Acta Agronomica Sinica最新文献

The genetic diversity of 95 major commercial inbred rice cultivars (Oryza sativa L. subsp. indica) released in South China from 1949 to 2005 were evaluated using 300 simple sequence repeat (SSR) markers distributing evenly on the whole rice genome. A total of 236 polymorphic loci were detected with 776 alleles. The number of allele per locus ranged from 2 to 12 with an average of 3.29. Only 2–4 alleles were found at 206 loci, which accounted for 87.3%. The average polymorphism information content (PIC) value of polymorphic loci was 0.42, which varied with chromosomes. Chromosome 10 had the greatest values in allele number per locus and PIC, and chromosome 5 had the lowest values. The allele number per locus showed an increase trend in the cultivars released from the 1950s to the 1970s and declined afterwards. Analysis of molecular variance (AMOVA) disclosed the significant genetic variation (P < 0.001) among cultivars from different decades, although it only explained 3.77% of the total genetic variation. The genetic distance among cultivars was decreased from the 1950s to the 2000s. According to clustering analysis with COMPLETE method, the 95 cultivars were grouped into 5 clusters at genetic similarity coefficient of 0.685, and several core parents were found in the cultivars released in each decade. The results indicate that the genetic diversity of indica rice cultivars in South China is in a low level and even narrowing after the 1970s. Thus, the genetic basis of indica rice cultivars should be broadened through incorporating new variability into existing rice germplasm in breeding programs.

Sichuan Province has the largest wheat (Triticum aestivum L.) producing area in Southwest China. It is crucial to understand the quality potential and stability for the major commercial cultivars and to provide guidance to farmers regarding wheat production in this province. Seven representative cultivars were planted in 5 ecological localities of Sichuan under two nitrogen rates from 2006 to 2008. Eight quality traits and 2 end-use production (noodle and bread making) scores were determined. The average of 3-year test weight, grain protein content, wet gluten content, Zeleny sedimentation, falling number, flour water abstraction, dough developing time, stability time, noodle score of dry white Chinese noodle, and bread score were 777 g L⁻¹, 12.3%, 25.1%, 32.9 mL, 326 s, 56.5%, 3.0 min, 4.5 min, 78.5, and 62.2, respectively. In a combined analysis of variance, the effects of genotype, environment, and their interaction were significant for almost all traits tested. For test weight, Zeleny sedimentation, falling number, flour water abstraction, and noodle score of dry white Chinese noodle, the influences between years were greater than differences between locations; whereas, for protein content, wet gluten content, dough developing time, stability time, and bread score, location had a greater influence than year. Increasing nitrogen rate significantly improved most quality traits and raised bread score, but had no influence on noodle score. Stability analysis revealed that Chuanmai 39 was stable for bread quality with the highest bread score value, while Chuanmai 37 was stable for most quality traits with the highest noodle score. This result indicates that Chuanmai 39 and Chuanmai 37 can be favorably used in wheat quality improvement in Sichuan Province.

Sugarcane related genera and species are important germplasm resources in sugarcane breeding. The internal transcribed spacer (ITS) sequence of 120 Saccharinae accessions that belong to 8 genera and 37 species were used to analyze their genetic relationships and construct phylogentic relationships with Pennisetum purpureum as an outgroup. The results showed that the sequence lengths were 200–208 bp for ITS1, 215–221 bp for ITS2, and 164 bp for 5.8sDNA with variable sites of 91, 93, and 18, respectively. The informative sites were 70, 68, and 9 for ITS1, ITS2, and 5.8sDNA, and the GC contents were 60.4%–69.1%, 66.1%–73.4%, and 54.1%–58.0%, respectively. According to the ratio of the variable sites and the ratio of informative sites to all sites, ITS sequence had richer variance than 5.8sDNA sequence, and the variance of ITS1 sequence was richer than that of ITS2 sequence. The result of genetic distance analysis revealed that that Miscanthus and Triarrhena were the closest genera to Saccharum, followed by Erianthus and Narenga, and genera Microstegium, Spodiopogon, and Imperata represented the furthest relationships with Saccharum. In the phylogenic tree constructed using neighbor-joining and maximum parsimony methods, the sugarcane related genera and species were separated into 10 groups. Erianthus arundinaceus should be classified into Erianthus genus rather than in Saccharum genus. Triarrhena is likely to be involved in Miscanthus. The 2 species from Narenga were sepearted in different groups, of which N. porphyrocoma was grouped with E. rockii, and N. allax was in an independent group. The Erianthus and Miscanthus species went to different groups, indicating the complex genetic relationships within genera.

This study aimed at guiding fertilizer management for Bt cotton cultivar SCRC28 growing in coastal saline soil in the Yellow River Delta area in Shandong Province, China. SCRC28 was planted in the soils with high, middle, and low salinity under 3 fertilizer treatments, namely control (no fertilizers), NPK, NP, and NK. The effects of different fertilization treatments on nutrient assimilation, Na⁺ assimilation, net photosynthetic rate (P_n), dry matter accumulation, and lint yield of Bt cotton were investigated. Compared to the corresponding controls, the NP and NPK treatments had significantly higher nutrient uptake levels in plants in the 3 types of saline soils, and significantly lower levels of Na⁺ uptake, especially the NPK treatment. The nutrient use efficiencies in agronomy of cotton in the NPK treatment were the highest among treatments regardless the salinity level. The N use efficiencies in agronomy were 0.20, 1.95, and 2.07 kg lint kg⁻¹ under the low, middle, and high salinity level, respectively; the P use efficiencies in agronomy were 0.87, 8.35, and 8.71 kg lint kg⁻¹, respectively; and the K use efficiencies in agronomy were 0.26, 2.89, and 3.77 kg lint kg⁻¹, respectively. The NPK treatment also maintained the highest levels of leaf area, chlorophyll content, and P_n among fertilization treatments in the 3 types of saline soils. The NPK treatment obtained the highest biomass and lint yield among the treatments, and the link yields were enhanced, compared to the corresponding controls, by 2.53%, 28.67%, and 30.47% in the low, middle, and high salinity soils, respectively. The effect of fertilization was obviously in the middle or high salinity fields. In this study, the fertilization quantities were based on the salinity level of soil. The NPK treatments were applied with N 165 kg ha⁻¹ plus P₂O₅ 38.57 kg ha⁻¹ plus K₂O 111.5 kg ha⁻¹ in the middle salinity soil and N 135 kg ha⁻¹ plus P₂O₅ 32.14 kg ha⁻¹ plus K₂O 74.35 kg ha⁻¹ in the high salinity soil. Therefore, rational fertilization schemes are recommended according to the salinity level of soil in order to alleviate nutrition obstacles and improve cotton nutrition, which ultimately result in the increases of nutrient use efficiencies in agronomy and cotton yield.

TT1 gene encodes a WIP domain protein with Zn-finger, which is essential for seed coat development and organ color in Arabidopsis. The mutation of this gene causes transparent testa. The BjTT1 gene was cloned from B. juncea using homology-based cloning and rapid-amplification of cDNA ends (RACE) strategy. A modified allele-specific PCR procedure was developed for assaying single nucleotide polymorphisms (SNP) of the BjTT1 gene. The full length of BjTT1 sequence was 2197 bp with only one intron. The cDNA sequence of BjTT1 was 1412 bp in length including 903 bp of open reading frames. This gene encodes a deduced polypeptide of 300 amino acids with a predicted molecular weight of 33.97 kD and an isoelectric point of 6.99. The genomic sequence of BjTT1 showed 99% and 85% identity with that of BnTT1 and AtTT1, respectively. The reverse transcription-polymerase chain reaction (RT-PCR) analysis showed the expressions of BjTT1 in the seed coats of both black-seeded near-isogenic lines NILA and NILB. Based on sequence comparisons between BjTT1 genes from parents with different seed coat colors and between the NILB mutant and its wide type parent, nucleotide variations at 8 sites inside the BjTT1 coding region were detected, but mutations at these sites had no effect on seed coat color. The allele-specific PCR of BjTT1 could distinguish the yellow-seeded and black-seeded parents.

Thirty-six pairs of polymorphic SRAP markers were used to construct DNA fingerprint of 18 cassava (Manihot esculenta Crantz) varieties. Among the total 320 amplified bands, 235 (73.4%) were polymorphic with an average of 6.5 bands per primer pair. The unweighted pair-group method with arithmetic average (UPGMA) cluster showed 4 major groups at similarity index of 0.734. Two primer combinations, Me1/Em5 and Me24/Em10, had the highest efficiency to distinguish cassava varieties, which were applicable to develop the DNA fingerprints of the 18 cassava varieties. The amplified bands were converted into binary codes with presence (1) and absence (0), and each variety had a unique 18-digital code. The confident probability of the DNA fingerprint was as high as 99.9996%.

Seed dormancy evaluated by germination index (GI) is often regarded as a main and pivotal component of observed genetic variation for pre-harvest sprouting (PHS). Improving seed dormancy can decrease or avoid PHS damage to wheat before harvest. However, it is difficult to accurately evaluate seed dormancy under field conditions. In this study, 4 simple sequence repeat markers (Xbarc57, Xbarc294, Xbarc310, and Xbarc321) on the short arm of chromosome 3A and a gene-based marker (Vp1-b2) on 3BL were used for genotyping 138 micro-core collections of Chinese wheat and landraces. Rich alleles were detected using these markers, and most of them were significantly correlated with GI value. A significant association between the 5 markers and seed dormancy was found according to General Linear Model. Vp1-b2 and Xbarc294 had larger effects on seed dormancy than other markers, which accounted for 65.8% and 61.2% of phenotypic variation, respectively. Combination of the 5 marker gave the largest estimation of GI variation in the 138 wheat genotypes (95.9%), followed by marker combination Vp1-b2/Xbarc294 (89.1%), and marker combination Vp1-b2/Xbarc321 had the smallest effect (79.4%). This result indicated that seed dormancy of tested genotypes was mainly associated with 2 loci on 3AS and 3BL.

The objectives of this study were to disclose the mechanism of dry matter translocation and nitrogen (N) utilization under rice–wheat rotation and to propose optimum rate of N application. In a field experiment from 2007 to 2009 at the Changshu Agroecological Experiment Station, Chinese Academy of Sciences, Changshu, China, 4 levels of N fertilizer were designed during the growing period of rice and wheat. Among the N application treatments, N rates were 125 kg ha⁻¹ + 94 kg ha⁻¹ (rice season + wheat season) for N1, 225 kg ha⁻¹ + 169 kg ha⁻¹ for N2, 325 kg ha⁻¹ + 244 kg ha⁻¹ for N3, and zero N fertilizer applied (NO) served as the control. The results showed no significant increases in rice and wheat yield when the N application rates exceeded 225 kg ha⁻¹ and 169 kg ha⁻¹ in rice and wheat seasons, respectively. The dry matter accumulations at anthesis stages of rice and wheat were increased with the increment of N rate. However, the contributions of dry matter translocation from vegetative organs to grains before flowering were reduced in both crops when more N fertilizer was applied. The N agronomic efficiencies and physiological efficiencies in rice and wheat declined with the increase of N rate, but there was no significant difference between the N2 and N3 treatments. The N1 treatment had the largest average marginal productions for both rice (13.1 kg kg⁻¹) and wheat (17.4 kg kg⁻¹), followed by the N2 treatment (9.1 kg kg⁻¹ for rice and 16.7 kg kg⁻¹ for wheat), and the N3 treatment showed much smaller marginal productions than other treatments with only 3.1 kg kg⁻¹ for rice and 2.4 kg kg⁻¹ for wheat. Therefore, the N2 treatment could maintain relatively high translocation rates of dry matter, N use efficiencies and economic benefits in both rice and wheat.

Changes in microtubule distribution and chromosome behavior in autotetraploid rice during meiosis of pollen mother cell (PMC) were observed in detail using indirect-immunofluorescence laser scanning confocal microscopy. The result showed that microtubule distribution pattern in PMC of the autotetraploid rice was similar to that of the diploid rice during meiosis, but the microtubule behaviors were different, e.g., longer circumferential microtubules and more spindle microtubules in autotetraploid rice. At prophase I, microtubules were decreased in number and distributed unevenly at leptotene. At zygotene, microtubules with unobvious polar distribution formed a diffuse network. At pachytene, nucleolus disintegrated and distorted microtubules structures were found. At diplotene, no circumferential microtubule was found and microtubules depolymerization was observed in advance. At diakinesis, microtubules were decreased in number. Perinuclear microtubules were knitted abnormally. At metaphase I, many abnormalities appeared in spindle. At telophase I, phragmoplast was abnormal, and speckled microtubules were found in the cell. At telophase II-tetra stage, 2 daughter cells did not separate, and microtubules randomly arranged in trifission. These results showed that microtubule abnormal reorganization pattern had a close relationship with abnormal chromosome behavior, which may act synergistically on pollen fertility and seed setting rate of autotetraploid rice.

Gene AhNCED1 plays a vital role in regulation of abscisic acid (ABA) biosynthesis in peanut (Arachis hypogaea L.) plants in response to drought stress. Two binary vectors harboring AhNCED1 gene, p35S::ORF and pAtNCED3p::ORF, were established, which were driven by the CaMV 35S promoter from pCAMBIA1301 and the AtNCED3 gene promoter from wild type Arabidopsis, respectively. Wild type and 129B08/nced3 mutant Arabidopsis plants were separately transformed with Agrobacterium harboring p35S::ORF or pAtNCED3p::ORF vector, resulting in 35S::ORF-WT and A3p::ORF-B08 transgenic plants, accordingly. The stable expression of AhNCED1 gene in Arabidopsis plants was confirmed with duplex reverse transcription PCR (RT-PCR). The wild type, 129B08/nced3 mutant, and the transgenic Arabidopsis plants were subsequently tested for sensitivity to exogenous ABA and tolerance to osmotic stress. The results showed that the ABA sensitivity was declined in the 129B08/nced3 mutant and increased in the Arabidopsis plants ectopically expressing AhNCED1 gene. Under sorbitol stress, the relative germination rate of 129B08/nced3 mutant seeds was far lower than that of the wild type seeds. However, the relative germination rate of A3p::ORF-B08 transgenic seeds was close to that of the wild type seeds, which was significantly higher than that of 129B08/nced3 mutant seeds. The relative germination rate of 35S::ORF-WT transgenic seeds was higher than that of the wild type seeds in the treatment of 300 mmol L⁻¹ sorbitol. When treated with 300 mmol L⁻¹ sorbitol, the leaves of 129B08/nced3 mutant plants were highly chlorotic, and root formation and seedling growth were severely inhibited. In contrast, at this concentration of sorbitol, the leaves of A3p::ORF-B08 transgenic seedlings were only slightly chlorotic, just similar to those of the wild type plants. There was almost no influence on the growth of 35S::ORF-WT transgenic seedlings under the sorbitol treatment. Based on the results of germination assay and phenotypic evaluation, the 129B08/nced3 mutant was hypersensitive to the nonionic osmotic stress induced by sorbitol, and ectopic expression of peanut AhNCED1 gene reverted the hypersensitivity of 129B08/nced3 mutant Arabidopsis to sorbitol and conferred enhanced osmotic stress tolerance in transgenic Arabidopsis plants.