Comparative studies on the changes of total soluble proteins and protease activity in Georgian commercial peanuts contaminated by Aspergillus flavus

The presence of Aspergillus species is an indicator of storage conditions, which also suggests the possibility of several biochemical changes in grains. A comparative change in total soluble proteins and protease activity was determined in commercial peanut seeds collected from Georgia State. Protein contents of healthy peanuts, naturally contaminated peanuts and then artificially inoculated peanut seeds with A. flavus were estimated by Bradford method, and protease activity was also determined by using the Protease Detection Kits. Protein contents and the protease activity of the peanuts varied from sample to sample. The soluble protein content of seeds was significantly higher in healthy peanuts than in artificially inoculated or naturally infected peanuts with A. flavus. Protease activity was found to be higher in artificially inoculated seeds than in either naturally infected or healthy peanuts. Level of soluble proteins in buffer extracts of contaminated seeds decreased with incubation time, and protease activity increased with incubation time. These changes may be attributed to host response due to infection, contribution by A. flavus or due to biochemical alterations that occur naturally during the transition from endosperm to seedling during incubation period.     

Anatomical and biochemical aspects of interaction between roots of chickpea and Fusarium oxysporum f. sp. ciceris race 2

Roots of the susceptible “JG-62” and resistant “WR-315” chickpeas (Cicer arietinum L.) were inoculated with a conidial suspension of Fusarium oxysporum f. sp. ciceris. Anatomical and biochemical studies were carried out in a time-course manner to elucidate the infection process and plant defence reactions. Scanning electron microscope images revealed fungal colonisation in the root hair region. Early occurrence of fungal biofilms associated with the infected “JG-62” root epidermis was also visualised. After 96 h of inoculation, a gradual accumulation of polysaccharide positive deposits was observed in the xylem vessels of the infected “JG-62” roots. Fungal mycelium was observed in the vessel lumen of infected “JG-62” after 22 days of inoculation. Due to fungal invasion during this period, some of the vessels also appeared collapsed in “JG-62”, whereas vessels in “WR-315” remained intact. The host plant defence responses specifically linked to the susceptible interactions were the induction of ascorbate peroxidase, guaiacol peroxidase and superoxide dismutase in roots and shoots.     

Evaluation of some fungal diseases and yield of groundnut in groundnut-based cropping systems

A study on the evaluation of some fungal diseases and yield of groundnut in groundnut-based cropping systems was conducted in 2002 and 2003 planting seasons. Analysis of variance indicated that intercropping was highly significant on leaf spot disease severity 0.76; 0.75, rust 2.75; 2.69, as well as percentage defoliation 78.42%; 78.10% in 2002 and 2003, respectively. Plant population was significant on leaf spot severity 4.52, 4.60 rust 2.76; 366 and defoliation 226.5; 441.1 fungal as well as yield, while interactions were not significant on the fungal diseases and yield. Sole groundnut recorded significantly high severity of the fungal diseases investigated but low yield, when groundnut was intercropped with maize and melon and recorded the lowest yield in 2002 and 2003 respectively. 250,000 plants/ha recorded the lowest severity of the diseases investigated, while 444,444 plants/ha recorded the highest. Sole groundnut also recorded the highest percentage defoliation 79.37%, 79.25% when groundnut was intercropped with maize recorded the lowest 77.06%; 77.60%. 250,000 plants/ha had the lowest defoliation when 444,444 plants/ha had the highest 80.75% 82.13% in 2002 and 2003, respectively. Sole groundnut recorded the lowest in the majority of yields when intercropped with maize and with melon recorded a high yield and yield components in 2002 and 2003, respectively. The microorganisms identified were Cercospora spp., Aspergillus linked and Blastomyces.     

Biological control of Botrytis cinerea on tomato using naturally occurring fungal antagonists

Abstract

In order to evaluate the potential of naturally occurring filamentous fungi having potential as biocontrol agents effective against grey mould and post-harvest fruit rot caused by Botrytis cinerea on tomato, fungal saprophytes were isolated. They were obtained from leaves, fruits and flowers belonging to different species of cultivated and spontaneous Solanaceous plants collected at the horticultural area of La Plata, Argentina. Of 300 isolates screened for inhibition of B. cinerea using the dual culture technique on agar plate, 12 strains inhibited strongly mycelial growth of the pathogen. Among the antagonists one isolate of Epicoccun nigrum (126), four of Trichoderma harzianum (110, 118, 248 and 252) and four isolates of Fusarium spp. decreased the spore germination of B. cinerea between 30 and 70%. These isolates were probed on tomato fruits to evaluate their biocontrol activity against post-harvest grey mould. In growth chamber tests, E. nigrum (27), F. equiseti (22, 105) and T. harzianum (118, 252) reduced the diameter of fruit lesions by 50 – 90% and were selected for further biocontrol assays of tomato plants in the greenhouse. Although there were not significant differences between the treatments and the control, F. equiseti (105), E. nigrum (27) and T. harzianum (118) reduced by 20, 22 and 22 respectively the disease on whole plants. The targeted application of isolates of E. nigrum, T. harzianum and F. equiseti provides a promising alternative to the use of fungicide spray to control B. cinerea on tomatoes.     

Biotechnological approaches to develop bacterial chitinases as a bioshield against fungal diseases of plants

Fungal diseases of plants continue to contribute to heavy crop losses in spite of the best control efforts of plant pathologists. Breeding for disease-resistant varieties and the application of synthetic chemical fungicides are the most widely accepted approaches in plant disease management. An alternative approach to avoid the undesired effects of chemical control could be biological control using antifungal bacteria that exhibit a direct action against fungal pathogens. Several biocontrol agents, with specific fungal targets, have been registered and released in the commercial market with different fungal pathogens as targets. However, these have not yet achieved their full commercial potential due to the inherent limitations in the use of living organisms, such as relatively short shelf life of the products and inconsistent performance in the field. Different mechanisms of action have been identified in microbial biocontrol of fungal plant diseases including competition for space or nutrients, production of antifungal metabolites, and secretion of hydrolytic enzymes such as chitinases and glucanases. This review focuses on the bacterial chitinases that hydrolyze the chitinous fungal cell wall, which is the most important targeted structural component of fungal pathogens. The application of the hydrolytic enzyme preparations, devoid of live bacteria, could be more efficacious in fungal control strategies. This approach, however, is still in its infancy, due to prohibitive production costs. Here, we critically examine available sources of bacterial chitinases and the approaches to improve enzymatic properties using biotechnological tools. We project that the combination of microbial and recombinant DNA technologies will yield more effective environment-friendly products of bacterial chitinases to control fungal diseases of crops.     

Genomics-based precision breeding approaches to improve drought tolerance in rice

Rice (Oryza sativa L.), the major staple food crop of the world, faces a severe threat from widespread drought. The development of drought-tolerant rice varieties is considered a feasible option to counteract drought stress. The screening of rice germplasm under drought and its characterization at the morphological, genetic, and molecular levels revealed the existence of genetic variation for drought tolerance within the rice gene pool. The improvements made in managed drought screening and selection for grain yield under drought have significantly contributed to progress in drought breeding programs. The availability of rice genome sequence information, genome-wide molecular markers, and low-cost genotyping platforms now makes it possible to routinely apply marker-assisted breeding approaches to improve grain yield under drought. Grain yield QTLs with a large and consistent effect under drought have been indentified and successfully pyramided in popular rice mega-varieties. Various rice functional genomics resources, databases, tools, and recent advances in “-omics” are facilitating the characterization of genes and pathways involved in drought tolerance, providing the basis for candidate gene identification and allele mining. The transgenic approach is successful in generating drought tolerance in rice under controlled conditions, but field-level testing is necessary. Genomics-assisted drought breeding approaches hold great promise, but a well-planned integration with standardized phenotyping is highly essential to exploit their full potential.     

Isolation of Coal Degrading Fungus from Drilled Core Coal Sample and Effect of Prior Fungal Pretreatment on Chemical Attributes of Extracted Humic Acid

Fungal degradation of low rank coal has appeared as an alternative technique for exploitation of non-fuel options. A fungal isolate, MW1, was isolated and coal sample was subjected to fungal pretreatment. The residual coal was processed for extraction of humic acid for determining the effect of such pretreatment. Extracted humic acid was analyzed on the basis of elemental composition and spectroscopy. Fungal pretreatment caused improvement in oxygen content, E₄/E₆ ratio, and absorption bands related to humic materials. Conclusively, pretreatment resulted in improving chemical attributes of humic acid molecule, thus, warranting supplementary high-tech investigations for the optimization of process upscale.     

Considerations in the grouping of plant and fungal taxa for an epidemiologic study

Although exposure to airborne pollen grains and fungal spores has been implicated as a causative factor for acute exacerbation of asthma, the few epidemiologic studies that have attempted to evaluate the relationship between these bioaerosols and asthma have used only total counts (ignoring the relative importance of different taxa) or a few predominant pollen or spore types (ignoring less abundant but potentially relevant groups). This paper reports the development of hypothesis‐driven exposure metrics (based on known aeroallergen associations with allergic asthma and other hypersensitivity diseases, pollen allergen cross‐reactivity, and the presence of local sources in the city of Fresno, California, USA) for a 3.5 year epidemiologic study of childhood asthma. Outdoor regional and neighborhood concentrations of pollen and spores were measured using Hirst‐type, 7‐day samplers. Indoor and outdoor residential concentrations were measured at 84 selected homes with similar 24‐hour slit impactors. All pollen and spore concentrations were recorded in 2‐hour intervals to assist in understanding diurnal fluctuations in aeroallergen concentrations, identify exposures during the time periods that children are outdoors, and study interaction between aeroallergens and other air contaminants, which were the primary focus of the study. The 124 pollen taxa that were observed were reduced to 15 categories and the 66 fungal and algal taxa were reduced to five categories that will be used in microenvironmental models to generate individual daily exposure estimates for each of the 315 children. These new exposure metrics will allow examination of health effects for taxa traditionally associated with allergy and those with locally elevated concentrations in combination with exposures to other indoor and outdoor air contaminants.     

Understanding the genetic basis of invasiveness

Invasive species provide excellent study systems to evaluate the ecological and evolutionary processes that contribute to the colonization of novel environments. While the ecological processes that contribute to the successful establishment of invasive plants have been studied in detail, investigation of the evolutionary processes involved in successful invasions has only recently received attention. In particular, studies investigating the genomic and gene expression differences between native and introduced populations of invasive species are just beginning and are required if we are to understand how plants become invasive. In the current issue of Molecular Ecology, Hodgins et al. ( 2013 ) tackle this unresolved question, by examining gene expression differences between native and introduced populations of annual ragweed, Ambrosia artemisiifolia. The study identifies a number of potential candidate genes based on gene expression differences that may be responsible for the success of annual ragweed in its introduced range. Furthermore, genes involved in stress response are over‐represented in the differentially expressed gene set. Future experiments could use functional studies to test whether changes in gene expression at these candidate genes do in fact underlie changes in growth characteristics and reproductive output observed in this and other invasive species.