Outer Leaf Sheaths Research Articles

Dimorphopterus blissoides (Hemiptera: Heteroptera: Blissidae): recent spreading of a neonative species in the Pannonian Basin.

Dimorphopterus blissoides (Baerensprung, 1859) (Hemiptera: Heteroptera: Blissidae) is recorded for the first time from Slovakia and Iran. We provide also additional records of D. blissoides from Bulgaria, Croatia, Greece, Hungary and Romania, and review the distribution of the species. The species is currently spreading in the Pannonian Basin, reaching its northern distribution limit in southern Slovakia. We confirm its development on Phragmites australis, with preference to the loose outer leaf sheaths of the galls of Lipara lucens Meigen, 1830 (Diptera: Chloropidae), where the specimens develop during summer as well as hibernate during winter.

Overexpression of a Cytosolic 6-Phosphogluconate Dehydrogenase Gene Enhances the Resistance of Rice to Nilaparvata lugens.

The pentose phosphate pathway (PPP) plays an important role in plant growth and development, and plant responses to biotic and abiotic stresses. Yet, whether the PPP regulates plant defenses against herbivorous insects remains unclear. In this study, we cloned a rice cytosolic 6-phosphogluconate dehydrogenase gene, Os6PGDH1, which encodes the key enzyme catalyzing the third step in the reaction involving the oxidative phase of the PPP, and explored its role in rice defenses induced by brown planthopper (BPH) Nilaparvata lugens. Levels of Os6PGDH1 transcripts were detected in all five examined tissues, with the highest in outer leaf sheaths and lowest in inner leaf sheaths. Os6PGDH1 expression was strongly induced by mechanical wounding, infestation of gravid BPH females, and jasmonic acid (JA) treatment. Overexpressing Os6PGDH1 (oe6PGDH) decreased the height of rice plants and the mass of the aboveground part of plants, but slightly increased the length of plant roots. In addition, the overexpression of Os6PGDH1 enhanced levels of BPH-induced JA, jasmonoyl-isoleucine (JA-Ile), and H2O2, but decreased BPH-induced levels of ethylene. Bioassays revealed that gravid BPH females preferred to feed and lay eggs on wild-type (WT) plants over oe6PGDH plants; moreover, the hatching rate of BPH eggs raised on oe6PGDH plants and the fecundity of BPH females fed on these were significantly lower than the eggs and the females raised and fed on WT plants. Taken together, these results indicate that Os6PGDH1 plays a pivotal role not only in rice growth but also in the resistance of rice to BPH by modulating JA, ethylene, and H2O2 pathways.

The Movement of Fusarium oxysporum f.sp. cubense (Sub-Tropical Race 4) in Susceptible Cultivars of Banana.

Fusarium wilt, caused by the fungus Fusarium oxysporum f.sp. cubense (Foc), is one of the most important and destructive diseases in banana crops worldwide. There have been numerous studies into the infection process of this soil-borne pathogen; however, the extent of research into the movement of the pathogen through the rhizome and into the rest of the plant is limited. Furthermore, little is known about the movement of the pathogen once it reaches the aerial components of the plant. A strain of Foc sub-tropical race 4, genetically transformed with green fluorescent protein (GFP) gene, was used to monitor the movement of the pathogen through two susceptible cultivars, Cavendish ‘Williams’ (Musa AAA) and Lady Finger (Musa AAB). Visualization of the pathogen in planta demonstrated its presence in the roots, the rhizome and in the outer leaf sheaths of the pseudostem prior to the appearance of external symptoms. Within the non-senescing leaf sheaths, the migration of Foc was confined to the xylem vessels; this included those where the vascular tissue was visibly discolored, as well as those, which were apparently healthy. As senescence of leaf sheaths occurred, chlamydospores developed within the gas spaces, while formation of sporodochia, and hyphal growth were apparent on the outer surface of senescing leaf sheaths. These results generate a greater understanding of the epidemiology of Foc, providing much needed knowledge to assist in the future management of Fusarium wilt incursions, as well as enhancing protocols for ongoing on-farm hygiene and biosecurity.

Influence of UV Radiation on the Physical-chemical and Mechanical Properties of Banana Fiber

Surface treatments done in banana fibers (BFs) can generate significant superficial structural changes enabling the production of mechanically stronger composites. In this way, the objective of this study was to evaluate the physicochemical and mechanical properties of banana fibers of Prata specie from inner and outer leaf sheaths, when irradiated with UV light (λmax = 400 nm) during 7 (UV7) and 15 (UV15) days. Structural and microstructural characterizations for non- and irradiated fibers were performed by, FT-IR spectroscopy and Scanning Electron Microscopy (SEM), which showed the influence of UV irradiation on BFs surface and chemical structure. The Ea involved in the thermal degradation process of InNatura fiber (188.2 kJ.mol–1) was obtained using Differential Thermal Analysis (DTA/TG). The results obtained from mechanical characterization showed that the UV7 fibers presented significant improvement in tensile strength (89.77 MPa) and elastic modulus (238.94 MPa) as compared to tensile strength (69.99 MPa) and elastic modulus (87.40 MPa) of InNatura fibers. Statistical analysis using two-way ANOVA has showed that there were no differences between mechanical properties of BFs from inner to outer leaf sheaths. UV radiation has proved to be a clean method for BF surface treatment, which can improve the mechanical properties of composites based on these fibers.

Impact of polyphenols from banana pseudostem on sunflower oil stability

The present investigation is focused on the potential use of banana pseudostem, which otherwise is disposed off as a waste, as a source of polyphenols or antioxidants. The polyphenols extracted from the outer leaf sheaths of 3 Indian banana (Musa spp.) cultivars namely, ‘Nendhran’, ‘Robusta’, and ‘Kathali’ were tested for antioxidant activities. The extracts showed effective DPPH, hydroxyl, and superoxide radical scavenging ability. Among the banana cultivars, ‘Nendhran’ followed by ‘Robusta’ contained the highest total phenolic (110.45 and 94.03 mg GAE/g extract, respectively) and total flavonoid (49.62 and 38.61 mg QE/g extract, respectively) contents and antiradical activity. Further, the study was aimed to evaluate the protective effects of the polyphenolic extracts in stabilizing sunflower oil, tested in terms of peroxide value, free fatty acid contents, and p-anisidine values in comparison with the synthetic antioxidants, butylated hydroxyanisole and butylated hydroxytoluene. In addition, the antioxidant activity and total phenolic contents of the extract-treated oil samples were also monitored to obtain a complete perspective of the influence exerted by the polyphenols in oil stability. The results demonstrated that polyphenols from pseudostem of banana cultivars are potent source of natural antioxidants and might serve as a substitute for synthetic antioxidants in oil industry.

Comparison of liquid culture methods and effect of temporary immersion bioreactor on growth and multiplication of banana (Musa, cv. Dwarf Cavendish)

Four different liquids, as well as solid culture methods used in shoot propagation of banana were compared. Treatments studied were solid medium (A), liquid medium with immersion of plants (B), liquid medium with cotton culture support (C), liquid medium aerated by bubbling (D), and liquid medium with a temporary immersion bioreactor system (TIB) for 20 min every 1 h (E). After 4 weeks of culture, shoots in liquid medium with immersion and liquid medium aerated by bubbling showed none too little proliferation. Shoots in the solid medium and those cultured in liquid medium containing cotton culture supported played multiplication rates of 2.7 to 3.5 with the highest multiplication rate (> 7.00) observed in the explants that were subjected to the TIB in the medium. Three treated groups differed in the accumulation of dry matter; the lowest weight (around 0.6 g) was observed in treatments B and D, while 2 to 4 times greater accumulation was observed in the explants in the solid medium and those cultured in the liquid medium with a cotton culture support. The highest multiplication rates and weight gains were observed in the liquid medium with a TIB (E). Shoots in liquid medium continuously aerated by bubbling, displayed hyperhydricity of the outer leaf sheaths. However, this was not observed with temporary immersion of explants. Keywords: Banana, micropropagation, dwarf cavendish, temporary immersion bioreactor (TIB)

Impact of defoliation severity on photosynthesis, carbon metabolism and transport gene expression in perennial ryegrass.

Defoliation severity affects grass regrowth. The changes to biological processes affecting regrowth induced by severe defoliation are not fully understood, nor have they been investigated at a molecular level in field-grown plants. Field-grown perennial ryegrass (Lolium perenne L.) plants were defoliated to 20, 40 or 60mm during winter. Throughout regrowth, transcript profiles of 17 genes involved in photosynthesis and carbon metabolism or transport were characterised in stubble and lamina tissue. Although defoliation to 20mm reduced residual lamina area and stubble water-soluble carbohydrate reserves compared with plants defoliated to 40 or 60mm, net herbage regrowth was not reduced. Transcript profiles indicated a potential compensatory mechanism that may have facilitated regrowth. At the one-leaf regrowth stage, plants defoliated to 20mm had greater abundance of photosynthesis-related gene transcripts (rca, rbcS1, rbcS2, fba, fbp and fnr) and 20% greater stubble total nitrogen than plants defoliated to 60mm. A greater capacity for photosynthesis in outer leaf sheaths may be one potential mechanism used by severely defoliated plants to compensate for the reduced residual lamina area; however, this premise requires further investigation.

Phases of Infection and Gene Expression of Fusarium graminearum During Crown Rot Disease of Wheat

Fusarium graminearum causes head blight (FHB) and crown rot (CR) diseases in wheat. Compared with FHB, CR symptom development occurs slowly, usually taking 4 to 8 weeks to become visible. To characterize CR development, we used histological and real-time quantitative polymerase chain reaction analyses to assess fungal colonization during a timecourse of infection. Three distinct phases of infection were identified: i) initial spore germination with formation of a superficial hyphal mat at the inoculation point, ii) colonization of the adaxial epidermis of the outer leaf sheath and mycelial growth from the inoculation point to the crown, concomitant with a drop in fungal biomass, and iii) extensive colonization of the internal crown tissue. Fungal gene expression was examined during each phase using Affymetrix GeneChips. In total, 1,839 F. graminearum genes were significantly upregulated, including some known FHB virulence genes (e.g., TRI5 and TRI14), and 2,649 genes were significantly downregulated in planta compared with axenically cultured mycelia. Global comparisons of fungal gene expression with published data for FHB showed significant similarities between early stages of FHB and CR. These results indicate that CR disease development involves distinct phases of colonization, each of which is associated with a different fungal gene expression program.

Penetration into rice tissues by brown planthopper and fine structure of the salivary sheaths

AbstractThe fine structure of the salivary sheaths in plant tissues can provide important information on homopteran probing and ingestion behaviors. Salivary sheaths secreted by the brown planthopper (BPH), Nilaparvata lugens (Stål) (Homoptera: Delphacidae), and their tissue pathway were investigated using light, scanning electron, and transmission electron microscopy. About half of the salivary flanges on the surface of the food substrate were connected with internal salivary sheaths. Only 43% of the salivary sheaths showed side branches. Many sculpture‐like protuberances and small cavities had been formed on the outer surface of the salivary sheath, but the sheath lumen circumferences were sealed. Brown planthoppers showed a preference for probing and leaving salivary sheaths in the susceptible rice variety TN1 rather than in the resistant variety B5 during the first 2 days of the experiments. The salivary sheaths in rice tissues reached the inner tissue layer of the leaf sheaths and stems, but were mostly observed to end in the first and second layer of the leaf sheaths. Brown planthoppers also preferred to probe into the thick segment of the outer leaf sheath. After ingestion by the insect, the cytoplasm in both phloem and companion cells degraded and the main organelles were lost. Numerous small vesicles were found in most of the phloem cells, but cell walls remained intact. Large numbers of symbiont‐like structures were observed inside the salivary sheath lumen. These results indicated that BPH has complicated feeding behaviors, which warrants further investigation.

UJI EFEKTIVITAS NEMATODA ENTOMOPATOGEN (RHABDITIDA: Steinernema DAN Heterorhabditis) SEBAGAI MUSUH ALAMI NON-ENDEMIK PENGGEREK BATANG PADI KUNING (Scirpophaga incertulas)

Efficacy Tests of Entomopathogenic Nematodes (Rhabditida: Steinernema dan Heterorhabditis) as Non-endemic Natural Enemies of Yellow Rice stem Borer (Scirpophaga incertulas). Yellow rice stem borer (Scirpophaga incertulas) is a chronic insect pests of irrigated rice and difficult to control. Entomopathogenic nematodes from the genus Steinernema and Heterorhabditis are promising biological control agents for this pest as their infective juveniles (IJs) are capable of seeking and infecting insect living in moist, cryptic habitat such as galleries created by stem borer larvae. Thirteen indigenous and exotic Steinernema and Heterorhabditis sprayed to rice seedlings in laboratory with nematodes at concentrations of 0.5 or 2.0×104 IJs ml-1 water caused larval mortality between 7–93%. Further test in greenhouse on nematodes that had >50% efficacy showed that an indigenous isolate, H. indicus INA H17, was the most effective among the tested nematodes in killing larvae or pupae (78%). Reduction in plant damage caused by the insects could not be demonstrated as the trials was limited to potted plants. The survival ability of nematodes on rice plants was evaluated by using INA H4 as an example. A low percentage of INA H4 IJs (0.5%) persisted in inner leaf sheath until 7 days post application, while IJs on leaf surface and outer leaf sheath survived only until 2 and 48 hours post application, respectively. Improvement of application strategies including repeated spray, addition of antidessicant and adjusment of spray volume and application at damage threshold or plant critical period are deemed necessary to enhance nematode efficacy and reduce plant damage in the field.

Comparison of imidacloprid with carbamate insecticides, and the role of planting depth in the control of false wireworms, Somaticus species, in maize

A nitromethylene insecticide (imidacloprid) was compared in laboratory experiments with three carbamate insecticides (carbofuran, carbosulfan and furathiocarb) for the control of false wireworms, Somaticus spp., in maize. In further greenhouse experiments, the effect of planting depth on the action of the above-mentioned insecticides and another two carbamates, benfuracarb and thiodicarb, was determined. The active ingredient of all insecticides was systemically translocated to the leaves. Imidacloprid had an antifeedant action in the subterranean stems, inhibiting larval feeding deeper than the outer leaf sheath. This restricted feeding resulted in lower larval mass gain than in carbamate treatments. Severe damage to maize stems in carbamate treatments indicated the absence of antifeedant action. The number of damaged plants increased with increasing planting depth, irrespective of the insecticide used. However, although the extent of damage was similar at all planting depths for a particular insecticide, the damage index value of imidacloprid-treated plants was significantly lower than that of carbamate-treated plants.

Mechanism of control of eyespot disease in winter wheat by the fungicide prochloraz

Winter wheat plants grown in troughs and infected with the eyespot pathogen ( Pseudocercosporella herpotrichoides) were sprayed with prochloraz at growth stage (GS) 31 and 39 using a hydraulic nozzle sprayer and with a drop-leg spray system at GS 39. Some plants received artificial rain (4 mm) 1 or 4 days after spraying and were compared with those not receiving rain, with respect to foliar and stem-base fungicide deposits, as well as control of eyespot disease. Single pot-grown plants were treated topically with prochloraz inside the leaf axils and examined for redistribution of the fungicide by rain as well as the effect on eyespot disease. Rain redistributed the fungicide deposited by the hydraulic nozzle spray system from the initial site of deposition to the base of the crop at GS 31 and 39 and significantly suppressed eyespot disease development. No similar effects were found on the crop sprayed by the drop-leg system. The effect of rain on plants treated by topical placement of the fungicide in leaf axils was to redistribute prochloraz downwards between the outer leaf sheath and the stem, thus suppressing eyespot disease.

Comparison of methods of liquid medium culture for banana micropropagation

Five different liquid medium culture methods for meristem propagation of bananas were investigated and compared with solid medium culture. Treatments studied were: gelled culture medium (treatment 1); liquid medium with immersion of the plants (treatment 2); liquid medium with cellulose culture support (treatment 3); liquid medium with partial immersion of the plants (treatment 4); liquid medium aerated by bubbling (treatment 5); liquid medium with temporary immersion of the explants for 20 min every 2h (treatment 6). After 20 days of culture, three culture groups with statistically different multiplication rates were observed: -shoots in simple liquid medium and those on cellulose substrate proliferated little or not at all, -shoots on gelled medium, those subjected to partial immersion and those in aerated medium displayed multiplication rates of 2.2 to 3.1, and - the highest multiplication rate (>5) was observed in explants subjected to temporary immersion in the medium. Two groups of treatments differed in the accumulation of dry matter: the smallest weight (around 0.5 g) was observed in treatments 1, 2, 3 and 4, and accumulation was 2 to 5 times greater in the explants in aerated liquid medium and those subjected to temporary immersion. The highest multiplication rates and weight gains were observed in aerated treatments (treatments 4 and 5). Shoots in liquid medium continuously aerated by bubbling displayed hyperhydricity of the outer leaf sheaths. This was not observed with temporary immersion of explants.

Production and Pathogenicity to Wheat of Pseudocercosporella herpotrichoides Conidia

AbstractWeekly estimates of numbers of Pseudocercosporella herpotrichoides conidia on naturally infected wheat straw, made from February to July 1982, showed there were most conidia (8.1 × 106 per straw) in February and least (1.9 × 104 per straw) at the end of June. The viability of these spores remained high throughout this period, with an average of 85 % germination after 24 h.After removal of spores produced in the field, straws were incubated at 5, 10, 15, 20 or 25°C and subsequent sporulation assessed after 3 or 5 weeks. The optimum temperature for spore production was 5°C and very few spores were produced at 25°C. There was no difference in viability between spores produced at different temperatures.Wheat seedlings placed amongst infected straw collected and retained spores on the upper and lower surfaces of all leaf blades and on outer leaf sheaths. Both naturally dispersed spores and spores sprayed on to plants were not removed by subsequent rainfall.When wheat seedlings were inoculated between the coleoptile and outer leaf sheath with different numbers of P. herpotrichoides spores, lesion development was most rapid in seedlings inoculated with the greatest numbers of spores. However, after incubation for 12 weeks visible lesions were present on all plants inoculated with > c. 10 spores.

The selection of pupation sites by the stalk‐eyed fly Diopsis thoracica (Diptera: Diopsidae) and pupal parasitism in some rice cultivars

SUMMARYSix rice cultivars (lines (TKM6, OS6, ADNY 11, IR28, Rexero and IR579‐48‐1) were used to determine the pupation sites of Diopsis thoracica and their effects on pupal parasitism. There was a general preference for pupation on the first three outer leaf sheaths. Preference was also observed for healthy tillers compared with damaged ones, except in OS6 where there was no significant difference between pupation on healthy and damaged tillers. Pupae on the first two outer leaf sheaths were heavily parasitised by the eulophid Tetrastichus (Neotrichoporoides) sp. (Hymenoptera). The level of parasitism ranged from 17·6% in OS6 to 58·8% in Rexero, with an overall mean of 38·9% for the entire experimental plot. The number of parasites per pupa ranged from 0·5 in OS6 to 3·0 in Rexero, with an overall mean of 1·37. There was a strong relationship between (a) parasitism (%) (r = 0·68); (b) number of parasites per pupa per variety (r = 0·90) and pupal length. The relationship between parasitism (%) and parasite density was very strong (r = 0·89), but a marginal improvement in relationship was obtained when parasitism (%) was correlated with log parasite density (r = 0·94), thus possibly suggesting weak interaction between the parasites.

Contribution of basal portion of shoot to N2 fixation associated with wetland rice

Oryza sativa grown in flooded soil were transferred to water culture solution and acetylene reduction activities (ARA) of intact plants and rootless plants were measured for 5 h. Relative rate of ARA associated with the rootless wetland rice plant as compared with an intact plant varied from 8 to 100 percent, depending on the growth stage and varieties of rice and highest at the early stage (3 weeks after transplanting) for all varieties tested (IR26, Latisail, Khao Lo, and JBS236). ARA of shoots was associated with basal parts of the shoots about 3 cm from the base of wetland cultivated rice andOryza australiensis. Phyllospheric ARA was negligible except for senescent outer leaf sheaths. Microaerophilic N2-fixing bacteria also inhabited basal parts of shoots (outer leaf sheaths and stems) of wetland rice. These findings suggest that N2-fixation is partly associated with the shoots of wetland rice plants.

Heterotrophic 15N2 Fixation and Distribution of Newly Fixed Nitrogen in a Rice-Flooded Soil System

Rice (Oryza sativa L.) plants growing in pots of flooded soil were exposed to a (15)N(2)-enriched atmosphere for 3 to 13 days in a gas-tight chamber. The floodwater and soil surface were shaded with a black cloth to reduce the activity of phototrophic N(2)-fixing micro-organisms. The highest (15)N enrichments were consistently observed in the roots, although the total quantity of (15)N incorporated into the soil was much greater. The rate of (15)N incorporation into roots was much higher at the heading than at the tillering stage of growth. Definite enrichments were also found in the basal node and in the lower outer leaf sheath fractions after 3 days of exposure at the heading stage. Thirteen days was the shortest time period in which definite (15)N enrichment was observed in the leaves and panicle. When plants were exposed to (15)N(2) for 13 days just before heading and then allowed to mature in a normal atmosphere, 11.3% of the total (15)N in the system was found in the panicles, 2.3% in the roots, and 80.7% in the subsurface soil. These results provide direct evidence of heterotrophic N(2) fixation associated with rice roots and the flooded soil and demonstrate that part of the newly fixed N is available to the plant.

Fixation of Dinitrogen-15 Associated with Rice Plants

Rice plants (IR26 and Latisail) obtained at near heading stage from a wetland field were transferred to water culture and exposed to N(2) in a gas-tight growth chamber for 7 days to measure N(2)-fixing activities associated with the rice. The activities measured varied from 6.5 to 11.6 mumol of N(2) fixed per hill per day. The outer leaf sheath had about 2.5 times higher N(2)-fixing activities per unit weight than the root. Slight activities were also found in the basal node and inner leaf sheath. Wrapping basal parts of the stem with aluminum foil did not decrease the activities of N(2) fixation in these parts. Thus, the outer leaf sheath as well as the root are N(2)-fixing sites in rice plants. N(2) fixation found in above-ground parts is not due to photoautotrophic organisms. Less than 10% of the fixed nitrogen was translocated from the fixing sites to the leaf blades and the young panicles.

Leptosphaeria salvinii . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Leptosphaeria salvinii [Magnaporthe salvinii] . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Oryza sativa . DISEASE: Stem rot of rice ( Oryza sativa ). Symptoms are usually first seen at the later growth stages. Necrotic lesions begin on the outer leaf sheath near the water line; these spread gradually to the inner sheaths and the stem base. At about maturity lodging may occur and sclerotia will be found within the tissues. Partial sterility is caused and grain becomes light and chalky. Late infection can lead to small tillers but whether the pathogen caused excessive tillering, as earlier reports stated, is in doubt. Sclerotia form conidia when floating free or detached on moist substrata. Symptoms seem to vary with the growing conditions. GEOGRAPHICAL DISTRIBUTION: Widespread with host (CMI Map 448, ed. 1, 1968). Additional records not mapped are: Costa Rica, Indonesia, Laos, Panama, Peru. TRANSMISSION: Probably largely through the sclerotia; the role of the conidium and ascospore has been little studied. Viability of the sclerotium is variable, depending on temperature and substratum conditions (11: 599; 47, 182), and a period of 6 yr has been reported (20: 381). Both sclerotia and perithecia survive high summer temperatures (46, 1574).