Identification and characterization of virulence-related effectors in the cucumber anthracnose fungus Colletotrichum orbiculare

The anthracnose fungus Colletotrichum orbiculare invades hosts and establishes biotrophy, later switching to necrotrophy, together with the secretion of an arsenal of effectors. In this review, we describe current progress in the study of pathogen effectors. We identified three virulence-related effectors in C. orbiculare, and revealed part of the strategy for effector-mediated infection, including suppression of immunity triggered by particular effectors. The virulence-related effectors accumulate in a unique interfacial region between C. orbiculare and cucumbers around the neck of primary biotrophic invasive hyphae. We found that the secretion of effectors toward the interface involves exocytosis and SEC22-dependent ER-Golgi traffic.     

Pseudomonas putida BP25 alters root phenotype and triggers salicylic acid signaling as a feedback loop in regulating endophytic colonization in Arabidopsis thaliana

Endophytic Pseudomonas putida BP25 (PpBP25) triggered density dependent alterations on Arabidopsis thaliana Col-0 growth. Endogenous colonization of PpBP25 was found regulated within Arabidopsis that caused induction and repression of 131 and 74 plant genes, respectively. Induced genes like WRKY33, AtRLP19, ATL2, ATEXO70B2, pEARLI, RPS2, CBP60G, PLA2, CRK18, ATFBS1, DREB2A, TIR, RAP2.4, and MOS1 were components of defense and salicylic acid (SA) signaling. Development associated genes were found significantly repressed. Biased activation of phytohormone signaling with their associated fitness costs on plant growth was observed. The data suggests that PpBP25 colonization triggered expression of defense genes that restricted its own population in a feedback loop besides causing altered root phenotype.     

Phenotypic variation in Azospirillum brasilense Sp7 does not influence plant growth promotion effects

The Azospirillum genus comprises free-living, plant growth-promoting, nitrogen-fixing bacteria found in the rhizosphere of plant roots. Azospirilla are able to promote plant growth mainly through improvement of root development. Bacterial surface components, such as extracellular polysaccharides and proteins, are involved in root colonization. Phase variation – or phenotypic variation – is one of the mechanisms by which microorganisms adapt to environmental changes. This phenomenon is characterized by the presence of a sub-population of the bacteria presenting a different phenotype relative to the major population. In this study we characterized phenotypic variation of Azospirillum brasilense Sp7. When plated on solid media, some A. brasilense colonies were shown to possess a much more mucoid morphology, producing 7.5–8 times more exopolysaccharide with different monosaccharide composition than the parental strain Sp7. The rate of appearance of this kind of variant colonies was 1 in 5000, in agreement with the accepted rate for the phase/phenotypic variation phenomenon. The variants were significantly more resistant to heat and UV-exposure than the parental strain and displayed genomic changes as seen by the different band patterns following ERIC-PCR, BOX-PCR and RAPD analyses. In plant inoculation experiments under greenhouse conditions, with maize, wheat, soybean and peanuts, the EPS overproducing variants performed as similar as the parental strain. Therefore, EPS overproduction did not confer an apparent advantage to A. brasilense in terms of induction of plant growth promotion.     

Mutualistic interaction of rhizobacteria with arbuscular mycorrhizal fungi and its antagonistic effect on Fusarium oxysporum in Carica papaya seedlings

There are numerous studies evaluating biocontrol of root rot by using the antagonistic effects of either arbuscular mycorrhizal fungi (AMF) or rhizobacteria, but usually independently. Fewer studies, although growing in number, report on evaluating the effectiveness of concurrent fungi–bacteria inoculation in combating root rot; and furthermore, there are none to date reported with papaya. In this study, an indigenous Pseudomonas sp. (PPV3) was isolated from roots of papaya (Carica papaya L. cv. Maradol) and used with an AMF complex (MTZ01) consisting of four fungi Glomus intraradices, Glomus mosseae, Glomus etunicatum and Gigaspora albida to inoculate roots of papaya in order to determine their antagonistic effects against Fusarium oxysporum, individually and in combination. It was found that with inoculation with PPV3 and MTZ01 protection was highest (85%) and had reduced disease (10%) as well as reducing F. oxysporum colonization in papaya seedlings. Inoculations with MTZ01 or PPV3 showed an efficacy of 54 and 60%, with a level of disease severity of the 38 and 22%, respectively. The combination of the AMF complex (MTZ01) with rhizobacterial Pseudomonas sp. (PPV3) modified the effects of F. oxysporum and provided increased protection for C. papaya than either acting alone. These results suggest that rhizobacteria and arbuscular mycorrhizal fungi acting together formed a mutualistic relationship that enhances disease control against F. oxysporum and stimulates growth in C. papaya.     

Acute toxicity and sublethal effects of methoxyfenozide and thiodicarb on survival,development and reproduction of Helicoverpa armigera (Lepidoptera: Noctuidae)

The cotton bollworm Helicoverpa armigera (Hubner) is one of the most destructive pest insects in Iran and many other countries. In this study, lethal and sublethal effects of methoxyfenozide, and thiodicarb were evaluated against H. armigera larvae that fed on insecticide-treated artificial diet. The effects of methoxyfenozide and thiodicarb were assessed in 3rd instars. Methoxyfenozide and thiodicarb showed LC₅₀ values of 4 and 639 mg a.i./ml, respectively, in H. armigera larvae. Sublethal effects on development, adult longevity, and reproduction were observed in H. armigera larvae that survived exposure to an LC₃₀ of the insecticides. Larvae that were exposed to an LC₃₀ concentration of methoxyfenozide exhibited lower pupal weight and increased larval and pupal developmental times compared with thiodicarb treated larvae or control larvae. Adults that were exposed as larvae to an LC₃₀ concentration of methoxyfenozide or thiodicarb showed reduced fecundity (35% and 30%, respectively) compared to control adults. The tested insecticides significantly reduced adult longevity. The longevity of adult females that as larvae were treated with an LC₃₀ concentration of methoxyfenozide or thiodicarb was reduced by 28% and 23%, respectively, in comparison to control females. We predict that the combination of lethal and sublethal effects of the insecticides, especially methoxyfenozide, will induce significant effects on field population dynamics of H. armigera.     

Effect of cold storage on vitamin C,phenolics and antioxidant activity of five orange genotypes [Citrus sinensis (L.) Osbeck]

The effect of cold storage on antioxidant profile and the antioxidant activity of five sweet orange genotypes [Citrus sinensis (L.) Osbeck], three blood (pigmented) varieties with different anthocyanin contents (‘Tarocco Messina’, ‘Tarocco Meli’ and ‘Moro’) and two blond varieties (‘Ovale’ and ‘Valencia late’), stored at 6 ± 1 °C for 65 d was investigated. During fruit storage, anthocyanins, hydroxycinnamic acids, vitamin C, flavanones and total phenolics were determined, and juice antioxidant capacity was measured by two different in vitro tests (DPPH scavenging activity and inhibition of induced linoleic acid peroxidation). The results showed an increase in anthocyanins, flavanones and hydroxycinnamic acids and a slight decrease in vitamin C in the blood oranges. Cold storage negatively affected flavanone concentration, while positively influenced vitamin C in blond orange varieties. Both antioxidant activity tests showed an increase in antioxidant capacity during storage caused mainly by phenolic accumulation (blood oranges) and vitamin C increase (blond oranges). Finally, correlations between antioxidant activity and total or individual phenolic components were examined.     

Agropyron elongatum HMW-glutenins have a potential to improve wheat end-product quality through targeted chromosome introgression

After screening of 177 disomic addition lines (DALs) of wheat (Triticum aestivum) containing a pair of chromosomes from different alien species, we found that the chromosome 1E addition line of Agropyron elongatum, that is known to be a potential genetic resource for drought and salinity tolerance, showed potential for improvement of bread-making quality of wheat. This was indicated by increased SDS sedimentation, specific sedimentation, mixograph peak time and SE-HPLC analysis of polymeric proteins. This addition line spontaneously gave rise to a substitution line for chromosome 1D in subsequent generations that showed weak dough strength. Analysis of the x-type HMW-glutenin subunit sequence of Ag. elongatum from DAL1E indicated that it closely resembled the x-type sequence of the A and B genomes of wheat, and the y-type was intermediate between x- and y-type HMW-glutenin subunit genes. From these observations, it was inferred that 1E-encoded seed storage proteins have considerable potential for improvement of wheat end-product quality if transferred to specific chromosomes such as 1A of Chinese Spring (CS) wheat, which has a negative overall effect on bread-making quality.     

Bruising injury of persimmon (Diospyros kaki cv. Fuyu) fruits

This study was performed to monitor the deterioration of bruised persimmon (Diospyros kaki cv. Fuyu) fruits. Freshly harvested fruits were bruised by dropping them from a height of 50 cm onto a steel board and then stored at 0 or 20 °C in temperature controlled chambers for up to 4 weeks. Immediately after the bruising, no visible injury on the fruits was evident, but the fruits deteriorated rapidly during storage. The skin tissues of the fruits stored at 20 °C became more reddish with the duration of the storage, but no such changes were found with the fruits stored at 0 °C. The increase in redness of the skin tissues appeared to be associated with storage temperature, but not with the bruising. The skin tissues also became darker when stored at 20 °C than at 0 °C and this tendency was more obvious with the bruised fruits. Flesh firmness decreased rapidly during storage except for the non-bruised fruits stored at 0 °C. Even the non-bruised fruits rapidly lost their flesh firmness at 20 °C. No significant changes in lipid peroxidation, as expressed by malondialdehyde production, were found between the bruised and the non-bruised fruits during the storage either at 0 °C or at 20 °C. This implies that the fruit deterioration caused by bruising is not due to the consequences of lipid peroxidation. Polyphenol oxidase activity increased more rapidly in the bruised fruits than in the non-bruised fruits during storage. The bruising had more effect on increasing polyphenol oxidase activity than did the storage temperature. Although the increase in polyphenol oxidase activity appeared to be associated with the visual deterioration of the bruised fruits, it did not exactly correspond to the physical deterioration. These results indicate that polyphenol oxidase is not the only factor influencing the deterioration associated with bruising. Cell wall hydrolases are currently being assayed to determine if they also contribute the deterioration following bruising.     

Determining the spirit yield of wheat varieties and variety mixtures

Four winter wheat varieties and the four possible three-component mixtures derived from them were included in a trial in Scotland. The site produced low grain protein levels and there were significant yield and specific weight differences between varieties. The variety Deben significantly out-yielded the varieties Claire and Riband, both with and without fungicide treatment, but produced grain with significantly lower spirit yield than Claire. Protein contents and thousand corn weights were good predictors of spirit yield in a reference population of wheat samples, but thousand corn weights did not correlate with spirit yield in the trial, as Claire combined small grain with high spirit yield. The relationship between protein and spirit yield was shown to change at lower protein levels and to differ between varieties. Reduction in spirit yield as protein increased was greater in Deben than in a better distilling variety like Consort. A rapid means of predicting spirit yield, based on small-scale measurement of hot water extract and protein content, was devised and a good association between predicted and measured spirit yield was observed in both the reference population and the trial. Mixtures containing cvs. Claire and Deben did not demonstrate the adverse effects on yield and spirit yield observed, respectively, for these varieties, and a mixture comprising cvs. Claire, Consort and Deben significantly out-yielded Claire and gave higher spirit yields than Deben. These benefits, together with the potential yield stability and disease reduction characteristics of wheat mixtures, make them a viable commercial option for distilling.