Polysaccharide Elicitor from the Endophyte <i>Bionectria</i> sp. Fat6 Improves Growth of Tartary Buckwheat under Drought Stress

Drought can limit the growth and reduce the yield of crops, but the safe and effective bio-approach to improve the drought resistance of crops is very little. We conducted an experiment in which we monitored the effects of polysaccharide from the endophyte Bionectria sp. Fat6 on the growth of Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn) seedlings under control and drought-stressed conditions by determining gas exchange, photosynthesis parameters, photosynthetic pigment contents, and metabolite accumulation. Results indicated that the polysaccharide from endophyte stimulated plant growth and increased the aboveground biomass, root mass, and root/shoot ratio of Tartary buckwheat. Application of the polysaccharide to drought-stressed plants resulted in a significant increase in the net photosynthetic rate, stomatal conductance, and transpiration rate of Tartary buckwheat and decreased the intercellular CO₂ concentration. The contents of chlorophyll a, chlorophyll b, chlorophyll a + b, and carotenoids in leaves were higher in polysaccharide-treated seedlings than that in control. Polysaccharide notably increased the soluble protein and proline content and decreased the malondialdehyde content in Tartary buckwheat leaves. The endophytic polysaccharide may protect Tartary buckwheat against drought by improving leaf gas exchange and photosynthetic capacity, and altering concentrations of protective metabolites. Together, these changes may compensate for the negative impacts of drought stress on the growth of Tartary buckwheat. Thus, the polysaccharide from the endophyte Bionectria sp. Fat6 may be an effective biotic elicitor and a promising bio-approach to improve Tartary buckwheat production worldwide.     

Physiological and Biochemical Mechanisms of Exogenous Calcium Chloride on Alleviating Salt Stress in Two Tartary Buckwheat (<i>Fagopyrum tataricum</i>) Varieties Differing in Salinity Tolerance

Salt stress is one of the most serious abiotic stresses limiting plant growth and development. Calcium as an essential nutrient element and important signaling molecule plays an important role in ameliorating the adverse effect of salinity on plants. This study aimed to investigate the impact of exogenous calcium on improving salt tolerance in Tartary buckwheat cultivars, cv. Xinong9920 (salt-tolerant) and cv. Xinong9909 (salt-sensitive). Four-week-old Tartary buckwheat seedlings under 100 mM NaCl stress were treated with and without exogenous calcium chloride (CaCl₂), Ca²⁺ chelator ethylene glycol tetraacetic acid (EGTA) and Ca²⁺-channel blocker lanthanum chloride (LaCl₃) for 10 days. Then, some important physiological and biochemical indexes were determined. The results showed that salt stress significantly reduced seedling growth, decreased photosynthetic pigments, inhibited antioxidants and antioxidant enzyme activities. However, it increased the reactive oxygen species (ROS) levels in the two Tartary buckwheat cultivars. Exogenous 10 mM CaCl₂ application on salt-stressed Tartary buckwheat seedlings obviously mitigated the negative effects of NaCl stress and partially restored seedlings growth. Ca²⁺-treated salt-stressed seedlings diplayed a suppressed accumulation of ROS, increased the contents of total chlorophyll, soluble protein, proline and antioxidants, and elevated the activities of antioxidant enzymes compared with salt stress alone. On the contrary, the addition of 0.5 mM LaCl₃ and 5 mM EGTA on salt-stressed Tartary buckwheat seedlings exhibited the opposite effects to those with CaCl₂ treatment. These results indicate that exogenous Ca²⁺ can enhance salt stress tolerance and Ca²⁺ supplementation may be an effective practice to cultivate Tartary buckwheat in saline soils.     

The Endosperm-Specific Expression of <i>YUCCA</i> Genes Enhances Rice Grain Filling

Grain filling is a crucial process that affects yield in rice (Oryza sativa L.). Auxin biosynthesis and signaling are closely related to rice yield; therefore, it is important to understand the effects of auxin biosynthesis on rice grain filling to improve crop yield. In this study, we used physiological and molecular strategies to identify the roles of auxin in rice grain filling. Exogenous application of auxin (IAA) or auxin analogues (2, 4-D) to young spikelets and flag leaves improved the seed-setting rate and yield per spike. Furthermore, real-time quantitative PCR assays confirmed that nine members of the OsYUCCA family of auxin biosynthetic genes were upregulated during grain filling, implication that auxin biosynthesis plays a major role in grain development. The specific expression of either Arabidopsis AtYUCCA1 or OsYUCCA2 in the endosperm or leaves resulted in increased expression of OsIAA genes and auxin content of seeds, as well as increased grain filling and seed-setting rate. This result establishes that the auxin content in grains and leaves is important for grain development. Our findings further highlight the potential applications for improving rice yield by elevating targeted gene expression in specific tissues.     

GC-MS Analysis of Metabolites in Filling Grains of Rice-Tartary Buckwheat (<i>Fagopyrum tataricum</i>) in Comparison to Conventional Tartary Buckwheat

Rice-Tartary buckwheat (RTB) is a special germplasm of Tartary buckwheat. In this study, the appraisal of taste quality between RTB and conventional Tartary buckwheat (CTB) was presented, and the metabolites in kernels at three typical grain filling stage (GFS) were investigated. Unlike CTB, RTB showed thin shell seeds without longitudinal furrows at maturity, which was easily artificially dehulled. Sense organ test indicated that RTB exhibited better taste quality because of the higher values of appearance, viscosity, taste and summary were appraised. In total, 92 metabolites were identified in kernels using GM-MS metabolomics platform. The levels of most metabolites changed greatly during grain filling and a large numbers of metabolite-metabolite correlations were found by Pearson correlation coefficient analysis. ANOVA analysis identified 61 differentially expressed metabolites between RTB and CTB, while Venn diagram analysis screened 35 common differential metabolites. Compared with CTB, RTB showed similar levels of lysine and methionine, indicated that RTB own excellent nutritional value. Additionally, RTB exhibited significantly up-regulated levels of most sweeteners (sugars and polyols), which might contribute to better taste. This work provides the first comprehensive metabolomics analysis of kernels between RTB and CTB, which may potentially provide theoretical basis for further research.     

Genotypic differences in Al resistance and the role of cell-wall pectin in Al exclusion from the root apex in Fagopyrum tataricum

Background and Aims

Aluminium (Al) toxicity is one of the factors limiting crop production on acid soils. However, genotypic differences exist among plant species or cultivars in response to Al toxicity. This study aims to investigate genotypic differences among eight cultivars of tatary buckwheat (Fagopyrum tataricum) for Al resistance and explore the possible mechanisms of Al resistance.

Methods

Al resistance was evaluated based on relative root elongation (root elongation with Al/root elongation without Al). Root apex Al content, pectin content and exudation of root organic acids were determined and compared.

Key Results

Genotypic differences among the eight cultivars were correlated with exclusion of Al from the root apex. However, there was a lack of correlation between Al exclusion and Al-induced oxalate secretion. Interestingly, cell-wall pectin content of the root apex was generally lower in Al-resistant cultivars than in Al-sensitive cultivars. Although we were unable to establish a significant correlation between Al exclusion and pectin content among the eight cultivars, a strong correlation could be established among six cultivars, in which the pectin content in the most Al-resistant cultivar ‘Chuan’ was significantly lower than that in the most Al-sensitive cultivar ‘Liuku2’. Furthermore, root apex cell-wall pectin methylesterase activity (PME) was similar in ‘Chuan’ and ‘Liuku2’ in the absence of Al, but Al treatment resulted in increased PME activity in ‘Liuku2’ compared with ‘Chuan’. Immunolocalization of pectins also showed that the two cultivars had similar amounts of either low-methyl-ester pectins or high-methyl-ester pectins in the absence of Al, but Al treatment resulted in a more significant increase of low-methyl-ester pectins and decrease of high-methyl-ester pectins in ‘Liuku2’.

Conclusions

Cell-wall pectin content may contribute, at least in part, to differential Al resistance among tatary buckwheat cultivars.     

播种季节和种植方式对多年生苦荞主要农艺性状的影响

该研究选取六个多年生苦荞新品系,对春季、秋季直播与秋季再生其主要农艺性状进行调查。结果表明:(1)不同播种季节对多年生苦荞新品系主花序的花粉可育率、总结实率、有效结实率、植株株高、主茎粗、主茎分枝数、主茎节数、籽粒百粒重、单株粒数、单株产量的影响均达到显著或极显著水平;秋播主花序花粉可育率、总结实率、有效结实率、植株主茎分枝数、籽粒百粒重、单株粒数、单株产量均极显著高于春播;植株株高、主茎粗、主茎节数均极显著低于春播;主花序花朵大小、籽粒种子长宽比无显著差异。(2)不同种植方式对主花序花粉可育率、有效结实率、植株主茎节数及籽粒百粒重的影响达到显著或极显著水平;秋季再生主花序花粉可育率、籽粒单株粒数显著高于秋季直播;主花序有效结实率、植株主茎粗、主茎节数、籽粒百粒重显著低于秋季直播;主花序花朵大小、总结实率、植株株高、主茎分枝数、籽粒种子长宽比、单株产量无显著差异;相关分析表明,各生长季节下主花序有效结实率及单株粒数与单株产量的相关系数均最高。(3)所有参试品系中,1612-241秋季直播的单株产量显著高于其他品系; 1612-16、1612-33秋季再生单株产量较正季优势显著。该研究结果有助于筛选出适宜一季播种两季收获的优良品系,为今后多年生苦荞的选择育种提供线索基础。     

Effects of High Temperature and Strong Light Combine Stress on Yield and Quality of Early <i>Indica</i> Rice with Different Amylose Content during Grout Filling

High temperature (HT) accompanied with strong light (SL) often occurs in early indica rice production during grout filling stage in southern China, which accelerates grain ripening. Two indica rice cultivars with different amylose content (Zhongjiazao17, ZJZ17, high amylose content; Xiangzaoxian45, XZX45, low amylose content) were grown under control (CK), HT, and HT+SL conditions during grout filling to determine the effects on grain yield and quality of rice. The results showed that compared with CK, HT and HT+SL significantly reduced the 1000-grain weight and filled grain rate whether in high or low amylose content early indica rice cultivars during grout filling, resulting in a significantly lower grain yield. Meanwhile, HT and HT+SL significantly decreased the milled rice rate, brown rice rate and head rice rate, whereas significantly increased chalky rate and chalky degree; and breakdown decreased and setback, pasting temperature increased in the cultivars, leading to the poor processing, appearance and cooking and eating quality of early indica rice cultivars. Compared with HT, the yield of ZJZ17 was significantly decreased under HT+SL, due to the lower 1000-grain weight. However, the effect of HT+SL on rice quality varied in the cultivars. In general, the yield and rice quality of ZJZ17 were relatively poor under HT+SL. Our results suggested that HT and HT+SL during grout filling had significant damage to the yield and quality of early indica rice cultivars, especially HT+SL, while the high amylose cultivar ZJZ17 showed a higher negative effect under HT+SL.     

光周期对苦荞芽菜生长与品质的影响

苦荞(Fagopyrum tataricum)芽菜是一种新兴健康食品,该研究通过不同光周期(0、4、8、12、16和20 h·d~(-1))处理苦荞芽菜,测定其生物量、叶绿素和主要营养成分的含量以及黄酮合成相关基因的表达水平,以明确不同光周期对苦荞芽菜品质的影响机理。结果表明:(1)随着苦荞芽菜生长时间的增加,芽菜生物量总体呈上升趋势,16 h·d~(-1)光周期时芽菜生长状态最好,鲜重最大。(2)不同光周期对苦荞芽菜各营养成分含量的影响有所差异,可溶性糖含量在芽菜萌发第2天开始逐渐下降,10 d后含量仅为第2天的13.5%～14.5%;花青素含量在芽菜萌发第2天光周期为12 h·d~(-1)时最高(2.16 mg/g),不同光周期处理4～10 d后均显示出降低趋势;芦丁是苦荞芽菜中主要的黄酮类化合物,芦丁含量在不同光周期处理后有所变化且适当的光照有利于其合成和积累,并在处理第4天光周期为16 h·d~(-1)时含量最高(59.60 mg/g)。(3)qRT-PCR分析表明,不同光周期处理的苦荞芽菜中各黄酮合成相关基因的表达量在第2天最高,随生长周期其表达量均不同程度降低,但黄酮醇合成支路关键酶基因FtFLS1和花青素支路基因FtDFR2表达量上升、且显示出强烈的光诱导特征。研究发现,光周期对苦荞芽菜的生物量影响较大,黑暗有利于胚轴伸长,长光周期(16 h·d~(-1))有利于鲜重的增加;在苦荞萌发过程中,苦荞芽菜可溶性糖、花青素和芦丁含量整体呈减少趋势,可溶性糖和花青素含量均在光周期16 h·d~(-1)处理第2天时最高,芦丁含量在光周期为16 h·d~(-1)处理第4天时最高,建议苦荞芽菜在光周期为16 h·d~(-1)生长4 d时采食。     

<i>In vitro</i> Evaluation of Seed Germination in Twelve Alfalfa Cultivars under Salt Stress

Alfalfa (Medicago sativa L.), when exposed to abiotic stress such as salinity, suffers significant losses in yield and productivity. The present study evaluated the salinity tolerance of 12 alfalfa cultivars in vitro using five concentrations of sodium chloride (NaCl), ranging from 0 to 250 mmol L⁻¹ . The results obtained in the current study revealed that the Saudi cultivars, Kasimi and Hassawi, and the German cultivar (Berlin) had the highest salinity tolerance in terms of germination percentage (GP), corrected germination rate index (CGRI), days to reach 50% germination (GT50), and ability to form cotyledonary and true leaves. Under mmol L⁻¹ NaCl, the Saudi cultivar Kasimi cultivar showed GP, CGRI, and GT50 of 55.20%, 123.15, and 3.77 days, respectively. Similarly, the German cultivar (Berlin) showed GP, CGRI, and GT50 of 50.06%, 86.61, and 5.17 days, respectively. These findings might reveal a pivotal aspect in salt tolerance in alfalfa. Our results will help to select salt-tolerant alfalfa cultivars that could thrive in arid and semi-arid areas with salinity problems.     

Assessing allometric models to predict vegetative growth of mango (Mangifera indica; Anacardiaceae) at the current-year branch scale

? Premise of the study: Accurate and reliable predictive models are necessary to estimate nondestructively key variables for plant growth studies such as leaf area and leaf, stem, and total biomass. Predictive models are lacking at the current-year branch scale despite the importance of this scale in plant science. ? Methods: We calibrated allometric models to estimate leaf area and stem and branch (leaves + stem) mass of current-year branches, i.e., branches several months old studied at the end of the vegetative growth season, of four mango cultivars on the basis of their basal cross-sectional area. The effects of year, site, and cultivar were tested. Models were validated with independent data and prediction accuracy was evaluated with the appropriate statistics. ? Key results: Models revealed a positive allometry between dependent and independent variables, whose y-intercept but not the slope, was affected by the cultivar. The effects of year and site were negligible. For each branch characteristic, cultivar-specific models were more accurate than common models built with pooled data from the four cultivars. Prediction quality was satisfactory but with data dispersion around the models, particularly for large values. ? Conclusions: Leaf area and stem and branch mass of mango current-year branches could be satisfactorily estimated on the basis of branch basal cross-sectional area with cultivar-specific allometric models. The results suggested that, in addition to the heteroscedastic behavior of the variables studied, model accuracy was probably related to the functional plasticity of branches in relation to the light environment and/or to the number of growth units composing the branches.     

Sources of Nitrogen in Combination with Systems of Irrigation Influence the Productivity of Modern Rice (<i>Oryza sativa</i> L.) Cultivars during Dry Season in Sub-Tropical Environment

In irrigated agricultural systems, nitrogen (N) and water are the vital resources for sustainability of the crop production in the modern era of climate change. The current study aimed to assess the impact of water and N management on the productivity of irrigated rice cultivars. In the context, a field observation was done at the research farm of Bangladesh Agricultural University, Mymensingh, during dry seasons in consecutive two years (2018–2019 and 2019–2020). The experiments were set up following split-plot design assigning water management in the main plots, nitrogen management in the sub-plots, and the cultivars were approved in the split-split plot with three replications. After two years observation, it was revealed that rice cultivar Binadhan-8 gave the maximum value of leaf area index, number effective tillers hill^-1 and grains panicle^-1 which lead to the higher grain yield (GY). Substantial relationships were observed among the concentration of N, growth, total dry matter (TDM) and N content, N uptake, N utilization effectiveness, and GY. However, with little exception, the Combined effect of water and N, cultivars and water management were varied significantly for all parameters. Finally, the results of the current study concluded that application of irrigation at 8 days after the disappearance of ponded water and source of 105 kg N ha^-1 from PU + Poultry manure are the best management approach for the excellent performance of rice cultivar Binadhan-8.     

Intraspecific responses of <Emphasis Type="Italic">Fagopyrum esculentum</Emphasis> to enhanced ultraviolet B radiation

The effects of supplemental UV-B radiation on crop growth, morphology, reproduction and physiology were studied in three cultivars of Fagopyrum esculentum Moench (buckwheat) originating from high elevation (Qinghai-Tibet plateau) and lower altitudes (The Sichuan Basin). Our results showed that common buckwheat was sensitive to UV-B stress. Plant growth, development, and reproduction were inhibited by elevated UV-B radiation. Plant lipid oxidation and polyphenol oxidase (PPO) activity increased with increasing UV-B radiation, along with the concentration of phenylpropanoid compounds, superoxide dismutase (SOD) activity and ascorbic acid (Asa) concentration were also enhanced at the lowest level of supplemental UV-B radiation but decreased at the higher level of enhanced UV-B. While, a cultivar originating from elevated locations had lower dry matter accumulation and was more tolerant to UV-B radiation than cultivars originating from lower elevations. The effects on leaf thickness and increased antioxidant capacity could be linked with the improved performance of cultivar originating from high elevation when exposed to enhanced UV-B radiation. We conclude that UV-B tolerance should be considered prior to introducing or breeding common buckwheat cultivars from lowland cultivation to regions at high elevation such as the Qinghai-Tibet plateau.     

Improved Tolerance of Three Saudi Pearl Millet Cultivars (<i>Pennisetum spicatum</i>) to Salt Stress by Mycorrhiza

Seeds of three Saudi pearl millet cultivars (Pennisetum spicatum) from three regions (Madinah, Khulais and Jaizan) were inoculated with arbuscular mycorrhizal fungus Glomus mosseae obtained from the Agriculture Research Center of Giza, Egypt to enhance their salt tolerance. Five different NaCl concentrations (0, 30, 60, 90, and 120 mM) were used for treating cultivars with and without mycorrhiza. Growth rates, chlorophyll content, chlorophyll fluorescence (Fv/Fm), proline content and gas exchange were measured to determine the effect of salinity on these cultivars. The results indicated that compared to cultivars without mycorrhiza, all cultivars with mycorrhiza had enhanced growth and physiological parameters including shoot and root length, area and number of leaves, fresh and dry weights of shoots and roots, chlorophyll contents and gas exchanges at 0 and 30 mM of salinity. In addition, the measurements of the different growth rates showed higher growth performance of the cultivars from Madinah and Khulais than the cultivar from Jaizan. However, all cultivars with and without mycorrhiza showed significant reductions in growth rates, chlorophyll contents and gas exchanges at a salinity of 60 mM than those grown at 0 and 30 mM. Moreover, the values of Fv/Fm were significantly reduced in all cultivars with and without mycorrhiza grown at 60 mM than in those grown at 0 mM and 30 mM. Proline contents indicated a progressive increase with the elevation of NaCl concentration stress. The proline contents in the mycorrhiza-inoculated cultivars were significantly higher than those in the non-inoculated cultivars. On the other hand, all cultivars with and without mycorrhiza underwent senescence within four weeks of growth at salinity concentrations of 90 mM and 120 mM. Therefore, relatively low salinity must be maintained to achieve high growth rates and gas exchanges of these inoculated cultivars.     

Performance of Soft Rice (<i>Oryza sativa L</i>.) Grown in Early Season in China

Eating quality is of paramount importance to rice (Oryza sativa L.) consumers and soft rice with low amylose content has become popular in China. This study was conducted to evaluate the performance of soft rice grown in the early season (ES) dominated by non-soft rice. Field experiments were conducted in Yongan and Santang, Hunan Province, China from 2016-2018. Results showed that grain amylose content in soft rice cultivars was consistently lower in the ES compared to the late season (LS). The lower grain amylose content in the ES compared to the LS was partly attributed to higher average daily mean temperature during grain filling. No significant relationship was observed between grain yield and seed amylose content in ES rice. Soft rice cultivars produced a similar average grain yield to non-soft rice cultivars in the ES. These results encourage breeders to develop more ES rice cultivars with soft texture to meet the consumer demand for this type of rice.     

Rice (<i>Oryza sativa</i> L.) Breeding among Hassawi Landrace and Egyptian Genotypes for Stem Borer (<i>Chilo agamemnon</i> Bles.) Resistance and Related Quantitative Traits

Rice stem borer (Chilo agamemnon Bles.) is a primary insect pest of rice and is a major limiting factor to rice production. Breeding for insect-resistant crop varieties has been an economic way of integrated pest management (IPM) as it offers a viable and ecologically acceptable approach. This study was aimed to evaluate rice genotypes for their resistance against rice stem borer. Seven parental genotypes with twenty one F1 crosses were evaluated for genotypic variation in field experiments. Analysis of variance revealed significant differences for the studied traits in almost all crosses and parents. In addition, the mean squares of parents versus their crosses were signifi- cant for stem borer resistance and other associated traits. Moreover, both general combining ability (GCA) and specific combining ability (SCA) variances were highly significant for all characters studied in the F1 generation. Based on GCA, 4 genotypes (Sakha101, Gz6903-3-4-2-1, Gz9577-4-1-1 and Hassawi) exhibited highly significant negative values for stem borer resistance (–0.53, –1.06, –0.18 and –0.49, respectively) indicating they are the best combiners for stem borer resistance. Based on SCA analysis, nine cross combinations showed highly significant negative effects for stem borer resistance. Similarly, the cross Giza178 Hassawi was the best combination with significantly highest value for early maturity. In addition, seven crosses showed highly significant negative SCA for plant height trait. On the other hand, for panicle length, number of primary branches/panicle, panicle weight and 1000-grain weight, seven, four, eight and six crosses showed highly significant positive SCA, respectively. The result further revealed that the non-additive dominance genetic variance was higher than the additive variance for all evaluated traits indicating that non-additive genetic variances have a role in their inheritance. The broad-sense heritability estimates were high for all the studied traits. The stem borer resistance was significantly correlated with panicle weight and 1000-grain weight, which also showed a highly significant correlation with grain yield/plant. Thus these traits can be effectively employed in a breeding program to confer resistance against stem borer infestation in rice. It was further supported by biplot analysis, which clustered these potentially important traits into two quadrants showing their importance in any future breeding program to control stem borer infestation. This study has contributed valuable information for evaluation of genetic diversity in the local rice germplasm and its utilization in futuristic rice genetic improvement programs.     

苦荞种质主要农艺性状的变异及其对单株粒重的贡献研究

对180份苦荞种质资源的8个主要农艺性状进行了评价,并对单株粒重与其他7个农艺性状之间进行了相关性分析和通径分析。结果显示,主要农艺性状的变异系数为8.10%~39.40%;简单相关分析表明,单株粒重与单株粒数、主茎分支数呈极显著正相关;偏相关分析表明,单株粒重与单株粒数、千粒重呈极显著正相关;多元回归和通径分析均表明,单株粒数、千粒重是影响单株粒重的主要因素,其中单株粒数影响最大。系统聚类分析表明,180份苦荞种质资源可划分为5类,其中第Ⅲ类(包括47份供试材料)的综合农艺性状较好,主要表现为主茎分枝能力强、单株粒数多、单株粒重和单株米粒重高,可作为优异基因资源进一步开发利用,也为以增加单株米粒重与出米率为选育目标的苦荞薄壳育种提供依据。     

High-quality Fagopyrum esculentum genome provides insights into the flavonoid accumulation among different tissues and self-incompatibility

Common buckwheat (Fagopyrum esculentum) and Tartary buckwheat (Fagopyrum tataricum), the two most widely cultivated buckwheat species, differ greatly in flavonoid content and reproductive mode. Here, we report the first high-quality and chromosome-level genome assembly of common buckwheat with 1.2 Gb. Comparative genomic analysis revealed that common buckwheat underwent a burst of long terminal repeat retrotransposons insertion accompanied by numerous large chromosome rearrangements after divergence from Tartary buckwheat. Moreover, multiple gene families involved in stress tolerance and flavonoid biosynthesis such as multidrug and toxic compound extrusion (MATE) and chalcone synthase (CHS) underwent significant expansion in buckwheat, especially in common buckwheat. Integrated multi-omics analysis identified high expression of catechin biosynthesis-related genes in flower and seed in common buckwheat and high expression of rutin biosynthesis-related genes in seed in Tartary buckwheat as being important for the differences in flavonoid type and content between these buckwheat species. We also identified a candidate key rutin-degrading enzyme gene (Ft8.2377) that was highly expressed in Tartary buckwheat seed. In addition, we identified a haplotype-resolved candidate locus containing many genes reportedly associated with the development of flower and pollen, which was potentially related to self-incompatibility in common buckwheat. Our study provides important resources facilitating future functional genomics-related research of flavonoid biosynthesis and self-incompatibility in buckwheat.     

Combination of 6-Benzylaminopurine and Thidiazuron Promotes Highly Efficient Shoot Regeneration from Cotyledonary Node of Mature Peanut (<i>Arachis hypogaea</i> L.) Cultivars

Efficient in vitro plantlet regeneration is an important step to successfully transform genes for the improvement of agronomic traits. A combination of 6-benzylaminopurine (BAP) and thidiazuron (TDZ) plant growth regulators was applied to evaluate shoot regeneration capacity whereas α-naphthalene acetic acid (NAA) combination with 6-benzylaminopurine (BAP), and 2, 4-dichlorophenoxyacetic acid (2, 4-D) with 6-benzylaminopurine were tested to optimize root induction for two peanut cultivars. The result showed combination (BAP with TDZ) was found to be effective in promoting shoot. The highest shoot regeneration frequency (93%) was obtained on a medium supplemented with 4 mg/L BAP and 0.5 mg/L TDZ while an average regeneration frequency (87%) was achieved in a medium containing combinations of 2 mg/L BAP with 1 mg/L TDZ. The shooting rate increased for both cultivars as the concentrations of BAP increased and TDZ decreased. The highest rooting rate (93%) was obtained on a medium supplemented with 3.5 mg/L NAA with 2.5 mg/L BAP for both cultivars. The rooting rate increased as the concentration of auxin to cytokinin ratio increased. The maximum rooting rate (83%) was obtained on MS medium supplemented with 0.3 mg/L 2, 4-D with 0.2 mg/L BAP for the cultivar N3. The result indicated that BAP with NAA was much better than BAP with 2, 4-D in rooting rate. Thus, the protocol developed was genotype independent and effective for peanut tissue culture.