[กรมวิชาการเกษตร]
[สถาบันวิจัยพืชไร่]
[ศูนย์วิจัยพืชไร่ระยอง]
[สถานีทดลองพืชไร่ปราจีนบุรี]
[ภาคตะวันออก]
BREEDING AND VARIETAL IMPROVEMENT IN THAILAND1/
Jarungsit Limsila2/ ,Atchara Limsila2/, Watana Watananonta2/ and Kazuo Kawano3/
ABSTRACT
In Thailand cassava breeding is the responsibility of the Rayong Field Crops Research Center of the Department of Agriculture (DOA), and Kasetsart University (KU). From 1975 to 1992, six cultivars have been released for industies use, i.e. Rayong1, Rayong 3, Rayong 60, Rayong 90, Sri Racha 1 and Kasetsart 50. All these recommended cultivars are widely adopted by farmers, but the area planted with improved cultivars was increasing only slowly due to the low multiplication rate of cassava. Therefore, in 1992 the Government approved the allocation of 11 million US dollars for the DOA and the Deparment of Agricultural Extention (DOAE) to rapily multiply stakes of those cultivars and distribute those to the farmers, in order to replace about 240,000 ha of Rayong 1 with new high- yield cultivars by the year 1996. According to the most resent survey by DOAE, this target has been well accomlishrd before the end of the project period.
During the past three years, the cassava breeding program in Thailand continued to emphasize selection for high yield and high dry matter content, as well as some other desirable traits, especially high total plant weight and harvest index, and good plant type, germination and survival under stressful conditions. One of our successes has been the release of another industrial cultivar, Rayong 5, in October 1994. Rayong 5 is superior to Rayong 1 in many aspects. It has been adopted and is spreading rapily in many part of the country.
For Thai cassava breeders it seems to be increasingly more difficult to produce new clones that can surpass the excellent cultivars KU 50 and Rayong 5; however, some of our new clones, such as CMR33-57-81 and CMR33-53-181 appear quite promissing, and CMR33-57-81 may be released as Rayong 72 in the next 2-3 years.
INPRODUCTION
Cassava in Thailand is produced mostly for the export in the form of hard pellets, chips and starch, and the major markets are in the EU countries. During the past ten years (1985-1994) there has generally existed a stituation of overproduction, since the demand for cassava roots was less than 20 million tons, while the supply was usually over 20 million tons. The Government was well ware of this problem and became even more concerned when the EUs CAP Reform was gradually implemented between 1993 and 1995. In 1992, the Thai Government established the policy to .
.
1/ Paper in Cassava Breeding, Agronomy and Farmer Participatory Research in Asia Proceedings of the Fifth Regional Workshop held in Danzhou, Hainan, China, Nov 3-8 1996. P 48-54.
2/ Rayong Field Crops Research Center, Huay Pong, Rayong, Thailand.
3/ CIAT, Dept. Agriculture, Chatuchak, Bangkok, Thailand.
reduce the cassava planting area from 1.5 million ha to 1.28 million ha by encouraging farmers to replace cassava with fruit trees, fast growing trees, pastures and livestock.
In 1995 the area under cassava was reduced to 1.3 million ha and the production was only 18 million tons. However, contrary to expectations, the cassava root price went up to 1.20 baht per kilogram, which had never happened before. It look as if the Government had been successful in reducing the cassava planting area, but in fact the drastic decline in cassavaarea was a direct result of the low cassava root price during the previous two years, 1993 and 1994. In response to the attractive price of cassava in 1995, it can be predicted that the cassava planting area will rapidly increase again after this year.
While the Government tried to decrease the cassava planting area during the past few years, at the same time it encouraged farmers to change from the local cultivar, Rayong 1, to the newly released cultivars, in order to improve the efficiency of production. The Department of Agriculture(DOA) and the Department of Agricultural Extention (DOAE) of the Ministry of Agriculture and Cooperatives initiated a five year project, starting in 1992, to rapidly multiply stakes of the improved cultivars and to distribute these to the farmers. The projects target is that Thailand will have an area under new improved cultivars of about 240,000 ha by the year 1996. According to the DOAE statitics, this target has already been accomplished during the 1995/96 planting season. The national average yield is expected to increase from 13.75 t/ha to 14.68 t/ha at the end of project.
CASSAVA VARIETAL IMPROVEMENT
Background
Since 1975 and until 1992, the Rayong Field Crops Research Center of the Field Crops Research Institute of DOA, and Kasetsart University (KU) have released six cultivars for industrial use and one cultivar for direct human consumption. The background and the outstanding characteristics of those cultivars are described in table 1.
Breeding Objective
The main objectives of cassava breeding in Thailand is to improve root yield and dry matter content (or starch content) in order to satisfy the needs of the farmers and the factories. It was suggested by Kawano (1988) and Rojanaritpiched et al. (1995) that cassava yields should be improved through the simultanious improvement of total biomass and harvest index. Aside from the above important characteristics, the following characteristics are also our breeding and selection criteria:
- early harvestability
- good plant type (tall and non- or less- branching)
- good stake quality (germination and storage duration)
- good root shape with white flesh
- tolerant to major pests and diseases
Table 1. Background and outstanding charcteristics of seven released cultivars.
Year Background and outstanding
Cultivar Released Parents characteristics
Rayong 1 1975 unknown Selected from local land race.
Exellent agronomic traits. Relatively
High yield. Moderately resistant to
Major pests and diseaes. Well
Adapted to low inputs.
Rayong 3 1983 (F) MMex 55 Selected from CIAT F1 hybrid seeds.
(M) Mven 307 High dry matter content
Rayong 60 1987 (F) Mcol 1684 Selected from CIAT F1 hybrid seeds.
(M) Rayong 1 High fresh yield . Recommended for
early harvesting. Exellent agronomic
traits.
Srirscha 1 1991 (F) Mcol113XMCol22 Selected from KU F1 hybrid seeds.
(M) Rayong 1 Exellent agronomic traits. High dry
matter content.
Rayong 90 1991 (F) CMC76 Selected from DOA F1 hybrid seeds.
(M) V43 High dry matter content. Relatively
high yield.
Kasetsart 50 1992 (F) Rayong 1 Selected from KU F1 hybrid seeds.
(M) Rayong 90 High yield and high dry matter conent.
Well adapted to unfavorable conditions
Rayong 2 1984 (F) Mcol 113 Selected from CIAT F1 hybrid seeds.
(M) Mcol 22 Recommended for human
consumption. Relatively high yield ,and
carotene and vitamin A contents. Low
HCN content.
Recent Progress
During the past three years, the DOA has released one industrial cultivar called Rayong 5, and has tested two promising clones, i.e. CMR33-57-81 and CMR33-53-181, in farmers fields.
Rayong 5 previously identified as CMR25-105-112, was obtained from across between 27-77-10 and Rayong 3, made in 1982 at the Rayong field crops research center. It was released by DOA on October 28, 1994. It is one of attempts to improve cassava cultivars through an improvement of the top parts along with the roots. Table 2, in which data from hundreds of trials are compiled, indicates that Rayong 5 is higher to total plant weight and harvest index, and has higher root yields than Rayong 1, Rayong 3, Rayong 60 and Rayong 90.
Rayong 5 is now widely adopted by cassava growers due to it high yield and other outstanding properties, such as ease harvest due to its good root dhape and root formation, good germination and drought tolerance. Table 3 shows the yields of Rayong 5 when planted in the early rainy season and in the late rainy season, compared with those of Rayong 1. Its fresh root yield, dry root yield and dry matter content were higher than those of Rayong 1 by 20, 31 and 9% in the early rainy season plantings, respectively. For the late rainy season plantings, Its fresh root yields was higher than Rayong 1 by 28%, parly due to the better survival of plants of Rayong 5 during the dry season.
Promising clones
It seems to be increasingly more difficult for Thai cassava breeders to create new cassava clones that are superior to the already exiting excellent cultivars Kasetsart 50 and Rayong 5. However, two promising cassava clones, CMR33-57-81 and CMR33-53-181, were selected by the Rayong Field Crops Research Center staff from crosses made in 1990.
Table 2. Yield parameters of Rayong 5 compared with all previously released cultivars. Data from Regional Yield Trials and On Farm Trials conducted from 1988 to 1993.
R5 R1 R3 R60 R90 KU50
Top yield (53 trials)
Total plant weight (t/ha) 39.8 38.6 30.1 37.4 37.3 39.4
Leaf and stem weight (t/ha) 14.3 16.2 11.1 13.8 13.7 14.6
Harvest Index 0.64 0.58 0.63 0.63 0.63 0.63
Root yield (120 trials)
Fresh root yield (t/ha) 27.6 22.7 19.9 26.5 24.7 25.3
-Relative to R1 (%) 121 - 88 117 109 111
Dry matter content (%) 34.8 32.3 35.3 32.5 36.0 35.5
Dry root yield (t/ha) 9.7 7.4 7.1 8.7 8.9 9.1
-Relative to R 1 (%) 131 - 96 117 120 123
Table 3. A verage yield of Rayong 5 and Rayong 1 when planted in the early rainy season and in
the late rainy season from 1988 until 1993.
Rayong 5 Rayong 1 % Relative to R 1
Early rainy season planting (78 experiments)
Fresh root yield (t/ha) 26.9 22.5 119
Dry matter content (%) 34.8 31.8
Dry root yield (t/ha) 9.4 7.2 130
Late rainy season planting (42 experiments)
Fresh root yield (t/ha) 29.0 22.6 128
Dry matter content (%) 35.0 33.2
Dry root yield (t/ha) 10.3 7.7 134
CMR33-57-81 was obtained from a cross between Rayong 1 and Rayong 5 ,while CMR33-53-181 was obtained from crossing OMR26-14-9 with Rayong 1. The progenies were evaluated in eight Regional Trials and in 15 On-farm Trails during the 1994/95 and 1995/96 seasons. The trials were conducted in two major cassava planting areas of the country, the Northeastern Region (Nakon Ratchasima, Khon Khen, Maha Sarakarm, Kalasin, Roi Et, Mukdahan and Sakhon Nakon provinces), and the Central Region (Ryong, Chonburi, Chantaburi,Prachinburi and Suphanburi provinces).
The data from 11 trials in the Central Region and 12 trials in the Northeastern Region during the 1994/95 and 1995/96 seasons are presented in Table 4. Considering the fresh root yield, dry matter content, dry root yield, total biomass and harvest index of the two promising clones and the check varieties, i.e. Rayong 1, Rayong 90 and Rayong 5, from each region and the average of the two regions, the following conclusions could be dawn:
-CMR33-57-81 and CMR33-53-181 produced higher fresh root yields, dry root yields and total biomass than Rayong 1, Rayong 90 and Rayong 5 in both regions, while maintaining a high harvest index at the same level as that of Rayong 5.
-CMR33-57-81 performed excellently in the Northeastern Region, while CMR33-53-181 performed very well in the Central Region.
-The root dry matter contents of the two promising clones are higher than that of Rayong 1, but not as high as those Rayong 90 and Rayong 5.
CMR33-57-81 and CMR33-53-181 are now in the On-farm Trials and are expected to be released specifically for each region in the next 2-3 years.
Activities through CIAT
Since 1985 the DOA has provided cross-pollinated (CMR) and open-pollinated (OMR) F1 seeds to CIAT for distribution to other cassava producing countries in Asia. From 1985 to 1993 74,568 F1 seeds were provided to CIAT and another 27,570 seeds were provided during the past three years (Table 5). Kawano (1993) indicated that the Thai breeding materials were well-adapted to the semi-arid and seasonally dry lowland tropics; therefore, they are offering excellent selection in most national cassava breeding programs in Asia.
Table 4. Fresh root yield, dry matter content, dry root yield, total biomass and harvest index of
CMR33-53-181 and CMR33-57-81 compared with check varieties in Regional and On-farm
Trials during 1994/95-1995/96.
Central Region Northeastern Region Average
(11 trials) (12 trials) (23 trials)
Fresh root yield (t/ha)
CMR33-53-181 32.9 32.0 32.4
CMR33-57-81 28.9 36.0 32.6
Rayong 1 24.3 25.4 24.9
Rayong 5 27.4 28.5 28.0
Rayong 90 28.1 24.9 25.2
Dry matter content (%)
CMR33-53-181 31.9 34.4 33.2
CMR33-57-81 31.3 34.8 33.2
Rayong 1 30.0 32.9 31.5
Rayong 5 33.3 35.4 34.4
Rayong 90 34.2 34.6 34.3
Dry root yield (t/ha)
CMR33-53-181 10.3 11.1 10.7
CMR33-57-81 9.0 12.6 10.9
Rayong 1 7.1 8.6 7.9
Rayong 5 9.0 10.2 9.6
Rayong 90 8.5 8.8 8.6
Total biomass (t/ha)
CMR33-53-181 44.6 52.7 49.0
CMR33-57-81 37.8 55.1 47.2
Rayong 1 39.0 46.7 43.2
Rayong 5 37.4 49.3 43.9
Rayong 90 37.8 44.0 41.1
Harvest index
CMR33-53-181 0.69 0.63 0.66
CMR33-57-81 0.72 0.67 0.69
Rayong 1 0.60 0.56 0.58
Rayong 5 0.69 0.61 0.65
Rayong 90 0.67 0.59 0.63
In May 1995, Thailand had an opportunity to be the host of a Workshop on Cassava Breeding Methods and Practices, organized by CIAT for Asian cassava researchers. The workshop provided the paticipants with ample opportunities for learning from the Thai varietal improvement and dissemination programs and for sharing experiences among each other.
Table 5. Number of cassava F1 hybrid seeds exchanged between CIAT and the DOA.
Year Number of seeds
Hybrid seeds introduced from CIAT 1975-1993 137,448
- 9,843
- 11,964
1996 9,781
Total 169,036
Hybrid seeds provided to CIAT 1975-1993 74,568
- 7,678
- 8,669
1995 11,223
Total 102,138
REFERENCES
Kawano, K. 1998. CIAT cassava germplasm development in Asia Cooperation with National
Programs. In: R.H. Howeler (Ed.) Cassava Breeding and Agronomy Research in Asia. Proc.
2nd Regional Workshop, held in Rayong, Thailand. Oct. 26-28, 1987. Pp.117-126.
Rodjanaridpiched, C., A. Limsila, D. Supraharn, O. Boonseng. P. Poolsanguan, C. Thiraporn and K.
Kawano. 1995. Recent progress in cassava varietal improvement in Thailand. In: R.H.
Howeler (Ed.) Cassava Breeding, Agronomy Research and Technology Transfer in Asia.
Proc. 4th Regional Workshop, held in Trivandrum, Kerala, India. Nov. 2-6, 1993.