[show abstract][hide abstract] ABSTRACT: A total of 105 transgenic rice lines independently transformed with a pea ferritin gene (Fer) were previously obtained. After seven generations of selfing and β-glucuronidase (GUS) assisted selection, 82 transgenic lines with stable agronomic traits were got. Among the 82 transgenic lines, two high-iron transgenic rice lines Fer34 and Fer65, with the iron contents in the milled rice being 4.82 and 3.46 times of that of the wild type Xiushui 11, respectively were identified. In the two transgenic lines, the exogenous Fer gene was highly expressed, and inherited as a single locus. The transgene had no negative effect on the agronomic traits of rice plant, other mineral nutritional components, appearance quality and eating quality of the milled rice, indicating that these two lines were elite high-iron breeding lines. Furthermore, the practical application and further studies facilitating utilization of the two elite breeding lines were discussed.
[show abstract][hide abstract] ABSTRACT: Milled rice (Oryza sativa L.) is composed of approximately 90% starch. The properties of starch have considerable effects on cooked rice palatability and consumer acceptability. Starch pasting viscosity parameters serve as important indices in the estimation of eating, cooking, and processing qualities of rice. In the present study, four cytoplasmic male-sterile (CMS) lines and eight restorer (R) lines have been used in an incomplete diallel cross to analyze seed effects, cytoplasmic effects, maternal gene effects, and their genotype x environment (GE) effects on the following starch pasting viscosity parameters: breakdown (BD), consistency (CS), and setback (SB). The results demonstrated that the total main genetic variances (V(G)) accounted for over 64% of the total genetic variance (V(G) +V(GE)) for the three traits, indicating that these traits were mainly controlled by the main genetic effects in addition to the GE interaction effects. The estimated total narrow-sense heritability were 67.8%, 79.5%, and 79.5% for BD, CS, and SB, respectively. The general heritability (h(2)(G)) accounted for over 75% of the total heritability (h(2)(G) +h(2)(GE)), indicating that early selection would be effective for those traits and the selection efficiencies were relatively stable in different environments.
[show abstract][hide abstract] ABSTRACT: Comparative analysis revealed that a xantha rice mutant (cv. Huangyu B) had higher ratios of chlorophyll (Chl) a/b and carotenoids/Chl, and higher photosynthetic efficiency than its wild type parent (cv. II32 B). Unexpectedly, the mutant
had higher net photosynthetic rate (P
N) than II32 B. This might have resulted from its lower non-photochemical quenching (qN) but higher maximal photochemical efficiency (FV/FM), higher excitation energy capture efficiency of photosystem 2 (PS2) reaction centres (FV′/FM′), higher photochemical quenching (qP), higher effective PS2 quantum yield (ΦPS2), and higher non-cyclic electron transport rate (ETR). This is the first report of a chlorophyll mutant that has higher photosynthetic
efficiency and main Chl fluorescence parameters than its wild type. This mutant could become a unique material both for the
basic research on photosynthesis and for the development of high yielding rice cultivars.
[show abstract][hide abstract] ABSTRACT: AbstractThrough integrated molecular and biochemical investigations and by using a common mutant line in molecular mapping, we have shown that the SSIIa gene, previously reported to be responsible for the starch granule gelatinization temperature (GT) differences between indica and japonica rice varieties, might also control the GT variations among certain indica varieties. This effect is mediated through differences in the amounts of SSIIa protein bound to starch granules leading to differences in the structure of amylopectin molecules synthesized. For the first time it was shown, that the amylopectin type accounted only for the GT differences between varieties with different SSIIa alleles, but not between varieties carrying a common SSIIa allele. In the latter case, another gene, alk2(t), with a genetic distance of 3.93 cM from the Wx gene, was identified as being responsible for the GT variations. Based on the thermal properties and amylopectin chain length profile characteristics, it is postulated that the SSIIa gene has at least three different alleles, one in japonica rice and two in indica rice varieties, whereas alk2(t) has at least two alleles for either low or high GT. Thus, the rich diversity of the GT character in rice very probably results from various combinations of these alleles.
[show abstract][hide abstract] ABSTRACT: A xantha mutant (yellow plant) was induced by gamma rays irradiation of a cytoplasmic male sterile (CMS) maintainer line II32 B of rice (Oryza sativa L.). It was identified earlier as a low gelatinization temperature mutant and named as Mgt-1. Through a series of backcrosses of Mgt-1 to CMS line II32 A, a new CMS line was developed and named as Huangyu A (B). Genetic analysis showed that the xantha mutation was controlled by a single recessive locus, and all F1 plants from crosses of Huangyu A (B) with other normal green varieties showed normal green leaves. The xantha mutation resulted in reduction of photosynthetic pigments content at various levels, e.g., 48% of chlorophyll a (Chl a), 71% of chlorophyll b (Chl b), and 30% of carotenoids (Car), and consequently increased the ratios of Chl a/Chl b and Car/Chl in Huangyu A (B) against II32 A (B). Unexpectedly, Huangyu A (B) had higher photosynthetic rates in comparison with II32 A (B), and so did the F1 plants of Huangyu A/R3027 as against those of II32 A/R3027. Huangyu A had similar male sterility completeness and stability as II32 A, but the former showed significantly better combining ability than the latter. The yellow color made the seedlings and plants of Huangyu A (B) visually distinguishable from the green ones and thus it was a very distinct marker applicable for rapid testing and efficient increasing varietal purity in seed and paddy production of hybrid rice.
[show abstract][hide abstract] ABSTRACT: The segregation mode of transgenes was investigated in the transgenic progenies of three rice varieties (lines) produced by Agrobacterium-mediated transformation. The transgenic lines all contained the Bacillus thuringiensis cry1Ab gene, under the control of a maize ubiquitin promoter, and linked in tandem with gusA and hpt genes. PCR analysis showed the transgenes cry1Ab and gusA co-segregated in all self and crossed progenies tested. Therefore, GUS bio-assay of leaf or endosperm tissues was used to monitor transgene segregation in the experiment. It was found that the ratio of positive to negative plants was significantly smaller than 3:1 in all heterozygous plants derived progenies, which implied the segregation biased from typical Mendelian mode for a single dominant gene. Less GUS positive plants, and consequently less homozygous transgenic lines than expected were recovered from the self progenies. Transgenic heterozygous plants (+/-) were crossed as female or male parent to conventional rice varieties (-/-), and the ratio of gusA positive (+/-) to negative (-/-) plants was investigated in test F1 population. When used as female parent, the segregation fit to 1:1, but significantly smaller than 1:1 when used as male parent. The seed-set of transgenic Nipponbare progeny was investigated individually for GUS positive and negative plants. It was found that the positive plants had an average seed-set of 64.5%, significantly lower than that of negative plants (77.9%). The biological and genetic basis of distorted segregation of transgenes was discussed and deduced on the basis of above results, and the authors are inclined to ascribe these phenomena to the poor competitive ability of pollens carrying transgenes.