Oilseed flax (LinumusitatissimumL.), an emerging functional cash crop of China
Oilseed flax (Linum usitatissimum L.) is one of the most important oil crops in alpine regions of North and Northwest China, which is an annual herb and belongs to Linaceae family and Linum genus. According to the application, Linum is often divided into three types, production oil, extraction fiber and both for production oil and extraction fiber. With the continuous understanding and development of the nutritional value of oil flax, demand for the oil and other products are increasing. Oilseed flax has increasingly become an important functional cash crop of China. To improve production of oil flax, researches in breeding, germplasm resources, cultivation, soil and fertilization needs to be concerned.
Effect of different film color mulching on dry matter and grain yield of oil flax in dry-land
Mulching can effectively maintain soil moisture; color of mulching film affects soil water storage capacity and further promote crop growth to improve grain yield. Field experiment was conducted to study effects of different film colors on dry matter accumulation (DMA) and grain yield of oil flax. Results showed that white plastic film mulching could increase leaf area, chlorophyll content and DMA. DMA of white film mulching and micro-ridge with soil covering was 53.0% higher than that of CK, and 7.8% higher than that of black film mulching. Mulching method also influenced DMA. Micro-ridge alone increased it by 13.7% than flat cultivation and soil covering improved another 7.6% under white film mulching. Both white and black film mulching with microridge could significantly improve grain yield. Black film mulching with micro-ridge and soil covering, white film mulching with micro-ridge and no soil covering significantly increased capsule number per plant, 1,000-grain weight and grain yield of oil flax, compared with CK. Grain yield increased 29.0% and 28.9% respectively. These results indicated that the above mulching methods were suitable for high yield cropping pattern in dry-farming regions.
Effect of nitrogen and phosphorus application on soil nitrogen morphological characteristics and grain yield of oil flax
In order to identify effects of nitrogen (N) and phosphorus (P) on soil nitrogen morphological characteristics and grain yield of oil flax, a two-factor experiment was conducted in a randomized complete block design in typical semi-arid and hilly-gully area of Loess Plateau with 3 replicates in 2013 and 2014. Two levels of N application included 150 kg/hm2 (N2) and 75 kg/hm2 (N1). P application included 150 kg P2O5/hm2 (P2) and 75 kg P2O5/hm2 (P1). Temporal and spatial variation of soil nitrate nitrogen (NO3-N) and ammonium nitrogen (NH4-N) contents in 0–60 cm soil layer, and relationship between soil NO3-N accumulation (SNA) and grain yield of oil flax were analyzed. Results showed that SNA increased with evaluated N application rate in different soil layers (0–20 cm, 20–40 cm and 40–60 cm). With the increased P application, SNA increased at N1 level but decreased at N2 level. SNA under N2P1 treatment increased by 73.33% in 2013 and 74.97% in 2014 respectively, compared with control treatment (CK) at maturity stage. Grain yield of oil flax also increased by 44.27% in 2013 and 56.55% in 2014, compared with CK under the same treatment. Correlation analysis showed that SNA in different soil layers were respectively positively correlated with grain yield. In conclusion, this research suggested that the optimal fertilizer application rate was 150 kg N/hm2 and 75 kg P2O5/hm2 in the Northwest of China.
Perspective on oil flax yield and dry biomass with reduced nitrogen supply
Field experiment was arranged in a randomized complete block design to determine effects of nitrogen (N) application levels (J0: 150 kg/hm2, J1: 120 kg/hm2, J2: 90 kg/hm2, J3: 60 kg/hm2) on regulating dry biomass accumulation, allocation and translocation, and grain yield of oil flax during 2018 cropping season. Significant promotion was observed in dry matter during accumulation stage of oil flax, when N rate was reduced by 40% (from 150 to 90 kg/hm2). Under J2 treatment, translocation of dry matter from vegetative organs to pod increased by 38.46% and 61.54% respectively, when compared with J1 and J0 treatment. Dry matter distribution proportion of pod at maturity increased 4.47%–7.61%, contribution rate of leaf to grain upgraded 5.09%–8.77%, and number of effective pods and grains per pod increased by 27.16%–45.38% and 6.49%–26.59% respectively compared to other treatments. As a result, seed yield of oil flax under J2 treatment was 2.23%–18.21% higher than those of other treatments. Our study recommended 90 kg/hm2 as the best N fertilizer level to improve seed yield of oil flax.
Dynamic changes of nutrient content in herbaceous peony seed
Herbaceous peony is a promising oilseed crop. ‘Hangshao’ and ‘Fenghuang Niepan’ are two cultivars with high yield and oil content. In this study, seed reserved nutrient of these two genotypes were investigated during seed development process. Results showed that ‘Hangshao’ and ‘Fenghuang Niepan’ matured approximately 85 d after flowering (DAF). The development process could be divided into four stages: seed formation and enlargement stage (S1), seed inclusion and enrichment stage (S2), crude fat rapid accumulation stage (S3) and dehydration and color transition stage (S4). During this process, 100-seed fresh weight (HFW) and 100-seed dry weight (HDW) increased, whereas water content (WC) decreased. HFW, HDW and WC for ‘Hangshao’ seed at 85 DAF were 28.56 g, 20.78 g and 37.50% respectively, whereas those for ‘Fenghuang Niepan’ seed were 27.2 g, 19.78 g, and 30.85% respectively. In terms of the primary metabolites measuring, soluble protein content was consistently low (only 2.24%–3.15%), while starch content was relatively high (5.60%–24.81%). They displayed a trend of gradual increasing in early stage, followed by rapid decline. Crude fat tended to accumulate continuously with a linear upward trend starting at 40 DAF, and its maximum level was reached at 85 DAF (27.57% for ‘Hangshao’ and 29.57% for ‘Fenghuang Niepan’). For the secondary metabolites determination, total phenols content was relatively steady, maintaining at 107.7–129.9 mg/g for both cultivars, while total flavonoids content varied within 25.33–65.33 mg/g for ‘Hangshao’ and 24.33–52.37 mg/g for ‘Fenghuang Niepan’. The maximum level for both cultivars occurred at 55 DAF. Furthermore, crude fat content was found to be highly correlated with WC by correlation analysis and linear regression model definition (P 0.01 and r ¼ 0.954). Thus, WC was recommended for evaluating crude fat in peony seed. These findings could provide scientific reference for high-yielding production practice for oleaginous peony plant.
Identification of candidate gene for resistance to broomrape (Orobanche cumana) in sunflower by BSA-seq
Broomrape (Orobanche cumana) is one of the most important parasitic plants that drastically reduces sunflower yield. The majority of existing resistance varieties have become insufficient for crop protection. Breeding for broomrape resistance is regarded as the most effective and environmentally friendly control measure. In this paper, mapping of a resistance gene for broomrape races E was performed in a recombinant inbred line population by bulk segregate analyses (BSA) combined with genotyping by-sequencing technology. One QTL with resistance candidate genes was mapped on 5 kb interval location from 157,393,001 to 157,850,000 on chromosome 3, the other QTL was located at 5,000 bp interval location from 173,910,001 to 173,915,000 on chromosome 14. Genomic region on candidate interval of chromosome 3 revealed 6 genes with potential resistance for broomrape including transcription factor MYB1R1, Phylloplanin, histone-lysine N-methyltransferase, methylglutaconyl-CoA hydratase, fasciclin-like arabinogalactan protein and fatty acid dehydrogenase. Two resistant genes on candidate interval of chromosome 14 were discovered with potential resistance for broomrape, which were ABC transporter C family member and Ethylene-responsive transcription factor. These precise locations would be valuable for selecting resistant genotypes in future.
Cloning and expression analysis of HXK1 gene from Jatropha curcas L.
HXK (Hexokinase) gene family and the role of JcHXK1 in Jatropha curcas L. were explored. Totally 4 HXK genes JcHXK1, JcHXK2, JcHXK3 and JcHKL1 were identified and complete ORF of JcHXK1 was cloned. Functional domain, phylogenetic evolution and low-temperature expression characteristics were analyzed. Results showed that full-length JcHXK1 cDNA was 1497 bp, encoding 498 amino acids with molecular weight of 53.81 kDa and pI of 5.03. Further phylogenetic evolutionary analysis demonstrated HXK1 protein was clustered into 6 small branches and 2 large branches. Sequence alignment showed that HXK1 contained several conserved glycine residues and hydrophobic channels. Prokaryotic expression vector of JcHXK1 was constructed and 12% SDS-PAGE detection showed that it was highly expressed in E. coli. These research was expected to lay a foundation for further gene functional verification and cold signal transduction mechanism for HXK1 in Jatropha curcas L.
Breeding dominant genic male sterility restorer line of Brassica napus L.
To facilate breeding process of Brassica napus, a microspore culture and molecular marker-assisted screening combined system were proposed in this research. At early flowering stage, F1 offspring of hybridized combination HY15A HF06 was used as donor for microspore culture to analyze effects of colchicine concentration on embryogenic and diploid rates of microspore. Treatment with 50 mg/L colchicine resulted in embryogenic rate of 3.56 embryos/bud, which was substantially higher than control (0.78 embryos/bud). A total of 1,387 embryos and 862 single plants were obtained after induction culture. Ploidy detection was performed for the regenerated plants by flow cytometry. Diploid rates of microspores treated with 50 mg/L and 70 mg/L colchicine were 17.2% and 21.0% respectively, which was significantly higher than control (10.5%). Totally 108 single plants that doubled successfully were randomly selected and screened using molecular marker BE10. Approximately 54 of 108 plants generated a 305 bp amplification product, whereas the other 54 plants showed a 398 bp band, thereby satisfying 1:1 separation ratio (x2 0.05 ¼ 0.0093). These coincided with field identification results. Findings of this study indicated that homozygous breeding material could be obtained by microspore culture in a short time, thereby remarkably accelerate breeding.
Marker gene excision in transgenic Brassica napus via Agrobacterium-mediated Cre/lox transient expression system
Oilseed rape (Brassica napus L.) is one of the most important oil crops in the world. However, study on marker-free transgene of B. napus for bio-safety purpose is limited in this allotetraploid crop. In order to advance marker gene excision research, a newly designed Cre/lox system combining crossing and auto-excision strategy was introduced into B. napus. The system consists of 2 sets of independent vectors including pC35Spro::T7RP carrying T7 RNA polymerase and pCT7pro::Cre carrying T7 promoter respectively. After hybridization of 2 according types of transgenic B. napus, marker gene would be removed as T7 RNA polymerase facilitate T7 promoter to promote Cre gene expression. Totally 52 and 46 positive T0 transgenic lines of these 2 vectors were obtained after identification by PCR and test trip. T1 plants from 3 T0 positive pC35Spro::T7RP lines and 2 T0 positive pC35Spro::T7RP lines were identified as single copy according to segregation ratio and were chosen for crossing. However, expression of CP4 EPSPS (glyphosate resistance gene) and OXY (bromoxynil resistance gene) were not found in F1 progeny, which proved that the excision was not complete. The possible reasons for our limited success were investigated and detailed analyses were performed. Although this system is not applicable for generating transgenic B. napus free from selectable marker gene, it provided valuable experience and clue for further improvement of this technique. Many other advantages and further improvement will be progressed in future work.