Review of Research Situation of Lagenaria siceraria (Molina) Standl.

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1. College of Horticulture and Landscape, Tianjin Agricultural University, Tianjin 300384, China; 2. Art of Gourd (Tianjin) Cultural Communication Co., Ltd., Tianjin 301804, China

Abstract Lagenaria siceraria (Molina) Standl. Var.hispisa (Thund.) Hara is an annual creeping herb of the family Cucurbitaceae. It has high nutritional value and medicinal value, and it is a high-quality vegetable with low sugar and many kinds of vitamins. This paper introduced the current research situation of L. siceraria (Molina) Standl. from medicinal value, cultivation management technology and processing technology. Besides, it discussed main points of future researches on the basis of existing research, to promote the development of L. siceraria (Molina) Standl.

Key words Lagenaria siceraria (Molina) Standl. Var.hispisa (Thund.) Hara, Cucurbitacin, Cultivation management, Processing

1 Introduction

Lagenariasiceraria(Molina)Standl.var.hispisa(Thund.) Hara is an annual creeping herb of the family Cucurbitaceae, also called bottle gourd, vegetable gourd, edible gourd, sweet gourd, and its dried product is called dry scoop.L.siceraria(Molina) Standl. is native to Japan. In 1988, it was introduced to Northeast China and Shandong, and now it has been successfully introduced in Liaoning, Jilin, Shanxi, Gansu, Jiangsu, Guangxi, Shandong,etc., and the planting area is still expanding rapidly.L.siceraria(Molina) Standl. has high edible value and medicinal value. The tender fruit, tender seedlings and young leaves are edible. The rich flesh of the fruit not only contains nutrients such as vitamins, glucose and fructose, but also contains a variety of elements such as calcium (Ca), phosphorus (P) and potassium (K), and many kinds of amino acids. The leaves, tendril, vines, flowers, seeds and shells ofL.siceraria(Molina) Standl. can be used as medicine, and have the effect of "treating heart heat, benefiting small intestine, moistening heart and lung, and treating urolithic stranguria". Modern medicine usesL.siceraria(Molina) Standl. and their products to treat hyperlipemia, hypertension, diabetes, arteriosclerosis, and has made a new highly effective anticancer drug, cucurbitacin[1]. In the context of rapid development of market economy,L.siceraria(Molina) Standl. has become one of the vegetable crops with low investment and high income and earned foreign exchange. With the continuous understanding of the edible and medicinal value ofL.siceraria(Molina) Standl., the demand forL.siceraria(Molina) Standl. is also increasing year by year, so the market potential for developingL.siceraria(Molina) Standl. production and processing is very enormous, and its prospects are very broad.

2 Research of medicinal value

Cucurbitacin is a highly oxidized tetracyclic triterpenoids secondary biomass element extracted from Cucurbitaceae plants. It is a bitter aglycone component and a characteristic compound of more than 100 species of more than 30 genera of Cucurbitaceae plants[2]. There are many kinds of cucurbitacin structure, but the widest one in the natural world is cucurbitacin B, and other structures are formed in the process of plant reproduction by cucurbitacin B and cucurbitacin E under certain enzymatic reaction[3- 5].

At present, the most in-depth study is cucurbitacin B and cucurbitacin E, but most of the studies focus on the pharmacological action of cucurbitacin. Only a few studies touch on the extraction and activity of cucurbitacin, and the studies on the extraction of cucurbitacin fromL.siceraria(Molina) Standl. is even fewer. Shan Haifengetal.[6]extracted cucurbitacin B from muskmelon base by ethanol reflux extraction method, and compared the ethanol concentration, solid-liquid ratio, extraction time and extraction times by orthogonal experiment, and found that under the optimum extraction conditions of 65% ethanol as solvent, at 80℃, the solid to liquid ratio of 11∶1, reflux extraction time of 0.5 h, and 3 extraction times, the relative extraction rate of cucurbitacin B was the best, up to 86.15%. Using 65% ethanol and anhydrous ethanol heating reflux extraction, Wei Rongetal.[7]prepared the extract of muskmelon base powder and fiber; through HPLC determination of concentration of cucurbitacin B, E and I in the extract, they found that the extraction rate of anhydrous ethanol was higher than 65% ethanol, and the content of cucurbitacin in muskmelon base powder is higher than that in muskmelon base fiber. At present, only Fan Hongetal.[8-10]studied the extraction process and bacteriostatic action of cucurbitacin B and cucurbitacin E inL.siceraria(Molina) Standl. They extracted cucurbitacin B and cucurbitacin E fromL.siceraria(Molina) Standl. by the ultrasonic extraction technique, and determined the optimal extraction conditions were as follows: the solid to liquid ratio of 1∶10, the solvent concentration of 70%, the ultrasonic time of 15 min, ultrasonic power of 500 W; under such conditions, the yield of cucurbitacin B and cucurbitacin E was 0.799% and 0.695%, respectively; using the four kinds of macroporous resins, they isolated and purified the cucurbitacin and got the optimal resin was XAD-16, the content of cucurbitacin B in the purified product was up to 68%, and the content of cucurbitacin E reached 14%; on this basis, they carried out the bacteriostatic experiment onEscherichiacoli,SaccharomycescerevisiaeandAspergillusnigerusing cucurbitacin B and cucurbitacin E, and finally determined the lowest inhibitory concentration range ofE.coli,S.cerevisiae, andA.niger.

3 Cultivation management technologies

L.siceraria(Molina) Standl. is a vegetable that likes warm and strong sunlight. Its stems and leaves are lush and its roots are developed. It is mainly distributed in the cultivated layer at 20-30 cm and horizontally distributed in the range of 300 cm. When the temperature reaches 20℃, the seeds begin to germinate; when the soil temperature reaches 20-30℃, the field planting can be started and the plants grow rapidly. In the whole growth period, the temperature should be kept within the range of 25-30℃.L.siceraria(Molina) Standl. needs more water and fertilizer during the growth period, so it should be cultivated under excellent irrigation conditions.

3.1SeedtreatmentThe seeds are sterilized by soaking in 150 times 40% formalin for 20 min, taken out, washed with water and then immersed in warm water at 40℃ for 90 min, taken out and washed with water for 3-4 times. The sterilized seeds are immersed in water at 30℃, seeds with poor maturity of white skin are soaked for 10-12 h, seeds with good maturity of brown skin are soaked for 15-20 h, and the seeds are fully absorbed and then taken out, then a small slit is opened on soaked seeds[11]. Place the seeds evenly on a layer of sterile sawdust or sand, and place a layer of gauze in a container, cover with a dry towel to promote germination. The germination temperature is generally 27-30℃, the lowest temperature can’t be lower than 25℃, the highest can’t be higher than 32℃, flipped once a day, it can germinate within 4-5 d, and the germinated seeds are taken out and placed in a container in the cool place indoors, and it is necessary to control the growth of the buds to wait for sowing.

3.2Cultureofseedlings

3.2.1Preparation of seedling bed. Nursery bed should select the flat place, in leeward side, close to water source, has excellent water drainage, and convenient management. The area of the seedling bed can be determined according to the planting area, generally 80 plants/m2. At the bottom of the seedling bed, place 8-10 cm horse dung or broken grass, and lay a layer of fine soil, step solidly and flatly. Besides, the seedling bed is disinfected with 70% dikesone wettable powder at 0.3-0.6 g/m2, and the shed is buckled . After the seeds are sown, another small shed is buckled on the seedling bed[12].

3.2.2Preparation of nutritional soil. It is preferred to use field soil which has not been applied with a herbicide such as Pursuit or Chlorimuron-ethyl, and mix with turfy soil or humus,and sift it well, then mix with sieved and thoroughly decomposed farmyard manure at a ratio of 7∶3[13]. Add superphosphate at a ratio of 0.1%, add the Zinc Dimethyldithiocarbamate at a ratio of 0.005%, and mix well for experiment.

3.2.3Bagging sowing. Put the nutritional soil into a 10 cm × 15 cm nutrition bag, put 20 tablets of diammonium phosphate as the base fertilizer at the bottom 1/3 of the bag, and poke the nutrition bag with 2 to 4 holes with 8-10 mm aperture at the bottom, or cut the bottom corner of the nutrition bag to allow water to penetrate[14]. The nutrition bags should be placed neatly on the seedling bed (spacing of 1 cm), and the water should be poured fully. Sowing after the topsoil is dry. The sowing time is April 5-10. Punch a 3 cm deep hole in the middle of the nutrition bag with a wooden stick, place the germinated seeds with the bud hole facing downward, cover the soil, then water one time.

3.2.4Management of the seedling bed. Before germination, it is not necessary to provide ventilation, and keep warm and moist, so as to increase the soil temperature. After germination, it is necessary to control the temperature inside the shed. After 50% cotyledons sprout, appropriate ventilation and cooling should be carried out. The daytime temperature should be in the range of 25-28℃, the noon temperature should not exceed 30℃, and the night temperature should be not lower than 15℃. If these two critical values are exceeded, it is necessary to take measures such as wind protection and covering. Within 5-7 d before transplanting, it is necessary to take off the shed according to the temperature and growth of the seedlings in warm and sunny days, to harden the seedlings. When the true leaves grow to 2 to 3 leaves, the water is sprayed once a day, and the pesticides such as chlorothalonil and methyl thiophanate are used to prevent and cure theRhizoctoniasolaniKuhn (sheath blight) andPythiumaphanidermatum(damping off). When the true leaves grow to 4 to 5 pieces, settle the center, pinch out the tips, to prevent them from spindling. It is feasible to use phoxim granules, deltamethrin emulsifiable concentrate, trichlorfon emulsifiable concentrate and wheat bran as baits to prevent and control mole crickets, cockroaches and rats.

3.3Sitepreparationandtransplanting

3.3.1Site selection, preparation, and fertilization. It is preferred to choose well-drained, deep topsoil, and fertile sandy loam or loam, and avoid continuous cropping of melons. It is preferred to prepare the site in the beginning of autumn. If the site preparation in spring should be completed within one week before transplanting, at the row spacing of 3.8-4 m and plant spacing of 1.2-1.4 m, the ploughing depth of 25-30 cm, and the ploughing should be followed by harrowing, and pressing. It is necessary to dig holes with a diameter of 30 cm and depth of 20 cm, and apply 3-5 kg of high-quality farmyard manure, 150-200 g of diammonium phosphate, and 40 g of potassium sulfate as the base fertilizer[15].

3.3.2Transplantation. The field planting should be finished in the middle and late of May. Before transplanting, it is necessary to water the nutrition bags fully, take out the nutrition bags, conduct transplanting by clear water planting method, that is, the seedlings are planted according to the plant spacing, and the water is poured after soil is covered, and the cotyledons should be about 5 cm above the ground. After field planting, pay attention to observe the growth and survival of seedlings, so as to make up the seedlings promptly.

3.4Fieldmanagement

3.4.1Pinching the tips, smoothing the vines, and pruning. The apical dominance ofL.siceraria(Molina) Standl. is strong, so that the lateral buds are dormant and it is difficult to germinate lateral vines. However, the fruiting part is often in the lateral vine, thus, it is required to promptly pinch the tips and prune, so as to increase the number of fruits per unit area. When the main vine generates 4 to 5 true leaves, it is necessary to top the vines, and the son vines begin to grow. Then, select two vines with better and equal growth status and symmetrical position from 4 to 5 son vines, remove other son vines. In this period, earth up one time, make the melon seedlings incline towards the downwind direction, to avoid turning over of the seedlings. When the son vines grow to 120-150 cm, it is necessary to top the vines in 6 to 7 leaves to promote generation of fruiting vines; keep the fruiting vines, and remove the unnecessary lateral vines and axillary buds, to promote the growth of fruiting vines and flower buds differentiation; when the fruits on the fruiting vines reach the expected number, pinch the tip in 5-7 leaves behind the fruits, to promote fruit development and prevent falling of fruits[16].

3.4.2Artificial pollination.L.siceraria(Molina) Standl. is a parthenocarpic, monoecious, and usually entering the full bloom period at 17:00. Therefore, it is preferred to conduct artificial pollination after 17:00. When the male flower pollen is mature, pollination can be carried out. Firstly, remove the newly opened male flower , remove the corolla, and gently apply the pollen to the female stigma of the different plant with the stamen. After pollination, bend the female flower below the leaf to increase the fruit setting rate.

3.4.3Topdressing and watering. It is necessary to conduct topdressing promptly after generation ofL.siceraria(Molina) Standl.. Ren Yuanli[17]used a method of applying fertilizers through pricking holes or radiating in areas 50 cm around seedlings, implemented topdressing of 150 g of urea for each plant, and the topdressing time is determined according to the growth status. Guo Mu[18]applied 225 kg of urea or 150 kg of ammonium nitrate for one hectare of land, and then applied fertilizer through foliar spraying.

L.siceraria(Molina) Standl. likes wet but does not like waterlogging. If drought occurs in flowering and fruiting period, it is necessary to water two times; if rainy season coincides with the flowering and fruiting period, it is necessary to prevent waterlogging, to accelerate the expansion of fruits and increase the yield.

3.4.4Laying grasses. After intertilling and topdressing, it is necessary to lay straws or pine needles under the vines promptly according to the growth status, to prevent vines, leaves and fruits from rotting.

3.4.5Prevention and control of plant diseases and insect pests. The diseases and insect pests ofL.siceraria(Molina) Standl. mainly include aphids, blight, anthracnose,etc., and are generally controlled by conventional pesticides. It is recommended to use 1 000 times spray of 80% dichlorvos emulsifiable concentrates, 1 500-2 500 times liquid spray of 10% imidacloprid wettable powder or 1 000 times solution of 40% dimethoate emulsifiable concentrate to control aphids; use 500 times solution of 50% carbendazim wettable powder or 400-500 times solution of 50% thiophanate-methyl wettable powder to control the blight; use 600 times solution of 75% carbendazim or 500 times solution of mancozeb wettable powder to control the anthracnose[14].

In summary,L.siceraria(Molina) Standl. has relatively strong resistance to pests and diseases, and almost no pests and diseases occur when planted for the first time.

4 Processing technologies

L.siceraria(Molina) Standl. is large in volume, high in water content, and it is difficult to store and transport, thus it is necessary to study the deep processing technology ofL.siceraria(Molina) Standl. TakingL.siceraria(Molina) Standl. as raw materials, Zhu Zhu[19]rapidly fermentedL.siceraria(Molina) Standl. pickles with Direct Vat Set starter. The optimum fermentation conditions were determined by single factor experiment and orthogonal experiment to be 0.003% of the powder input and fermentation temperature 30℃.The amount of salt added was 4%, and the amount of mixed strain powder during fermentation had the greatest effects on the quality ofL.siceraria(Molina) Standl. pickles, followed by the fermentation temperature. Sun Yuanbinetal.[20], using the vacuum dynamic pickling method, developed low-saltL.siceraria(Molina) Standl. pickles. Through orthogonal experiment, the optimal pickling process parameters were determined as pickling temperature 20℃, vacuum 85 kPa, stirring speed of 1 r/min for dynamic pickling vacuum pickling machine, and salt solution concentration of 2%. The pickling temperature and vacuum have a significant effect on the quality ofL.siceraria(Molina) Standl. pickles. Cao Ying[21]studied the processing technology of low-sugarL.siceraria(Molina) Standl. candied fruit. The single-factor experiment and orthogonal experiment were used to determine the optimal processing parameters: sugar concentration of 60%, sugar soaking time of 110 min, drying time of 2.5 min, and the optimal single factor values were 60% for sugar solution concentration and 90 min for sugar soaking time. Under such conditions, the sensory score of the candied fruit was 515.

However, the most common method of processingL.siceraria(Molina) Standl. is sun drying , and then cut into strips to make "L.siceraria(Molina) Standl. strips", which can be exported to the foreign countries and called "dry scoop". When theL.siceraria(Molina) Standl. fruit weighs about 10-15 kg, it generally can be harvested. It is usually harvested on the first day, cut into slips and dried on the next day. When the water content of theL.siceraria(Molina) Standl. strip is reduced to 20%, it is bound according to the grade, the strips are fumigated about 24 h, generally 1 kg of sulfur can fumigate 1 000-1 500 kg ofL.siceraria(Molina) Standl. strips[22]. In recent years, due to market demand, growers will also process sulfur-freeL.siceraria(Molina) Standl.strips. In other words,L.siceraria(Molina) Standl. strips are not dried with sulfur during the processing, but dried by natural light drying or boiler drying line to produce green pollution-free products[23].

5 Conclusions

In recent years, with the adjustment of planting structure, the planting area ofL.siceraria(Molina) Standl. is also expanding year by year. As one of the vegetable crops for export earning,L.siceraria(Molina) Standl. has obvious development advantages, andL.siceraria(Molina) Standl. culture is also becoming an important support for developing the characteristic culture and economy. At present, the research onL.siceraria(Molina) Standl. mainly focuses on cultivation and processing techniques, and there are few studies about nutrients and cucurbitacin extraction technology inL.siceraria(Molina) Standl., so it has broad research prospects and value for researchers. This paper is expected to lay a certain theoretical foundation for the development and utilization ofL.siceraria(Molina) Standl.