Current situation of cassava in Vietnam and the breeding of improved cultivars

Vietnam is now probably the second largest exporter of cassava products after Thailand with 2.00 -4.00 million tones of cassava dry chip (Table 6a). and about 0.4 -0.8 million tones of tapioca starch exported, respectively. Mainland China remained the biggest importer of Vietnamese cassava and accounted for 90 per cent of the industry’s export income. South Korea and Taiwan were the second and third biggest importers. Demand has soared, largely due to demand from China, which uses the root to produce ethanol. The total export in year 2009 around 4 million tonnes of cassava chip exports and more than 350 thousand tones of cassava starch and flour. Prices of cassava chip exports fell to a low of $135 a tonne at the beginning of year 2008, but have since risen to between $180 and $195 a tonne in last December 2009

A case study of cassava market in the Central provinces of Vietnam . On average. labour cost accounts for 59.9% of cassava production costs. In some regions. like the Binh Dinh and the Gia Lai. this may be for 52.8% and 68.7%. respectively (Table 7)

Table 7: Production costs and returns per ha in the central provinces of Vietnam

The average labour requirement for cassava production is 125 mandays/ha. The second largest cost item is fertilizer. constituting 41.8% in Binh Dinh and 24.7% in Gia Lai. depending on farmers’ investment in fertilizer. With the selling price of fresh root of 900 VND/kg; farmers can earn 10.720 to 11.200 thousand VND/hectare. The total variable cost of cultivation in Feb. 2008 was about US$ 455- 567.5/ha. at an average root yield of 22.0 t/ha. the production cost would be US$ 20.68- 25.79 /t fresh roots. Gross income is US$ 1.155- 1.237.5 /ha. Net income is US$ 670 - 700/ha. Reporting of farmers in : 32% of fresh root has been processed by farmers for exportation; 27% total fresh root for cassava starch processing, 22% of fresh root farmers sell to processing households, 19% farmers use for animal feeding or domestic consumption.

The objectives of further genetic improvement of cassava varieties in Vietnam are: 1) to increase the yield potential, dry matter content and starch content, and enhance early harvestability; 2) Identification of cassava high-yield varieties suited to different agro-ecological zones and the integration of these into smallholder farming systems. 3) identifying the best cassava varieties for bioethanol production, In addition, the work above on breeding and pre-breeding lines will help define the breeding strategies for increased crop productivity and bioethanol production.

The trials (Table 9) include two trials for the Conservation of Elite Germplasm (CEG) and F1 Seeding Trials (F1). two Single Row Trials (SRT). two Preliminary Yield Trials (PYT). and two Standard Yield Trials (SYT).

The screening of quality characteristics likely to be related to improved fermentability continues with three pre-breeding accessions that have interesting traits for crossing and development into high-yielding varieties . The new advanced cassava varieties KM297, KM228, KM318, KM325, KM397, KM21-12, SC5, HB60 are being undertaken in the Regional Yield Trials (RYT) of Tay Ninh, Ninh Thuan. and Yen Bai provinces (Table 10 Table 11, Table 12, Table 13 and Table 14)

The aims of the cassava breeding are: to select and release new varieties with high-yield capacity of 35-40 t/ha, a starch content of 27-30%, a growing period of 8-10 months, erect stems, short internodes, less branching, compact canopy, uniform root size, white root flesh and suitable for industrial processing. As a result, two new cassava varieties KM140 and KM98-5 have been identified and released in South Vietnam in year 2007 and 2009; one new cassava variety KM98-7 also have been identified and released in North Vietnam in year 2008 with the yield higher than local check KM94. These varieties are being transferred to a large number of households in Vietnam.

Cassava variety KM140 is a hybrid selected from KM98-1 x KM 36 cross in 1998 (Figure 3). Thirty cassava comparison experiments and two experiments for determining the best harvesting time of some cassava cultivars were carried out. On red soil in South East region. experiments were planted at beginning of rainy season and harvested after planting from 6,7,8,9,10,11 and 12 months. On grey soil. planted at beginning rainy season and harvested after 10,11 and 12 months.


Figure 3. Cassava variety KM140 is a hybrid selected from KM98-1 x KM 36 cross
The data revealed that KM140 has fresh root yield of 33.4 – 35.0 ton/ha. starch content of 26.1 -28.5%. starch yield of 9.5 – 10.0 ton/ha; better than that of KM94. Content of HCN in KM140 is 105.9 mg/kg dry matter. it can be used as fresh consumption. lower than that of KM94; its harvest index was 65%. good resistance to pests and diseases (Figure 4) .



Figure 4. In South East region. lanting at beginning rainy season and harvesting at 7.8 and 9 months after. KM140 gave fresh root yields of 23.5, 26.7 and 28.7 ton/ha. Respectively, equal to that of KM94.

In South East region. planting at middle of rainy season and harvesting 10 months later revealed that all cassava cultivars gave low starch content (16.6%-22.5%). If harvested 11 months after planting. almost cultivars had starch content around 25% satisfying the requirement of processors. If harvested 12 months after planting most of the cultivars gave good fresh root yield and starch content. but this would cause inconveniences for next crop cultivation. Planting at beginning rainy season and harvesting at 7.8 and 9 months after. KM140 gave fresh root yields of 23.5. 26.7 and 28.7 ton/ha. respectively. equal to that of KM94. Starch content of KM140 harvested 8 months after planting was 28.4% higher than of KM94 (26.2%). with signnificant difference (Figure 5).

KM140, KM98-5, KM98-7, SM937-26. KM98-1 are now playing an important role in cassava production in South East and Central Coastal regions. Central Highlands in the South (Tran Cong Khanh, Hoang Kim, Vo Van Tuan, Nguyen Huu Hy, Dao Huy Chien, Pham Van Bien, Reinhardt Howeler and Hernan Ceballos 2009, 2007, Tran Cong Khanh 2007; Vu Van Quy 2009, Le Van Luan 2008, Nguyen Thi Cach 2007).

Two new cassava varieties KM98-7 and KM21-12 are being transferred to a large number of households in the Northern mountainous areas (Nguyen Trong Hien, Ha Dinh Tuan, Nguyen Thi Ngoc Binh 2009; Trinh Phuong Loan, Nguyen Trong Hien, Dao Huy Chien, Tran Ngoc Ngoan, Nguyen Viet Hung et al. 2008).

3.2 Improvement of crop productivity
The productivity of cassava can be increased by selection of the most appropriate varieties as well as by using the most appropriate cultural methods of production. including appropriate fertilizer applications. soil erosion control. and intercropping. Trials have been established at the pilot sites in Dong Nai. Yen Bai. and Thua Thien Hue provinces to determine (i) the agronomic potential of intercropping systems that include cassava with sweet sorghum. or maize. or groundnut; (ii) the best management practices for these cropping systems, with particular reference to integrated soil fertility management and soil erosion control; and (iii) the best. high yielding varieties of sweet sorghum. maize. and groundnut to intercrop with cassava.
The varieties selected for evaluation with cassava were: Six sweet sorghum lines from ICRISAT (ICSB38. PVK801. ICSR93034. ICSV574. NTJ2. and IS41333). one groundnut cultivar from ICRISAT (ICGV91114). and six new maize varieties from NLU and HARC in Viet Nam. In addition. two pigeon pea cultivars (ICP7035 and ICPL 20092) were obtained from ICRISAT for evaluation.
Two on-farm trials using cassava variety KM140 intercropped with maize variety VN25- 99 are being undertaken at the pilot site in Tay Hoa village. Trang Bom district. Dong Nai province to determine best management practices for cassava-maize cropping systems (Table 15 and Figure 6).


Table 15. Data on two on-farm trials using cassava variety KM140 intercropped with maize variety VN25- 99 in Tay Hoa village. Trang Bom district, Dong Nai province

Cropping systems 1	Cassava				Maize seed yield (t/ha)	Net Profit (1000000d)
	Root yield (t/ha)	Top yield (t/ha)	DM content (%)	DM yield (t/ha)
Grey soil
Cassava monoculture	34.5	27.8	39.7	13.69	0	15.38
Cassava + Maize (1)	25.0	24.7	38.5	9.63	3.50	20.76
Cassava + Maize (2)	32.7	25.4	38.9	12.72	1.44	18.64
Cassava + Maize (3)	33.9	28.4	41.3	14.00	2.68	25.40
Red soil
Cassava monoculture	38.6	32.5	38.7	14.93	0	17.86
Cassava + Maize (1)	28.9	28.3	37.0	10.69	4.40	27.38
Cassava + Maize (2)	37.5	30.6	37.6	14.10	2.20	25.20
Cassava + Maize (3)	36.9	31.8	38.2	14.10	3.56	30.00

1) One rows of cassava intercropped with one rows of maize. cassava 1.00m x0.75m. maize 1.00m x0.2m
2) Two rows of cassava intercropped with one rows of maize. cassava 1.00m x0.75m. maize 2.00m x0.2m
3) Two rows of cassava intercropped with two rows of maize. cassava (0.75m x 2 rows) x 0.75m. maize

(0.75m x 2 rows) x 0.2m ; cassava chips: 2700 d/kg; maize dry seeds: 5000d/kg. 1USD = 18.000d

Similar on-farm trials using cassava variety KM94 intercropped with groundnut varieties L14. HL25 are being undertaken to determine best management practices for cassava- peanut cropping systems (Table 16). Three of the cassava-peanut on-farm trails are being implemented at the pilot site in Phong My village, Phong Dien district, Thua Thien Hue province, and another in Tay Hoa village. Trang Bom district. Dong Nai province, and Mau Dong village, Van Yen district, Yen Bai province.

1. 
   Cropping partern: Cassava (spacing 1.00 x 0.80 m) one rows of cassava intercropped with one rows of groundnut. spacing 0.50 m between rows x 0.20 m between plant x 2 seeds)
   
2. 
   Cropping partern: Cassava (spacing 1.00 x 0.80 m) one rows of cassava intercropped with two rows of groundnut. spacing 0.30 m between rows x 0.20 m between plant x 2 seeds)
   
3. 
   Cassava fresh root: 1000d/kg; Groundnuts with shell : 18.000d/kg. 1USD = 18.000VND
   

Vietnam is a classic example of how cassava can contribute to rural industrialization and development. Previously. people were reluctant to grow cassava because they thought that cassava caused soil degradation and produced low profits. But in reality one hectare of cassava can produce 60-80 tones of fresh roots and leaves. The situation has changed because of the development of sustainable cultivation techniques and new high-yielding varieties with the availability of a large and growing market demand. Cassava has become a cash crop in Vietnam. Cassava chips and starch is now being produced competitively, and cassava markets are promising. The combination of wide spread production of fresh cassava roots and the processing of cassava into chips starch and ethanol has created many jobs, has increased exports. attracted foreign investment. and contributed to industrialization and modernization of several rural areas.

After twenty years of development (1991-2010). intensive cassava research and extension have changed cassava from being a food crop to being an industrial crop. Cassava in Vietnam is now promising for export and domestic use. VNCP was agreed to emphasize the following five topics:

1. 
   Determination of an appropriate strategy for cassava research and development cooperation with processing factories in establishing areas with a stable source of raw materials; use of cassava for bio- ethanol.
   
2. 
   Selection of cassava doubled haploid lines derived from materials of CIAT and applying mutation in cassava breeding; Selection and dissemination of high-yielding varieties with high starch contents; Selection and development varieties with high root yield, short duration and improvement of quality and nutritional value of cassava.
   
3. 
   Research on integrated cultivation techniques and transfer of appropriate cultivation techniques to farmers to increase the productivity and economic efficiency of cassava production in different eco-regions.
   
4. 
   Research on the development of cassava processing technologies; Use of cassava leaves and roots in animal feeds and food processing. Cassava starch, ethanol effluent and byproducts transformation into animal feed and fertilizers.
   
5. 
   Development of local and export markets for cassava products.