Acta Agronomica Sinica最新文献

To facilitate the application of simple sequence repeat (SSR) markers in molecular marker-assisted selection (MAS) of upland cotton (Gossypium hirsutum L.), a linkage map harboring 192 SSRs was constructed from the CRI-G6 population (Acala 1517 × Dezhou 047) using mixed-model-based composite interval mapping (MCIM) method. This map was used to detect quantitative trait loci (QTLs) associated with cotton yield traits in 3 environments. In the separate analysis, 24 main-effect QTLs were identified including each one stable QTL for seed yield, lint yield, lint percentage, seed index, and boll number per plant. In the joint analysis, 14 main-effect QTLs and 20 pairs of additive–additive epistatic QTLs were detected including 6 main-effect and 7 pairs of epistatic QTLs with environmental interactions. Eight main-effect QTLs were mapped in the same regions using both methods. Some main-effect QTLs with stability in different growing environments had phenotypic contributions larger than 10%, and these QTLs are candidate genes/loci in MAS of upland cotton.

The gene encoding betaine aldehyde dehydrogenase (BADH) has been transformed into alfalfa (Medicago sativa L.) and resulted in 42 transgenic plants with improved salt tolerance. However, these transgenic lines were derived from the same transformant vector, which were unable to distinguish them from each other using common methods. For differentiating these transformants at molecular level, thermal asymmetric interlaced polymerase chain reaction (TAIL-PCR) was performed to separate the T-DNA flanking sequences for identifying transgenic plants in event-specific detection. A total of 6 sequences flanking either the left or the right borders of the T-DNA were obtained. The left border sequence of T-DNA was completely deleted from the vector and not integrated into the genome of alfalfa in the transgenic plant B196. Although the left border flanking sequence in the transgenic plant B127 was reserved, it was filled with a DNA sequence of unknown origin. The forward and backward primers for PCR were designed based on the characteristics of the flanking sequences originating from the vector sequence and the alfalfa genomic sequence adjacent to the integrated vector sequence, respectively. According to the result of PCR amplification in the 42 BADH-transgenic lines, plants B106, B125, B127, B138, B157, B158, B289, B295, and B305 presented the same amplification banding pattern. Plants B196, B203, B220, and B223 exhibited the same banding pattern, which was different from that amplified from other plants. These results indicated that the plants with identical amplification banding patterns may come from the same transformation event.

Very-long-chain fatty acids (VLCFAs) are critical components in cuticular waxes, sphingolipids, and triacylglycerols in higher plants. Biosynthesis of VLCFAs is catalyzed by the fatty acyl-CoA elongase, a membrane-bound enzymatic complex containing 3-ketoacyl-CoA synthase (KCS), 3-ketoacyl-CoA reductase (KCR), 3-hydroxacyl-CoA dehydratase (HCD), and trans-2,3-enoyl-CoA reductase (ECR). In this study, the primers were designed based on multiple alignments of trans-2,3-enoyl-CoA reductase (ECR) gene sequences from Arabidopsis thaliana and other plants, and the full-length cDNA, here designated BnECR, and the corresponding genomic sequences were isolated from Brassica napus using rapid amplification of cDNA ends method (GenBank accession numbers FJ899705 and FJ899705). The sequence of BnECR cDNA was 1328 bp in length excluding the poly dA tail, and the corresponding genomic sequence was 2093 bp. BnECR was composed of 4 exons and contained a 163 bp 5′ untranslated region (5′ UTR) and a 233 bp 3′ UTR. The deduced BnECR protein was 310 amino acid in length with a molecular weight of 735.78 kD and an isoelectric point of 9.52. The critical functional sites K₁₄₄ and R₁₄₅ in AtECR were unchanged in BnECR. The G₂₂₅SGGYQIPR/HG₂₃₄, which presented a non-classical NADPH-binding motif, was found in the C-terminal of BnECR. NCBI Blastn, multiple alignments and conserved domain search showed that BnECR had the highest homology to A. thaliana AtECR. RT-PCR analysis showed that BnECR was ubiquitously expressed in B. napus and preferentially expressed in the stem. The transcript level of BnECR at mid and late stages of seed development in low erucic acid rapeseed cultivar was obviously lower than that in high erucic acid rapeseed cultivar, suggesting that BnECR was involved in biosynthesis of erucic acid. The 933 bp open reading frame of BnECR was subcloned into the yeast-Escherichia coli shuttle vector pYES2.0. The recombinant plasmid was transformed into Saccharomyces cerevisiae wild type strain By4743 and the mutant strain YDL015c. With galactose as inducer, the transformant was cultured to induce the expression of BnECR. The gas chromatographic result indicated that BnECR was overexpressed effectively in S. cerevisiae, and the content of erucic acid reached 1.34% of the total fatty acid in the recombinant strain, an increase of 52% over the control. Functional complementation of BnECR in an ECR-deficient mutant yeast demonstrated that BnECR mediated the biosynthesis of VLCFAs. The results suggest that BnECR should be functional orthologue of AtECR.

Resistance to sheath blight is generally controlled by polygenes in rice (Oryza sativa L.) and varies greatly among cultivars. At present, very few germplasms can be used as resistant parents in rice breeding. A total of 166 indica hybrid rice combinations collected from 11 provinces in southern China were evaluated for the resistance to sheath blight at seedling stage using artificial inoculation method. According the disease indexes (DIs) to 5 isolates of Rhizoctonia solani, the 166 hybrid combinations were classified into 5 types based on dynamic clustering analysis (DCA), with the ratios of 1.2% for resistance (R), 13.9% for moderate resistance (MR), 36.1% for moderate susceptibility (MS), 43.4% for susceptibility (S), and 5.4% for high susceptibility (HS); but no combination was immune or highly resistant to the disease. K-you 88 and Zhongyou 9801 showed relatively high resistance at seedling stage, but their adult resistance should be further evaluated. The discriminant function for each resistance type was calculated using Bayes method, and the accuracy rate for discrimination was 96.39%. The average DI ranged from 2.84 to 7.64 with an average of 5.27. The concept of synthetic disease index (SDI) was also introduced to classify the 166 hybrid combinations, which is the overall resistance performance to total isolates tested. Based on SDI grading criteria, the 166 hybrid combinations were also divided into R, MR, MS, S, and HS types with the ratios of 1.2%, 13.3%, 63.3%, 21.7%, and 0.6%, respectively. The SDI classification system was significantly correlated with the DCA system (r = 0.81, P < 0.01), showing that both methods can be used for evaluating the disease resistance. The DCA method is suitable for seedling screening under the uniform growth condition. The SDI method is independent on test time, place, and batch, and thus can be applied in relatively complicated conditions. Twenty-six combinations were identified as resistant (R or MR) indica hybrid rice using both methods. The genetic distances among these combinations ranged from 0.04 to 0.71. Twenty-two of them were grouped in the same clade after cluster analysis using unweighted pair group method with arithmetic mean (UPGMA) method. This result and pedigree analysis showed a narrow genetic background of the resistant hybrid combinations.

C-repeat binding factor (CBF) is a kind of transcription factor that regulates expression of a number of genes related to abiotic stresses. Three CBF genes were isolated from the genomic DNA of Gossypium hirsutum L. cultivars Gh12 and Gh36 and G. barbadense L. cultivar Gb7124. Cotton CBF gene encodes 184 amino acids, containing the CBF-family signature PKRRAGRKKFQETRHP and FADSAW. Southern blotting result showed that CBF genes were present as the form of gene family in the genome of cotton. Northern blotting result indicated that GbCBF1 was induced by low temperature, drought, salt, and abscisic acid. This gene was constructed into plant expression vector pCambia2301, in which the gene was driven by 35S and NOS promoters separately. Plant expression vectors were then transferred into Nicotiana tabacum L. cultivar NC89 using Agrobacterium-mediated transformation method. Twenty-six transgenic tobacco lines were obtained after kanamycin screening and PCR detection. After PCR and reverse tanscription PCR analyses in partial T₁ transgenic plants, the GbCBF1 gene was confirmed to be transcripted and inherit in offspring normally. Under low temperature stress, the electrolytic leakage rate of transgenic tobacco was lower than that of the wild type tobacco; however, free proline and soluble sugar contents of transgenic tobacco were higher than those of the wild type tobacco. This result indicated that GbCBF1 enhances cold tolerance in transgenic tobacco.

Cadmium (Cd) is a heavy metal element toxic to plant, animals and humans. Planting ramie varieties in Cd contaminated soils can prevent Cd flow into food chains. In this study, the Cd tolerance of 9 ramie genotypes was compared in hydroponic culture and field microplot experiments, and the indicators to evaluate the tolerance were analyzed. In the hydroponic culture experiment, significant genotypic variations were found in plant height, leaf number per plant, shoot dry weight, and root dry weight in different Cd treatments; and shoot dry weight was significantly correlated with plant height, SPAD reading of leaf, and root dry weight. In the field experiment, shoot dry weight was significantly correlated with plant weight, stem diameter, and bark thickness. These phenotypic traits could be used as indicators for Cd tolerance evaluation. Clustering analysis based on the comprehensive tolerance of both experiments showed 3 groups of the 9 ramie genotypes, which were characterized with high, moderate, and low tolerance to Cd. For screening ramie genotypes with Cd tolerance, plant height, SPAD reading of leaf, shoot dry weight, and root dry weight can be used as selection indicators in hydroponic culture experiment.

Based on the established genetic linkage maps of Brassica napus L., QTLs for difference in oil content between high latitude (Wanzhou, Chongqing, China) and low latitude (Beibei, Chongqing, China) environments were detected using the composite interval mapping model. The mapping populations, SWU-1 and SWU-2, contained 188 and 219 recombinant inbred lines, respectively. In the SWU-1 population, the oil content differences ranged from 0 to 18.66% between the 2 environments, and 2 difference QTLs were located in the linkage groups 6 and 7 with the phenotypic contributions of 10.3% and 12.4%, respectively. In the SWU-2 population, the oil content differences ranged from 0.43% to 17.17% between the 2 environments. Three difference QTLs were located in linkage groups 8 and 14, which explained 6.6–10.6% of the phenotypic variation each. The oil content difference was significantly correlated with growing environment (P < 0.01), and the coefficient of variation was 58.24%. This indicates the presence of environment-insensitive QTLs associated with oil content in rapeseed genotypes. In both environments, no visible linkage relationship was observed between QTLs for oil content difference and QTLs for oil content. Therefore, it is inferred that sensitive and insensitive genes to environment might have a different expression system to oil synthesis genes in Brassica napus L.

Synthetic hexaploid wheat (SHW), a carrier of multiple elite genes, is an important genetic resource in improvement of common wheat (Triticum aestivum L.). Chuanmai 42 is a wheat cultivar with high-yield potential and resistance to strip rust (Puccinia striiformis f. sp. tritici), which was developed by crossing and backcrossing Syn769 (an elite synthetic hexaploid wheat) with Sichuan commercial wheat cultivars. For understanding the genetic effects of the introgression loci from SHW in Chuanmai 42, a total of 78 introgression loci of SHW were tested in Chuanmai 42 using 1029 simple sequence repeat (SSR) markers. Using 127 recombinant inbred lines (RILs, F₈) in Chuanmai 42 (introgression loci) and Chuannong 16 (Chuannong 16 loci) backgrounds, the genetic effects of the introgression loci were evaluated across 6 environments in Sichuan Province, China from 2006 to 2009. One locus from the SHW parent, Barc1183, was detected in Chuanmai 42. It was located on the long arm of chromosome 4D after idenfication using the 4DS and 4DL telosomic lines of Chinese Spring and the 4D(4A) and 4D(4B) substitution lines of Longdon (T. turgidum subsp. durum). This locus had positive effects on increasing tiller number per plant, number of effective spikes, grains per square meter, harvest index, and grain production rate. The average yield of the 6 growing environments was increased by 8.9% when comparing locus Barc1183 in Chuanmai 42 to that in Chuannong 16. Therefore, Barc1183 from SHW is a candidate locus in high-yield breeding of wheat.

Continuous cropping obstacle is one the most important problems in tobacco (Nicotiana tabacum L.) production. To alleviate continuous cropping obstacle based on management of soil ecology, the effects of different fertilizers were tested using tobacco cultivar K326 growing in a field with 12-year consecutive cultivation. The rhizospheric soil was sampled to investigate the changes in functional diversity of microbial flora in different treatments. The results showed that the autotoxic allelopathic potential was maximal for the monoculture soil treated with traditional compound fertilizer, and minimal for the soil treated with farmyard manure. According to the result of BIOLOG analysis, traditional compound fertilizer was conducive to the growth of microbial flora feeding on amino acids and amine as carbon sources, the commercial organic fertilizer to the growth of microbial flora using carboxylic acids as a carbon source, and farmyard manure to the growth of microbial flora using carbohydrate, fatty acids, and phenolic acids as carbon sources. Principal component analysis indicated that the first 2 components were related to carbon sources, which accounted for 74.37% and 25.63% of the data variation. The carbon source of carbohydrate, fatty acids, and phenolic acids mainly contributed to the separation of the 2 principal components. The autotoxic allelopathic potential of tobacco rhizospheric soil was positively correlated with the average well color development (AWCD) value of microbial flora feeding on carbohydrate and phenolic acids as carbon sources, and negatively correlated with that of the microbial flora using the carbon source of fatty acids. In addition, for the growth of microbial flora in monoculture soil, farmyard manure was the best, followed by commercial organic fertilizer, and traditional compound fertilizer was the worst.

Introducing enzymes involved in photosynthesis of C₄ plants into rice (Oryza sativa L.) is supposed to enhance the photosynthesis and crop productivity. However, only a few researches showed that the photosynthesis and crop productivity have been improved by introducing phosphoenolpyruvate carboxylase (PEPC) gene into rice. In the present study, the photosynthetic rates (P_n) in 42 rice lines overexpressing PEPC gene were investigated. The average P_n value of transgenic lines was almost the same as that of the wild type (control) in paddy field, but was much higher than that of the control in upland field. Only a few transgenic lines showed higher P_n in paddy field and most of them showed higher P_n in upland field. Similar results were found in the water controlled experiment. Two transgenic lines with different relative activities of PEPC (10 and 25 folds) were selected to study their photosynthesis under different water potentials (0, −20, and −40 kPa). In both lines, the P_n values were similar to that in the wild type under normal condition (0 kPa) and higher under drought conditions (−20 kPa and −40 kPa). In both experiments, the transgenic lines had higher P_n under drought conditions, with a slower decreasing rate than the wild type. Therefore, the present results suggested that the overexpressed PEPC could not improve the photosynthetic rate of transgenic rice plants. But the photosynthetic rate of transgenic rices declined slowly under drought condition. It is supposed that PEPC might be involved in drought resistance to decrease the inhibition of drought stress on photosynthesis in rice.