The resistance of vegetative, booting, and flowering stage plants of a variety of an aromatic rice, Oryza sativa L., transformed with a Bacillus thuringiensis Berliner cry1Ab gene under control of the maize phosphoenolpyruvate carboxylase (PEPC) promoter was evaluated against four lepidopterous rice pests--the stem borers Chilo suppressalis (Walker) (Lepidoptera: Crambidae) and Scirpophaga incertulas (Walker) (Lepidoptera: Pyralidae), and the foliage feeders Cnaphalocrocis medinalis Guenée (Lepidoptera: Pyralidae) and Naranga aenescens Moore (Lepidoptera: Noctuidae). Plants of the cry1Ab-transformed line (no. 827) were more resistant to young larvae of S. incertulas, C. suppressalis, and C. medinalis than control plants at the vegetative stage but not at the flowering stage. Survival of 10-d-old stem borer larvae did not differ on cry1Ab plants and control plants at either the vegetative or flowering stage, but the development of 10-d-old C. suppressalis larvae was retarded on the vegetative stage cry1Ab plants. Immunological analysis also showed an apparent decline in Cry1Ab titer in leaf blades and leaf sheaths at the reproductive stage. In experiments comparing three fertilizer treatments (NPK, PK, and none), there was a significant interaction between fertilizer treatment and variety on larval survival only in whole-plant assays at booting stage with C. suppressalis. On cry1Ab plants, larval survival did not differ significantly among the three fertilizer levels, whereas on control plants survival was highest with the NPK treatment. cry1Ab plants tested at the sixth and seventh generations after transformation were more resistant than control plants to N. aenescens and C. suppressalis, respectively, suggesting that gene silencing will not occur in line 827. The results of the experiments are discussed in terms of resistance management for B. thuringiensis toxins in rice.

Allele mining exploits the deoxyribonucleic acid (DNA) sequence of one genotype to isolate useful alleles from related genotypes. The international project to sequence the genome of Oryza sativa L cv. Nipponbare will make allele mining possible for all genes of rice and possibly related cereals. We used a rice calmodulin gene, a rice gene encoding a late embryogenesis-associated protein, and salt-inducible rice gene to optimize the polymerase chain reaction (PCR) for allele mining of stress tolerance genes on identified accessions of rice and related germplasm. Two sets of PCR primers were designed for each gene. Primers based on the 5' and 3' untranslated region of genes were found to be sufficiently conserved so as to be effective over the entire range of germplasm in rice for which the concept of allelism is applicable. However, the primers based on the adjacent amino (N) and carboxy (C) termini amplify additional loci.

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