In the present study, quantitative trait loci (QTLs) controlling seed storability based on relative germination rate (%) were dissected using a saturated linkage map and a recombinant inbred lines (RILs) derived from a cross of japonica cultivar Asominori (Oryza sativa L.) and indica cultivar IR24 (Oryza sativa L.). A total of three QTLs (qRGR-1, qRGR-3 and qRGR-9) were detected on chromosomes 1, 3 and 9 with LOD score ranging from 3.45 to 6.95 and the phenotypic variance explained from 16.72% to 28.63%. The IR24 alleles were all associated with seed storability at all the three QTLs. The existence of these QTLs was conWrmed using IR24 chromosome segment substitution lines (CSSLs) in Asominori genetic background (AIS). By QTL comparative analysis, the QTL, qRGR-9 on chromosomes 9 appeared to be consistent with another rice population, this region may provide an important region for isolating this responsible gene. These results also provide the possibilities of enhancing Seed storability in rice breeding program by markerassisted selection (MAS) and pyramiding QTLs.
It has been reported that the susceptibility of insect herbivores to entomoviruses is affected by phytochemicals ingested during the acquisition of viral inoculum on the foliage of host plants. However, the relationship between this susceptibility and phytochemicals is poorly understood. To test this hypothesis of plant‐mediated effects on this susceptibility, we measured the effects of foliage from three plants, soybeans (Glycine max), collards (Brassica oleracea) and water convolvuluses (Ipomoea aquatica), on the susceptibility of larval beet armyworm (Spodoptera exigua) to nucleopolyhedrovirus (NPV), and analysed six foliar chemicals (total phenolics, peroxidase [POD], catalase [CAT], superoxide dismutase [SOD], endochitinase and exochitinase) in the three plants, respectively. The results of exponential modelling indicated that the LD50s (median lethal dose) of NPV to larvae increased with the increase in both phenolics and POD but declined with the increase in four other foliar chemicals, while the opposite trend was found between median lethal time (LT50) of NPV and the six foliar chemicals. This study reveals that phenolics and POD decrease host susceptibility to the entomoviruses and that CAT, SOD, endochitinase and exochitinase increase this susceptibility.
The short field-life of Bacillus thuringiensis (Bt) insecticidal crystal protein has limited its use. When the Bt toxin is produced in Pseudomonas fluorescens it can be encapsulated and retain its effectiveness for two to three times longer than other Bt formulations. In order to improve Bt expression, we have synthesized cryIA(c) Bt delta-endotoxin encoding region (GenBank AF537267) according to the usage codon of P. fluorescens and transformed the Bt toxin expression cassette into P. fluorescens strains. T7 RNA polymerase and the T7 promoter system were used to control expression of Bt toxin. SDS-PAGE and Western blotting assay revealed that the delta-endotoxin was expressed as 8% of the total protein in P. fluorescens. In in vitro tests, release of toxin from dead bacteria was demonstrated. Supplementation of diets with Bt toxin-containing Pseudomonas bacterium resulted in high mortality of cabbage butterfly ( Pieris brassicae) larvae.
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