Article

Molecular Breeding

, Volume 3, Issue 5, pp 401-414

First online:

Enhanced resistance to two stem borers in an aromatic rice containing a synthetic cryIA(b) gene

  • Behzad GhareyazieAffiliated withDivision of Plant Breeding, Genetics and Biochemistry, International Rice Resaerch InstituteRice Research Institute of Iran
  • , Faramarz AliniaAffiliated withEntomology and Plant Pathology Division, International Rice Research InstituteRice Research Institute of Iran
  • , Corazon A. MenguitoAffiliated withDivision of Plant Breeding, Genetics and Biochemistry, International Rice Resaerch Institute
  • , Leila G. RubiaAffiliated withDivision of Plant Breeding, Genetics and Biochemistry, International Rice Resaerch Institute
  • , Justina M. de PalmaAffiliated withDivision of Plant Breeding, Genetics and Biochemistry, International Rice Resaerch Institute
  • , Evelyn A. LiwanagAffiliated withDivision of Plant Breeding, Genetics and Biochemistry, International Rice Resaerch Institute
  • , Michael B. CohenAffiliated withEntomology and Plant Pathology Division, International Rice Research Institute
  • , Gurdev S. KhushAffiliated withDivision of Plant Breeding, Genetics and Biochemistry, International Rice Resaerch Institute
  • , John BennettAffiliated withDivision of Plant Breeding, Genetics and Biochemistry, International Rice Resaerch Institute

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Abstract

Rice cultivars of isozyme group V include high-quality, aromatic rices that are difficult to improve by traditional methods because of the loss of quality characters upon sexual hybridization. Their low-tillering plant type predisposes them to economic loss from attack by stem borers, a group of insects to which they are susceptible. We report here the enhancement of stem borer resistance in cv. Tarom Molaii through transformation by microprojectile bombardment. Embryogenic calli derived from mature seeds were bombarded with gold particles coated with plasmid pCIB4421, carrying a synthetic truncated toxin gene based on the cryIA(b) gene from Bacillus thuringiensis, and plasmid pHygII, carrying the hygromycin phosphotransferase (hpt) selectable marker gene. Inclusion of 50 mg/l hygromycin B in culture media from bombardment through to rooting of plantlets eliminated escapes. The procedure generated three independent hpt transformants of which two also contained the cryIA(b) gene. One such line (No. 827) produced truncated (67 kDa) CryIA(b) protein equivalent to about 0.1% of total soluble protein. The cryIA(b) gene was controlled by the promoter of the maize C4 PEP carboxylase gene and was expressed in leaf blades but was not expressed to a detectable level in dehulled mature grain. Line 827 contained about 3 copies of the cryIA(b) gene which segregated as a single dominant Mendelian locus in the second (T1) and third (T2) generations and co-segregated with enhanced resistance to first-instar larvae of striped stem borer (Chilo suppressalis) and yellow stem borer (Scirpophaga incertulas). T2 line 827-6 homozygous for the cryIA(b) gene showed no dead hearts or whiteheads after infestation with stem borers, whereas T2 line 827-25 lacking the gene averaged 7 dead hearts per plant and 2.25 whiteheads per plant. These results establish that transformation of high-quality rices of group V is a feasible alternative to sexual hybridization.

Bacillus thuringiensis Chilo suppressalis biolistic rice Scirpophaga incertulas transformation