Antimicrobial Activity of Pinus Wallachiana Against Fusarium Oxysporum f. sp. Cubense and Analysis of its Fractions by HPLC

Fusarium wilt has ruined banana production and poses a major threat to its industry because of highly virulent Fusarium oxysporum f. sp. cubense (Foc) race 4. The present study focused on the efficacy of Pinus wallachiana and its organic fractions against Foc in in vitro and greenhouse experiments. The presence of polyphenols in the fractions was also investigated using High Performance Liquid Chromatography (HPLC). The in vitro tests carried out for the leaf extract of P. wallachiana showed its inhibitory effect on the mycelial growth and based on this evidence, further characterization of fractions were done. Complete mycelial inhibition and the highest zone of inhibition against Foc was observed for the n-butanol fraction in vitro, while the n-hexane and dichloromethane fractions showed lower disease severity index (DSI) in greenhouse experiments. The fractions were further analysed by HPLC using nine polyphenolic standards, namely quercitin, myrecitin, kaempferol, rutin, gallic acid, trans-ferulic acid, coumeric acid, epicatechin and catechin. The highest content of polyphenols, based on standards used, was quantified in the n-butanol fraction followed by the ethyl acetate fraction of the leaf extract. This is the first report of antimicrobial activity of Pinus wallachiana against Foc to the best of our knowledge.

Transmission and pathogenicity of papaya virus E: insights from an experimental papaya orchard

A study was conducted to investigate epidemiological aspects of papaya virus E (PpVE), a cytorhabdovirus commonly found in papaya (Carica papaya L.) plantings of Ecuador. Besides papaya, PpVE was found in three Fabaceae weeds, including Rhynchosia minima, Centrosema plumieri and Macroptilium lathyroides; the latter being the species with the highest virus prevalence. Greenhouse experiments showed that in M. lathyroides, single infections of PpVE induce only mild leaf mosaic, whereas in mixed infections with cowpea severe mosaic virus, PpVE contributes to severe mosaic. In papaya, PpVE did not induce noticeable symptoms in single or mixed infections with papaya ringspot virus. Transmission experiments confirmed that whiteflies (Bemisia tabaci) transmit PpVE in a semi-persistent, non-propagative manner.

Nitrogen Fixation by Paenibacillus Polymyxa WLY78 is Responsible for Cucumber Growth Promotion

Aims To study nitrogen contribution to cucumber derived from nitrogen fixation of Paenibacillus polymyxa WLY78.Methods The nif gene cluster deletion mutant (ΔnifB-V) of P. polymyxa WLY78 is constructed by a homologous recombination method. The GFP-labeled ΔnifB-V mutant was used to inoculate cucumber and to study colonization by confocal laser scanning microscope. The effects of plant-growth promotion were investigated by greenhouse experiments. The nitrogen fixation contribution was estimated by 15N isotope dilution experiments. Results Deletion of nif gene cluster of P. polymyxa WLY78 resulted in complete loss of nitrogenase activity. Observation by laser confocal microscopy revealed ΔnifB-V mutant can effectively colonize cucumber root, stem and leaf tissues, like wild-type P. polymyxa WLY78. Greenhouse experiments showed that inoculation with P. polymyxa WLY78 can significantly enhance the lengths and dry weights of cucumber roots and shoots, but inoculation with ΔnifB-V mutant can not. 15N isotope dilution experiments showed that cucumber plants derive 25.93% nitrogen from nitrogen fixation performed by P. polymyxa WLY78, but the ΔnifB-V mutant nearly can not provide nitrogen for plant growth. Conclusions This present study demonstrates that nitrogen fixation performed by P. polymyxa WLY78 is responsible for cucumber growth promotion.

Laxogenosides Enhance Yield and Quality of Raphanus sativus L. Under Greenhouse Condition

Laxogenoside-C (LG-C) has BRs-likely activity and with higher activity stability. In this study, the LG-C and SsS (the mixture of Laxogenoside-A, -B, and -C; isolated from the Smilax scobinicaulis C.H. Wright) were used to conduct the seeding treatment and greenhouse experiments with different application time and concentrations, to clarify the effect on yield and quality of radish (Raphanus sativus L.) for development of a new plant growth regulator. The results showed that 10 μM LG-C and SsS increased hypocotyls, elongation and cotyledon weight compared with other treatment. The greenhouse experiments indicated that the interaction effect of plant growth regulator types and application time was significant for all parameters except for phosphorus content. An application of LG-C or SsS produced a higher yield than multiple times. Compared with T0 treatment, LG-C and SsS sprayed at root enlargement (T4) increased yield by 25.33% and 24.10%, respectively. T4 treatment of LG-C produced the highest yield and free amino acid and phosphorus, but the other parameters not. T4 treatment of SsS not only had the highest yield and water-soluble carbohydrates and water-soluble protein but also improved the other radish quality. In conclusion, this study indicated that the application of SsS at root enlargement with 10 μM improved radish root tubers yield and quality.

Identification of tomato accessions as source of new genes for improving heat tolerance: from controlled experiments to field

Background Due to global warming, the search for new sources for heat tolerance and the identification of genes involved in this process has become an important challenge as of today. The main objective of the current research was to verify whether the heat tolerance determined in controlled greenhouse experiments could be a good predictor of the agronomic performance in field cultivation under climatic high temperature stress. Results Tomato accessions were grown in greenhouse under three temperature regimes: control (T1), moderate (T2) and extreme heat stress (T3). Reproductive traits (flower and fruit number and fruit set) were used to define heat tolerance. In a first screening, heat tolerance was evaluated in 219 tomato accessions. A total of 51 accessions were identified as being potentially heat tolerant. Among those, 28 accessions, together with 10 accessions from Italy (7) and Bulgaria (3), selected for their heat tolerance in the field in parallel experiments, were re-evaluated at three temperature treatments. Sixteen tomato accessions showed a significant heat tolerance at T3, including five wild species, two traditional cultivars and four commercial varieties, one accession from Bulgaria and four from Italy. The 15 most promising accessions for heat tolerance were assayed in field trials in Italy and Bulgaria, confirming the good performance of most of them at high temperatures. Finally, a differential gene expression analysis in pre-anthesis (ovary) and post-anthesis (developing fruit) under heat stress among pairs of contrasting genotypes (tolerant and sensitive from traditional and modern groups) showed that the major differential responses were produced in post-anthesis fruit. The response of the sensitive genotypes included the induction of HSP genes, whereas the tolerant genotype response included the induction of genes involved in the regulation of hormones or enzymes such as abscisic acid and transferases. Conclusions The high temperature tolerance of fifteen tomato accessions observed in controlled greenhouse experiments were confirmed in agronomic field experiments providing new sources of heat tolerance that could be incorporated into breeding programs. A DEG analysis showed the complex response of tomato to heat and deciphered the different mechanisms activated in sensitive and tolerant tomato accessions under heat stress.

Induction of defence related enzymes and biocontrol efficacy of Trichoderma harzianum in tomato plants infected with Fusarium oxysporum and Fusarium solani

<p>Fusarium wilt of tomato plants caused by<em> Fusarium oxysporum </em>Schlecht. emend. Snyder &amp; Hansen and<em> Fusarium solani</em> (Mart.) Sacc. are serious problem limiting tomato production worldwide. Biological control has emerged as one of the most promising alternatives to chemical fungicides. The biological control capability of a <em>T. harzianum </em>isolate against <em>F. solani</em> and <em>F. oxysporum</em> has been investigated. It inhibited colony growth of two <em>Fusarium</em> species by more than 80 % in dual culture tests. Results of greenhouse experiments revealed that disease severity in the tomato plants co-inoculated with <em>T. harzianum</em> was significantly lower than plants only infected with the <em>Fusarium</em> pathogens. Tomato plants inoculated with the antagonistic <em>T. harzianum</em> isolate, showed enhanced peroxidase and polyphenol oxidase activities in greenhouse experiments and increased resistance to <em>F. solani</em> and <em>F. oxysporum</em>. The <em>T. harzianum</em> isolate indirectly affected the <em>Fusarium </em>pathogens by enhancing plant defence.</p>

Comparison of Paenibacillus polymyxa wild-type and Nif− mutant in colonization, plant-growth promotion and nitrogen fixation contribution

Aims This study aimed to compare the effect on colonization, plant-growth promotion and nitrogen fixation contribution by inoculation with Paenibacillus polymyxa wild-type and Nif−mutant. Methods Paenibacillus polymyxa wild-type and Nif− mutant was labeled with GFP and then the GFP-labeled bacteria were used to inoculate cucumber. The colonization patterns of P. polymyxa WLY78 in these plants were observed under the confocal laser scanning microscope. The effects of plant-growth promotion were investigated by greenhouse experiments. The nitrogen fixation contribution was estimated by 15N isotope dilution experiments. Results Observation by laser confocal microscopy revealed that both P. polymyxa WLY78 and ΔnifB-V mutant can effectively colonize cucumber root, stem and leaf tissues. Greenhouse experiments showed that inoculation with P. polymyxa WLY78 can significantly enhance the lengths and fresh wights of cucumber roots and shoots, but inoculation with ΔnifB-V mutant can not. 15N isotope dilution experiments showed that cucumber plants derive 25.93% nitrogen from nitrogen fixation performed by P. polymyxa WLY78, but the ΔnifB-V mutant nearly can not provide nitrogen for plant. Conclusions This present study demonstrates that nitrogen fixation plays an import role in promoting plant growth.

Will Rising Temperatures Make Rice Too Toxic?

Greenhouse experiments reveal how higher temperatures act to elevate arsenic levels in rice and may help focus efforts to solve a crisis threatening food systems around the world.