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Cucurbit Genetics Cooperative Report 23:83-85 (article 280) 2000

Research and Application of Seed Coating Agent for Cucurbit Crops in China

Zhao Jioqiang and Cheng Zhihui

Horticultural Department, Northwest Sci-Tech University of Agriculture & Forestry, Yangling, Shaanxi 712100, P.R. China

Seed Coating Agents (SCAs) are compounds effective in protecting seed and young seedlings from attack by disease and insects. They may also supply nutrition for young seedling growth. SCAs are composed of active and inactive components. The former may include different kinds of insecticide, germicide, trace element fertilizer, plant growth regulator, etc. The latter includes membrane forming agents and warning color material. Since the 1980's, countries such as America, the former Soviet Union, Japan, and other western countries have obtained notable results in application of seed coating technology. Although seed coating agent research in China just started in the early 1980's, more than 30 kinds of SCAs have been developed, of which more than 24 have been put into commercial use. In China, SCAs are applied mainly to the most important crops such as rice, wheat, maize and cotton. The crop area sown with SCA treated seed reached 26,000,000 Ha by the end of 1998 and increases each year.

Generally, SCAs are designed according to region or to protect against the plant disease and insect pest expected to occur. They should have long efficacy (the effect can last for 40-60 days), and be absorbable, transferable and stable. The main type of SCAs in China are as following:

Pesticide and fertilizer compound type. China is a country with vast territory and greatly varied soil type. However, most of the soil is deficient in trace elements or infected by soil-borne disease. Therefore, most SCAs developed in china belong to pesticide-fertilizer compound type. For example, the eighteen SCAs developed by the China agriculture University from 1980 through 1985 are all this type.

Non-poisonous ecological type. The current trend in China is the development of a series of non-poisonous ecological type SCAs to meet the needs of non-environment polluting crop production. This type of SCA utilizes microbes in its membrane as the active component. Therefore, they not only accelerate plant growth but also improve and protect the environment. "ZSB Ecological SCA" developed by the Seed Company of Zhejiang Province is an example of this type which has been applied to field crop production.

Region specialized type. Because China has a vast territory, varied ecotype, and different kinds of diseases and pests, the Chinese SCAs have a regional character. Generally, they are divided into two groups: southern type and northern type. There are also SCAs designed for specific regions.

Main components of Chinese SCA. The main chemical components of SCAs are considered to be either active or inactive components. Active chemical components refer to the material that can affect seed and seedlings such as pesticides, trace element fertilizers, plant growth regulators and microbes. the main active components used in chinese SCA at present are shown in Table 1.

Inactive chemical components are agents that maintain the physicochemical properties of the SCA, such as compounds related to membrane-formation, suspension, expander, acidity, adjustment adhesive, warning color, etc. Membrane-forming technology is critical for seed coating. The main component of the membrane-forming materials we are using is dissolvable dispersing-oseands and their derivatives such as acacia, substitution cellulose, etc. Some synthetic chemical compounds such as epoxyethane or poly-vinyl alcohol are also included. New types of components and technology such as hyper-moisture-absorbing resin SCA, seed embedded with mycose and ultra-micro powder seed coating technology are also being applied.

Main varieties of SCAs being used and produced in China at present. At present, more than 30 varieties of SCAs have been registered in china. SCA applied to vegetable crops are shown in Table 2.

Other SCAs with good effect on vegetables now shown in Table 2 include: SCA Special for Gourd Vegetables and SCA Special for Cowpea, developed by the Vegetable Institute of Guangdong Province; Vegetable SEed Coating Agent No. 1, developed by the Tianjin Vegetable Institute; Eggplant SEed Coating Agent No. 1 and cucumber SEed Coating Agent No. 1, developed by the Northwest Sci-Tech Agriculture & Forestry University.

Effects of SCA on Gourd Vegetables. In gourd vegetables, SCAs are mainly used on watermelon, muskmelon and cucumber.The effects of these SCA on gourd vegetables are as follows.

On seed storage and germination. Seed longevity can be prolonged greatly by seed coating. Pu Hanli (1997) reported that the germination rate of coated seeds was 30% higher than that of the control after storage for 5 months and 66% higher after storage for 8 months. Germination rate, germination energy and germination index of cucumber seed coated with "Cucumber SEed Coating Agent No. 1", developed by Meng Huanwen (Horticulture Department of NSTUAF), were respectively, 5.78%, 1.27% and 6.63% higher than that of the control. The experiments on cucumber and tomato by Ma Wenhe (1999) showed that the germination rate was above the control level. Pu Hanli tested the effects of a gourd SCA on gourd vegetables and found that the field germination rate was increased on all tested crops and the best effect was shown on luffa (39/4% higher than that of the control.)

On growth energy and resistance of seedlings. Many researches have shown that seedlings from coated seed have higher growth energy and greater ability to withstand adverse ecology. Pu Hanli (1997) found that the ability to survive adverse ecology of luffa seedlings from coated seeds was 41.5% higher than that of the control. It was reported that root growth was improved and R/T ratio increased 150% and 180% respectively for cucumber and green pepper seed coated with Vegetable Seed Coating Agent No. 1.

On blossom and bearing of fruits. Due to better growth and increased ability to withstand adverse ecology, the plants from coated seeds bear fruits earlier. Pu Hanli's experiments demonstrated that plants grown from coated luffa seeds produced heavier fruit 10 days earlier than the control group. Benincasa hispida seedlings in nutritive cube field planted from coated seeds grew better and stronger. Their female flowers bloomed 5 to 6 days earlier and the fruits ripened 7 to 8 days earlier than that of the control.

Problems and Prospects. China is a country with large-scale vegetable production. The production area reached 11,270,000 ha by the end of 1998. Chinese cabbage seed production alone came up to 1140 tons. At present, seed production is being carried out all over China. Use of SCAs is increasing at an average rate of 30 percent each year. Therefore, there is a great market for SCAs in China. On the other hand, the vegetable seed coating industry is still at its beginning stages. Few SCAs are specially designed for vegetables, and development of SCAs for certain regional diseases are even fewer. Additionally, more attention should be paid to non-poisonous and non-polluting ecological types. Finally, the production ability should also be enlarged.

Table 1. The Main Active Components of Chinese SCA.

Kind of SCA

Active component

Pesticide

Carbofuran, Carbosulfen, Imidaproprid, Teflathrin, Frpronil, Lindane

Germicide

Carbendazim, Thiabendazole, Thiophanate, Triodimend Diniconazole, Carboxin, Captan, Thriam, Rhizolex, Imizalil Dimetachtalone, Metalaxyl, Mencozeb, Hymexazol, Zineb, Zinc, Methabearsibatem Myclobutanil, Fenpiclonil Tebuconazole, Cyproconazole

Plant growth Regulator

Pactobulrazole, Samiseren, Chlomequat, Triadimefon

Trace element

Zinc, Manganese, Iron, Molybdenum

Table 2. SCA Applied to Vegetables in China.

SCA
Crops to be applied
Prevent objects
No. 5 Muskmelon, watermelon and other vegetables Vegetable Fusarium wilt, Vertcillium wilt, Damping off, Web blight, Wilt and Anthracnose
No. 7 Watermelon, rape and other vegetables Vegetable and Watermelon Fusarium, Anthracnose, etc.
No. 9 Watermelon and other vegetables Watermelon and Vegetable anthracnose, Fusarium, Web blight, Damping off, Elemental deficiency
No. 10 Watermelon, beet and other vegetables Soil insects, Angular leaf spot, Fusarium wilt Anthracnose, Physiological disease, Increased yield
No. 32 Watermelon Soil and foliar disease and insects
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Page citation: Wehner, T.C., Cucurbit Genetics Cooperative;
Created by T.C. Wehner and T. Ng, 1 June 2005; design by C.T. Glenn;
send questions to T.C. Wehner; last revised on 21 April, 2008