| Greenhouse crop production has become the important part of sustainable development of our agriculture industry. Baiyin city is located in the central region of Gansu province with adequate sunshine and temperature, suitable for developing energy-saving greenhouse production. Its greenhouse area had reached 4784.3hm2 until the year of 2004 with total yield up to 350,000 tones. Greenhouse vegetable production has become the real pillar industry of Baiyin city, greatly enriching the vegetable baskets of the residents in Baiyin city as well as in northwest provinces or cities.Chili pepper is one of the important cultivated crops in greenhouses of Baiyin city with annual area of about 133 hm~2 and yield of 80,000 tones. It is mainly planted in three periods: 1. planted in late autumn and harvested in winter and spring; 2. planted in early spring; 3. planted in autumn and harvested around the year. Due to its huge yield and top quality, it boasts high reputation in Gansu and surrounding provinces. The sustainable development of chili pepper is increasingly affected by the soil-born diseases such as Phytophthora blight, Fusarium wilt, Phytophthora root rot, etc. In the study, the survey on the occurrence of Phytophthora blight was carried out at more than 20 villages of 8 townships in Baiyin and Pingchuan districts of Baiyin city. The incidence, development and affecting factors of Phytophthora blight were gotten to provide the scientific evidences for control of the disease.Through symptom observation in the fields, culture of separated pathogens on PDA in laboratory and trapping spores from cucumber plants, the pathogen, Phytophthora capsici Leonian, infecting chili pepper plants in Baiyin, was investigated. Phytophthora blight occurred at Jingyuan and Jingtai counties, Baiyin and Pingchuan districts of Baiyin city. The average incidence was 15—30% (partly more than 30%) with severity of 3～5 degrees. According to the survey and observation at the fixed sites at Pingbu and Dongwan townships, the disease began to occur soon after planting chili pepper in autumn, reaching its first occurrence peak with the incidence of 11.7%～21.7% from late November to early-medium December when the temperature in / out of greenhouse was still high; its second occurrence peak turned up from March to May when chili pepper was in the stage of high yield.The key pathogenic factors affecting the occurrence of Phytophthora blight of greenhouse chili pepper included the differences of cultivars' resistance to disease, pathogen amount in soil, soil temperature, air temperature and humidity, irrigation methods and ecological management measures. The occurrence of Phytophthora blight was closely related with the temperature and humidity. The pathogen grew in the temperature range from 8℃to 38℃, and its optimal development temperature was 30℃When the field temperature reached 25～30℃as well as relative humidity surpassed 85%, Phytophthora blight occurred severely. In the study, it was showed that with flood irrigation the ratios of the diseased plants of Longjiaol and Longjiao2 were 6.07% and 0.36～1.71% respectively, and that of Jiamusi chili pepper was 16.20～19.29%, therefore there existed distinct differences of resistance to Phytophthora blight among chili pepper cultivars. Drip irrigation could control the irrigation amount efficiently, decreasing greenhouse humidity and the incidence of Phytophthora blight to 6.7%～8%; flood irrigation could not control the irrigation amount, increasing greenhouse humidity and the incidence of Phytophthora blight to 16.2%～23.1%. Rational crop rotation could not only improve soil's fertility and soil's physical -chemical property, but also reduce the pathogen population and the occurrence of Phytophthora blight. Therefore in practice, the following ecological measures were adopted to control irrigation amount and lower greenhouse humidity: establishing high cultivation ridges, covering the larger furrows with crop straw, hanging light-reflecting curtain on the rear wall of greenhouse, using drip irrigation, etc.Different types of chili pepper variations were used as the rootstock. The grafting methods, the survival ratio of grafted unions, growth and development of grafted unions of different rootstock-scions' combinations, disease -controlling effects, impact of grafting on crop yield and quality, etc, were investigated to prove the feasibility of production of grated chili pepper, and to demonstrate that grafting cultivation could become an effective approach of overcoming the physiological disturbance of greenhouse chili pepper planted in the same field for several years. The experiment results showed that when stocking pepper and scioning pepper had 6～8 true leaves and 5～7 true leaves respectively with semi-lignified stem of 2～3mm in diameter, the grafting was carried out, which facilitated the intergrowth compatibility of grafted unions and their survival ratio was above 85%. Thought different types of rootstocks produced the different impact on chili pepper plants' growth, but in general grafting improved plants' growth vigor. After grafting, plant height plant width, the height of first key branch, stem diameter and the number of harvested peppers were increased compared with those of check treatments, and furthermore the flowering date was advanced by 6～7 days and the harvesting date by 3-4 days. The disease severity and the incidence indexes of most grafted plants were lower than those of check plants. The disease severity of self-rooted chili pepper plants was increasing following plants' growth.Based on the yield analysis, the early yield differences among A3D3, A3D2, A3D4 and A3D1, and that between CK2 and CK1 did not reach the significant level; the early yield difference between A3D3 and CK2 reached significant level, and that between A3D3 and CK1 turned out to be extremely significant. The total yield differences among four treatments did not reach significant level, but reached significant level compared with those of CK2 and CK1; furthermore the total yield differences among A3D2. A3D3, A3D1 and CK1 reached extremely significant level; that between CK2 and CK1 did not reach significant level. There were no evident differences on fruit appearance and internal quality between fruits from grafted chili pepper plants and self-rooted plants, but some treatments' results were better than those of check plants to some extent.According to the experiments, it was concluded that grafting chili pepper with disease - resistant rootstock by splitting method was a very effective approach to control Phytophthora blight, and played a positive role in increasing chili pepper yield and quality. The disease-controlling and yield-increasing technique was easy to learn and simple to practice, and exhibited bright prospect for being extended in larger area. The most important point was selection of the suitable rootstock for greenhouse chili pepper. The rootstock should possess the following properties: good compatibility with chili pepper cultivar, high resistance to diseases, easy access to the seed, larger root system, strong growth vigor and no negative impact on chili pepper quality. In order to apply the grafting technique in a larger area, the further studies need to be conducted to increase the survival ratio, resistance to diseases and stress and high yielding of grafted unions. The technical operation program suitable for local greenhouse conditions also needs establishing. |
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