Toxin-based in-vitro selection and its potential application to date palm for resistance to the bayoud Fusarium wilt

The Major Stilbene Compound Accumulated in the Roots of a Resistant Variety of Phoenix dactylifera L. Activates Proteasome for a Path in Anti-Aging Strategy

The main objective of the present study is to estimate, through differential analysis, various biological activities of total phenolics content in alcoholic extracts of three date palm varieties sensitive or resistant to Fusarium oxysporum. sp Albidinis. Here, stilbene products with antioxidant and bioactive capacities were evidenced in resistant variety Taabdount (TAAR). Furthermore, the methanolic fraction of the TAAR-resistant date palm variety contains a significant product, determined by LC-MS/MS and 1H, 13C NMR, belonging to the family of hydroxystilbenes, which exhibits antioxidant capacities, inhibits the mushroom tyrosinase activity, and activates and exerts a protective effect on hypochlorite-induced damage in 20S proteasome of human dermal fibroblast aged cells. Altogether, the present results indicate that hydroxystilbene present in resistant Phoenix dactylifera L. should be studied to understand the way that the stilbene could exert anti-aging ability.

Gnotobiotic evaluation of Dalbergia sissoo genotypes for resistance against Fusarium solani via dual culture set up

BACKGROUND

Dalbergia sissoo (shisham), an important multipurpose tree native to the Indian subcontinent and also planted in other countries, has been afflicted with large scale mortality in all age groups due to wilt disease, causing huge economic losses. Fusarium solani f. sp. dalbergiae (Fsd) has been identified as one of the causal organisms for wilt disease in D. sissoo. One of the approaches of disease resistance studies involves co-cultivation of trees and pathogens under controlled conditions to screen resistant tree genotypes. A gnotobiotic condition, where the pathogen is known, enables accurate screening of disease-resistant genotypes. In the present study, ten genotypes of D. sissoo were cloned in vitro and evaluated against two strains of Fsd in a dual culture setup under gnotobiotic conditions with an objective to identify resistant genotypes of D. sissoo against Fsd.

RESULTS

Callus and plantlets of ten genotypes of host plant multiplied in vitro were inoculated with conidial suspension of two strains of Fsd at three concentrations; 1 × 101, 1 × 103, and 1 × 105 conidia/ml. Gnotobiotic evaluation of dual culture setup shows variations among genotypes in their response towards in vitro Fsd infection; and two genotypes (14 and 66) exhibited resistance against Fsd strains. Callus of genotypes 14 and 66 significantly restricted the fungal mycelium growth whereas callus of remaining genotypes was completely infested by Fsd mycelium within 9 days. Similarly, plantlets of genotype 14 and 66 had lesser disease severity and remained green and had fewer necrotic lesions in roots whereas plantlets of the remaining eight genotypes died within 15 days.

CONCLUSION

Gnotobiotic evaluation of callus and plantlets of ten genotypes of D. sissoo against Fsd strains has reduced time and space otherwise required for field trials. Genetic variations amongst the genotypes resulted in varying responses towards virulent Fsd strains and only two out of ten genotypes showed promising resistant characteristics. In dual culture setup, both callus and plantlets of the same genotypes responded similarly against Fsd strains, which signify that in vitro screening can be used as an indirect selection method for disease resistance.

Microcalli Induction in Protoplasts Isolated from Embryogenic Callus of Date Palm

Date palm (Phoenix dactylifera L.) production is severely hampered due to several pests and diseases. Biotechnological tools such as protoplast fusion appear as an alternative to ensure rapid genetic improvement and multiplication of this species. However, establishment of an effective system of plant regeneration from protoplasts culture is a prerequisite for date palm somatic hybridization. In this chapter, we describe an effective protocol to induce microcalli in protoplasts isolated from nodular callus of important Algerian date palm cultivars. In this protocol, the main factors influencing the isolation (i.e., enzymatic solution, mannitol concentration, duration, and mode of maceration) of protoplasts from the calli of Algerian date palm cultivars were optimized. Purified protoplasts were cultured on a semisolid medium supplemented with a hormonal balance of auxin and cytokinin to obtain microcalli formation.

A simplified Protocol to Induce Callogenesis in Protoplasts of Date Palm (Phoenix dactylifera L.) Cultivars

BACKGROUND

In Algeria, date palm is currently confronted to the Bayoud disease. Biotechnological tools such as protoplastsfusion can appear as an alternative to ensure rapid multiplication and improvement of this species.

OBJECTIVES

Callogenesis induction in protoplasts isolated from embryogenic callus of three date palm cultivars.

MATERIALS AND METHODS

Some factors influencing the isolation and culture of protoplasts segregated from the calli of three date palm (Phoenix dactylifera L.) cultivars (Deglet Nour, Akerbouch and Degla Beida) were studied. Protoplasts of each cultivar were cultured on a semi-solid medium supplemented with various hormonal balances.

RESULTS

Maceration with an enzymatic solution containing 1.5% cellulase and 1% macerozyme R10 in the presence of 0.5 M mannitol for more than 16 h with gentle agitation allows isolation of a great number of viable protoplasts. In addition, purification of protoplasts on a cushion of 21 or 25% sucrose was effective in cell debris removal and maximum recovery. The culture of isolated protoplasts on a semi-solidified Murashige and Skoog medium, with 0.3% agarose, 2 mg. L-1 2,4-D and 0.5 mg.L-1 BAP allowed good viable protoplast maintenance as well as cell wall regeneration. After more than two months of culture, cell divisions were still occurring and microcalli became visible to the naked eye, containing a large number of cells.

CONCLUSIONS

The developed protocol can be useful for application of somatic hybridization to improve date palm cultivars.

Trichoderma genes in plants for stress tolerance- status and prospects

Many filamentous fungi from the genus Trichoderma are well known for their anti-microbial properties. Certain genes from Trichoderma spp. have been identified and transferred to plants for improving biotic and abiotic stress tolerance, as well for applications in bioremediation. Several Trichoderma genomes have been sequenced and many are in the pipeline, facilitating high throughput gene analysis and increasing the availability of candidate transgenes. This, coupled with improved plant transformation systems, is expected to usher in a new era in plant biotechnology where several genes from these antagonistic fungi can be transferred into plants to achieve enhanced stress tolerance, bioremediation activity, herbicide tolerance, and reduction of phytotoxins. In this review, we illustrate the major achievements made by transforming plants with Trichoderma genes as well as their possible mode of action. Moreover, examples of efficient application of genetically modified plants as biofactories to produce active Trichoderma enzymes are indicated.

Plants versus fungi and oomycetes: pathogenesis, defense and counter-defense in the proteomics era

Plant-fungi and plant-oomycete interactions have been studied at the proteomic level for many decades. However, it is only in the last few years, with the development of new approaches, combined with bioinformatics data mining tools, gel staining, and analytical instruments, such as 2D-PAGE/nanoflow-LC-MS/MS, that proteomic approaches thrived. They allow screening and analysis, at the sub-cellular level, of peptides and proteins resulting from plants, pathogens, and their interactions. They also highlight post-translational modifications to proteins, e.g., glycosylation, phosphorylation or cleavage. However, many challenges are encountered during in planta studies aimed at stressing details of host defenses and fungal and oomycete pathogenicity determinants during interactions. Dissecting the mechanisms of such host-pathogen systems, including pathogen counter-defenses, will ensure a step ahead towards understanding current outcomes of interactions from a co-evolutionary point of view, and eventually move a step forward in building more durable strategies for management of diseases caused by fungi and oomycetes. Unraveling intricacies of more complex proteomic interactions that involve additional microbes, i.e., PGPRs and symbiotic fungi, which strengthen plant defenses will generate valuable information on how pathosystems actually function in nature, and thereby provide clues to solving disease problems that engender major losses in crops every year.