Sufficiency Rice

By Assoc. Prof. Dr. Apichart Vanavichit and team

Global warming means rice growing today faces major floods and widespread outbreaks of diseases and insect pests, especially in the irrigated areas of the central region and the lower north, where rice farming systems and chemical fertilizer use are high. All of this makes rice growing environmentally destructive. Research has shown that high-rate N fertilizer speeds the release of N2O, an important greenhouse gas. High use of fertilizer and pest control substances therefore makes today's rice growing not environmentally friendly.

The approach to breeding environmentally friendly rice began in 2003 (B.E. 2546), funded by the National Science and Technology Development Agency (NSTDA), starting with developing Khao Dawk Mali 105 to tolerate flash floods (Hom Mali 80). Later, genes for resistance to bacterial leaf blight and brown planthopper were stacked together in the Khao Dawk Mali 105 genetic background, followed by breeding Hom Mali rice for drought and saline-soil tolerance. At the same time, glutinous RD6 was also improved to resist blast, giving the glutinous rice Thunya Sirin (Figure 1).

Figure 1: Status of Thai Hom Mali rice breeding

At present, rice breeding stacks many useful genes in the same variety to obtain environmentally friendly rice, with a Gene Pyramiding system developed to be as fast and efficient as possible. This is a long-term strategy to sustain food security and prosperity. New environmentally friendly rice varieties must resist diseases and insect pests at a level high enough that farmers no longer need pest control substances. The new varieties developed can therefore be called sufficiency rice, greatly reducing the production cost per rai for farmers who grow them. Examples of environmentally friendly sufficiency rice bred by the Rice Science Center and the Rice Gene Discovery Unit are ‘Hom Mali+4’ and Pinkaset+4, supported by the Agricultural Research Development Agency (Public Organization).

In developing the rice ‘Hom Mali+4’, the breeding approach stacked more than 10 genes/QTLs, comprising genes for resistance to bacterial leaf blight, neck blast, brown planthopper, flash flood tolerance and cooking quality, in the genetic background of Khao Dawk Mali 105, using the Essentially Derived Varieties (EDV) technique. That is, genes were stacked through backcrossing, transferring genes from donor to recipient (Khao Dawk Mali 105) and tracking selection of the target trait again and again until a new recipient line with the added target trait on the original recipient genetic background was obtained, called a near-isogenic line (NIL). The target genes in each EDV, 4 lines in all, namely Hom Mali 80 (Sub 1A), Hom Mali 821 (xa5+ Xa21), Thunya Sirin (qBL1, qBL11) and Hom Mali 803 (Bph), were then stacked together to give the new rice “Hom Mali+4”, which still gives yield and cooking quality no different from Khao Dawk Mali 105, but shows clearly different yield potential from Khao Dawk Mali 105 when facing disease, insects or flash floods, to which the original Khao Dawk Mali 105 had no resistance at all.

For the high-yielding, low-glycemic-index irrigated rice “Pinkaset+4”, the rice was bred to have all target traits quickly with a short ‘pseudo-backcrossing’ technique, transferring flood tolerance and resistance to blast, bacterial leaf blight and brown planthopper from 4 donor lines into the genetic background of Pinkaset 3, an already high-yielding fragrant rice, using molecular markers for selection. This gave the pure line “Pinkaset+4”, with more than 10 loci for resistance to disease and insects, flood tolerance and cooking quality in one plant, in only 4 years. This new variety yields more than 1 ton per rai and has a lower glycemic index than Indian basmati rice. Pinkaset+4 will be a hope for farmers in irrigated areas who want a rice variety with a distinctive product identity wanted by health-conscious consumers. In addition, growing the new variety will help reduce chemicals used to control diseases and insect pests, because the line is already resistant to brown planthopper, blast and bacterial leaf blight (Figure 2).

Figure 2: Steps in developing Pinkaset+4 as a photoperiod-insensitive fragrant rice with high yield, resistance to blast, bacterial leaf blight and brown planthopper, flood tolerance and a low glycemic index, by successfully stacking resistance genes and cooking quality in the same plant within 4 years

Breeding team

Rice Science Center and Rice Gene Discovery Unit, Kasetsart University, Kamphaeng Saen Campus, Nakhon Pathom

รศ.ดร.อภิชาติวรรณวิจิตร                  ดร.ธีรยุทธ   ตู้จินดา            ดร.มีชัย เซี่ยงหลิว              Dr. Jonaliza L. Siangliw

ดร.วินิตชาญ รื่นใจชน                      ดร.วินธัย กมลสุขยืนยง        ดร.ศิริพัฒน์ เรืองพยัคฆ์        ดร.ศิวเรศ อารีกิจ

นายเอกวัฒน์ ไชยชุมภู                     นายอนุชา พลับพลา            นายเอกพล ภูวนารถนฤบาล  นายเกียรติพงศ์ คัมภีรศาสตร์

นางสาวสุภาพร พรหมพันธุ์                นายวิศรุต สุขะเกตุ