Acta Agronomica Sinica最新文献

Wheat strong-gluten quality is closely correlated with combinations of high-molecular-weight glutenin subunits (HMW-GS) and low-molecular-weight glutenin subunits (LMW-GS). A multiplex PCR system was established to evaluate the loci for HMW-GS and LMW-GS in wheat (Triticum aetivum L.). The multiplex PCR system confered molecular markers for Ax1/Ax2*, Bx7^OE, Dx5, Glu-A3d, Glu-B3i genes, and Glu-B3 locus, and proved to be effective and stable to amplify specific bands on target loci in 12 wheat cultivars with known gene/locus combinaitons. Using this multiplex PCR system, 62 major cultivars from Shaanxi Province, China were evaluated. The results showed that the frequencies were 56.5% for Ax1/Ax2*, 9.6% for Dx5, 33.9% for Glu-A3d, 1.6% for Glu-B3i, and 64.4% for Glu-B3, whereas gene Bx7^OE was not detected. Most cultivars carried 2 genes (locus) with the frequency of 48.3%, followed by cultivars carrying a single gene or locus (33.9%). The frequency of cultivars carrying 3- or 4-gene (locus) combinations was 11.3%. The remaining cultivars (6.5%) were free of any elite gene (locus). Therefore, the frequency of combination of multiple strong-gluten subunit genes (locus) was low in the cultivars from Shaanxi Province, which could be improved with introduced germlasm. The multiplex PCR system developed may serve as a rapid and efficient method to select breeding materials carrying multiple genes (locus) associated with strong-gluten subunit.

Gene nia plays an important role in regulation of nitrogen metabolism in plants. This gene has been cloned in many crops except for sugar beet. In this study, a cDNA clone associated with nitrate reduction was isolated from a diploid species of sugar beet (Beta vulgaris L.) using homologous cloning technique. A novel full-length cDNA (GenBank accession number EU163265), termed nia, was obtained using rapid amplification of cDNA ends (RACE). The full length of nia gene is 3247 bp. The open reading frame of this gene is 2718 bp in length, which encodes 905 amino acids with the theoretical molecular weight of 102 kD and the isoelectric point of 6.12. Southern blotting results proved that nia presents in low copies in Ty7, and the clone obtained belongs to NADH-NR genes. The nia transcripts under nitrate nitrogen (NO₃-N) and ammonium nitrogen (NH₄-N) treatments were detected through semiquantitative PCR analysis, and the efficiency of mRNA synthesis from each sample was estimated via quantitative PCR of glyceraldehyde-3-phosphate dehydrogenase (GAPDH). In the NH₄-N treatment, nia was up-regulated with low concentration of NH₄⁺, but inhibited by high concentration of NH₄⁺. In the NO₃-N treatment, the nia expression level was enhanced with the increase of NO₃⁽ concentration. When exposed to 30 mmol L⁽¹ KNO₃, nia exhibited the highest expression 4 h after treatment and a significantly reduction 6 h after treatment.

The cereal cyst nematode (CCN) of wheat has become a severe disease in recent years. Heterodera filipjevi is a new pathogenic nematode in China. For screening resistant resources to H. filipjevi, the resistance of 75 wheat cultivars or lines from the International Maize and Wheat Improvement Center (CIMMYT) was evaluated in greenhouse and field conditions using relative resistance index (RRI) and Pf/Pi ratios, with the nematode from Xuchang population, Henan Province, China. No cultivar was immune to H. filipjevi. However, line 6R(6D) was highly resistant in both test conditions. Lines CROC_1/AE.SQUARROSA(224)//OPATA*1, CROC_1/AE.SQUARROSA (224)//OPATA*2, MACKELLER, CPI 133842, CPI 133814, and TRIDENT were moderately resistant to H. filipjevi in the greenhouse test. In the field test, CPI 133842, CPI 133814, DURATI, and TURCAN#39 showed a high resistant reaction with RRI values ranging from 0.90 to 0.96. Fourteen lines including ID-2150, BAXTER, and MACKELLER were moderately resistant to H. filipjevi. The disease severity was heavier in the greenhouse test than in the field test, and resistance identification in the greenhouse is much easier and reliable. The results indicated that relative resistance index (RRI) is an efficient index for evaluating the resistance of wheat cultivars to CCN.

The objective of this study was to understand the relationship between cooking quality and lipid content and components in milled rice of different cultivars, and the regulation of nitrogen on lipid quality in japonica rice (Oryza sativa L.). Under 7 nitrogen conditions with 4 total nitrogen levels and 2 split ratios, the RVA parameters and contents of crude lipid, lipid components, and amylose were assayed in 6 cultivars. Genotype significantly affected the content and components of lipid in milled rice. The milled rice of small-panicle cultivars had higher contents of crude lipid and starch lipid and lower non-starch lipid in milled rice than that of the large-panicle cultivars. The effect of nitrogen on lipid content and components in milled rice was smaller than that of genotype, and varied among genotypes. The content of crude lipid was significantly and negatively correlated with breakdown value, and the content of starch lipid was significantly and negatively correlated with amylose content, setback value, and consistency viscosity. The results indicate that rice cooking quality can be promoted through cultivar improvement aiming at increasing starch lipid content in milled rice.

To elucidate the phenotypic correlations among root and shoot traits in elite hybrid rice (Oryza sativa L.), 7 root and 10 shoot traits in an RIL population of Xieyou 9308 and 2 reciprocal backcross populations (BCF₁) derived from the RILs were determined under hydroponic culture and field experiment conditions. All traits, except for root diameter, panicle number per plant and grain-setting rate, were significantly different between the 2 recurrent parents, and transgressive segregations and continuous distributions were observed in either root traits or shoot traits in the RIL or BCF₁ populations. In the root traits, root length was positively correlated with total root length, dry root weight, root surface area, root volume, and number of root tips; however, root diameter was negatively correlated with other root traits. In the shoot traits, heading date, plant height, panicle length, spikelet number per panicle, grain-setting density, and grain yield per plant showed significant and positive correlations with all root traits except for root diameter. These results provide applicable shoot indices for indirect selection of root traits and valuable information for super hybrid rice breeding.

Information on advances in wheat (Triticum aestivum L.) productivity is essential for genetic improvement on yield potential. Four yield potential trials with totally 59 leading cultivars from Sichuan, Yunnan, Gansu, and Xinjiang, China were conducted using a randomized complete block design with 3 replications under controlled environments in 2 successive cropping seasons from 2007 to 2009. The experimental sites were located in Chengdu in Sichuan, Lijiang in Yunnan, Wuwei in Gansu, and Changji in Xinjiang. Molecular markers were used to detect the presence of dwarfing genes and 1B/1R translocation. The results indicated that the annual genetic gains in yield were 0.73% in Sichuan, 0.34% in Yunnan, 0.58% in Gansu, and 1.43% in Xinjiang. There was no obvious trend of yield component improvement for yield increase in Sichuan; while reduced spikes per square meter and increased kernels per spike were the main factor for yield increase in Yunnan; increased kernels per spike were the main factor for yield increase in Gansu; and increased kernel weight of main spike and harvest index were the main factor for yield increase in Xinjiang, together with the contribution from reduced plant height and earlier maturity. It also indicated that the dwarfing genes Rht-B1b and Rht-D1b were all from International Maize and Wheat Improvement Center (CIMMYT) lines, and the significant progresses of genetic gain in yield in the 4 provinces were mainly due to the direct and indirect use of CIMMYT germplasm. Stripe rust resistance was the main contribution of CIMMYT germplasm in Sichuan and Yunnan; while CIMMYT germplasm contributed to high yield potential with high kernel number per spike, short plant height, and wide adaptability in Xinjiang and Gansu.

The objectives of this study were to understand the characteristics of nitrogen accumulation and partition in different types ofrapeseed (Brassica napus. L) and explain the mechanism of nitrogen efficiency for seed production. A total of 98 conventional rapeseed varieties in 6 types of nitrogen use efficiency for grain production (NUEg) were planted under N0 (pure nitrogen 0 kg ha⁻¹) and N1 (pure nitrogen 150 kg ha⁻¹) conditions in 2007 and 2008. The dry matter weights and nitrogen contents of different parts of plants at ripening stage were determined. Significant difference of NUEg was observed among varieties, and seed yield of rapeseed was increased with NUEg. NUEg had no significant correlation with total nitrogen accumulation, but was negatively correlated with the ratios of nitrogen distribution in stem (r = −0.5941, P < 0.01 in treatment N0; and r = −0.4141, P < 0.01 in treatment N1) and shell (r = −0.6007, P < 0.01 in N0; and r = −0.5374, P < 0.01 in N1) and positively correlated with the ratio of nitrogen accumulation in seed (r = 0.7954, P < 0.01 in N0; and r = 0.7239, P < 0.01 in N1). Besides, NUEg had significant correlation with total number of seeds (r = 0.5945, P < 0.01 in N0; and r = 0.5412, P < 0.01 in N1). Both NUEg and total amount of nitrogen accumulation had significant impacts on rapeseed yield. Therefore, rapeseed variety should be developed with high levels of nitrogen accumulation and translocation into seeds.

AP2/EREBP transcription factors play an important role in plant development, hormone response, and responses to biotic and abiotic stress. OsASIE1, a member of the EREBP subfamily of AP2/EREBP transcription factors in rice (Oryza sativa L.), is determined to be involved in abiotic stress response. OsASIE1 expression was induced by drought and salt stresses. In addition, an electrophoresis mobility shift assay (EMSA) revealed that the AP2 domain of the OsASIE1 protein can bind to both DRE (dehydration-responsive element) and GCC box (ethylene response element, ERE) in vitro. All these results indicate that OsASIE1 may participate in abiotic stress response by regulating the expression of downstream genes with DRE and GCC box binding. Overexpression of OsASIE1 in transgenic rice plants might be used to improve tolerance to salt stress.

For undertanding the genetic stability of rice (Oryza sativa L.) aneuploid during its asexual propagation, a telotetrasome (2n+·8S+·8S) was selected from the progenies of a rice telotrisome (2n+·8S), and preserved by asexual reproduction. One of the extra short arms (·8S) was easily lost in the asexual propagation offspring of 2n+·8S+·8S, resulting in morphological variation. The behaviors of the 2 extra ·8S were observed using fluorescence in situ hybridization (FISH) technique. One of the 2 extra ·8S was found without detectable centromeric satellite repeat (CentO) and centromere-specific retrotransposon (CRR), and failed to be transmitted stably; whereas the other extra ·8S contained CRR but no detectable CentO, which could be transmitted stably during asexual propagation. However, the extra ·8S contained both CentO and CRR sequences in the initial telotrisomic line (2n+·8S). Therefore, the CentO and CRR sequences of the extra ·8S may be randomly lost during asexual propagation, which results in instable inheritance in aneuploid rice with extra ·8S.

This study aimed at seeking the genetic possibility of coinstantaneous improvement of kernel yield and lysine content in maize (Zea mays L.). Fifteen inbred lines selected from 5 basic maize populations were crossed with 5 elite inbred lines derived from different heterotic groups according to the NCII design. In 2009, 75 combinations were evaluated in Zhengzhou and Xuchang, Henan Province, China. The lysine contents in kernels of parents, F₁, and F₂ populations were determined using near infrared reflectance spectroscopy (NIRS) method, and analyzed in the model of triploid seed endosperm-cytoplasm-maternal effect. In addition to the 3 genetic systems of seeds, maternal effect, and cytoplasm effect as the predominating element, environmental factor was also found to affect the lysine content in kernels. The genetic main-effect (V_G), which was composed of 24.6% seed effect (V_A+V_D), 19.7% cytoplasm effect (V_C), and 55.7% maternal effect (V_Am+V_Dm), explained 76.3% of the total genetic variance (V_G+V_GE). The maternal heritability for lysine content (40.98%) was much higher than the seed heritability (17.86%) and cytoplasm heritability (14.29%). Besides, no significant correlation was found between the lysine content and grain yield (r = −0.0269, P > 0.05). Therefore, it is feasible to improve both kernel yield and lysine content simultaneously in maize breeding. In breeding practice, the parental lines with high lysine content, especially the female line, are the genetic basis, and diverse crosses among parents in different heterotic groups provide a wide platform for selecting both high yield and lysine content in the progenies.