Cassava cultivar KM140

SELECTION AND DEVELOPMENT OF CASSAVA CULTIVAR KM140

Tran Cong Khanh1, Hoang Kim2, Vo Van Tuan1, Nguyen Huu Hy1, Dao Huy Chien3, Pham Van Bien1, Reinhardt Howeler4 and Hernan Ceballos4

1. Institute of Agricultural Sciences for Southern Vietnam (IAS), 121 Nguyen Binh Khiem St., Ho Chi Minh city, Vietnam (website: http://www.ias.org.vn ; http://www.iasvn.org )
2. Nong Lam University; Linh Trung Ward, Thu Duc District, Ho Chi Minh City, Viet Nam. Website: http://www.hcmuaf.edu.vn ; http://360.yahoo.com/hoangkim_dhnl )
3. Vietnamese Academy of Agricultural Sciences (VAAS) Van Dien, Thanh Tri, Ha Noi, Viet Nam;
4. International Center for Tropical Agriculture (CIAT), Cali, Colombia; h.ceballos@cgiar.org; CIAT), FCRI, Dept. of Agriculture, Chatuchak, Bangkok, 10900 Thailand CIAT-Bangkok@cgiar.org

Source: IAS, Research Highlight 2006, p.17-20

ABSTRACT
In Vietnam, cassava has rapidly changed its role from a food crop to industrials crop, with a high rate of growth during the first years of the 21 st Century. There are now 53 cassava processing factories in operation and another seven factories under construction, with a total processing capacity of 2.2-3.8 million tones of fresh roots/year. Total cassava starch production in Vietnam was about 800,000 -1,200,000 tonnes, of which 70% was exported and 30% used domestically. The main objectives of cassava breeding in Vietnam is improve root yield and starch content and enhance early harvestability to spread the time of harvest. Cassava variety KM140 is a hybrid selected from KM98-1 x KM 36 cross by Hung Loc Agricultural Research Center (HARC) in 1998. KM140 was widely tested, demonstrated and selected by most members of Viet Nam Cassava Research and Extension Network (VNCP) and cassava growers. In 2006, more than 10,000 ha of KM140 were planted in Dong Nai, Tay Ninh, Binh Phuoc, Binh Duong, DakLak, Kon Tum, Binh Dinh, Quang Ngai, Thua Thien- Hue, Quang Binh, Nghe An, Thanh Hoa, Yen Bai and Lao Cai. KM140 is a short growth duration variety (best harvesting time 7-9 months after planting) with fresh root yield 33.4 ton/ ha (higher than KM94), starch content 27% and starch yield about 9.5 ton/ha for 7-9 months after planting, HCN content about 105.9 mg/kg of root dry matter, good root shape with white flesh, high adaptability to various production conditions. KM140 is a supplementary variety for main variety KM94 in order to extend harvesting time.

Key words: cassava breeding; KM140 cassava variety.

INTRODUCTION
Cassava (Manihot esculenta Crantz) is a staple food crop for mor than 500 million peoples around the world. The crop is also served as raw materials for livestock, candy, alcohol, noodle, seasoning industry. Cassava originated in South America and expended wildly to Asia, Africa and being cultivated in 100 countries in a range from 39oN to 30oS. World total area cultivated to cassava in 2005 was 18.69 million hectares with average fresh root yield od 10.87 tons per hectare, total production of 203.34 million tons, export commodities of 6.9 million tons (including tapioca, dry slice and starch) maily from Thailand, Vietnam and Indonesia (FAOSTAT 2006). Cassava is attracting attentions from many institutions, agencies (FAO, CIAT, IITA, Bill Gate Foundations, Rockerfeller Foundations). Cassava cultivation is considered as a major food-safety strategy in many countries in Africa, where malnutrition has grown almost double over the last two decades. Cassava is also a source of raw materials for livestock industry with reasonable prices in many countries of America and Asia.

Cassava in Vietnam has been rapidly changed its role from food crop to industrial one in the beginning of 21st Century. In 2005, area planted to cassava was 390,000 hectares, with total production of 5.7 million tons of fresh root and average yield of 14,61 tons per hectare (FAOSTAT 2006). As compared to the year 1999, the production increased threefold; fresh root yield augmented twofold with increasing rate of 14.7% annually.

Vietnam has become second most important cassava exporters ranging after Thailand. Cassava starch has become as one of the top seven promising exporting commodities and is attracting attentions from many local government authorities. In Vietnam, there are 53 cassava processing factories with capacity about 3.8 million tons of fresh root annually; and there are above 2000 small farmer cassava processors (feed processing factories not included) produce 800,000-1,200,000 tons of starch annually, of which 70% for export and 30% used domestically.

In Asia, Vietnam has made the fastest progress in application of new technologies in breeding and new cultivar propagation (Kazuo Kawano 2001, CIAT Review 2005). Such progress has been considered as a result of many factors, of which the success in breeding and application of new technologies were the main contributing factors (Hoang Kim et al. 2006).

The Ministry of Agriculture and Rural Development (MARD) has planned to remain cassava area around 380,000 to 400,000 hectares from 2006 -2010 and efforts to increase fresh root yield from 14.61 ton/ha in 2005 to 18 ton/ha in 2010 and total production from 5.7 million tons in 2005 to 7.6 million tons in 2010 by using new technologies, especially in breeding.

To meet the demands raising cassava cultivation, we have caried out the study on the development of cassava cultivar with good yield and qualities for different ecological zones in South Vietnam, in collaboration with Root Crop Center- Institute of Agricultural Science and Technology of Vietnam.

The objectives of this study were to breed and develop new cassava cultivars with growth duration from 7-10 months (1-2 months earlier as compared to cultivar KM94) with the same starch yield. New cultivars must have good appearance in root tube, white flesh, less bitterness, straight plant, shot nodes, small plant diameter, resistant to pests and diseases.

MATERIALS AND METHOD
Currently, the cassava breeding program in Vietnam is evaluating about 123,566 hybrid seeds introduced from CIAT/Colombia, and is producing itself more than 48,848 hybrid seeds from 9-15 cross combinations. At Hung Loc Agricultural Research Center there are ten cassava breeding experiments conducted every year, and 18-24 regional trials are conducted in different cassava producing regions in collaboration with various institutions, universities and provincial extension offices. Cassava variety KM140 is a hybrid selected from KM98-1 x KM 36 cross in 1998.

Thirty cassava comparison experiments and two experiments for determining the best harvesting time of some cassava cultivars were carried out. On red soil, 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.

RESULTS AND DISCUSSION
Cassava cultivar comparison (1998-2005)
Data of 30 cassava comparison experiments from 1998 to 2005 (Table 1) revealed that KM140 has fresh root yield of 33.4 ton/ha, starch yield of 9.5 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.

KM140 is now playing an important role in cassava production in South East and Central Coastal regions, Central Highlands and the mountainous areas in the North (Quang Binh, Nghe An, Thanh Hoa, Yen Bai, Lao Cai). KM94 has been recognized by CIAT as one of the best cultivars in Asia (CIAT Review, 2005).

Determination of optimal harvesting time
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. Considering above results and reason, it is recommended that the best harvesting time is 11 months after planting.

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 that of KM94 (26.2%), with signnificant difference.

CONCLUSION
After 7 years (1998-2005) of breeding and selection at HungLoc Agricultural Research Center and testing- demonstrations over provinces, the prominent cultivar KM 140 has appeared to satisfy the objectives of study:
- Best harvesting time must be between 7 to 9 months after planting at beginning rainy season in South Eastern region of Vietnam.
- Fresh root yield of 33.4 ton/ha, starch content of 26.1 -28.5%; Starch yield of 9,45 ton/ ha.
- HCN content in KM140 root flesh is 105.9 mg/kg of dry matter.
- Erective and short inter-node plants, non branching in South Eastern region, low branching in Western Highland Plateau and in the Northern provinces.
- Uniform root shape, white root flesh which are satisfying the market preference and processing requirements.
- Resistance to pests and diseases.