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NEXT GENERATION OF VEGETABLE GRAFTING UTILIZATION UNDER BIOTIC AND ABIOTIC STRESS FOR VEGETABLE PRODUCTION IN THAILAND

 

Surapong Dumrongkittikul, Anyamanee Auvuchanon

Department of Horticulture,

Faculty of Agriculture at Kamphaeng Sane,

Kasetsart University, Thailand

Email: surapong.d@ku.ac.th and anyamanee.a@ku.ac.th

 

ABSTRACT

The climate change phenomenon causes short-term rains or drought in Thailand. The severe drought situation brings contaminated salt water from the sea to both surface and underground waters. The salinity causes problems in vegetable production, especially in the Chao Phraya basin area. In addition, epidemic diseases and nematodes also pose problems in the production area. To solve such problems, one approach is to use a rootstock that can grow well in drought and saline soil which is resistant to diseases and nematodes. The Department of Horticulture, Faculty of Agriculture at Kamphaeng Saen, conducted a research to improve the rootstock utilization for production with such species as pumpkin and eggplant.

Keywords: grafting, plant stress, plant diseases

INTRODUCTION

The total land of Thailand is 126,755,176 acres. Land use can be divided into three parts: (1) forest (2) agriculture and (3) others (non agriculture). The total area of agricultural land is 46.55% of total land in Thailand (Fig. 1).

Fig 1. Land use in Thailand

 

Thailand’s agricultural land use between 2008 and 2012 is classified according to commodities: paddy field (47.06%); field crops such as corn, sugar cane, cassava and etc. (21.00%); orchards (23.12%); vegetable and floriculture (0.91%); and other crops (7.92%).

Although the area of vegetable production in Thailand is smaller than paddy fields and field crops, the productivity and income of vegetable production is about 10 times higher. The average of vegetable land use is 218,389 hectares. These areas are planted to  chili, watermelon, cucumber, eggplant, tomato, and pumpkin. Crop production  is recorded at 32,782; 11,121; 10,268; 7,201; 3,300; and 3,055 hectare, respectively (Table 1) (http://www.agriinfo.doae.go.th/).

 

Table 1. The area of agriculture in Thailand from year 2008-2012 (in hectares).

 

Problems of agriculture land use in Thailand

In 2016, agriculture in Thailand faces severe drought. Normally, the rainy season is from May to October. However, in 2016, Thailand had short rain season that caused drought, especially in the Chao Phraya basin area, which is the main area of vegetable production in Thailand. Because of drought, the seawater diffuses to the underground river and the agricultural water sources which caused  high salinity problems in the area. Fresh water for vegetable production should not be higher than 0.5 - 0.75 g/l. In Fig. 2, the map shows Nonthaburi, where a huge vegetable production area has 3.47 g/l. salinity level (http://www.agriinfo.doae.go.th/).

Fig 2.  Salinity observed in Chao Phraya basin area (March 30 – April 5, 2016)

 

Environmental stresses not only affect the crop yield and quality, but also induce other problems to vegetable production in Thailand, such as diseases and insects. New tolerance/resistance varieties are keys to solve these problems. The high performance varieties are able to be used directedly on growing vegetables. The good performance of rootstocks for grafted vegetables is an important technique to prevent soil-borne diseases and environmental stresses such as drought and salinity. Grafting technique was used to Fusarium oxysporum Schltdl in cucurbit crops and bacterial wilt in tomato (King et al., 2008)

Horticulture department, Faculty of Agriculture at Kamphaeng Saen, Kasetsart University

The breeding group of the Horticulture department, Faculty of Agriculture at Kamphaeng Saen, Kasetsart University has three main responsibilities falling under the category of  fruits, flowers, and vegetable breeding programs. The fruit breeding team improves a new guava variety called KU guard # 1 that is root-knot nematode tolerant and is widely used as rootstock for guava production in Thailand. The vegetable breeding program focuses on the breeding of pumpkin and with funding from Kasetsart University and Ministry of Science and Technology. The program has several proposals:

  1. Pumpkin improvement focusing  on high beta-carotene with high yield and disease resistance;
  2. Genetic diversity of eggplant and pumpkin germplasm evakuation using morphological traits and molecular markers;
  3.  QTL mapping for beta-carotene and virus resistant traits; and
  4. Association mapping and environmental stress tolerance in eggplant

Germplasm evaluation

The germplasm is collected from Thai commercial cultivars, landrace (from northern, northeast, and western parts of Thailand) and commercial cultivars from several countries.  They are evaluated for their agronomic performance and molecular markers. Then, crossing and selection are made to release new cultivars with high yield, beta-carotene (pumpkin), salt / drought and heat stress tolerance (eggplant).

The vegetable breeding program is used as an example for horticultural breeding classes (both lecture and laboratory classes) with the purpose of developing new cultivars for high nutrition and high adaptation to adverse environment. The classes are set through the integration of knowledge and discipline of genetics (molecular, population, quantitative genetics and cytogenetic), statistics, and agriculture.

1. Pumpkin germplasm evaluation

In Thailand, most commercial pumpkin cultivars belong to Cucurbita moschata and some commercial cultivars are C. maxima called Japanese pumpkin. The area of Japanese pumpkin production is in northern Thailand (in the mountains). It cannot be grown in the central region, especially at Kamphaeng Saen due to diseases (Fig. 3).

Fig 3. The problem of Japanese pumpkin production at KU Kamphang Saen campus (a) C. moschata; (b) young plant of C. maxima; and (c) C. maxima at 3 weeks after pollination
 

2. Eggplant germplasm evaluation

Eggplant is classified as non-saline tolerant vegetable that cannot be grown on soils with salinity higher than 1.2 g/l (Arunin. 1996). The breeding program in Thailand has released a new eggplant cultivar including round eggplant, long eggplant with white, green, and purple skin. We evaluated 50 eggplant cultivars for salinity tolerance at low medium and high salinity. We got 24 and 1 salinity tolerant eggplant cultivars under 5 g/l and 11 g/l salinity levels, respectively (Table 2).

 

Table 2. Salinity and salt concentration

 

We continue to evaluate 11 eggplant cultivars from 24 5 g/l salinity tolerant cultivars. Results showed two cultivars can tolerate salinity of up to 7.5 g/l (Fig. 4).

Fig 4.    Eggplant evaluation for salt stress in greenhouse (a) and the eggplant that can be tolerance to salinity at 5 g/l. (b).

 

Vegetable grafting

Even though vegetable grafting is not popular in Thailand, it is useful to obtain and study vegetables that are resistant to both biotic and abiotic stresses. From germplasm evaluation, we have two purposes to use vegetable grafting for biotic and abiotic stress conditions. First, using C. moschata as rootstock for C. maxima to prevent bacterial wilt and to be able to grow at the central region of Thailand by evaluating at least 20 landrace cultivars for their rootstock. Besides, we have the program to develop interspecific hybridization between C. moschata (Thai pumpkin landrace) and C. maxima (commercial cultivars) for higher resistance. Second, Tropical Vegetable Research Center (TVRC), Kasetsart university collected eggplant Solanum melongena several types. We will evaluate eggplant cultivars and other species such as S. benth, S. torvum, and S. stramonifolium that tolerate salt stress at 7.5 g/l and 11 g/l levels and use these cultivars as rootstock to produce eggplant and tomato at Chao Phraya basin. We expect that grafting will become a common technique applied in both solanaceous and cucurbit crops in Thailand.

CONCLUSION

Grafting is a key technique used to solve vegetable production problems in Thailand. The success of grafting is to insert scion onto the rootstock which is resistant to drought and salt, diseases and nematodes. Grafting technique is important and valuable to the Thai farmers.

REFERENCES

Arunin, 1996

Department of Agricultural Extension. 2016. http://www.agriinfo.doae.go.th/. Bangkok, Thailand.

King, S. R., A. R. Davis and A. Levi. 2008. Grafting for Disease Resistance. Hort Science; 43(6).


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