Grain Yield, Quality and 2-Acetyl-1-Pyrroline of Fragrant Rice in Response to Different Planting Seasons in South China

Climate conditions is an important factor affected the fragrant rice growth and development.In order to study the effects of different planting seasons on fragrant rice performance in South China,present study was conducted with three planting seasons(early season(April to July),middle season(June to September)and late season(August to November))and three fragrant rice cultivars,‘Basmati-385’,‘Meixiangzhan-2’and‘Xiangyaxiangzhan’.The results showed that the highest grain yield and grain 2-acetyl-1-pyrroline(2-AP,key component of fragrant rice aroma)content were both recorded in late season treatment while the fragrant rice in middle season treatment produced the lowest grain yield,grain filling percentage,1000-grain weight and gain 2-AP content.The highest contents of precursors(proline,pyrroline-5-carboxylic acid and 1-pyrro-line)which related to 2-AP biosynthesis were recorded in late season treatment compared with early season treatment and middle season treatment.The highest activities of enzymes(proline dehydrogenase,pyrroline-5-carboxylic acid synthetase and ornithine transaminase)which involved in 2-AP biosynthesis were also observed in late season treatment.Moreover,the fragrant rice cultivars in late season possessed the lowest chalk rice rate,chalkiness as well as the highest brown rice rate,head rice and protein content.Thus,the optimal season for fragrant rice production in South China is the late season.

Epoxiconazole Improved Photosynthesis,Yield Formation,Grain Quality and 2-Acetyl-1-Pyrroline Biosynthesis of Fragrant Rice

Epoxiconazole is a triazole compound.However,the effects of epoxiconazole on crop productivity and quality were rarely reported.In this study,we investigated the effects of epoxiconazole application on yield formation,grain quality attributes,and 2-acetyl-1-pyrroline(2-AP)content in fragrant rice.A three-year field experiment was carried out with a fragrant rice variety,Meixiangzhan 2.At the heading stage,0,0.02,0.04,0.08,0.16 and 0.32 g/L epoxiconazole solutions were foliar applied to fragrant rice plants,respectively.The results showed that epoxiconazole application significantly increased grain yield,seed-setting rate and 1000-grain weight.Chlorophyll content and net photosynthetic rate of fragrant rice during the grain-filling stage significantly increased due to epoxiconazole application.Foliar application of epoxiconazole at 0.08 g/L increased grain protein content and decreased both chalky rice rate and chalkiness area ratio of fragrant rice.Epoxiconazole also substantially increased grain 2-AP content by inducing the regulation in contents of related synthetic precursors,including proline,pyrroline-5-carboxylic acid,Δ1-pyrroline and methylglyoxal.Overall,foliar application of epoxiconazole could be used for the improvement in grain yield,grain quality and 2-AP content in fragrant rice production when applied concentration at 0.08-0.32 g/L.Our findings provided the new roles of epoxiconazole in crop production.

Effects of Different Vermicompost Rates on Growth,2-Acetyl-1-Pyrroline,Photosynthesis and Antioxidant Responses of Fragrant Rice(Oryza sativa L.)Seedling

Vermicompost is an organic fertilizer contains multiple nutrient elements.However,the application of vermicompost in fragrant rice production is rarely reported.In order to study the effects of vermicompost application on fragrant rice(Oryza sativa L.)seedling performances,present study was conducted with two fragrant rice cultivars and four vermicompost rate treatments(0(CK),2.5(Wo1),5.0(Wo2)and 10.0(Wo3)g kg−1).The results showed that vermicompost treatments significantly increased dry weight of fragrant rice seedling by 8.31–32.56%compared with CK.21.10–59.13%higher net photosynthetic rates and 10.66–59.16%higher chlorophyll contents(chlorophyll a,chlorophyll b and total chlorophyll)were recorded in vermicompost treatments than CK.Application of vermicompost also significantly increased 2-acetyl-1-pyrroline(2-AP,the key compound of fragrant rice aroma)content and reduced the transcript level of gene BADH2 which related to 2-AP biosynthesis in fragrant rice seedling.Moreover,compared with CK,vermicompost treatments enhanced activities of superoxide dismutase,peroxidase,catalase by 24.42–28.66%,24.98–25.73%and 22.45–23.57%,respectively.11.54–40.53%lower malonaldehyde contents were recorded in vermicompost treatments in related to CK.In conclusion,vermicompost improved growth,increased 2-AP content and might enhance stress resistant of fragrant rice seedling.

Effects of Exogenousα-Ketoglutaric Acid on 2-Acetyl-1-Pyrroline,Yield Formation and Grain Quality Characters of Aromatic Rice

The improvement of grain quality in aromatic rice is very important for farmer to increase their income.Present study was conducted with a two-year field experiment and three aromatic rice cultivars in order to study the effects of exogenousα-ketoglutaric acid on yield formation,grain quality characters and the biosynthesis of 2-acetyl-1-pyrroline(2-AP,key component of aromatic rice’s fragrance)in aromatic rice.At heading stage,0.50 mmol L^(-1)(T1)and 1.00 mmol L^(-1)(T2)α-ketoglutaric acid solutions were overhead sprinkle to aromatic rice plants,respectively while the treatment which was overhead sprinkled with distilled water was set as control(CK).The results showed that 17.34%-33.04%and 21.39%-34.74%higher grain 2-AP contents were recorded in T1 and T2 treatments,respectively.Compared with CK,T1 and T2 treatments significantly reduced the transcript level of gene BADH2 which is related to the 2-AP biosynthesis in aromatic rice.3.86%-7.51%higher grain protein contents and 1.15%-3.37%higher head rice rates were also recorded inα-ketoglutaric acid treatments than CK.Moreover,T1 and T2 treatments remarkably decreased the chalky rice rate,chalkiness and grain amylose content.However,there was no remarkable difference in grain yield and related trails(effective panicle number,grain number per panicle,seed-setting rate and 1000-grain weight)among CK,T1 and T2 treatments.In conclusion,application of exogenousα-ketoglutaric acid enhanced 2-AP biosynthesis and improved grain quality of aromatic rice.

Enhancement of Ultrasonic Seed Treatment on Yield,Grain Quality Characters,and 2-Acetyl-1-Pyrroline Biosynthesis in Different Fragrant Rice Genotypes

Fragrant rice is popular for the good grain quality and special aroma.The present study conducted a field experiment to investigate the effects of ultrasonic seed treatment on grain yield,quality characters,physiological properties and aroma biosynthesis of different fragrant rice genotypes.The seeds of three fragrant rice genotypes were exposed to 1 min of ultrasonic vibration and then cultivated in paddy field.The results of present study showed that ultrasonic seed treatment increased grain yield of all fragrant rice genotypes but the responses of yield formation to ultrasonic were varied with different genotypes.Compared with control,ultrasonic seed treatment increased grain 2-acetyl-1-pyrroline(2-AP,the key component of fragrant rice aroma)content by 13.40%–44.88%.Ultrasonic seed treatment also reduced the crude protein contents in grains.The head rice rate,rice length,chalky rice rate,and chalkiness degree were influenced by ultrasonic for one or two fragrant rice genotypes.The activities of peroxidase and superoxide dismutase were also enhanced due to ultrasonic seed treatment.In conclusion,ultrasonic seed treatment increased grain,regulated grain aroma and quality,and improved stress resistance of fragrant rice varieties.

Comparison of 2-Acetyl-1-Pyrroline (2AP) in Rice Leaf at Different Growth Stages Using Gas Chromatography

Aromatic rice lines were examined for 2-Acetyl-1-Pyrroline (2AP) content in leaf tissue at five different growth stages (tillering, panicle initiation, 50% heading, booting, and maturity). A small plot trial with plot size of 1.42 m × 4.88 m (7 row-plots) was arranged in completely randomize design with three replications. Dry-seeded, delayed flood cultural practice was used in this study. The experiment was conducted at three locations. The average 2AP concentrations in leaf tissue at tillering stages were higher than the other four growth stages. 2AP levels were declined when rice plant reached booting. AP levels decreased slightly at heading stage and decreased significantly at maturity. There was no significant different between 2AP in leaf at 50% heading from three locations as well as the 2AP content in rice grain. Correlations between 2AP in leaf and 2AP in grain were significantly in all five growth stages. The highest correlation coefficient was found between 2AP in leaf at booting and grain (r = 0.811**) and lowest was in the leaf at harvest (r = 0.564**). Results indicated that 2AP could be determined in leaf tissue at early growth stage.

Enriching Iodine and Regulating Grain Aroma,Appearance Quality,and Yield in Aromatic Rice by Foliar Application of Sodium Iodide

Applying iodine fertilizers to cultivate iodine-rich crops for daily intake is an effective approach for iodine supplementation,especially for aromatic rice.Field experiments were conducted during the early growing seasons of 2021 and 2022 to evaluate the impacts of foliar application of iodine fertilizer on aromatic rice and to explore the optimal iodine fertilizer concentration.At the full heading stage,six different concentrations of sodium iodide solutions of 0%(CK),0.010%(T1),0.025%(T2),0.050%(T3),0.075%(T4),and 0.100%(T5)were applied to indica aromatic rice cultivars Meixiangzhan 2 and Xiangyaxiangzhan.The results showed that sodium iodide treatments significantly increased the iodine and sodium contents in both leaves and grains.Compared with the CK,the T1 and T2 treatments increased the 2-acetyl-1-pyrroline(2-AP)content in mature grains by 8.41%-101.66%and 13.58%-74.60%,respectively.Improvements in the contents of 1-pyrroline-5-carboxylic acid,proline,1-pyrroline,and methylglyoxal,as well as the activity of proline dehydrogenase were also detected.Additionally,sodium iodide treatments remarkably decreased the chalky grain rate,chalkiness area,and chalkiness degree of aromatic rice,with the T2 treatment exhibiting a 17.79%-47.42%decrease in chalkiness degree compared with the CK.Meanwhile,T1 and T2 treatments showed beneficial impacts on chlorophyll content,photosynthetic characteristics,and yield components,while T3,T4,and T5 treatments exhibited adverse effects on leaf and grain yields.The linear discriminant analysis revealed significant differences between treatments.The correlation analysis and piecewise structural equation modeling showed that the iodine and sodium influenced the photosynthetic characteristics and chlorophyll content of the leaves,thereby regulating the 2-AP biosynthesis and yield components,ultimately affecting the 2-AP content and yield.Overall,this study suggests that foliar application of 0.025%sodium iodide is an effective method to enrich the iodine content in rice grains,improve the grain aroma and appearance quality of aromatic rice,without detrimental effects on grain yield.

Abiotic and Biotic Factors Controlling Grain Aroma along Value Chain of Fragrant Rice:A Review

The aroma of fragrant rice is one of the grain quality attributes that significantly influenceconsumer preferences and prices in world markets. The volatile compound 2-acetyl-1-pyrroline (2AP) isrecognized as a key component of the aroma in fragrant rice. The variation in grain 2AP content amongvarious fragrant rice varieties is associated with the expression of the badh2 gene, with 19 alleles havingbeen identified so far. The grain 2AP content is strongly influenced by environmental and managementfactors during cultivation as well as post-harvest conditions. This review pinpointed the major abiotic andbiotic factors that control grain 2AP content. Abiotic factors refer to water, temperature, light quality,fertilizer application (both macro- and micro-nutrients), and soil properties, including salinity, while bioticfactors include microorganisms that produce aromatic compounds, thus influencing the grain aroma infragrant rice. Post-harvest management, including storage and drying conditions, can significantly impactthe grain 2AP content, and proper post-harvest conditions can intensify the grain aroma. This reviewsuggests that there are rice varieties that can serve as potential sources of genetic material for breedingrice varieties with high grain aroma content. It offers an overview of recent research on the major factorsaffecting the aroma content in fragrant rice. This knowledge will facilitate further research on theproduction of high-quality rice to meet the demands of farmers and consumers.

Sensory Phenotypic and Molecular Identification of Aromatic Rice Accessions Cultivated in Benin

Rice is one of the most widely cultivated cereals in the world, and its aroma is increasingly in demand. With the advancement of research, a major rice flavor gene has been identified on rice chromosome 8. It encodes non-functional betaine aldehyde dehydrogenase leading to the accumulation of 2-acetyl-1-pyrroline which is the major olfactory compound that confers the fragrant character to rice. The aroma of rice is considered a special trait of enormous economic importance that determines the prime price in world trade. To satisfy the needs of the population and reduce rice imports into Benin, we conducted this study to identify aromatic rice accessions grown in Benin. Seventy-two rice accessions collected across Benin were PCR amplified with three SSR markers RM 7049, Aro 7, and RM 223, linked to the fgr (fragrance of rice) aroma gene. Molecular analysis revealed that 12 of the 72 accessions, namely Bagou 19, Bagou 22, Tchaka 34, Foun 15, Tchaka 41, Nana 32, Kan 61, Kung 69, Kung 67, Bagou 20, Agbab 101 and Koum 55 possess the fgr gene and can be considered as aromatic rice accessions. A sensory phenotypic test using KOH was carried out on rice accessions carrying fgr gene. Of the twelve positives, only one had the smell of aromatic rice, like the Azucena control. These results show that Benin also has aromatic rice varieties that can be sold on national and international markets.

Germplasm Resources,Genes and Perspective for Aromatic Rice

Aromatic rice is considered an important commodity in the global market because of its strong aroma and eating and cooking quality.Asian countries,such as India and Pakistan,are the leading traders of Basmati rice,whereas Thailand is the major supplier of Jasmine rice in the international market.The strong aroma of rice is associated with more than 300 volatile compounds,among which 2-acetyl-1-pyrroline(2-AP)is the principal component.2-AP is a phenotypic expression of spontaneous mutations in the recessive gene OsBadh2 or Badh2.The present review focuses on the origin,evolution and diversity of genetic resources of aromatic rice available worldwide.A brief discussion is presented on the genes responsible for quality traits along with details of their molecular genetics.This compilation and discussion will be useful for future breeding programs and the biofortification of quality traits of aromatic rice to ensure food security and nutritional need.

Studies on Flavonoids ⅩⅩ——A Novel Synthesis of β-Naphthaflavanones From 1-Acetyl-2-naphthol

1-Acetyl-2-naphthol was treated with aromatic aldehydes in the presence of piperidine for the preparation of the hydroxynaphthachalcones. However, the experimental result showed that the expected product was not formed, but the β-naphthaflavanones were obtained instead. The synthesis of β-naphthaflavanones from β-naphtholethanone directly using piperidine as catalyst has not been reported so far.

Rice Aroma: A Natural Gift Comes with Price and the Way Forward

Aromatic rice belongs to a small but important sub-group of rice,which is highly regarded for its excellent aroma and superior grain quality.Aromatic rice,especially Basmati-and Jasmine-type rice,is being traded at a high price in the local and global markets.Genetically,rice aroma is a phenotypical expression of spontaneous recessive mutations of the OsBadh2 gene(also known as fgr/badh2/osbadh2/os2AP gene).These mutations inhibit the flow ofγ-aminobutyraldehyde(GAB-ald)toγ-aminobutyric acid(GABA),and consequently,the accumulated GAB-ald is diverted to a potent flavour component 2-acetyl-1-pyrroline(2AP)by a non-enzymatic reaction with methylglyoxal.The natural incidence of non-functional osbadh2 mutation along with selection and nursing by the farmer from the ancient time makes rice aroma as a prominent natural gift.As GABA and methylglyoxal play significant roles in stress tolerance,and their biosynthesis is strictly regulated in rice plants,the accumulation of 2AP in aromatic rice depends on the interaction of various genetic and environmental factors,and its production may come at some costs of sacrificing tolerance.This review focused on some potential underlying genes in the 2AP and GABA biosynthesis pathways,and analyzed most aspects of aroma formation in rice,and summarized the molecular mechanism of aroma production together with its genetic and non-genetic influencing factors.The present review also stated approaches to produce high-quality aromatic rice via developing novel cultivars and with good agronomic knowledge-based practice.

Composition and Development Prospects of Scented Rice

Containing higher aromatic composition,scented rice is better than ordinary rice varieties in taste and nutrition. Major composition of scented rice is 2-acetyl-1-pyrroline( 2-AP). Different scented rice varieties have different content of 2-AP. The content of 2-AP is not only influenced by genetic factors,but also closely connected with types and content of nutrition elements in soil,soil moisture management,environmental temperature,and storage. 2-AP synthesis and regulation are possibly connected with Proline and enzyme.

Establishment and application of an accurate identification method for fragrant soybeans

In order to screen the aroma characteristics of soybean,a new method was established which can quickly quantify the content of 2-acetyl-1pyrroline(2-AP),an important compound related to soybean aroma,using gas chromatography-mass spectrometry(GC-MS).Based on peak profile,total peak area and retention time as test indexes,an accurate identification method for fragrant soybeans was established.The optimum parameters of the protocol consisted of column temperature70℃,sample injector temperature 180℃,optimum extraction alcohol content 1 m L,Na Cl content 0.1 g,ultrasonication time10 min,and extraction time 1 h,which were established by using the orthogonal test of single factors and three factors with four levels(L_9(3)^4).2-AP content of leaves had significant correlations with seeds,which were easier to measure.The protocol was simple and easy to carry out,consumed only small amounts of reagents,and provided accurate and reliable results with good reproducibility.A total of 101 soybean genotypes from different geographical sources were analyzed using this protocol.The results showed that the average content of 2-AP was 0.29 mg L^(–1),ranging from 0.094 to 1.816 mg L^(–1),and the genetic diversity index was 0.54.Among all genotypes-tested,they were classified into three grades,including seven elite genotypes identified as"grade one fragrant soybeans",which were Zhonglong 608,Heinong 88,Ha13-2958,Hongmiandou,Heinong 82,Huangmaodou,and Jiyu 21.These results provide both an identification technique and several elite aroma genotypes for gene discovery and good quality breeding in soybean.

Creation of aromatic maize by CRISPR/Cas

Aroma is an important quality parameter for breeding in rice(Oryza sativa).For example,the aromatic rice varieties basmati and jasmine rice,with a popcorn-like scent,are popular worldwide and routinely command a price premium.2-acetyl-1-pyrroline(2AP)is a key flavor compound among over 200 volatiles identified in fragrant rice.A naturally fragrant germplasm exists in multiple plant species besides rice,which all exhibit lower activity of BETAINE ALDEHYDE DEHYDROGENASE 2(BADH2).However,no equivalent aromatic germplasm has been described in maize(Zea mays).Here,we characterized the two maize BADH2 homologs,ZmBADH2a and ZmBADH2b.We generated zmbadh2a and zmbadh2b single mutants and the zmbadh2a-zmbadh2b double mutant by CRISPR/Cas in four inbred lines.A popcorn-like scent was only noticeable in seeds from the double mutant,but not from either single mutant or in wild type.In agreement,we only detected 2AP in fresh kernels and dried mature seeds from the double mutant,which accumulated between 0.028 and 0.723 mg/kg 2AP.These results suggest that ZmBADH2a and ZmBADH2b redundantly participate in 2AP biosynthesis in maize,and represent the creation of the world's first aromatic maize by simultaneous genome editing of the two BADH2 genes.

山栀茶中一个新的三萜类化合物

为了研究山栀茶(Radix Pittospori)的化学成分,运用多种色谱方法进行分离纯化,从其氯仿提取物中分离得到2个三萜类化合物,并根据理化性质和波谱数据鉴定其结构分别为22-acetyl-21-(2-acetoxy-2-methylbutanoyl)-R1-barrigenol(1)和3α-hydroxyl-20-demethylisoaleuritolic-14(15)-ene-28,30-dioic acid(2)。其中,化合物1为新的三萜类化合物,化合物2为首次从该植物中分离得到。