Host specificity and biology ofHeteropsylla spinulosa [Hom.: Psyllidae] introduced into Australia and Western Samoa for the biological control ofMimosa invisa

The biology and host specificity of the psyllidHeteropsylla spinulosa Muddiman, Hodkinson & Hollis collected fromMimosa invisa Von Martius, was studied in Brazil and in Australia. Oviposition was recorded on 19 of 100 plant species tested but nymphs died without feeding, except onM. invisa. H. spinulosa was shown to be specific toM. invisa and was subsequently released and established in Australia and Western Samoa.      

Competitive interactions between Microdochium nivale var. majus, M. nivale var. nivale and Fusarium culmorum in planta and in vitro

Microdochium nivale var. majus and var. nivale are economically important fungal pathogens of cereal seedlings, stem bases and ears, as is the toxigenic species Fusarium culmorum. Competition experiments on seedlings support an earlier report of differential host preference between the varieties of M. nivale on wheat and rye seedlings at 15 degrees C, but showed that it does not extend across a broad range of temperatures. The studies showed that, although interaction is disadvantageous to the less virulent pathogen, it does not confer an advantage to the more virulent pathogen. In mixed inoculum experiments on wheat seedlings at 15 degrees C and 20 degrees C, F. culmorum suppressed the growth of both varieties of M. nivale. However, if M. nivale var. majus became established on the seedlings, it was able to co-suppress colonization of wheat seedlings by F. culmorum. In contrast M. nivale var. nivale did not suppress F. culmorum significantly. The growth of M. nivale var. majus and F. culmorum was also co-suppressed in liquid culture. Significantly, the accumulation of deoxynivalenol mycotoxin was also reduced in the mixed in vitro culture compared with axenic culture of F. culmorum. However, in vitro interaction studies on solidified media were of only limited use in predicting the outcome of competitions in planta.     

Using simulated herbivory to predict the efficacy of a biocontrol agent: the effect of manual defoliation and Macaria pallidata Warren (Lepidoptera: Geometridae) herbivory on Mimosa pigra seedlings

Abstract  The effect of manual defoliation, and real and simulated herbivory by the leaf-feeding moth Macaria pallidata on the growth and biomass of Mimosa pigra seedlings was assessed to determine the likely success of defoliating herbivores as biocontrol agents against the weed. Manual removal of at least half of all leaf material, maintained over a 6-week period, significantly suppressed plant growth, as did a single week of herbivory by M. pallidata larvae. This suggests that M. pallidata and other defoliators have the potential to be highly successful agents in the biological control program for M. pigra.     

Induced resistance activated by a culture filtrate derived from an avirulent pathogen as a mechanism of biological control of anthracnose in strawberry

In a previous report, it was described that strawberry plants pre-treated with an avirulent isolate of Colletotrichum fragariae (M23) acquired resistance to a virulent isolate of Colletotrichum acutatum (M11) causing anthracnose. In this report we present evidence that the eliciting activity can be found not only in conidial extracts but in culture supernatants of the avirulent pathogen as well. Plants of the cv. Pájaro treated with the culture filtrate (CF) derived from M23, 3 days prior to the inoculation with M11 showed significantly reduced disease severity as compared to control plants and the disease was completely suppressed when plants were pre-treated 7 days before the challenge inoculation with M11. The same effect was achieved when a single leaf was sprayed with CF, suggesting that the resistance acquired is systemic. Control treatments showed that none of the active extracts inhibited the growth of the virulent pathogen, indicating that the protection effect was due to the induction of a defense response. The latter was confirmed by the accumulation of reactive oxygen species (e.g. hydrogen peroxide, superoxide anion) and the deposition of lignin and callose, usually associated to plant defense, after the CF treatment. Experiments carried out with other strawberry cultivars treated with CF showed that also protected them against different virulent isolates, suggesting that the response observed is cultivar-nonspecific. These outcomes indicate that the protection against anthracnose in strawberry involves a phenomenon of induced resistance (IR) by action of defense-eliciting molecules produced by M23.     

Comparative characteristics of cell-free filtrates of Shigella flexneri of different virulence]

It was shown for the first time that the virulent Sh. flexneri strain grown on Luria broth differed from the avirulent one by the yield of readily released surface-located complexes--lipopolysaccharide (determined by rhamnose) and protein into the filtrate. There was no distinct correlation between the strain virulence and the content of rhamnose-determined lipopolysaccharide in the filtrate; growing bacteria in the presence of Ca and Mg ions had no significant influence on the lipopolysaccharide release into the filtrate. Protein release into the cell-free filtrate was thrice that in the virulent shigella strain than in the avirulent one. When bacteria were grown in the presence of Ca ions protein release from the virulent strain increased 1.5-fold and changed but little in the avirulent culture. Cell-free filtrates of the virulent strain produced toxic action on L tissue culture cells; in conjunctival infection of guinea pigs they caused some reduction of the LD50 of the virulent strain and sharply aggravated the course of the infectious process. Heating of the filtrate at 100 degrees C for 15 min decreased their toxic action on L cells. The data obtained indicated that the active biological factor revealed in the virulent strain of Sh. flexneri was protein or its derivative.     

多效唑调节水稻植株生长的作用机理

多效唑处理水稻植株后使株高降低和分蘖增加,植株体内的GA类物质和IAA含量相应下降,乙烯释放率显著增加;用外源GA_3和氮肥能逆转多效唑的抑制作用而使株高增加,同时GA类物质含量也明显增加。因此,多效唑不仅调节体内的GA类物质含量,还能通过调节IAA含量和乙烯释放率而影响植物生长。     

Performance of Hybrids between Weedy Rice and Insect-resistant Transgenic Rice under Field Experiments： Implication for Environmental Biosafety Assessment

Transgene escape from genetically modified (GM) rice Into weedy rice via gene flow may cause undesired environmental consequences. Estimating the field performance of crop-weed hybrids will facilitate our understanding of potential introgression of crop genes (including transgenes) into weedy rice populations, allowing for effective biosafety assessment. Comparative studies of three weedy rice strains and their hybrids with two GM rice lines containing different insect-resistance transgenes (CpTl or BtlCpTI) indicated an enhanced relative performance of the crop-weed hybrids, with taller plants, more tillers, panicles, and spikelets per plant, as well as higher 1000-seed weight, compared with the weedy rice parents, although the hybrids produced less filled seeds per plant than their weedy parents. Seeds from the F1 hybrids had higher germination rates and produced more seedlings than the weedy parents, which correlated positively with 1000-seed weight. The crop-weed hybrids demonstrated a generally enhanced relative performance than their weedy rice parents in our field experiments. These findings indicate that transgenes from GM rice can persist to and introgress into weedy rice populations through recurrent crop-to-weed gene flow with the aid of slightly increased relative fitness in F1 hybrids.     

Studies on Metabolic Products of Hypochnus sasakii Shirai

A considerable amount of p-hydroxyphenylacetic acid was isolated from the culture filtrate of Hypochnus sasakii.

p-Hydroxyphenylacetic acid induced wilt of soybean plant and retarded the growth of rice seedlings at concentrations up to 1:20,000. The O₂ uptake in roots decreased in proportion to reduction of dry weight of rice seedlings.     

Isolation, purification and characterization of an antifungal molecule produced by Bacillus licheniformis BC98, and its effect on phytopathogen Magnaporthe grisea

AIMS: Isolation of bacterial antagonist for use in the biological control of phytopathogenic fungi like rice blast fungus, Magnaporthe grisea, and to further purify and characterize the antifungal molecule produced by the antagonist. METHODS AND RESULTS: Bacterial antagonist exhibiting highest antifungal activity against the rice blast fungus M. grisea was isolated from soil and identified as Bacillus licheniformis BC98. Besides M. grisea, the isolate also inhibited the growth of other phytopathogens such as Curvularia lunata and Rhizoctonia bataticola. Biologically active fractions were isolated from the culture filtrate and further fractionated by reverse-phase high-performance liquid chromatography (HPLC) enabling detailed structural characterization of a component of molecular mass 1035 Da. The active peptide was identified as surfactin after 500 MHz (1)H NMR analysis. Microscopic analysis of the effect of the antagonist on M. grisea revealed bulbous hyphae showing patchy and vacuolated cytoplasm when observed under the electron microscope. CONCLUSIONS: The antagonistic lipopeptide secreted by B. licheniformis BC98 and identified as surfactin, induced morphological changes in M. grisea, inhibiting its further growth, and thus exhibiting fungicidal activity. SIGNIFICANCE AND IMPACT OF THE STUDY: The antagonist inhibits germination of M. grisea, a potent rice phytopathogen, and therefore appears to be a potential candidate for control of rice blast disease.     

Effects of heavy metal salts on susceptibility of rice seedlings to brown spot disease

Heavy metal salts, known to induce phytoalexin production in different plant species, were used at dilute concentrations (10^-3 to 10^-5 M) in different treatments to control brown spot infection in rice seedlings caused by Drechslera oryzae. Foliage sprays, root-dips for 24 h at the time of transplanting, or seed soaking for 24 h provided moderate to substantial protection to rice seedlings, at different stages after treatment, against artificial inoculation with the pathogen or natural infection under field conditions and mostly caused significant reductions in symptoms. Of the three methods, greatest and most durable protection was achieved with the wet seed treatment. The number of successful infections was appreciably reduced in most treatments and some also inhibited lesion expansion. Ferric chloride and nickel nitrate were the most effective and mercuric chloride the least effective of the chemicals tested. There was no fungitoxicity in leaf diffusates from 3- and 5-wk-old seedlings that had been treated with heavy metal salts and only mild toxicity in that from untreated, inoculated seedlings. However, treated seedlings inoculated at the 3-and 5-wk stages produced leaf diffusates with significantly greater toxicities which were in proportion to their abilities to resist attack.     

Germination Promotant for Plants Seed,produced by Microorganisms

The culture filtrate of the Streptomyces sp. S-580 showed strong activity in promoting the germination of rice plant seeds. The culture conditions of the strain and fractionation of the active principles from the culture filtrate were investigated. The active crude syrup (A.C.S.) obtained is effective at the dilution of 10^?5 ~ 10^?8 for the germination of rice plant seeds, 10^?5~10^? for barley and oats seeds.     

Formation and activities of xylanhydrolysing enzymes of Humicola grisea var thermoidea

A thermophilic fungus, Humicola grisea var thermoidea, produced in liquid culture two endoxylanases (1,4--d-xylan-xylanohydrolase, EC 3.2.1.8) with M _r of 95 (Xyl I) and 13 (Xyl II) kDa. PAGE of the crude culture filtrate and of each fraction obtained by gel filtration produced three and one band, respectively. Cross-reaction of the culture filtrate and each fraction with polyclonal antibodies prepared against Xyl II produced two and one precipitin bands, respectively. Hydrolysis of wheat straw and rice husk xylan was maximal using a combination of Xyl I and Xyl II. The products formed after hydrolysis, xylo-oligosaccharides and traces of xylose, indicated an endotype enzyme action and the co-operative activities of the xylanases.     

Malacorhinus irregularis for biological control of Mimosa pigra: host-specificity,life cycle,and establishment in Australia

Malacorhinus irregularis Jacoby (Coleoptera: Chrysomelidae: Galerucinae: Galerucini), from Mexico is identified as a potential biological control agent for Mimosa pigra L. (Mimosaceae), a serious weed of northern Australia and Asia. The adults feed on leaves of the host, and the larvae develop on seedlings, roots, and perhaps other plant parts. The damage to the target plant is substantial, indicating that this insect could be an effective control agent. Host-specificity tests examined the suitability of seedlings and leaves for larval development, and suitability of leaves for adult feeding. In no-choice tests, no larval development occurred on any of the 81 test plant species other than M. pigra. The extent of adult feeding on the test plants was negligible in the tests using a choice-minus-control design, being less than 1% of that which occurred on M. pigra. We conclude that M. irregularis is a specialist on its host and the risk associated with its release in Australia is low. It was released in infestations of M. pigra in the Northern Territory of Australia in 2000. Establishment and abundance was monitored at one site where the number and distribution of adult beetles fluctuated widely as soil moisture conditions varied through the seasons. Adults were found for two years after release and local defoliation of plants was attributed to this species. Although only limited observations were made, adult feeding was not recorded from Neptunia major (Benth). Windler plants growing in close proximity to M. pigra, indicating specificity under field conditions.     

Kenaf (Hibiscus cannabinus L.) core and rice hulls as components of container media for growing Pinus halepensis M. seedlings

The feasibility of replacing peat or perlite with rice hulls and ground kenaf core to grow a Mediterranean species (Pinus halepensis M.), was investigated. Treatments involved the following growing media: 70 peat:30 perlite as a control, 70 peat:30 rice hulls, 50 peat:50 rice hulls, kenaf (100%) and 60 kenaf:20 peat:20 rice hulls. The seedlings' quality and the physical and chemical properties of the substrates were evaluated. After this, the seedlings were planted in the field and their field performance was recorded. The results showed that the growth medium 70 peat:30 rice hulls can successfully be used for the production of P. halepensis, since the seedlings' nursery and field performance were similar to, or even better than those obtained with the control medium. The seedlings produced in the growth media containing kenaf did not attain a suitable planting size and showed poorer field performance than control seedlings.     

Evaluation of Epicoccum nigrum for growth, morphology and production of natural colorants in liquid media and on a solid rice medium

Four nonpathogenic and nontoxigenic Epicoccum nigrum strains were evaluated for their growth, morphology and pigment producing ability in three complex and one defined liquid media. Epicoccum nigrum IBT 41028 produced pigments in all the four media tested with a maximum pigment of 3.68 AU at 410 nm in M1 medium (unoptimized) containing 5 g/l yeast autolysate. The color hue of the crude pigment extracts ranged from 74 to 102 exhibiting dark orange to green-yellow color. Pelleted morphology was shown to have a positive influence on the pigment production by E. nigrum strain IBT 41028 in the liquid media, and the use of Bis-tris buffer was found to diminish or reduce the pellet formation. Since Monascus is a well known pigment producer on rice. Pigment producing ability of E. nigrum IBT 41028 was tested on rice and compared to liquid media with Monascus ruber IBT 7904 as control. Though, both genera preferred rice but E. nigrum produced 4.6 folds higher pigment in the liquid unoptimized fermentation medium compared to M. ruber. Solid phase extraction and subsequently HPLC-DAD analysis of the crude pigment extracts showed qualitative as well as quantitative variation in the pigment composition under solid and liquid cultivations.     

Genetic differentiation of charcoal rot pathogen, Macrophomina phaseolina, into specific groups using URP-PCR

Forty isolates of Macrophomina phaseolina, a pathogen causing charcoal dry root rot of soybean, cotton, and chickpea, were genetically characterized with universal rice primers (URP; primers derived from DNA repeat sequences in the rice genome) using polymerase chain reaction (URP-PCR). Out of 12 URPs used in this study, 5 primers were effective in producing polymorphic fingerprint patterns from the DNA of M. phaseolina isolates. Three primers (URP-2F, URP-6R, and URP-30F) were quite informative and produced high levels of polymorphism among the isolates of M. phaseolina. Analysis of the entire fingerprint profiles using unweighted pair-group method with arithmetic averages (UPGMA) clearly differentiated M. phaseolina isolates obtained from soybean, cotton, and chickpea hosts into specific groups. In this study, we found for the first time transferability and use of PCR primers derived from plant genomes to generate host-specific fingerprint profiles of M. phaseolina, a broad host range plant pathogenic fungus. These results demonstrate that URPs are sensitive and technically simple to use for assaying genetic variability in M. phaseolina populations.     

Detoxification of oxalic acid by pseudomonas fluorescens strain pfMDU2: implications for the biological control of rice sheath blight caused by Rhizoctonia solani

Rhizoctonia solani isolates varying in their virulence were tested for their ability to produce oxalic acid (OA) in vitro. The results indicated that the virulent isolates produced more OA than the less virulent isolates. In order to isolate OA-detoxifying strains of Pseudomonas fluorescens, rhizosphere soil of rice was drenched with 100 mM OA and fluorescent pseudomonads were isolated from the OA-amended soil by using King's medium B. These isolates were tested for their antagonistic effect towards growth of R. solani in vitro. Among them P. fluorescens PfMDU2 was the most effective in inhibiting the mycelial growth of R. solani. P. fluorescens PfMDU2 was capable of detoxifying OA and several proteins were detected in the culture filtrate of PfMDU2 when it was grown in medium containing OA. To investigate whether the gene(s) involved in OA-detoxification resides on the plasmids in P. fluorescens PfMDU2, a plasmid-deficient strain of P. fluorescens was generated by plasmid curing. The plasmid-deficient strain (PfMDU2P-) failed to grow in medium containing OA and did not inhibit the growth of R. solani. Both PfMDU2 and PfMDU2P- were tested for their efficacy in controlling sheath blight of rice under greenhouse conditions. Seed treatment followed by soil application of rice with P. fluorescens strain, PfMDU2, reduced the severity of sheath blight by 75% compared with the control, whereas PfMDU2P- failed to control sheath blight disease.     

Effect of extracellular products ofAulosira fertilissima on the growth of rice seedlings

Summary The effect of extracellular products fromAulosira fertilissima on the growth of rice seedlings (IR-8) has been studied. There is indication of liberation of a root-promoting hormone from the alga. The growth pattern of rice seedlings, treated with algal filtrate, parallels that of seedlings treated with gibberellic acid. An increased growth of rice seedlings results when they are treated with algal filtrate obtained from the exponential phase of the alga. The amino acid-treated seedlings do not show any marked increase in growth. Filtrate fromAnacystis nidulans, on the other hand, do not show any growth promoting response. The possibility of liberation of kinins byA. fertilissima does not appear to be involved.     

Effect of defoliation treatment on Mimosa pigra L. seedling survivability and resilience

Current advancements in the study of the theoretical basis of species interactions are helping scientists understand the basic parameters governing the dynamics of the interactions between generalist herbivores and their target plants. In practice, however, both inter- and intra-specific interactions between plants (as well as between herbivores and plants) within multispecies systems that are under the influence of interrelated biotic and abiotic variables are difficult to predict. Here, we discuss our findings on the effect of simulated herbivory on Mimosa pigra L. leaves on seedling survivability. In Malaysia, M. pigra, a semi-aquatic invasive plant introduced from the South American region, is already creating an ecological problem, especially in wetland habitats. To better understand the impact of herbivores on the M. pigra population, a simulated experiment of the herbivory effect on Mimosa seedlings was conducted. This experiment combined two treatments of simulated herbivory on the leaves of established Mimosa seedlings, that is, a two-level intensity treatment (50 and 100 % defoliation) and a seven-level frequency treatment (one to seven defoliations). The data suggest that Mimosa is highly resilient against herbivory. This plant was able to compensate for repeated losses, thus suggesting that the introduction of herbivores in an effort to totally eradicate the Mimosa population is unlikely to be successful.     

Transgenic indica rice expressing Mirabilis jalapa antimicrobial protein (Mj-AMP2) shows enhanced resistance to the rice blast fungus Magnaporthe oryzae

Mj-AMP2, a knottin-type antimicrobial peptide, in vitro inhibits the growth of several plant pathogenic fungi including Magnaporthe oryzae. We demonstrate that transgenic rice (Oryza sativa L.) plants expressing the Mj-AMP2 gene show enhanced resistance to M. grisea, the causal agent of the rice blast disease. Mj-AMP2 was efficiently expressed and the level of Mj-AMP2 ranged from 0.32% to 0.38% of the total protein in the transgenic rice plants. In vitro inhibitory activity assays with the crude protein extract from transgenic rice indicated that the Mj-AMP2 protein produced was biologically active. Constitutive expression of Mj-AMP2 in transgenic rice reduces the growth of M. grisea by 63% with respect to untransformed control plant, and no effect on plant phenotype was observed. Transgene expression of Mj-AMP2 gene was not accompanied by an induction of pathogenesis-related (PR) gene expression indicating that the transgene product itself is directly active against the pathogen. The results presented in this study suggest that the Mj-AMP2 gene could be a useful candidate for protection of rice plants against the rice blast fungus M. grisea.