Construction of Genetic Linkage Map Based on SSR Markers in Peanut(Arachis hypogaea L.)

Molecular genetic maps of crop species can be used in a variety of ways in breeding and genomic research such as identification and mapping of genes and quantitative trait loci （QTLs） for morphological, physiological and economic traits of crop species. However, a comprehensive genetic linkage map for cultivated peanut has not yet been developed due to the extremely low frequency of DNA polymorphism in cultivated peanut. In this study, 142 recombinant inbred lines （RILs） derived from a cross between Yueyou 13 and Zhenzhuhei were used as mapping population in peanut （Arachis hypogaea L.）. A total 652 pairs of genomic-SSR primer and 392 pairs of EST-SSR primer were used to detect the polymorphisms between the two parents. 141 SSR primer pairs, 127 genomic-SSR and 14 EST-SSR ones, which can be used to detect polymorphisms between the two parents, were selected to analyze the RILs population. Thus, a linkage genetic map which consists of 131 SSR loci in 20 linkage groups, with a coverage of 679 cM and an average of 6.12 cM of inter-maker distance was constructed. The putative functions of 12 EST-SSR markers located on the map were analyzed. Eleven showed homology to gene sequences deposited in GenBank. This is the first report of construction of a comprehensive genetic map with SSR markers in peanut （Arachis hypogaea L.）. The map presented here will provide a genetic framework for mapping the qualitative and quantitative trait in peanut.

Arbuscular mycorrhizal fungi combined with exogenous calcium improves the growth of peanut(Arachis hypogaea L.)seedlings under continuous cropping

The growth and yield of peanut are negatively affected by continuous cropping.Arbuscular mycorrhizal fungi(AMF)and calcium ions(Ca^(2+))have been used to improve stress resistance in other plants,but little is known about their roles in peanut seedling growth under continuous cropping.This study investigated the possible roles of the AMF Glomus mosseae combined with exogenous Ca^(2+)in improving the physiological responses of peanut seedlings under continuous cropping.G.mosseae combined with exogenous Ca^(2+)can enhance plant biomass,Ca^(2+)level,and total chlorophyll content.Under exogenous Ca^(2+)application,the F_v/F_m in arbuscular mycorrhizal(AM)plant leaves was higher than that in the control plants when they were exposed to high irradiance levels.The peroxidase,superoxide dismutase,and catalase activities in AM plant leaves also reached their maximums,and accordingly,the malondialdehyde content was the lowest compared to other treatments.Additionally,root activity,and content of total phenolics and flavonoids were significantly increased in AM plant roots treated by Ca^(2+)compared to either G.mosseae inoculation or Ca^(2+)treatment alone.Transcription levels of AhCaM,AhCDPK,AhRAM1,and AhRAM2 were significantly improved in AM plant roots under exogenous Ca^(2+)treatment.This implied that exogenous Ca^(2+)might be involved in the regulation of G.mosseae colonization of peanut plants,and in turn,AM symbiosis might activate the Ca^(2+)signal transduction pathway.The combination of AMF and Ca^(2+)benefitted plant growth and development under continuous cropping,suggesting that it is a promising method to cope with the stress caused by continuous cropping.

Drought-induced responses of organic osmolytes and proline metabolism during pre-flowering stage in leaves of peanut (Arachis hypogaea L.)

Peanut （Arachis hypogaea L.）, an improtant oil crop, usually encounters drought stress in the process of growth and development, especially at pre-flowering stage. In order to gain insight into the drought tolerance potentials based on osmolyte accumulation and metabolism of proline aspects of peanut, pot experiments were conducted with a split-plot design in Tai＇an, Shangdong Province, China in 2013 and 2014. Pre-flowering drought （PFD） stress and optinum irrigation （control, CK） were served as the main plots and the two peanut cultivars Shanhua 11 and Hua 17 served as sub-plots. Shanhua 11 was drought-tolerant cultivar and Hua 17 was drought-sensitive. The content of soluble sugars, soluble protein, free proline and other free amino acids, the activities of enzymes involved in proline metabolism, and malondialdehyde （MDA） content and ion leakage were all investigated in the two cultivars at pre-flowering stage. Results showed that PFD stress significantly increased the levels of soluble protein, free proline and free amino acid, and increased Al-pyrroline-5-car- boxylate synthetase （P-5-CS, EC 2.7.2.11） activity in the leaves of drought-tolerant and drought-sensitive cultivars. The activity of proline dehydrogenase （proDH） （EC 1.5.99.8） decreased under PFD stress in both cultivars. The leaves of the tolerant cultivar maintained higher increments of osmolyte levels, lower increments of MDA content and ion leakage, as well as a higher increased proportion of P-5-CS activity and higher inhibited proportion of proDH activity under water stress compared with the drought-sensitive cultivar. The study suggests that proline accumulation in peanut leaves under PFD can be explained by the higher enhanced activities of P-5-CS and higher inhibition of proDH. The results will provide useful information for genetic improvement of peanut under drought tolerance.

Functional Analysis of the Phosphoenolpyruvate Carboxylase on the Lipid Accumulation of Peanut(Arachis hypogaea L.) Seeds

Phosphoenolpyruvate carboxylase（PEPC;EC 4.1.1.31） catalyses phosphoenolpyruvate（PEP） to yield oxaloacetate,which is involved in protein biosynthesis.Pyruvate kinase（PK;EC 2.7.1.40） catalyzes PEP to yield pyruvate,which is involved in fatty acid synthesis.In this study,five PEPC genes（AhPEPC1,AhPEPC2,AhPEPC3,AhPEPC4,and AhPEPC5） from peanut have been cloned.Using a quantitative real-time RT-PCR approach,the expression pattern of each gene was monitored during the seed development of four peanut varieties（E11,Hebeigaoyou,Naihan 1,and Huayu 26）.It was found that these five genes shared similar expression behaviors over the developmental stages of E11 with high expression levels at 30 and 40 d after pegging（DAP）;whereas these five genes showed irregular expression patterns during the seed development of Hebeigaoyou.In Naihan 1 and Huayu 26,the expression levels of the five genes remained relatively high in the first stage.The PEPC activity was monitored during the seed development of four peanut varieties and seed oil content was also characterized during whole period of seed development.The PEPC activity followed the oil accumulation pattern during the early stages of development but they showed a significantly negative correlation thereafter.These results suggested that PEPC may play an important role in lipid accumulation during the seed development of four peanut varieties tested.

Sedative effects of peanut (Arachis hypogaea L.) leaf aqueous extracts on brain ATP, AMP, Adenosine and Glutamate/GABA of rats

Peanut (Arachis hypogaea L.) leaf aqueous extracts (PLAE) has been reputed to be a type of sleep-aid in China. To investigate the sedative effects and effect pathways of PLAE, rats (n = 31) were employed in two experiments and intragastrically administrated of (1) distilled water, PLAE (500 mg/kg body weight (BW)) and peanut stem aqueous extracts (PSAE, 500 mg/kg BW);(2) 0, 100 or 500 mg/kg BW of PLAE, respectively for at least 14 days. Six relevant neurotransmitters were measured finally. Experiment-1 (n = 16) results showed that the brain Lactate were significantly elevated (p < 0.05) in rat cerebrums after PLAE administrations, compared with Control and PSAE groups. In respect of brain energy system, significant degradations of the brain adenosine triphos- phate (ATP) (p < 0.05) were observed in the brainstems and even the whole brains of rats though PLAE treatments. Moreover, we found that the brain Adenosine monophosphate (AMP) were clearly decreased (p < 0.05) in rat cerebrum and brainstem regions, while the brain Adenosine revealed an increasing propensity (p = 0.076) in the cerebrums of freely behaving rats. After experiment-2 (n = 15), the γ-aminobutyric acid (GABA) concentrations were statistically (p < 0.05) enhanced and the ratios of Glutamate/GABA were simultaneously reduced (p < 0.05) in rat brainstems, no matter which one dose (100 or 500 mg/kg BW) of PLAE were used. Results indicated that PLAE could influence the target neurotransmitters that related to rat circadian rhythms in the specific brain regions, possessing the potentialities as a sedative or sleep-aid for hypnic therapy purposes.

Identification of main effect and epistatic QTLs controlling initial flowering date in cultivated peanut(Arachis hypogaea L.)

Initial flowering date(IFD)is closely related to mature period of peanut pods.In present study,a population of recombinant inbred lines(RIL)derived from the cross between Silihong(female parent)and Jinonghei 3(male parent)was used to map QTLs associated with IFD.The RIL population and its two parental cultivars were planted in two locations of Hebei Province,China from 2015 to 2018(eight environments).Based on a high-density genetic linkage map(including 2996 SNP and 330 SSR markers)previously constructed in our laboratory,QTLs were analyzed using phenotypic data and the best linear unbiased prediction(BLUP)value of initial flowering date by inclusive composite interval mapping(ICIM)method.Interaction effects between every two QTLs and between individual QTL and environment were also analyzed.In cultivated peanut,IFD was affected by genotypic factor and environments simultaneously,and its broad sense heritability(h2)was estimated as 86.8%。Using the IFD phenotypic data from the eight environments,a total of 19 QTLs for IFD were detected,and the phenotypic variation explained(PVE)by each QTL ranged from 1.15 to 21.82%.Especially,five of them were also detected by the BLUP value of IFD.In addition,12 additive QTLs and 35 pairs of epistatic QTLs(62 loci involved)were identifed by the joint analysis of IFD across eight environments.Three QTLs(qIFDB04.1,qIFDB07.1 and qIFDB08.1)located on chromosome B04,B07 and B08 were identified as main-effect QTL for IFD,which had the most potential to be used in peanut breeding.This study would be helpful for the early-maturity and adaptability breeding in cultivated peanut.

Cloning, Expression Pattern Analysis and Subcellular Localization of Resveratrol Synthase Gene in Peanut (<i>Arachis hypogaea</i>L.)

Resveratrol synthase (RS) is a key enzyme that plays a critical role in the resveratrol synthesis pathway. In this study, six RS genes were isolated and characterized from peanut variety “Zhenzhu Hong” by silico cloning and RT-PCR. Bioinformatics analysis showed that deduced amino acid sequences of the six cloned RS genes were highly conserved with a similarity from 95% to 99% when compared to the RS genes which had been deposited at the GenBank. The results of amino acid sequences analysis showed six RS proteins contained the Chal_Sti_Synt_N and ACP_Syn_III_C domains and can be classified to same family but with different evolutionary distance. Expression pattern analysis by QRT-PCR provided evidence indicating that the mRNA of six RS genes were primarily expressed in the peanut shell at different developmental stages with different expression levels, but only lower levels of them were evident in the peanut kernel. The subcellular localization of RS protein in onion epidermal cell was performed by Agrobacterium tumefaciens-mediated transformation and the green fluorescent was monitored by confocal fluorescence microscopy. The results indicated that, RS1 and RS5 were located in the nucleus and plasma membrane respectively, while the RS2, RS3, RS4 and RS6 were located in both nucleus inner membrane and plasma membrane. The data will provide basic information for elucidating the regulatory mechanisms and enzyme kinetics underlying the RS genes in the resveratrol synthase pathway.

Stress Responses of Peanut (<i>Arachis hypogaea</i>L.) Genotypes as Measured by Trigonelline Content after Exposure to UV-B Radiation

UV-B radiation has been widely documented as a stressor for plants that can cause decreased biomass, reduction in photosynthesis, and oxidative stress. Trigonelline is a secondary metabolite that is biosynthesized in some plants in response to abiotic stress such as UV-B irradiation. The objectives of this study were to examine biochemical stress responses for peanut plants (Arachis hypogaea L.) of four different genotypes (Spanish, Valencia, Virginia, and Runner) after exposure at various lengths to UV-B radiation and to examine the alteration of trigonelline biosynthesis due to the age of the plants. Peanut plants from the genotypes were exposed to UV-B radiation at three exposure times (60, 120, and 180 min);plants from two growth stages, the flowering (R1) and early maturity (R7), were used. Significant positive correlations (rs 0.29-0.74, P≤0.05) were found for trigonelline concentrations and UV-B exposure times. With longer exposure times of 180 min for plants at R7, trigonelline biosynthesis began as early as 10 days after treatment with 154.6 μg·g-1 DW and remained or increased by up to 71.5 μg·g-1 DW (46.3%) throughout the sampling intervals (10, 20, 30, 40, and 50 days after treatment) to a final value of 226.1 μg·g-1 DW. All four genotypes at R7 exhibited trigonelline concentrations 47.3% to 52.4% (71.6 to 96.5 μg·g-1 DW) higher than individuals at R1. Trigonelline biosynthesis at R7 was significantly (P<0.05) affected by all levels of UV-B exposure, whereas trigonelline concentrations at R1 were significantly influenced (P<0.05) by only the longer exposure times (120 and 180 min). No statistically significant difference was found in trigonelline concentration among the four different genotypes. UV-B irradiation had the greatest effect on plants at R7 after 120 and 180 min of exposure, as 15 out of 20 (75%) individuals had significantly higher (P<0.05) trigonelline concentrations.

Gomparative analysis of DGAT3（diacylglycerol acyltraiisferase 3） gene from different peanut （Arachis hypogaea L.） varieties

Cultivated peanut is one of the primary sources of vegetable oil and protein in developing countries. DG〉A73 family in peanut cotyledons has no membrane-bound regions suggesting that cytosol is one of the sites for triacylglycerol （TAG） biosynthesis in oilseeds. According to functional annotation and classification of 5 cDNA libraries, 12 unigenes were found with relation of peanut DGAT3 in different organs. Three clones of unigenes, OCP- contig168t OCPcontig12101-3 and OCPcontigl2388-1 were selected for sequencing. Full length sequence of DGAT3 was obtained, showing over 98% sequence similarity with peanut DGAT3 gene AY875644 or EU183333. Upon cluster analysis, DGAT3 of 40 culti- vars were divided into 3 types, namely AhDGATS-1, AhDGAT3-2 and AhDGAT3-3. Coding regions are 1023, 1038 and 1026 base pairs which encoded proteins with 340-, 345- and 341-amino acids, respectively. DGAT3-3 might be a novel gene type among the DGAT3 family which provides great help for studying DGAT3 gene evolution in peanut.

General and specialized metabolites in peanut roots regulate arbuscular mycorrhizal symbiosis

Arbuscular mycorrhizae(AM)fungi form symbiotic associations with plant roots,providing nutritional benefits and promoting plant growth and defenses against various stresses.Metabolic changes in the roots during AM fungal colonization are key to understanding the development and maintenance of these symbioses.Here,we investigated metabolic changes in the roots of peanut(Arachis hypogaea L.)plants during the colonization and development of AM symbiosis,and compared them to uncolonized roots.The primary changes during the initial stage of AM colonization were in the contents and compositions of phenylpropanoid and flavonoid compounds.These compounds function in signaling pathways that regulate recognition,interactions,and pre-colonization between roots and AM fungi.Flavonoid compounds decreased by 25%when the symbiosis was fully established compared to the initial colonization stage.After AM symbiosis was established,general metabolism strongly shifted toward the formation of lipids,amino acids,carboxylic acids,and carbohydrates.Lipid compounds increased by 8.5%from the pre-symbiotic stage to well-established symbiosis.Lyso-phosphatidylcholines,which are signaling compounds,were only present in AM roots,and decreased in content after the symbiosis was established.In the initial stage of AM establishment,the content of salicylic acid increased two-fold,whereas jasmonic acid and abscisic acid decreased compared to uncolonized roots.The jasmonic acid content decreased in roots after the symbiosis was well established.AM symbiosis was associated with high levels of calcium,magnesium,and D-(+)-mannose,which stimulated seedling growth.Overall,specific metabolites that favor the establishment of AM symbiosis were common in the roots,primarily during early colonization,whereas general metabolism was strongly altered when AM symbiosis was well-established.In conclusion,specialized metabolites function as signaling compounds to establish AM symbiosis.These compounds are no longer produced after the symbiosis between the roots and AM becomes fully established.

不同土壤类型对花生(Arachis hypogaea L.)籽实镉积累特性的影响

为了在不同土壤环境下选育出低镉(Cd)积累型花生品种以提高花生品质,以‘白沙1016号’品种花生(Arachis hypogaea L.)为供试作物,棕壤和潮土为供试土壤,采用盆栽试验的方法,研究了2种类型土壤对花生籽实Cd积累特性的影响。结果表明:2种类型土壤条件下的花生籽实生物量差异显著(P<0.05);在供试土壤Cd处理范围内(≤10.0 mg/kg),籽实生物量均随2种土壤Cd处理浓度增加呈"低促高抑"现象。花生籽实对土壤Cd的生物富集系数均随2种土壤Cd处理增加呈显著降低趋势(P<0.05),且土壤类型间差异不显著。花生籽实Cd含量和Cd生物富集量均随2种土壤Cd处理的增加而显著增加(P<0.05),但两者在棕壤介质中均显著大于潮土(P<0.05)。土壤类型对花生籽实Cd积累差异的影响主要体现在籽实Cd含量和生物富集量方面。而土壤pH、氧化还原电位(Eh)等均是影响籽实对Cd积累差异的重要因素。

Development and validation of simple sequence repeat markers from Arachis hypogaea transcript sequences

Simple sequence repeats(SSRs) are important molecular markers for assessing genetic diversity in Arachis hypogaea L. and many other crops and constructing genetic linkage maps for important agricultural traits. In this study, 29,357 potential SSRs were identified in 22,806 unigenes assembled from A. hypogaea transcript sequences. Of these unigenes, 1883 and 4103 were annotated and assigned in Kyoto Encyclopedia of Genes and Genomes Orthology and Eukaryotic Orthologous Groups databases, respectively. Among the SSR motifs, mono-(19,065; 64.94%) and trinucleotide(5033; 17.14%) repeats were the most common, and the three most dominant motifs were A/T(18,358; 62.54%), AG/CT(2804;9.55%), and AAG/CTT(1396; 4.76%). Polymerase chain reaction(PCR) primer pairs were designed for 4340 novel SSR markers and 210 new SSRs were validated using 24 A. hypogaea varieties. Of the 210, 191(91%) yielded PCR products, with 37(18%) identifying polymorphisms. The 37 polymorphic SSR markers detected 146 alleles(2–10 alleles per locus), and the average polymorphic information content was 0.403(with a range of 0.077 to0.819). The new SSRs enrich the current marker resources for A. hypogaea and may also be useful for genetic diversity analysis, functional genomics research, and molecular breeding.

A New Coumestan from Arachis hypogaea L.

A new coumestan, 3, 9-dihydroxy-4, 8-dimethoxycoumestan, was isolated from Arachis hypogaea L. together with two known compounds: 3, 9-dihydroxy-4-methoxycoumestan and 3, 9-dihydroxy-8-methoxycoumestan. The structure was established by spectroscopic methods.

Pb-Stress Induced Oxidative Stress Caused Alterations in Antioxidant Efficacy in Two Groundnut (<i>Arachis hypogaea</i>L.) Cultivars

Lead (Pb) is an important environmental pollutant extremely toxic to plants and other living organisms including humans. To assess Pb phytotoxicity, a pot culture experiment was carried out using two groundnut cultivars (Arachis hypogaea L. cultivar K6 and cultivar K9) on plant growth, ROS levels, lipid peroxidation, and antioxidant metabolism using biochemical, histochemical methods. Plants were grown in pots for 14 days, in the botanic garden, and subjected to Pb-stress (0, 100, 200, 400 and 800 ppm) by adding Pb (NO3)2 solution and further allowed to grow for 10 days. The results showed that cultivar K6 registered lower Pb accumulation than cultivar K9, however, localization of Pb was greater in roots than leaves in both groundnut cultivars. The Pb-stress results in an increase in free radicals (O2?- and H2O2) generation in both groundnut cultivars, but more significantly in cultivar K9 than K6. Pb-stress also caused significant changes in the rate of peroxidation as shown in the levels of malondialdehyde (MDA) content in roots and leaves of both groundnut cultivars. Free proline, ascorbic acid (AsA) and non-protein thiol (NP-SH) contents were increased in cultivar K6 due to Pb-stress, but less in cultivar K9. Pb treated plants showed increased levels of antioxidant enzymes such as superoxide dismutase (SOD), guaiacol peroxidase (GPX), ascorbate peroxidase (APX) glutathione reductase (GR) and glutathione S-transferase (GST). Isozyme band intensities of SOD, GPX and APX were more consistent with the respective changes in antioxidative enzyme activities. These results indicate that cultivar K6 possesses greater tolerance potential for Pb toxicity than cultivar K9.

花生PLT基因家族全基因组鉴定与表达分析

PLT家族是植物特有的一类转录因子,在植物胚胎、干细胞、分生组织及器官生长发育等过程都起着重要作用。本研究利用生物信息学技术在栽培种花生基因组中鉴定到12个PLT家族基因,分布在11条染色体上;AhPLT蛋白大多含有2个保守的AP2结构域,编码439~713个氨基酸,预测定位在细胞核或叶绿体中;AhPLT基因结构复杂,具有多样的短外显子结构,外显子数在5~8个之间,不同家族成员中分布不同的保守基序;AhPLT家族成员启动子区存在生长素、赤霉素和茉莉酸等激素相关的顺式作用元件。qRT-PCR结果显示,AhPLT1-B和AhPLT5-B分别在根中和种子中的表达量最高;两基因对激素IAA、6-BA和GA_(3)有不同的响应,其中AhPLT1-B受6-BA调控上调表达最显著,AhPLT5-B受6-BA、IAA和GA_(3)调控呈先升高后降低的表达模式。本研究为花生PLT基因的生物学功能研究提供了参考。

Phytochemical Constituents and Determination of Resveratrol from the Roots of <i>Arachis hypogea</i>L.

Two triterpenoid saponins, 6, 7, together with five known compounds were isolated from the roots of Arachis hypogea L. collected in Vietnam. Their structures were established by spectroscopic analysis (1D, 2D NMR and HRMS) as well as by comparison with those reported in the literature. Furthermore, the high content of resveratrol in the roots opens a new potential resource for pharmaceutical companies to prepare medicines from the wasted peanut roots.

花生栽培种与野生种(Arachis oteroi)人工杂交双二倍体的创制和鉴定

花生野生种是改良花生栽培种的重要基因资源。为了利用野生花生的抗性基因,本研究利用花生栽培品种豫花9331与二倍体野生种A.oteroi人工杂交,借助胚拯救和染色体秋水仙素加倍,创制一个双二倍体杂种Am E-4,并利用荧光原位杂交和分子标记技术准确鉴定了该双二倍体。观察结果表明,Am E-4的叶片与豫花9331存在显著差异,而主茎高、侧枝长和总分枝数等性状与豫花9331差异不显著。Am E-4开花期较豫花9331推迟60 d,结实性与荚果发育状况较差,不利于Am E-4的育种利用。同时,开发了57个追踪Am E-4中A.oteroi染色体的显性或共显性SSR标记,为创制和鉴定花生栽培种A.oteroi易位系或渐渗系奠定分子基础。

Antioxidant activity,total phenolic,and resveratrol content in five cultivars of peanut sprouts

Objective: To investigate the change in total phenolic compounds, antioxidant activity,and resveratrol content of five different germinated peanut cultivars.Methods: The germinated sprouts of five peanut cultivars(Kalasin1, Kalasin2, Konkaen,Konkaen4, and Tainan9) were extracted with 80% ethanol and collected as crude extract.The antioxidant capacities were determined with 2,2-diphenyl-1-picrylhydrazyl and ferric ion reducing antioxidant power method.The total phenolic compound was measured using the Folin–Ciocalteau assay.The qualification and quantification of resveratrol was performed by high performance liquid chromatography method.Results: Among the five cultivars, a three-day germination of Kalasin1 showed the highest phenolic content [(40.67 ± 2.62) mg gallic acid/g dry weight], expressed the highest 2,2-diphenyl-1-picrylhydrazyl antioxidant value [(80.51 ± 1.47) mmol/L Trolox/g dry weight], and ferric ion reducing antioxidant power antioxidant value [(171.33 ± 8.59)mmol/L ascorbic acid/g dry weight].However, the high performance liquid chromatography result of Kalasin2 significantly increased to the highest resveratrol content of(6.44 ± 1.26) mg/g dry weight on the second day of germination.Conclusions: The variation of phytochemical content in the peanut sprout is due to the effect of the peanut cultivar and the germination period.

Assessment of Photochemical Reflectance Index as a Tool for Evaluation of Chlorophyll Fluorescence Parameters in Cotton and Peanut Cultivars Under Water Stress Condition

The relationships between photochemical reflectance index （PRI） and the chlorophyll fluorescence parameters were examined to assess suitability of PRI as a remote-sensing tool for the chlorophyll fluorescence parameters. A greenhouse experiment was conducted using cotton and peanut crops under water stress condition. Five cotton and six peanut cultivars were grown using Andosole soil in pots maintained at two water levels; the control and water stress treatment （WS） of 100 and 50% of the daily transpiration, respectively. Higher non-photochemical quenching （NPQ） was exhibited by peanut than that of cotton by the water stress. On the other hand, the decreases of the actual quantum yield of photosystem II （△F/F＇m） and PRI by the water stress in cotton were larger than those in peanut. There were positively significant correlation coefficients between PRI and △F/F＇m in cotton at noon and in the afternoon including the control and WS. The correlations of PRI with NPQ were negatively significant at noon and in the afternoon for cotton, and in the afternoon for peanut. No clear relationship was found among these parameters in the morning probably due to the diurnal increase in global solar radiation. It was concluded that there would be a possibility to detect the effects of water stress on △F/F＇m and NPQ by PRI with some exceptions, although PRI could not note varietals differences in △F/F＇m and NPQ for each treatment.

Progress on genetic and genomic research for enhanced oil content and quality in peanut

Peanut or groundnut （ Arachis hypogaea L. ） is an important source of vegetable oil in the world. Genetic enhancement for high yield and high oil content has greatly contributed to enhanced pro-ductivity of peanut and increased supply of peanut oil. Further improving oil content and quality of peanut is still crucial for increasing productivity of arable land and market competitiveness of peanut oil. Based on investigation among the peanut germplasm accessions including wild Arachis species, the oil content could be as high as 65%. Heterosis has been observed for oil content in hybrids derived from diverse crossing parents. Segregates with enhanced oil content have been obtained by pyramiding different genes or alleles with major and minor additive effects. Improved testing techniques for oil content in breeding lines with reduced cost have accelerated breeding progress for high oil content. SSR markers associated with oil content have been identified by association and linkage analysis. The stability of oil content in peanut across seasons and locations is highly associated with cold tolerance, high nutrition efficiency and drought tolerance. Recent progress on improving fatty acids in particular marker assisted backcrossing breeding has contributed to higher quality peanut oil and other products. High oil peanut lines with im-proved resistance to aflatoxin production have been developed. The wild Arachis species would be of great value for peanut breeding in increasing oil content.