Natural Product Oligosaccharins - Effectively Respond To Plant Parasitic Nematodes With Outstanding Effects And No Resistance, Promoting Roots, Growth, And Safer To Use

1. Introduction

Plant Parasitic Nematodes are one of the important pathogens in global crop production, affecting over 3000 plants including vegetables, fruit trees, and food crops. At present, there are over 100 species of root knot nematodes reported internationally, with over 2000 host plants ^[1]. The most widely distributed species are mainly the southern root knot nematode M.incognita, Java root knot nematode M.javanica, peanut root knot nematode M.arenaria, northern root knot nematode M.hapla, and elephant bean root knot nematode M.entolobii ^[2]. According to FAO conservative estimates, the global annual loss caused by nematodes to food and fiber crops is approximately 12%, and the loss to vegetables, peanuts, tobacco, and certain fruit trees exceeds 20%, even reaching 50%, resulting in approximately 157 billion US dollars in global agricultural production losses. In China, the most common root knot nematodes on vegetables in the northern temperate regions are southern root knot nematodes and northern root knot nematodes, while the most common ones in the southern tropical and subtropical regions are southern root knot nematodes, Java root knot nematodes, peanut root knot nematodes, and elephant bean root knot nematodes ^[3], causing approximately $3.5 billion in annual losses.

Root knot nematodes mainly harm the roots of vegetables by parasitizing on the young roots of vegetable crops and forming root nodules, inducing plant cells to transform into specific feeding sites, which absorb nutrients to maintain the development and reproduction of root knot nematodes, thereby damaging the tissue structure and vitality of vegetable root cells, hindering the transportation of mineral nutrients and water, leading to yellowing and shrinking of plant leaves, nutrient imbalance, short, unstable, or poor fruiting ^[4].

The entire growth and development cycle of root knot nematodes, from egg hatching to larvae, then to adults, and finally to mating and laying eggs, is the life cycle of root knot nematodes. Usually divided into three stages: egg, larva, and adult. Research has found that the second instar stage of root knot nematodes is a key period for prevention and control. Data shows that under normal temperature and humidity conditions, southern root knot nematodes occur on average for about 40 days, with overlapping generations and a higher number of reinfection occurrences. Research has shown that the life cycle of root knot nematodes is closely related to local temperature and humidity, crop growth season, rainfall, etc. ^[5], and soil moisture and structure affect the hatching and survival of root knot nematodes ^[6].

Figure 1：Pathogenic status of plant parasitic root knot nematodes [www.191.cn]

Protected vegetables, especially in vegetable cultivation in solar greenhouses, are most severely affected by root knot nematodes due to their frequent continuous cropping and high environmental temperatures. According to reports, diseases caused by root knot nematodes in protected vegetables can directly lead to a 50% to 80% reduction in yield, which has become the main obstacle to the development of protected vegetables. In the Xinjiang region of China, root knot nematodes harm dozens of vegetables such as melons, tomatoes, eggplants, chili peppers, kidney beans, celery, spinach, etc., with the majority of Solanaceae (tomatoes) and Cucurbitaceae (cucumbers) crops being infected, usually resulting in a yield reduction of 10-20%, with severe cases ranging from 30% to 50%, and even causing crop failure. Seedling destruction incidents often occur ^[8]. In 2006, the root knot nematode on cucumbers and tomatoes in the Banfanggou greenhouse in Urumqi, China occurred seriously, resulting in a 65% to 70% reduction in cucumber and tomato production. In 2009, Du Lanying and others discovered a serious outbreak of cucumber root knot nematode in Hami, Xinjiang ^[9]. In 2011, root knot nematode was common in protected vegetable greenhouses in Korla City, and the incidence rate of some cucumbers, balsam pears, cowpeas, etc. reached 100% ^[10].

At present, chemical control measures are mainly taken to prevent and control root knot nematode, including the use of Carbofuran, Ethoprophos, Aldicarb, Abamectin, Fosthiazate, etc. However, these pesticides not only kill nematodes but also pose significant risks to vegetable and environmental safety. With the prohibition of a large number of highly toxic nematode control formulation and the accumulation of resistance of root knot nematodes to traditional nematode control formulation, the prevention and control situation of root knot nematode is severe ^[11]. In recent years, biostimulants and biologically derived nematode control formulation have shown a positive development trend, and there are more and more reports on the resistance of plant natural products to root knot nematodes. Yang Guodong et al. found that the root metabolites of resistant tomatoes have a repulsive effect on nematodes, while the root metabolites of susceptible tomatoes have an attractive effect on nematodes ^[12]. Wang Yanyan et al. found that the metabolites of highly resistant rootstocks can inhibit the egg hatching of nematodes when studying the metabolites of cucumber roots ^[13]. With the continuous improvement of environmental awareness and the gradual improvement of regulatory systems, green and safe nematode control formulations are increasingly being paid attention and favored by people.

2. Research Status Of Oligosaccharins

Oligosaccharins, also known as agricultural chitosan Oligosaccharins, refer to D-glucosamine β- The 1,4 glycoside linked oligosaccharide is a new type of oligosaccharide biological pesticide, which is obtained from the deacetylation of chitin in marine biological shells to chitosan and then enzymatic degradation, and can prevent and treat a variety of plant fungal diseases ^[14], viral diseases ^[15] and nematodes ^[16]. Oligosaccharins can induce crops to produce a chitinase to break down and absorb nematodes and egg shells, ultimately causing nematodes and egg death. Early or frequent use of Oligosaccharins on crops can increase the amount of chitinase produced by crops, thereby achieving the goal of preventing nematodes. Oligosaccharins, as biopesticide, have multiple mechanisms in disease prevention, disease resistance, and nematode control ^[17]. Therefore, Oligosaccharins are widely used as biopesticides for disease prevention, disease resistance, nematode control, and growth promotion in the agricultural field.

Figure 2: Structure of Oligosaccharins

Oligosaccharins not only have the ability to induce plants to actively improve their stress resistance, but also activate plant cells and stimulate plant growth. Their direct inhibitory effect on plant pathogens is also a necessary component of their disease resistance ^[18]. Shenxingming et al. studied that when tomato was sprayed with 5.0 ‰ Oligosaccharins solution, the growth indicators of tomato were the highest, with chlorophyll content (SPAD value) increasing by 35.97%, plant height increasing by 8.05%, stem diameter increasing by 4.01%, aboveground dry weight increasing rate by 19.56%, and flower number increasing rate by 28.25%. Compared with the water control, the root nodules decreased by 63.59%, with a relative control effect of 52.81%, indicating a strong control effect ^[19].

3. Research Progress In The Industrialization Of Oligosaccharins

(1) Registration Status Of Oligosaccharins

Statistical information shows that as of April 2023, there are a total of 62 registration information for Oligosaccharins in China, with active ingredient content ranging from 0.5% to 5%, mainly composed of fungicides. As a nematode control function, there are only two companies registered. Chengdu Newsun Crop Science Co., Ltd. (hereinafter referred to as Newsun) produces a 0.5% Oligosaccharins solution, which is one of the earliest biological control formulation in China to position Oligosaccharins as a root knot nematode control formulation.

Figure 3: Information on China's First Oligosaccharins Registration Certificate

(2) The Mechanism Of Action Of Chengdu Newsun 0.5% Oligosaccharins

Chengdu Newsun 0.5% Oligosaccharins, as a polysaccharide biopesticide to control root knot nematodes, is different from insecticides. After application, it quickly triggers the plant's defense response and induces the production of chitinase in crops to decompose and absorb the shell oligosaccharides in nematodes and egg walls, causing the dissolution of nematode body walls and egg walls, leading to the death of nematodes and eggs. At the same time, the large molecules of the oligosaccharides can be degraded into membrane substances that can form protective films at the roots, Wrap the root system to reduce nematode infection. At the same time, other natural active molecular groups in the formulation can inhibit nematode activity, achieve synchronous protection and treatment, and be environmentally safe without developing resistance.

Figure4: Effect of formulation treatment on root knot nematodes and the eggs

(3) Study on the Process of 0.5% Oligosaccharins Formulation

Chengdu Newsun utilizes advanced nano formulation technology, adopts special solubilization principles, and fully utilizes the physical and chemical properties of materials to carry out precise formula development. A stable nano formulation stability system was formed, and the best formula with high storage stability was obtained by combining multiple light scattering test, nanoparticle degree test, etc. Fully activating the active molecular groups in Oligosaccharins, targeting on root knot nematodes and method of control, taking into account insecticidal, root protection, growth promotion, and stress resistance and yield increase, comprehensively improving the field application effect of the product, laying a key foundation for the industrial promotion of Oligosaccharins in root knot nematode control.

Figure 5: Appearance and Water Dispersibility of 0.5% Oligosaccharins

Multidimensional stability data shows that the 0.5% Oligosaccharins formulation has good stability, and there is no stratification and precipitation phenomenon after cold and hot storage, fully meeting various complex field application environments.

Figure6: Multiple light scattering spectrum of 0.5% Oligosaccharins Formulation

(4) Research on the Application of 0.5% Oligosaccharins

Chengdu Newsun 0.5% Oligosaccharins relies on years of experience in natural product research and development, and has inherent advantages in formula production processes. The 0.5% Oligosaccharins product technology not only achieves excellent nematode control functions, but also promotes crop root growth, improves crop innate immunity and disease resistance. Secondly, macromolecules can be degraded into membrane substances to provide additional systemic protection, forming a protective film around the root system, further reducing infection.

The use of 0.5% Oligosaccharins in controlling tomato root knot nematodes in Shouguang, Shandong Province has good control effects. For tomato seedlings that may have been infected with root knot nematodes during transplantation, 0.5% Oligosaccharins diluted 500 times was used for irrigation prevention. New roots began to appear 5 days after treatment, and tomato plants grew vigorously 15 days after treatment. No root knot occurred 35 days after treatment, and the comprehensive reduction rate reached over 70%.

Figure 7: 0.5% Oligosaccharins for Controlling Tomato Root Knot Nematode

In Liaocheng, Shandong Province, the combination of 0.5% Oligosaccharins and reduced dosage chemical nematicide has excellent therapeutic effects on cucumber root knot nematodes. When used in combination with Fosthiazate, the reduction rate of cucumber root knot nematodes exceeded 87% after 10 days. After use, the population of root knot nematodes in the plots decreased significantly, with well-developed roots, robust plants, thick green leaves, and higher yields.

Figure 8: Comparison of the control effects of 0.5% Oligosaccharins on cucumber nematodes

Chengdu Newsun 0.5% Oligosaccharins not only has excellent control effects on root knot nematodes, but also promotes crop growth and alleviates the impact of pesticide application on crop growth. For celery, at the recommended concentration, the root length increased by an average of 15.38%, the stem diameter increased by an average of 3.64%, and the cumulative dry matter mass increased by an average of 4.35% 7 days after treatment, showing significant effects.

Figure 9: The effect of 0.5% Oligosaccharins on the growth of celery crops

Similarly, after 7 days of application on tomatoes, the root dry matter mass significantly increased by more than 15% compared to water, exhibiting excellent effects in promoting root growth and seedling strength.

Figure 10: Effect of 0.5% Oligosaccharins treatment on the root growth of tomato plants after 7 days

In summary, 0.5% Oligosaccharins have good control effects on crop root knot nematodes. Before nematodes occur, 0.5% Oligosaccharins diluted 500 times and then irrigated or soil drench can effectively prevent the occurrence of nematodes. In the early stages of nematodes, using 0.5% Oligosaccharins and chemical nematicide simultaneously can effectively inhibit the spread of nematodes while reducing the amount of chemical pesticides by 30%. At the same time, after treatment with 0.5% Oligosaccharins, the new roots of crops grew quickly, the roots were developed, the plants were robust, the leaves were thick and thick green, and there was no occurrence of pesticide damage.

4. The Development Potential and Prospects of Natural Product Oligosaccharins

Currently, the top three global markets for nematode control formulation are in the United States, Brazil, and Japan, accounting for approximately 70% of global nematode control formulation sales. In the next decade, the occurrence of nematode will significantly increase, and the growth space of the nematode control formulation market will continue to increase. According to a report published by Global Marketsand Markets, the compound annual growth rate of the global nematode control formulation market is expected to be 5.8% from 2023 to 2028, with the largest market located in North America and huge market space. The crops with the highest use of nematode control formulation globally are vegetables, followed by field crops and specialty crops such as medicinal herbs and flowers. In recent years, nematodes have rapidly spread in China, with the occurrence area of vegetable root knot nematodes alone exceeding 20 million acres, occurring in various parts of China and causing serious harm. Almost all vegetable crops in southern China are affected by nematodes, and the agricultural losses caused by root knot nematodes have reached as high as 70 billion yuan.

Due to increasingly stringent policies in developed countries, some chemical nematode control formulation have gradually withdrawn from the market and shifted towards organic agricultural cultivation. Fosthiazate and Abamectin have replaced the banned market capacity of 150 million for Aldicarb, while since October 1, 2018, the use of Carbofuran in sugarcane has been banned, and its 180 million market capacity is gradually being replaced by other formulation. Natural product nematode control formulation will be the fastest-growing category in the next 3-5 years. In addition, with the further improvement of people's food safety and environmental awareness, and against the backdrop of vigorously promoting the development of green, safe, and resource saving modern agriculture globally, efficient, low toxicity, and non-toxic environmentally friendly prevention and control formulation will have a more advantageous position, and the market prospects will be broader.

Oligosaccharins are derived from raw materials such as shrimp and crab shells, and are further degraded from chitin to chitosan. As an excellent natural product biopesticide, it has abundant raw material sources, controllable costs, and is produced through biodegradation methods that are environmentally friendly. By inducing the crop's own immune system to enhance crop disease and insect resistance, while promoting crop root growth, it is safe for humans, livestock, and the environment, in line with the development needs of green organic agriculture. Oligosaccharins have the opportunity to completely alleviate the problem of chemical residue in soil, indirectly reducing the resistance of nematode targets. Providing solid guarantees for food safety and agricultural product quality safety, contributing to the enhancement of agricultural value and sustainable development, promoting the healthy development of biotechnology, and promoting harmonious coexistence between humans and nature.

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