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Development of international standard differential set for blast resistance in rice (Oryza sativa L.)

Yoshimichi Fukuta1, Mary J. T. Yanoria1, Hiroshi Tsunematsu2, Tokio Imbe3, Hiroshi Kato4, Leodegario A. Ebron1 and Gurdev S. Khush1

1 International Rice Research Institute, DAPO Box 7777, Metro Manila, Philippines ,http://cpssrv2/irrihome/
Email y.fukuta@cgiar.org, gurdev@khush.org, lebron@cgiar.org, jyanoria@cgiar.org
2
Japan International Research Center for Agricultural Sciences, 1-1 Ohwashi, Tsukuba, Ibaraki, 305 Japan,
http://ss.jircas.affrc.go.jp
/Email htsunema@jircas.affrc.go.jp
3
National Institute of Crop Science4, 2-1-18 Kannondai, Tsukuba, Ibaraki, 305-8518 Japan, http://nics.naro.affrc.go.jp/
Email timbe@affrc.go.jp
4
Miyazaki Agricultural Experiment Station, Minemae 5851, Shimonaka, Sadowara, Miyazaki Prefecture, 880-0212 Japan
Email hkato@pref.miyazaki.jp

Abstract

The first international standard differential variety (ISDV) set composed of monogenic lines for targeting 24 blast (Pyricularia grisea) resistance genes-Pia, Pib, Pii, Pik-s, Pik, Pik-h, Pik-m, Pik-p, Pish, Pit, Pita (Pi4), Pita-2, Piz, Piz-5 (Pi2), Piz-t, Pi1, Pi-3, Pi5, Pi7 (t), Pi9, Pi11(t), Pi12 (t), Pi19, and Pi20, have been developed in rice (Oryza sativa L.) (Tsunematsu et al. 2000), and already distributed more than 15 countries through the IRRI-Japan Collaborative Research Project. Additionally, new ISDVs, near isogenic lines (NILs) for targeting 14 blast resistance genes -Pib, Pik-s, Pik, Pik-h, Pik-m, Pik-p, Pish, Pita (Pi4), Pita-2, Piz-5 (Pi2), Piz-t, Pi1, Pi5, Pi7 (t)-- with an Indica-type rice CO 39 genetic background will be also distributed in 2004. CO 39 NILs are the first sets of ISDVs for Indica-type rice. Two kinds of other differential variety sets, NILs with Chinese Japonica type susceptible variety Lijiangxintuanheigu and US-2 genetic backgrounds are also being developed in IRRI. These ISDVs will be able to be used world wide for pathological analysis of blast races and as sources of resistance genes in breeding programs.

Media summary

The first international standard differential variety (ISDV) sets for rice blast have been developed for targeting 24 resistance genes and for distribution by IRRI-Japan Collaborative Research Project.

Key words

Rice (Oryza sativa L.), differential variety, near-isogenic lines (NILs), blast (Pyricularia grisea ), resistance gene.

Introduction

Differential sets of rice (Oryza sativa L.) are an efficient tool to describe the pathogenicity of blast (Pyricularia grisea Sacc.) isolates and as sources of resistance for breeding programs. Yamada et al (1976) and Kiyosawa (1984) selected 12 differential varieties for resistance genes Pik-s, Pia, Pii, Pik, Pik-m, Piz, Pita, Pita-2, Piz-t, Pik-p, Pib, and Pit. These differential varieties were used in Japan especially, but these were not readily available in other countries. The genetic backgrounds of each variety are not uniform, and include more than one resistance gene. The additional gene(s) sometimes masked the reaction of the target gene, and the evaluation for pathogenicity of the blast isolate towards that resistance gene became difficult. In particular, some varieties including a resistance gene Pish indicated the conflicting reactions to isolates under tropical environments. Moreover, the number of resistance genes is not enough to evaluate the blast isolates all over the world, despite the more than 40 genes already reported. To solve these problems, it is necessary to develop new single resistance gene differential varieties representing as many different resistance genes as possible.

Materials and Methods

Three kinds of near isogenic lines (NILs) monogenic for 24 blast resistance genes were developed through a recurrent cycles of backcrossing.

Monogenic lines were developed by several backcrosses of resistance gene donors to a Chinese Japonica-type variety Lijiangxintuanheigu (LTH) as recurrent parent.

The other three NILs have with recurrent parents, LTH, Indica-type CO 39, and a high yield type rice US-2, and involved at least 6 backcrosses. In each backcrossed and selfed generation, the resistant plants were selected using avirulent blast isolates from the Philippines.

Inoculation and selection for resistance genes were continued from BCnF4 until BCnF11 to purify the lines and fix morphological traits.

Results

The monogenic NILs in CO 39 background are shown in Table .1. Monogenic lines and NILs were designated as IRBL, followed by the resistance gene and the abbreviation of the donor variety using its first one or two letters. Additionally, the designation for NILs were followed by the initial the recurrent parent.

Table 1. New international standard differential variety series used to evaluate rice blast virulence by IRRI-Japan Collaborative Research Project

Target gene

Designation name

Monogenic Lines

CO39 near isogenic lines(including Pia

Pia

IRBLa-A, IRBLa-C

-

Pib

IRBLb-B

IRBLb-IT13/CO, IRBLb-W/CO

Pii

IRBLi-F5

-

Pik

IRBLk-Ka

IRBLk-Ka/CO, IRBLk-Ku/CO

Pik-h

IRBLkh-K3

IRBLkh-K3/CO

Pik-m

IRBLkm-Ts

IRBLkm-Ts/CO

Pik-p

IRBLkp-K60

IRBLkp-K60/CO

Pik-s

IRBLks-F5, IRBLks-S

IRBLks-CO/CO

Pish

IRBLsh-S, IRBLsh-B

IRBLsh-S/CO,IRBLsh-B/CO, IRBLsh-Ku/CO

Pit

IRBLt-K59

-

Pita (Pi4)

IRBLta-K, IRBLta-CT2, IRBLta-CP1

IRBLta-Ya/CO

Pita-2

IRBLta2-Pi, IRBLta2-Re

IRBLta2-Pi/CO,IRBLta2-Re/CO, IRBLta2-IR64/CO

Piz

IRBLz-Fu

-

Piz5 (Pi2)

IRBLz5-CA

IRBLz5-CA/CO

Piz-t

IRBLzt-T

IRBLzt-IR56/CO

Pi1

IRBL1-CL

IRBL1-CL/CO

Pi3

IRBL3-CP4

-

Pi5 (t)

IRBL5-M

IRBL5-M/CO

Pi7 (t)

IRBL7-M

IRBL7-M/CO

Pi9

IRBL9-W

-

Pi11 (t)

IRBL11-Zh

-

Pi12 (t)

IRBL12-M

-

Pi19

IRBL19-A

-

Pi20

IRBL20-IR24

-

Monogenic lines

Monogenic lines including only a single gene in each genetic background and targeting for 24 different resistance genes --Pia, Pib, Pii, Pik-s, Pik, Pik-h, Pik-m, Pik-p , Pish, Pit, Pita (Pi4), Pita-2, Piz, Piz-5, Piz-t, Pi1, Pi-3, Pi5, Pi7 (t), Pi9, Pi11(t), Pi12 (t), Pi19, and Pi20, were developed by Tsunematsu et al. (2000) as the first international standard differential variety set.

These monogenic lines have been already distributed to more than 15 countries in the world and were used in the pathogenicity analysis and rice breeding as the sources of resistance genes.

Because these lines were bred using only a few backcrosses to a Chinese Japonica-type rice LTH as recurrent parent, their genetic backgrounds were not uniform. The resistances were fixed, but the morphological characters were varied across lines.

CO 39 NILs

A total of 31 NILs targeting 14 different resistance genes —Pib, Pik-s, Pik, Pik-h, Pik-m, Pik-p, Pi1, Pi7 (t), Pish, Pita, Pita-2, Piz-5, Piz-t and Pi5 (t) — were developed and characterized.

Each NIL posseses the target major gene for resistance aside from Pia as confirmed by the reaction patterns of monogenic lines to 20 standard Philippine isolates and its reactions were stable. And each NIL was morphologically similar to recurrent parent CO 39.

Thirty-one NILs with Indica genetic background were developed. Among them, 21 NILs for the 15 resistance genes will be available as a new set of ISDV with Indica-type genetic background in 2004 through IRRI.

LTH and US-2 NILs

The two kinds of NILs with different genetic backgrounds LTH and US-2 have been developed with as 17 and 16 resistance genes, respectively. For LTH NILs, it is necessary to generate and select the fixed lines in each line, because segregation for some morphological traits was still observed. In US-2 NILs, several lines will be backcrossed one or two more times and the selection and fixation for resistance and morphological traits will be continued until the F9 generation or more (Data are not shown).

Conclusion

The IRRI-Japan Collaborative Research Project and the International Network for Genetic Evaluation of Rice (INGER) will provide information of ISDVs and will accept seed requests for two sets; 31 monogenic lines targeting of 24 resistance genes and 21 CO 39 NILs targeting of 15 genes. The development of the other two NILs with LTH and US-2 genetic backgrounds and improvements of monogenic lines and CO 39 NILs is continuing to increase the number of different resistance genes represented.

Reference

Kiyosawa S, Ikehashi S ,Kato. H., and Ling, Z.Z. (1981) Pathogenicity tests of Philippine isolates of blast fungus using two sets of rice varieties. Japan J. Breeding 31, 367-376.

Tsunematsu H, Yanoria M.JT, Ebron LA, Hayashi N., Ando I., Kato H, Imbe T and Khush, GS (2000) Development of monogenic lines of rice for rice blast resistance. Breeding Science 50, 229-234

Yamada M., Kiyosawa S, Yamaguchi T, Hirano,T, Kobayashi T, Kushibuchi K and Watanabe S (1976) Proposal of a new method of differentiating races of Pyricularia oryzae Cavara in Japan. Ann. Phytopath. Soc. Japan 42, 216-219.

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