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Research on mycotoxins on rubber trees

It’s the Group’s research science including Dr. Ngo Xuan Kien from the Life Science Nano Research Institute, Kanazawa University, Japan, and Dr. Nguyen Bao Quoc from the Institute of Biotechnology and Environment, Nong Lam University, focusing on diagnostics research. and molecular pathology and Dr. Nguyen Anh Nghia from the Plant Protection Laboratory of the Vietnam Rubber Research Institute, focusing on research on disease control on rubber tree.

Status of rubber trees in Vietnam

According to the Research Group, the rubber tree (Hevea brasiliensis) was introduced to Vietnam in 1897. Over the past 100 years, the rubber tree has existed and developed from the traditional Southeast region to the Central Highlands and Duyen Hai. Central and Northwest. According to the Association of Nations Production of Rubber nature (ANRPC), by the end of 2020, Vietnam has 926,280 hectares of rubber, of which 720,000 hectares are being exploited with an average yield of 1,618 kg/ha/year (the highest in the world).

In 2020, with an output of 1,553 million tons and an export of 1,165 million tons, Vietnam is currently the third largest producer and exporter of natural rubber in the world after Thailand and Indonesia. Besides latex, rubber wood is an important source of raw materials contributing to the export turnover of the rubber industry, improving income for more than 265,000 smallholder households and more than 1,500 businesses in the rubber wood supply chain.

According to the Vietnam Rubber Association (VRA), in the 2016-2020 period, Vietnam’s rubber wood output is estimated at 3.89 million m3 of round logs/year and has the potential to reach 3. .22 – 13.10 million m3 of logs/year from 2021. Natural rubber is the raw material for the production of many essential products for human life such as tires, car components, gloves, shoe soles, conveyor belts, belts, elastic threads, pillow mattresses, sports balls…

Rubber wood harvested after a 20-30 year latex exploitation cycle is also a high-value product. Furniture products made from rubber wood are now very popular in the world. It can be said that Vietnam’s natural rubber manufacturing industry is very important and needs to be protected and developed sustainably in order to create jobs and stable incomes for millions of workers, as well as earn income. billions of USD per year from exporting latex and timber to Vietnam.

Fungal diseases and mycotoxins

Like other crops, rubber trees are also attacked by many diseases that adversely affect growth and yield. Scientists believe that Corynespora leaf fall (Corynespora Leaf Fall, CLF) caused by the fungus Corynespora cassiicola (Berk. & Curt.) Wei is one of the major diseases on rubber trees.

The disease occurs all year round and on all growth stages of rubber trees, causing especially serious damage to susceptible rubber clones. The disease attacks leaves and shoots, causes massive defoliation many times, reduces growth, yield and can cause tree death, causing heavy damage to the rubber industry in Vietnam and many countries.

Currently, we know that the fungus C. cassicola has 7 genes that can produce 7 types of toxin Cassiicolin (Cas1 – Cas7). However, genetic analyzes indicated that C. cassiicola only expressed 1 or a few specific Cas toxin during defoliation in susceptible rubber clones.

For example, in many recent studies, the research team of Dr. Nguyen Bao Quoc (Nong Lam University), Dr. Nguyen Anh Nghia (Vietnam Rubber Research Institute) and Dr. Nguyen Ngoc Bao Chau (Ho Chi Minh City Open University) Minh) isolated and detected genes in the fungus C. cassiicola infected on rubber grown in Vietnam mainly expressing Cas2 toxins.

Meanwhile, rubber clones grown in other countries around the world from the Americas to Asia with different climates and soils in Vietnam are infected with the fungus C. cassiicola, the fungus produces a specific type of Cas toxin. other brand. For example, the toxin-producing gene Cas1 was found mainly in the C. cassiicola fungal infection of rubber clones grown in Brazil or China.

Many basic scientific questions about the specific relationship between the rubber plant host and the disease fungus C. cassiicola have been raised by scientists in the industry without convincing answers. Until now, many studies have focused only on the identification of the toxin genes in C. cassiicola and the identification of genes involved in the immune response of the rubber plant host to infection with the fungus. or their Cas toxin through biochemical analysis and computational simulation.

In this line of research, scientists have identified and classified thousands of immune response genes to fungi and mycotoxins that differ between susceptible and resistant rubber clones.

Although these studies are very important, they do not solve the most convincing way to help us understand the specific mechanism of interaction between the host and mycotoxins and mycotoxins at the molecular level. The specific picture of the host-specific relationship between the pathogen and the pathogen is still very complex and ambiguous. Understanding the specific interaction mechanism between the host and the fungus and mycotoxins on rubber is extremely important, which will open up a new field to help us be proactive in developing control methods. fungal diseases effectively and safely on plants such as vegetables, flowers and many different food crops.

Understanding the importance of solving major outstanding problems in the world and in Vietnam, a group of Vietnamese and Japanese scientists under the leadership of Dr. Ngo Xuan Kien (Kanazawa University, Japan) and Dr. Nguyen Bao Quoc discovered for the first time the specific pathogenic properties of Cas1 and Cas2 toxins in rubber clones grown in Vietnam.

The basic question was asked to investigate and elucidate the mechanism of interaction and toxicity of Cas1 and Cas2 toxins on the cytoplasmic membrane containing plant lipid components. The plasma membrane in every cell plays an essential role in sustaining life at the cellular and tissue levels. At the molecular level, the research team for the first time in the world discovered and classified three important groups of plant lipids: sterols (stigmasterol, sitosterol), glycerolipids (DGDG, MGDG) and negatively charged phospholipids (DPPA). ) are lipid membrane components sensitive to Cas1 and Cas2 toxins.

If one of these three specific plant lipid membranes is missing, the cytotoxicity of Cas toxin on the cytoplasmic membrane is almost absent or occurs very weakly.

At the level of cytology and testing for Cas toxicity on rubber clones, the research team has classified and elucidated the specific toxicity mechanism of Cas toxin on protoplasmic membranes and rubber leaves. The most advanced techniques were used in this study such as high-speed atomic force imaging (HS-AFM), Cryo-SEM tomography, and high-resolution microscopy (STED Confocal FM). and other biochemical techniques.

The scientific research work has been rigorously reviewed and published in the leading prestigious American scientific journal on plant diseases (Phytopathology, 2022. -21-0397-R).

Through substantive scientific research cooperation, the Research Group has been establishing cooperation projects in scientific research and personnel training between Kanazawa University, University of Agriculture and Forestry, Vietnam Rubber Research Institute, and the University. Open Ho Chi Minh City, and many other Universities and Research Institutes of Vietnam. Many opportunities to train high-quality human resources (Master, PhD) have been opened for excellent Vietnamese students who wish to study and research in Japan.

New direction of applied research to control plant fungal diseases

Chemical measures have been recommended, namely the use of fungicides sprayed directly on the leaves to kill pathogens. However, due to the characteristics of rubber trees with high canopy (15-20m), specialized sprayers are required, leading to high costs and sometimes no economic benefits. In addition, the use of chemical drugs also pollutes the environment. Therefore, this should only be considered as a temporary solution in case the disease causes severe damage on a large scale.

The more radical solution is to plant disease-resistant or disease-resistant clones in high-risk areas. The creation of new clones is the routine work of rubber breeders.

Current advances in molecular biology research can help speed up breeding research. Understanding the mechanism of interaction between fungi-rubber plants-environment at the molecular level will help the work of breeding resistant or resistant varieties faster. Studying genetic characteristics to determine fungal strains is a necessary work.

Using diagnostics by molecular markers to quickly identify the source of the disease is also a research direction that needs to be promoted. Study on extraction, quantification and classification of lipid components in rubber clones to identify and control genes that synthesize plant lipids susceptible to fungal diseases and mycotoxins.

Moving forward, using CRISPR-Cas9 technology to create rubber clones resistant to fungal diseases will be of interest to scientists in research and application. At the same time, creating useful bacterial strains that increase lipopeptides such as Iturin, Fengycin, and Surfactin to purify and use lipopeptide antifungal active ingredients or antagonistic bacteria as biological control tools. creating a sustainable and safe agro-ecosystem.

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