%, S10은 94.1-98.4%로 나타났다. Phylogenetic tree 분석결과 옥수수에서 분리한 RBSDV S8 및 S10 모두 벼에서 분리된 RBSDV와 같은 그룹으로 분류되었다. Rice black-streaked dwarf virus (RBSDV) was reported to occur on maize plants in Gochang-gun of Jeonllabuk-do region in 2011. The symptoms typically include stunted and deformed leaves. Virus infected plants usually produce poor or no head. RT-PCR analysis of genomic dsRNA extracted from the plant confirmed the infection. Specific primers for full length genome of segments 8 and 10 were used for RNA amplification. Full-length genomes of S8 and S10 were cloned and sequenced. Sequence analysis revealed that the S8 and S10 sequences of the maize isolate were same with rice isolate in size, 1,936 nt and 1,801 nt, respectively. In comparison with rice RBSDV, S8 and S10 showed 94.9-99.6% and 94.1-98.4% sequence identity, respectively. Phylogenetic analysis showed that RBSDV S8 and S10 of maize plants are categorized into the same group as RBSDV of rice plant.

Population Structure of the Gibberella fujikuroi Species Complex Associated with Rice and Corn in Korea

Microbial Safety Team, National Academy of Agricultural Science, RDA, Suwon 441-707, Korea(Received on September 1, 2012; Revised on September 20, 2012; Accepted on September 23, 2012)Several species belonging to the Gibberella fujikuroispecies ( Gf ) complex are commonly associated with riceand corn, not only causing serious diseases, but alsoproducing fumonisins, a group of mycotoxins harmfulto animals and humans. To characterize the populationstructure of the putative fumonisin-producing Gf complexin Korea, we obtained 276 candidate isolates from riceand corn harvested in 2009 and 2010 by diagnosticpolymerase chain reaction with several specific primersets. Phylogenetic trees were constructed using multilocussequences (combined RPB2 and EF1A, totaling 1.6 kb)from these isolates. Among the 135 isolates from rice,F. fujikuroi (teleomorph: G. fujikuroi; 59.3%) and F.proliferatum (G. intermedia; 13.3%) were predominant,followed by F. concentricum (5.9%). Additionally, twenty-five (18.5%) rice isolates belonged in a distinct sub-clade of F. commune, a non-member of the Gf complex.In contrast, F. verticillioides was the most predominantspecies (38.3%) among the 141 corn isolates, and followedby F. fujikuroi (27.7%), F. proliferatum (14.9%), F. sub-glutinans (7.1%), and F. concentricum (2.8%). A singlemating type ( MAT1-1) was found predominantly amongthe Gf complex isolates examined. Possible distinct sub-clades were detected within the populations of F. fujikuroiand F. proliferatum; however, this needs further confir-mation. This is the first reported population-level charac-terization of putative fumonisin-producing Gf complexassociated with rice and corn in Korea.Keywords : fumonisin, Gibberella fujikuroi species com-plex, mating-type distribution, population structure, speciescompositionThe genus Fusarium is one of the most important fungalisolates associated with rice and corn because some membersof this group, such as the F. graminearum species complexand Gibberella fujikuroi species complex, are mycotoxinproducers as well as plant pathogens. The G. fujikuroi speciescomplex, a monophyletic lineage, consists of at least ninebiological species, formerly designated as mating populations(MPs) (Britz et al., 1999; Leslie 1999; Leslie et al., 2004),and numerous additional Fusarium anamorphs that areassigned to phylogenetically distinct species (Nirenbergand O'Donnell 1998; O'Donnell et al., 1998; O'Donnell etal., 2000). The Fusarium species in the G. fujikuroi species complexare distributed worldwide and cause serious diseases in awide variety of agricultural crops (Leslie 1999). These speciesalso produce a variety of toxic secondary metabolites andmycotoxins, including gibberellic acid (Cerda-Olmedo etal., 1994), moniliformin (Marasas et al., 1986), and fumoni-sins (Rheeder et al., 2002). Among these, fumonisins, agroup of polyketide-derived mycotoxins, have gained con-siderable attention because they have been associated withesophageal and liver cancer (Desjardins, 2006).To date, at least 15 Fusarium species, most belonging tothe G. fujikuroi species complex, are known to producefumonisins using a biochemical pathway catalyzed by apolyketide synthase (FUM1) (Proctor et al., 1999). Only afew species outside the G. fujikuroi species complex, suchas F. oxysporum, have the capacity for fumonisin produc-tion (Rheeder et al., 2002).As both rice grains and corn kernels are capable ofharboring the toxigenic G. fujikuroi species complex duringthe growing season, monitoring the fumonisin-producingFusarium species on these substrates is important. Severalspecies within the G. fujikuroi species complex are knownto be frequently associated with rice and corn. Three fumonisin-producing species, F. fujikuroi (MP-C,teleomorph: G. fujikuroi), F. proliferatum (MP-D, G. inter-media), and F. verticillioides (MP-A, G. moniliformis ), havebeen isolated from rice plants showing bakanae symptomsin Asia, Africa, Europe, and the United States (Amatulli etal., 2010; Carter et al., 2008; Desjardins et al., 2000;Desjardins et al., 1997; Hsuan et al., 2011; Wulff et al.,2010; Zainudin et al., 2008). The incidence of the latter wasrelatively lower than the first two species. F. verticillioidesis the most prevalent species on corn worldwide (Chulze et

Comparative evaluation of rice and sunhemp root inhabiting Pseudomonas fluorescens for optimized glucanase production

Exploitation of rhizosphere inhabiting Pseudomonas fluorescens for useful products like industrial enzymes remains largely less explored. Glucanase enzyme produced by P. fluorescens has wide range of application in food, textile and brewing industry, other than their antifungal activity for agricultural use. In our study, native isolates of P. fluorescens from rice and sunhemp rhizosphere varied in their preference to carbon and nitrogen source nutrients under in vitro conditions attributing to the possible difference in the metabolic profile of their respective ecological niche. The optimum conditions for maximum growth and glucanase enzyme production were a pH of 6.5 for both isolates and temperature of 37 and 40°C for rice and sunhemp isolates respectively. The rice rhizosphere isolate of the bacteria was a rapid producer of glucanase (24 h) compared to sunhemp isolate (48 h). Extracellularly secreted proteins were separated and partially purified by dialysis and sephadex column chromatography. Electrophoretic resolution of purified proteins in correlation with their enzyme activity revealed a 29 kDa isoform of glucanase in rice isolate and a 32 kDa isoform of the same in sunhemp isolate. In-gel activity assay was also performed to confirm the identity and activity of the purified protein. Key words: Glucanase, Pseudomonas fluorescens, purification, rice, sun hemp.