Báo cáo nghiên cứu nông nghiệp " Selection and development sweet potato varieties with high root quality for food processing in Northern and Central of Vietnam " potx

Collaboration for Agriculture and Rural Development (CARD) Program 288 RESULTS OF AN EVALUATION AND SELECTION OF NEW SWEET POTATO VARIETIES IN BAC GIANG, THANH HOA AND QUANG TRI PROVINCES Project title: Selection and development sweet potato varieties with high root quality for food processing in Northern and Central of Vietnam Code of the project : CARD 008/07 VIE Author(s): Nguyen Van Tuat 1 , Truong Cong Tuyen 1 , Nguyen Dat Thoai 1 , Truong Thi Thuy 1 , Tran Quoc Anh 1 , Nguyen Phan Anh 1 , Do Thi Lieu 1 , Nguyen Thi Hoai 1 , Les Copeland 2 , Peter Sharp 2 , and Richard Trethowan 2 P roject implementing organizations: Food Crop Research Institute, VAAS, Vietnam Sydney University, Australia SUMMARY The objectives of the CARD project entitled “Development and Selection of Commercial and High Quality Cultivars of Root and Tuber Crops for Processing Purpose in the Northern and Central Vietnam” between FCRI and Sydney University are to 1) Select a certain number of sweet potato cultivars from those designated by FCRI as potentially suitable for cultivating in locations in northern and centr al Vietnam and conduct field trials in selected locations to evaluate these cultivars according to yield and dry matter content for value - adding purposes; 2) Develop and evaluate processing methods for sweet potato, namely production of flour and starch fo r food processing and industrial applications, sweet potato chips, sweet potato wine; 3) Develop methods that can be used by small - holder farmers for fermenting leaves and stems of sweet potatoes into a silage - type product for animal feeding; 4) With the a ssistance of Australian experts, improve the science capacity of Vietnamese researchers and extension workers in modern techniques for plant improvement, storage and food processing technology, analysis of food quality; 5) Improve farmer’s knowledge and sk ills in cultivation of sweet potato as a part of a sustainable farming system and 6) Establish model sites to display advanced cultivation techniques, and organize field day meetings to disseminate knowledge to farmers. The project has been conducted in tw o years 2008 - 2009 and this report reflects the results of those activities in project sites that have been reviewed and discussed at the project completion meeting and the Public Forum in April 2009. The results of field trial and evaluating new sweet pota to varieties in Thanh Hoa, Quang Tri and Bac Giang provinces have indicated that among 11 varieties it has been chosen 3 good ones including VC68 - 2, VC 02 - 193 and VC 04 - 24 with the yield ranged from 13.64 to 23.6 tonnes/ha, compared to check control yielde d 10.13 to 14.9 tone/ha 1. Introduction The cultivation area of sweet potato in Vietnam annually ranging 200,000 - 250,000 ha, with an average yield of 8 ton nes per ha. Its product providing very high potential of material for processing. Sweet potato is g rowing well in various locations in northern and central VN, especially in regions where farmer income is low. In addition to its usefulness as a food for humans, and as a very good improver of soil fertility, texture and structure, sweet potato has high p otential CARD 008/07 VIE – Development of sweet potato varieties with high quality 289 for value adding and as a source of feed for animals from the unharvested parts. Using this crop can reduce the risk of major pests and diseases of other crops like rice and vegetables, thereby better protecting the agricultural environment. There is a market for products from tuber crops such as sweet potato, for example flour and starch as a raw material for industry in the manufacture of foods, confectionery, pharmaceuticals, paper and textiles. The demand of starch for industry in Vietnam annua lly is about one million tons, much of which is imported. The lack of good cultivars and relevant technology for cultivation and processing of sweet potato means that this crop is not achieving its great potential for contributing to increasing income and providing socioeconomic benefits for farmers in poorer regions. At FCRI, several sweet potato cultivars, such as sweet potato No.8, KB1, KL5, K4, K51, Advance 1, Advance 2 and Hoang Long, have been identified for their agronomic and adaptive traits, resist ance to key insect pests and diseases, and nutrient requirements. However, these cultivars have not been evaluated for yield and dry matter production and performance in processing. The central region and some northern provinces of Vietnam have suitable gr owing seasons for tuber crops. The cultivation of sweet potato crops in these regions needs to be investigated as part of a sustainable cropping system that increases farmer income. In this paper the research results conducted from 2008 - 2009 of the CARD pr oject "Selection and development sweet potato varieties with high root quality for food processing in Northern and Central of Vietnam ” are highlighted. 2. Research contents and methods 2 .1 Materials Ten varieties were collected from Food Crops Research In stitute, Hoang Long and local sweet potato varieties were used as the check varieties. 2 .2 Project sites - Food Crops Research Institute experiment farm - Bac Giang province (Bich Son - Viet Yen, Ngoc Chau - Tan Yen, Mai Trung - Hiep Hoa) - Thanh Hoa province (Nguyên Binh - Tinh Gia, Quang Luu - Quang Xuong, Dong Thanh - Dong Son) - Quang Tri province (Vinh Thai - Vinh Linh, Gio Hai - Gio Linh, Hai Quy - Hai Lang) 2.3 Research content - Evaluate and select new potato varieties in Bac Giang and Thanh Hoa based on quality and yield - Evaluate and select new potato varieties at FCRI based on quality and yield - Evaluate and select new potato varieties in Quang Tri based on quality and yield 2.4 Methodology  Experiment type - R andomized complete block design (RCBD ) - Study area: 11 varieties x 4 replications x 15 m 2 = 660 m 2 - Protection area: 340 m 2 - Total area for one experiment = 1,000 m 2  Planting method - Cut and plant sweet potato root with the clean tools in all of the locations. - Distance: the distance between two plants in a row was 0.2 m and the density was 40,000 plants/ha - Align the plant vertically to the bed surface  Planting time: - Thanh Hoa and Bac Giang: 5 - 10th October - Quang Tri: 15 - 20th Dece mber NV Tuat, TC Tuyen , N D Thoai, TT Thuy, TQ Anh, NP Anh, DT Lieu, NT Hoai, L . Copeland, P . Sharp & R . Trethowan 290  Fertilization application Fertilizer K g /ha Kg (NPK)/ha Cattle manure 15,000 - Urea 150 60 - 70 kg N/ha Super Phosphate 550 90 - 100 kg P/ha Kali 220 120 kg K/ha - Mix all of the cattle manure and super phosphate as well as 30% of urea and 30% of potassium for treatment before planting. - Half of the remaining Urea and Kali fertilizers were fertilized 20 - 25 days after planting. The other half was added in 40 to 45 days after planting.  Harvesting data collection - For each treatment, sweet potato roo ts were harvested from 4 m long section in the middle of the bed. - Sweet potato roots were inspected with criteria such as insects, diseases, breakage for each treatment. - Counting the number of roots for each treatment. - Weighing and grading roots: smal l <30g, medium 30 - 50g, large >100g.  Statistic analysis Data were collected by the Vietnamese participants and analysed statistically by the Australian experts. 3. Research results and discussions 3.1 Evaluate and select new potato varieties in Bac Gia ng and Thanh Hoa based on quality and yield The dry matter contents were determined for roots of the sweet potato varieties at all of locations in Bac Giang and Thanh Hoa, 2008 (Table 1). The highest dry matter content in these sweet potato varieties were 25.65% of HT2 and 25.38% of VC01. The values were much higher than those of Hoang Long (21.29%) and the local (20.49%). On the other hand, in the same varieties, the dry matter content in a location was different between locations. For example, HT2 had hig h dry matter content of 33.5% and 30.73% in S2 and S6, respectively but only 24.6% and 18.57% in S1 and S3, respectively. Therefore, varieties and environment caused different dry matter content of these sweet potato roots. The main factor was the winter in Bac Giang (S1) and Thanh Hoa (S3) influencing unfavourably dry matter content. Table 1: Dry matter content (%) in root of Sweet potato varieties in Winter season 2008 Sites Variety S1 S2 S3 S4 S5 S6 Mean KL5 20.13 20.63 19.17 20.97 18. 9 20.2 20.00 KB1 18.63 26.17 19.9 21.73 19.77 23.97 21.70 S ố 8 23.37 27.87 19.50 21.23 23.83 22.47 23.05 HT2 24.6 33.50 18.57 21.37 25.10 30.73 25.65 TM1 22.5 23.70 19.07 20.87 18.67 18.20 20.50 VC.01 27.53 29.10 19.13 23.00 27.13 26.40 25.38 VC.68 - 2 23.57 26.13 18.90 22.43 25.23 20.23 22.75 VC.97 - 6 - 3 24.1 2 0.67 18.97 22.77 20.67 20.50 21.28 VC 04 - 24 20.33 27.20 19.33 18.87 18.20 20.90 20.81 VC02 - 193 20.13 28.63 18.83 21.93 20.87 18.80 21.53 Hoang Long 21.57 24.47 18.17 22.87 21.77 18.90 21.29 Local variety 20.23 21.73 19.20 19.83 20.73 21.23 20.49 Mean 22.22 25.82 19.06 21.49 21.74 21.88 22.03 LSD (5%) 3.317 3.969 1.651 1.904 2.34 3.056 CV% 8.8 9.1 5.1 5.2 6.4 8.2 Note: S1= Bich Son - Viet Yen, Bac Giang S2= Cao Xa, Tan Yen, Bac Giang S3= Dong Quang, Dong Son, Thanh Hoa S4= Mai Trung, Hiep Hoa, Bac Giang S5= Nguyen Binh, Tinh Gia, Thanh Hoa S6= Quang Minh, Quang Xương, Thanh Hoa - Evaluation of root yield : Root yield of the new sweet potato varieties in Thanh Hoa and Bac Giang is shown in Table 2 . In general, all of the root yields were lower t han the expected CARD 008/07 VIE – Development of sweet potato varieties with high quality 291 potential yields due to the unfavourable weather in all locations. However, VC68 - 2, VC04 - 24 and VC02 - 193 achieved higher root yields of 13.75, 14.94 and 13.64 tonnes/ha, respectively, than Hoang Long and the local variety with 10.62 and 10 .13 tonnes/ha, respectively. The location S1 had the highest root yield of the six locations. Table2: Root yield (tonnes/ha) of sweet potato varieties in Winter 2008 Varieties S1 S2 S3 S4 S5 S6 Mean KL5 17.87 10.67 10.29 11.41 11.33 11.16 12.12 KB1 19.36 10.62 12.13 12.12 11.54 11.04 12.80 N o 8 17.78 10.73 10.47 10.61 10.82 11.24 11.94 HT2 15.13 9.38 9.64 10.51 10.54 11.62 11.14 TM1 14.42 12.00 11.22 11.29 11.98 9.42 11.72 VC.01 14.89 10.36 9.73 10.64 8.87 9.04 10.59 VC.68 - 2 19.29 13.56 13.8 0 11.88 12.93 11.02 13.75 VC.97 - 6 - 3 15.89 13.00 9.93 11.32 10.76 10.27 11.86 VC 04 - 24 22.62 11.13 12.51 15.16 14.33 13.87 14.94 VC02 - 193 19.51 12.00 11.78 14.30 13.56 10.69 13.64 Hoang Long 18.40 8.82 7.84 9.93 10.13 8.60 10.62 Local variety 18.73 10. 16 7.00 7.68 7.80 9.40 10.13 Mean 17.82 11.04 10.53 11.40 11.22 10.62 12.10 LSD 1.87 1.28 2.68 0.70 0.76 1.83 CV% 6.20 6.90 15.00 3.60 4.00 10.20 Note: S1= Bich Son - Viet Yen, Bac Giang S2= Cao Xa, Tan Yen, Bac Giang S3= Dong Quang, Dong Son, Th anh Hoa S4= Mai Trung, Hiep Hoa, Bac Giang S5= Nguyen Binh, Tinh Gia, Thanh Hoa S6= Quang Minh, Quang X ương, Thanh Hoa The dry matter content of vine - leaf of vine - leaves as shown in Table 3, varied from 10.62 to 12.22%. Most of the varieties had similar values of dry matter content but N o 8 had the highest average dry matter content of 12.22%. The dry matt er content of vine - leaves in Bac Giang (S2) and Thanh Hoa (S5) had high values of 11.52 and 12.56%, respectively. Table 3 . Dry matter content (%) in vine - leaf of sweet potato varieties in Winter season 2008 Varieties S1 S2 S3 S4 S5 S6 Mean KL5 11 .50 11.14 11.19 9.92 11.70 10.72 11.03 KB1 9.87 11.15 10.83 10.54 11.92 9.41 10.62 N o 8 12.97 12.05 12.13 11.82 13.61 10.733 12.22 HT2 11.75 11.19 12.01 11.42 13.10 11.74 11.87 TM1 10.10 11.51 11.90 11.08 12.56 9.52 11.00 VC.01 10.94 12.21 12.29 11.16 12.99 11.69 11.88 VC.68 - 2 12.90 8.75 10.28 10.34 11.36 10.74 10.73 VC.97 - 6 - 3 10.01 12.84 11.86 10.79 12.12 10.62 11.37 VC 04 - 24 10.03 12.57 11.33 9.24 11.31 10.10 10.76 VC02 - 193 9.54 11.31 11.30 11.25 13.23 9.37 11.00 Hoang Long 10.14 12.08 12.08 11. 89 13.51 10.64 11.72 Local variety 10.01 11.42 11.54 13.31 13.31 9.88 11.58 Mean 10.81 11.52 11.50 11.06 12.56 10.43 11.31 LSD 1.48 1.90 0.99 1.27 2.32 1.40 CV% 8.10 9.70 5.10 6.80 10.90 7.90 Note: S1= Bich Son - Viet Yen, Bac Giang S2= Cao Xa, Tan Yen, Bac Giang S3= Dong Quang, Dong Son, Thanh Hoa S4= Mai Trung, Hiep Hoa, Bac Giang S5= Nguyen Binh, Tinh Gia, Thanh Hoa S6= Quang Minh, Quang Xương, Thanh Hoa NV Tuat, TC Tuyen , N D Thoai, TT Thuy, TQ Anh, NP Anh, DT Lieu, NT Hoai, L . Copeland, P . Sharp & R . Trethowan 2 92 - The vine - leaf yields : The vine - leaf yields of the new varieties in Bac Giang and Than h Hoa in the winter season 2008 were calculated and presented in Table 4. - The unfavourable climate in the winter of 2008 affected the growth of the sweet potato varieties and reduced the vine - leaf yield. The highest yield was only 8.01 tones/ha from TM1 while Hoang Long and the local variety had very low yields of 5.95 and 6.85 tonnes/ha, respectively. - In the same varieties, the vine - leaf yield in various locations was different. Therefore, evaluation of adaptability of a variety to the environment is necessary . Table 4: Vine - leaf yield (tonnes/ha) of sweet potato in Winter season 2008 Varieties S1 S2 S3 S4 S5 S6 Mean KL5 8.36 3.71 6.51 8.69 10.83 3.36 6.91 KB1 7.87 3.24 4.31 8.37 10.16 3.24 6.20 N o 8 8.71 3.91 4.96 8.60 11.23 3.71 6.85 HT2 6.7 8 4.60 6.16 7.85 10.02 4.60 6.67 TM1 8.27 4.80 6.89 9.83 13.58 4.69 8.01 VC.01 8.33 4.60 6.18 9.03 12.10 4.40 7.44 VC.68 - 2 7.02 4.64 2.44 9.48 12.66 4.64 6.82 VC.97 - 6 - 3 7.69 11.13 4.69 8.99 11.13 3.64 7.88 VC 04 - 24 10.64 3.64 5.40 9.06 11.45 3.42 7.27 VC02 - 193 9.60 4.84 5.64 9.42 11.67 4.84 7.67 Hoang Long 6.96 3.33 3.89 7.99 10.20 3.33 5.95 Local variety 8.38 3.62 6.49 8.09 10.88 3.62 6.85 Mean 8.22 4.67 5.30 8.78 11.32 3.96 7.04 LSD 1.33 1.52 1.38 0.86 1.21 1.37 CV% 9.50 19.20 15.40 5.80 6.30 20.50 Note: S1= Bich Son - Viet Yen, Bac Giang S2= Cao Xa, Tan Yen, Bac Giang S3= Dong Quang, Dong Son, Thanh Hoa S4= Mai Trung, Hiep Hoa, Bac Giang S5= Nguyen Binh, Tinh Gia, Thanh Hoa S6= Quang Minh, Quang X ương, Thanh Hoa 3.2 Evaluate and select new potato varieties at the FCRI’ farm To compare with the other locations, these sweet potato varieties were also planted in Food Crops Research Institute. The criteria to evaluate the quantity were also measure d and presented in the table 5 below that: - The vine - leaf yield of the varieties was equal or lower than the one of the Hoang Long variety (control). - The root yield is an important value to be evaluated and selected a good variety. VC04 - 24 and VC02 - 193 produced the root yields with 21.7 and 18.9 tonnes/ha much higher than the control (Hoang Long) with only 11.1 tones/ha. CARD 008/07 VIE – Development of sweet potato varieties with high quality 293 Table 5 . Yields of sweet potato varieties studied at FCRI’ farm in 2008 Varieties Vine - leaf yield (tonnes/ha) Root yield (ton nes/ha) R oot weight (g) Number of root per plant (#) Grade ratio (%) >100g 30 - 100g <30g KL5 9.8 17.3 65.7 6.6 45.5 23.3 31.2 KB1 8.6 12.1 47.2 6.4 39.5 25.8 34.6 No 8 9.6 14.0 74.3 4.7 33.9 25.3 40.8 HT2 12.2 13.1 59.5 5.6 40.4 27.8 31.8 TM1 10 .7 18.6 66.5 7.0 31.5 33.7 34.8 VC.01 10.7 15.3 69.4 5.5 39.8 36.5 23.8 VC.68 - 2 6.8 13.5 49.6 6.8 33.9 23.8 42.3 VC97 - 6 - 3 10.5 14.5 55.9 6.5 39.3 25.4 35.3 VC04 - 24 10.1 21.7 60.2 9.0 30.7 37.6 31.8 VC02 - 193 10.8 18.9 53.1 8.9 36.6 27.0 36.4 Hoang Lon g 12.0 11.1 49.6 5.6 17.8 21.9 60.2 CV (%) 6.2 5.9 14.1 11.6 11.7 17.5 13.2 LSD0.05 1.28 1.28 14.2 1.10 5.97 7.0 6.97 Some quality criteria also were determined for the sweet potato root from all the varieties. The table 6 below presented that: - VC0 1 and VC68 - 2 achieved the highest dry matter contents with 27.5 % and 26%, respectively in all the varieties. These two varieties had the highest softness with score 5. These values of the varieties were much higher than Hoang Long (the control varieties). - Although VC04 - 24 and VC02 - 193 had the highest yields, the sweetness scores were only 4. It was concluded that that the VC01 and VC68 - 2 gave highest quality while VC04 - 24 and VC02 - 193 obtained highest quantity. Table 6 . Yields, dry matter content, sens ory value of sweet potato varieties in F CRI in Winter 2008 Varieties RDMC ( %) RDMY (tonnes/ha) SLDMC (%) SLDMY (tonnes/ha) Sweetness 1 - 5* Softness 1 - 5* KL5 20.5 3.5 8.1 0.8 5 1 KB1 21.9 2.6 9.2 0.8 3 1 No8 22.5 3.2 10.0 1.0 3 3 HT2 25.6 3.2 9.7 1.2 3 4 TM1 21.7 3.8 9.6 1.0 3 1 VC.01 27.5 4.1 9.3 1.0 4 5 VC.68 - 2 26.0 3.5 9.3 0.6 2 5 VC97 - 6 - 3 22.6 3.3 9.5 1.0 4 1 VC04 - 24 19.0 4.1 7.2 0.7 4 1 VC02 - 193 23.9 4.5 9.3 1.0 4 1 Hoang Long 21.5 2.3 10.3 1.2 4 2 CV% 1.7 6.6 6.4 7.7 LSD 0.05 0.56 0.3 3 0.85 0.1 * Note: - RDMC= Root dry matter content - SLDMC= Vine - leaf dry matter content - RDMY =Root dry matter yield - SLDMY= Vine - leaf dry matter yield - 1 - 5*: score 1= not soft, not sweet; score 3= soft, relative sweet; score 5 = very soft, very sweet CARD 008/07 VIE – Development of sweet potato varieties with high quality 294 3. 3 Evaluate and select new potato varieties at Quang Tri in Spring season 2009 At Quang Tri, the sweet potato crop was harvested in April 2009. The root, the vine and leaves were taken to determine for the weight, the yield and the other quantity criteria (Table 7). - The vine - leaf yield of all sweet potato varieties was improved very well. Most of the varieties had relatively high vine - leaf yield about 19.7 - 26.9 tones/ha. KL5 achieved with yield of 31.1 tonnes/ha, which was much higher than Hoang Long (control) with 19.9 tonnes/ha. - For the important criterion, the root yield was high with 21.6 from VC04 - 24 and 23.6 tonnes/ha from VC02 - 193. Hoang Long (control) and the local variety had the lowest root yields of 16.6 and 14.9 tonnes/h a, respectively. Table 7 . Yields of sweet potatoes in Quang Tri in the Spring Season 2009 Varieties Vine - leaf yield (tonnes/ha) Root yield (tonnes/ ha) Average root weight (g) Number of root per plant (#) Grade ratio (%) >100g 30 - 100g <30g KL5 3 1.1 19.3 106.9 4.5 28.5 36.2 35.3 KB1 22.5 19.6 98.9 4.9 31.5 35.9 32.7 No8 24.8 16.0 99.2 4.0 32.8 22.7 44.5 HT2 26.7 17.1 108.8 3.9 33.8 34.2 32.1 TM1 26.9 13.2 92.7 3.6 36.7 32.1 31.3 VC.01 28.7 10.6 74.5 3.6 39.7 40.0 20.3 VC68 - 2 19.7 18.9 106.8 4.4 36.5 32.8 30.7 VC.97 - 6 - 3 23.6 19.5 108.4 4.5 30.9 37.1 32.0 VC.04 - 24 23.4 21.6 122.2 4.4 28.6 38.2 33.2 VC.02 - 193 20.4 23.6 133.4 4.4 41.9 37.0 21.1 Hoang long 19.9 16.6 112.7 3.7 40.5 35.3 24.3 Local 23.6 14.9 107.1 3.5 40.4 33.4 26.2 CV(%) 3.0 4.3 8.3 8.6 - - - LSD 0.05 1.2 1.3 14.7 0.6 - - - The quality criteria of dry matter content and yield of root and vine - leaf, the sweetness and softness of root were also determined for all sweet potato varieties planted in Quang Tri at the spring seas on 2009 (Table 8). - In Quang Tri, all the varieties had high dry matter contents from 27.6 - 35.2%. There were 8 varieties with the dry matter content over 30% in which HT2 and VC01 achieved the highest contents with 34.7 and 35.2%, respectively. In additi on, the VC01 also obtained the highest dry matter yield with 4.0 tonnes/ha. - VC01 and VC68 - 2 had the best softness with score 5 which was much higher than the scores of Hoang Long with 2 and the local with 1. - KL5 and Local had the best sweetness with score 5 which was higher than the scores of Hoang Long with 4. The sweet potato varieties planted in the sandy soil along the coast, Quang Tri province also provided very high dry matter of root and vine - leaf. CARD 008/07 VIE – Development of sweet potato varieties with high quality 295 Table 8 . Yields, dry matter content, sensor y value of sweet potato varieties in Quang Tri (Spring season 2009) Varieties RDMC ( %) RDMY (tonnes/ha) SLDMC (%) SLDMY (tonnes/ha) Sweetness 1 - 5* Softness 1 - 5* KL5 27.6 3.9 12.8 5.3 5 1 KB1 29.3 2.7 12.0 5.7 3 1 N 8 31.4 3.4 13.8 5.0 3 3 HT2 34.7 3. 5 13.1 5.9 3 4 TM1 28.7 3.6 13.3 3.8 3 1 VC.01 35.2 4.0 14.0 3.7 4 5 VC68 - 2 30.6 2.7 13.8 5.7 2 5 VC.97 - 6 - 3 31.2 3.1 13.1 6.1 4 1 VC.04 - 24 28.0 3.5 14.7 6.0 4 1 VC.02 - 193 30.9 2.7 13.2 7.2 4 1 Hoang long 33.3 2.8 14.2 5.5 4 2 Local 30.2 3.0 13.0 4. 5 5 1 CV(%) 3.2 4.6 4.0 5.3 - - LSD(0.05) 1.6 0.3 0.9 0.4 - - * Note: - RDMC= Root dry matter content - SLDMC= Vine - leaf dry matter content - RDMY =Root dry matter yield - SLDMY= Vine - leaf dry matter yield - 1 - 5*: score 1= not soft, not sweet; s core 3= soft, relative sweet; score 5 = very soft, very sweet Figure 1 . New potential varieties of sweetpotato VC02 - 193 (left), VC68 - 2 (centre), VC04 - 24 (right ) 4. Conclusions and recommendation s 4.1 Conclusions - In Bac Giang and Thanh Hoa p rovinces, low temperatures and the short sunshine period of the winter season 2008 impacted negatively on the yields of vine - leaf and root of all sweet potato varieties at the locations. The varieties VC68 - 2, VC04 - 24 and VC02 - 193 have achieved the best roo t yields of 13.75, 14.94 and 13.64 tonnes/ha, respectively, which was higher than those of Hoang Long and the local check variety. - At the FCRI’s experiment station the varieties VC04 - 24 and VC02 - 193 have produced the highest root yields with 21.7 and 18.9 tonnes/ha while VC01 and VC68 - 2 provided the best sweetness and softness. - In Quang Tri province, the varieties VC04 - 24 and VC02 - 193 have obtained the highest root yield with 21.6 and 23.6 tonnes/ha, respectively. The highest dry matter contents we re found in HT2 and VC01 with 34.7 and 35.2%, respectively. The VC01 and VC68 - 2 had the best quality criteria about sweetness and softness. NV Tuat, TC Tuyen , N D Thoai, TT Thuy, TQ Anh, NP Anh, DT Lieu, NT Hoai, L . Copeland, P . Sharp & R . Trethowan 296 4.2 Recommendations Variety VC68 - 2 should be further improved for quality trait and VC04 - 24 and VC02 - 193 for high yield in order to introduce new sweet potato varieties for growing in Bac Giang, Thanh Hoa and Quang Tri provinces in the future. References 1. Đinh The Loc, Sweet potato and cultivation technology . Agriculture Publishing House, 1979. 2. Mai Thach Hoanh , Breeding of sweet potato with short duration for winter season by crossing. PhD. Thesis 1986. 3. Nguyen The Yen.1999. Breeding of sweet potato for animal feed. PhD. Thesis. 4. Quach Nghiem. Cassava and Sweet Potato Processing, Marketing and Utilization i n Vietnam. In: Products Development for Root and Tuber crops, Vol. I - Asia, CIP, Lima, Peru, 1992, p. 67 - 77. 5. V.D.Hoa. Utilization of synthetic haploid Ipomoea triad (HBK) G. Don. In: Sweet potato {Ipomoea batatas (L.) Lam} genetic in preferment . Ph.D . Dissertation, Univ. of the Philippines at Losbanos, 1994. 6. Vu Tuyen Hoang and et al. The breeding result of sweet potato with high quality. Results research 1986 - 1990 of FCRI, Agriculture Publishing House, 1990. 7. Vu Van Che, Nguyen Tan Hinh, Truong Cong Tuyen, Nguyen Thi Thuy Hoai and Dang Thi Hue. The breeding result of sweet potato with high dry matter content from material CIP and Japanese. Results research of FCRI 1999 - 2001, Agriculture Publishing House 2002. P.101 - 104. . PROVINCES Project title: Selection and development sweet potato varieties with high root quality for food processing in Northern and Central of Vietnam Code of the project : CARD 008/07 VIE Author(s): Nguyen. project entitled Development and Selection of Commercial and High Quality Cultivars of Root and Tuber Crops for Processing Purpose in the Northern and Central Vietnam between FCRI and Sydney University. 0.05 1.2 1.3 14.7 0.6 - - - The quality criteria of dry matter content and yield of root and vine - leaf, the sweetness and softness of root were also determined for all sweet potato varieties planted in Quang Tri