QTLs for Waterlogging Tolerance at Germination and Seedling Stages in Population of Recombinant Inbred Lines Derived from a Cross Between Synthetic and Cultivated Wheat Genotypes

Waterlogging is a widespread limiting factor for wheat production throughout the world. To identify quantitative trait loci （QTLs） associated with waterlogging tolerance at early stages of growth, survival rate （SR）, germination rate index （GRI）, leaf chlorophyll content index （CCI）, root length index （RLI）, plant height index （PHI）, root dry weight index （RDWI）, shoot dry weight index （SDWI）, and total dry weight index （DWI） were assessed using the International Triticeae Mapping Initiative （ITMI） population W7984/Opata85. Significant and positive correlations were detected for all traits in this population except RLI. A total of 32 QTLs were associated with waterlogging tolerance on all chromosomes except 3A, 3D, 4B, 5A, 5D, 6A, and 6D. Some of the QTLs explained large proportions of the phenotypic variance. One of these is the QTL for GRI on 7A, which explained 23.92% of the phenotypic variation. Of them, 22 alleles from the synthetic hexaploid wheat W7984 contributed positively. These results suggested that synthetic hexaploid wheat W7984 is an important genetic resource for waterlogging tolerance in wheat. These alleles conferring waterlogging tolerance at early stages of growth in wheat could be utilized in wheat breeding for improving waterlogging tolerance.

Identification and Evaluation of Cold Tolerance in Bitter Gourd (Momordica charantia L.) at Bud and Seedling Stages under Different Temperature Conditions

[ Objectives] This study was conducted to screen the temperature index most suitable for identification of cold tolerance in bitter gourd （Momordica charantia L. ） at bud and seedling stages. [ Methods] With six different bitter gourd germplasms as experimental materials, the cold tolerance at bud and seedling stages were identified and evaluated. [ Results] At 18℃ , the largest change range of germination potential among different gernlplasms was 11.3% -96.0%, and the largest change range of germination rate was 13.3% - 100.0% ; and the six germplasms could be divided into three grades of cold tolerance. Therefore, 18 9C is an ideal temperature for the identification of cold tolerance in bitter gourd germplasms at bud stage. At 20℃, the cold tolerance in bitter gourd germplasms at bud stage could also be divided into three grades, and the change ranges of germination potential and germination rate were larger than 50.0%, so 20℃ could serve as the candidate temperature for the identification of cold tolerance in bitter gourd germplasms at bud stage. After 1 d of treatment at 6℃, the six bitter gourd germplasms could be divided into three grades, and the cold injury index had the largest range of 20.31 - 84.38 and could serve as the temperature index for the identification of cold tolerance in bitter gourd at seedling stage. [ Conclusions] This study will provide reference for the identification of cold tolerance in bitter gourd at bud stage and seedling stage.

Changes in DNA Methylation Pattern at Two Seedling Stages in Water Saving and Drought-Resistant Rice Variety after Drought Stress Domestication

Recent studies revealed that DNA methylation plays an important role in plant growth and development. In this study, a water-saving and drought-resistant rice variety Huhan 3 was subjected to drought stress from tillering to grain-filling stages in six successive growth cycles. The variations in DNA methylation pattern between the original generation （Go） and the sixth generation （G6） were analyzed by using methylation sensitive amplification polymorphism method. The results revealed that the methylated loci accounted for 34.3% to 34.8% of the total loci. Among these methylated loci, 83.1% to 84.8% were full- and hyper-methylated and 15.2% to 16.9% were hemi-methylated. The DNA methylation level decreased from the three-leaf to four-leaf stages in Huhan 3. Differentially methylated loci （DML） between generations or/and between different developmental stages accounted for 4.0% of the total loci, most of which were only related to plant development （57.9%）. Compared to Go, the DNA methylation pattern of G8 changed after drought domestication, at the three-leaf stage, de-methylation accounting for 59.1%, while at the four-leaf stage, re-methylation for 47.9%. Genome-wide alternations of DNA methylation were observed between the two seedling stages, and DML mainly occurred on the gene＇s promoter and exon region. The genes related to DML involved in a wide range of functional biology and participated in many important biological processes.

Effects of Silicon Formulations on Cold Tolerance of Rice Seedlings

To investigate the effects of silicon formulations on the cold tolerance of rice seedlings,Song Japonica 16(not cold tolerant)and Dongnong 427(cold tolerant)rice varieties were used as test materials and four different types of silicon formulations,Si-50-G,Si-60-G,Si-T-G,and Si-E-G,were applied as foliar sprays at the seedling stage,and a control group CK(equal amount of distilled water)was set up.One week after the first silicon spray,two types of rice were subjected to low-temperature stress treatments at day/night temperatures of 12℃/10℃for 2,4,6,and 8 days.The effects of different silicon formulations on the chlorophyll,proline(Pro)and soluble sugar contents as well as superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT)activities of rice seedlings under low-temperature stress were compared to find out the effects of silicon formulations on the cold tolerance of rice seedlings.The results showed that silicon formulations could significantly increase the chlorophyll content of rice seedling leaves,with Si-50-G being the most effective,with a significant increment of 40.17%compared to the CK at 2 days of low temperature.Four silicon formulations significantly increased the proline content and soluble sugar content of rice leaves at low temperature for 4-8 days.For Song Japonica 16,the most significant increment in leaf POD activity was observed in Si-E-G treatment at 2,4 and 8 days of temperature stress,with 73.58%,20.95%and 217.24%increases compared to the CK,respectively.For 4 and 6 days of temperature stress,the most significant increase in CAT activity was observed in Si-E-G treatment,with 25.70%and 75.78%increases compared to the CK,respectively.For Dongnong 427,the Si-60-G treatment showed the highest increase in leaf SOD activity for 4 and 8 days of temperature stress,with significant increases of 58.15%and 82.76%compared to the CK,respectively,and the Si-E-G treatment showed the highest increase in leaf POD activity for 2 and 8 days of temperature stress,with significant increases of 97.75%and 245.10%compared to the CK,respectively.It showed that the spraying of silicon formulations could significantly enhance the cold tolerance of rice.This study provided a scientific basis for the rational use of silicon formulations to enhance cold tolerance in rice and had important theoretical and practical significance for ensuring sustainable high and stable rice yields in Heilongjiang Province,as well as for the development of silicon fertilizers.

Genome-wide Association Analysis of Ten Chilling Tolerance Indices at the Germination and Seedling Stages in Maize

Maize seedlings are very sensitive to chilling, especially during the transition phase from heterotrophic to autotrophic growth. Genetic dissection of the genetic basis of chilling tolerance would provide useful information for genetic improvement of maize inbreds. In this study, genome-wide association analysis was conducted to explore the genetic architecture of maize chilling tolerance at the seed germination and seedling stages with an association panel of 125 inbreds. Ten tolerance indices （ratios of the performance of 10 germination rates and seedling growth-related traits under chilling stress and control conditions） were investigated to assess the ability of chilling tolerance of the inbreds, and a total of 43 single nucleotide polymorphisms associated with chilling tolerance were detected, with none of them being related to chilling tolerance at both the germination and seedling stages simultaneously. Correlation analysis also revealed that the genetic basis of chilling tolerance at the seed germination stage is generally different from that at the seedling stage. In addition, a total of 40 candidate genes involving 31 of the 43 single nucleotide polymorphisms were predicted, and were grouped into five categories according to their functions. The possible roles of these candidate genes in chilling tolerance were also discussed.

QTL Mapping for Drought Tolerance at Stages of Germination and Seedling in Wheat (Triticum aestivum L.) Using a DH Population

Drought is a major constraint in many wheat( Triticum aestivum L.) production regions. Quantitative trait loci (QTLs) conditioning drought tolerance at stages of germination and seedling in wheat were identified in a double haploid (DH) population derived from the cross, Hanxuan10×Lumai14, using amplified fragment length polymorphism (AFLP) and simple sequence repeat (SSR) markers. Interval mapping analysis revealed that QTLs for drought tolerance at germination stage were located on chromosomes 1B, 2B, 5A, 6B, 7A and 7B, respectively, and the most effective QTL was mapped on chromosome 2B, explaining 27.2% of phenotypic variance. The QTLs for drought tolerance at seedling stage were located on 1B, 3B and 7B, respectively, and the most effective QTL was mapped on chromosome 3B, explaining 21.6% of phenotypic variance. Their positions were different from those of QTLs conferring drought tolerance at germination stage, indicating that drought tolerance at germination stage and seedling stage was controlled by different loci. Most of the identified QTLs explained 18% or more of phenotypic variance for drought tolerance at germination and seedling stage, and would be useful in future for marker assisted selection programs and cultivar improvement.

Thermal and photoperiodic requirements of the seedling stage of three tropical forest species

Air temperature and photoperiod play an important role in the seedling development for tropical forest species.Both variables are sensitive to climate,and so evaluating thermal and photoperiodic effects on seedling development is fundamental,especially for climate change studies.Methods to quantify thermal time and the energy required for plants to reach a development stage include air temperature and cardinal temperatures.The photoperiod will also affect physiological reactions of a plant and thus its development.Here we evaluated the six thermal time methods widely used to compute thermal requirement,and identified the influence of the photoperiod from the 2015 and2016 growing seasons and 12 sowing dates in Itajubá,Minas Gerais state,Brazil,on seedling development of three native tropical forest species Psidium guajava L.(Myrtaceae),Citharexylum myrianthum Cham.(Verbenaceae),and Bixa orellana L.(Bixaceae).The method used to quantify thermal time influenced the analytical results of seedling development;the one that considered three cardinal temperatures and compared them with the mean air temperature(Method5)performed better in computing thermal requirements.The influence of photoperiod on seedling development was inconclusive for the three species,but all three developed better in mild temperatures(between 13.3℃and 26.9℃)with a photoperiod shorter than 13 h.

Effects of Uniconazole on Physiological and Biochemical Properties of Roots of Different Sweetpotato Cultivars at Seedling Stage

Objective] This study almed to investigate the effects of uniconazoIe on physioIogical and biochemical properties of roots of different sweetpotato cuItivars at seedIing stage. [Method] Under hydroponic conditions in a greenhouse, the effects of exogenous uniconazoIe on physioIogical and biochemical properties of roots of different sweetpotato cuItivars at seedIing stage were analyzed under continuous drought stress simuIated by PEG-6000. [Result] Compared with normal water suppIy treatment （N）, drought treatment （D） decreased significantIy root Iength, root surface area, average root diameter and root voIume of Jishu 21 and Jihei 1; to be specif-ic, compared with Jishu 21, root Iength, root surface area and average root diame-ter of Jihei 1 decreased greatIy, but root voIume of Jihei 1 decreased sIightIy. SOD, POD, APX activities and MDA content of Jishu 21 and Jihei 1 increased, and root vitality of two sweetpotato cuItivars was reduced; to be specific, compared with Jihei 1, Jishu 21 exhibited significantIy improved SOD, POD, APX activities, sIightIy im-proved MDA content and remarkabIy reduced root vitality. IAA, GAs and ZR con-tents of Jishu 21 and Jihei 1 decIined at seedIing stage; ABA content of two sweetpotato cuItivars was improved; to be specific, compared with Jihei 1, IAA, GAs and ZR contents of Jishu 21 were reduced sIightIy, whiIe ABA content of Jishu 21 was improved sIightIy. Under stress conditions, uniconazoIe treatment increased sig-nificantIy root Iength and root surface area of Jihei 1 and increased sIightIy root voIume of Jihei 1 compared with Jishu 21; uniconazoIe treatment increased signifi-cantIy SOD, POD and APX activities and root vitality of Jihei 1 and decIined re-markabIy MDA content of Jihei 1 compared with Jishu 21; uniconazoIe treatment in-creased significantIy IAA, ZR and ABA contents of Jihei 1 compared with Jishu 21. [Conclusion] Drought-toIerant sweetpotato cuItivar Jishu 21 exhibits high pIasma membrane integrity and root vitality by increasing activities of antioxidant enzymes under drought stress and malntalning high contents of IAA, ZR and ABA. Unicona-zoIe exerts greater reguIatory effects on physioIogical and biochemical properties of drought-sensitive sweetpotato cuItivar Jihei 1 under drought stress.

Growth Performance of Phoebe bournei Generations in Seedling Stage

[Objective] The aim was to explore growth performance of Phoebe bournei in seedling stage.[Method] Based on 17 superior plus trees of Phoebe bournei,a seedling cultivation test was conducted in Jindong Forest Farm in Yongzhou,Hunan Province,exploring growth indices and analyzing seedling height and ground diameter.[Result] As per the selection rate at 20％,PB17,PB9 and PB12 were selected from the 17 species.Specifically,the seedling height averaged 36.52 cm of the selected three seedlings,which was higher by 16.1％ compared with average of 17 species （31.45％）.As for ground diameter,the selected species averaged 2.6 mm,which was higher （13.0％） compared with the average level （2.3 mm）.[Conclusion]Both of seedling height and ground diameter reached extremely significant differences,which indicated that half-sib families of Phoebe bournei have rich variations,with selection and breeding potential.

The Effects of UV-B Radiation on Maize at the Seedling Stage

In this study, maize plant seedlings were grown in soilless cultures, with and without ^-B radiation at a close of 5.4 kJt（m2-d）. Three clays later, it was found that the treatment of UV-B radiation significantly reduced such characteristics as biomass, plant height, leaf area, and so on. Also, the photosynthesis of the maize was inhabited, the anti-oxid activity decreased, and the MDA concentration increased with the UV-B radiation exposure. The maize presented visible hybrid vigor under the control condition, while the hybrid vigor under UV-B radiation barely emerged in biomass, plant height, leaf area, and physiological metabolic index.

Difference in Absorption of N, P and K among Different-Phosphorus Efficiency Soybean Genotypes at the Seedling Stage

The low-phosphorus efficiency soybean genotypes, D03, D05, D17 and D18, and the high-phosphorus efficiency soybean genotypes, D31, D34, D37 and D38 were selected. The soil culture experiment was conducted. There were 2 treat- ments, high phosphorus （＋P） and low phosphorus （-P）. The difference in absorption of N, P and K among different-phosphorus efficiency soybean genotypes at the seedling stage was analyzed. The results showed in the low phosphorus （-P） treat- ment, the P absorption amount differed among roots, stems and leaves of different high-phosphorus efficiency genotypes. The P absorption amount was positively relat- ed （P〈0.05, P〈0.01） to the dry weights of root, stem and leaves, but was negative- ly related to the utilization efficiency of phosphorus （P〉0.05）. The N and K absorp- tion amounts of root, stem and leaves all trended to decrease. The low phosphorus stress would inhibit the absorption of N, P and K in soybean plants at the seedling stage. However, the adaptability of the high-phosphorus efficiency soybean geno- types to low phosphorus stress was significantly higher than that of low-phosphorus efficiency genotypes.

Screening and identification of salt tolerance soybean varieties and germplasms

Soil salinization is a globally prevalent abiotic environmental stress.The imbalance of ions caused by high concentrations of sodium chloride results in a 40%reduction in soybean yield.Soybean,as an important crop for soil quality improvement,necessitates the identification of salt-tolerant varieties and germplasms to effectively utilize and enhance saline-alkali land.In this study,we assessed the salt tolerance of 435 soybean varieties and germplasms during the seedling stage.Among them,Qihuang34,You2104,Hongzhudou,Pamanheidou,and Osage exhibited grade 1 salt tolerance rates surpassing other tested materials.Furthermore,Hongzhudou and Qihuang34 demonstrated higher salt tolerance during germination and emergence stages based on their elevated rates of emergence,salt tolerance index,chlorophyll content,and shoot fresh weights.Overall findings provide valuable resources for molecular breeding efforts aimed at developing salt-tolerant soybean varieties suitable for cultivation in saline-alkali soils.

Mapping QTLs for Aluminum Tolerance in Introgression Lines of Wild Rice at Seedling Stage

In this study, wild rice chromosome segment substitution lines bred by Yuanjiang common wild rice and elite indica rice variety Teqing were used as ex-perimental materials to detect aluminum tolerancerelated QTLs based on the phe-notypic data of indoor and outdoor plant height inhibition rate and dry weight inhibi-tion rate at seedling stage. According to experimental results, 11, 18, 14 and 5 QTLs related with aluminum tolerance were detected respectively on different chro-mosomes. Analysis of phenotypic data of indoor and outdoor plant height inhibition rate indicated that QTLs around RM38 on chromosome 8 and RM277 chromosome 12 exhibited the highest contribution rates （12% and 11%）, belonging to major QTLs. Analysis of phenotypic data of indoor and outdoor dry weight inhibition rate indicated that the highest contribution rate was only 9% and 8%; therefore, no major QTL was detected. QTLs detected repeatedly were located on chromosomes 7, 8, 9, 11 and 12, respectively. Two QTLs were located on chromosome 8. QTLs around RM310 were detected three times and other QTLs were detected twice, which were identified as stable QTLs.

Changes of Antioxidative Enzymes and Lipid Peroxidation in Leaves and Roots of Waterlogging-Tolerant and Waterlogging-Sensitive Maize Genotypes at Seedling Stage

To better understand the physiological and biochemical mechanisms of waterlogging tolerance, waterlogging effects on lipid peroxidation and the activity of antioxidative enzymes were investigated in leaves and roots of two maize genotypes, HZ32 （waterlogging-tolerant） and K12 （waterlogging-sensitive）. Potted maize plants were waterlogged at the second leaf stage under glasshouse conditions. Leaves and roots were harvested 1 d before and 2, 4, 6, 8 and 10 d after the start of waterlogging treatment. Through comparing the activities of superoxide dismutase （SOD）, ascorbate peroxidase （APX）, glutathione reductase （GR）, catalase （CAT） and guaiacol peroxidase （POD） between waterlogging-tolerant and waterloggingsensitive genotype, we deduced that CAT was the most important H2O2 scavenging enzyme in leaves, while APX seemed to play a key role in roots. POD, APX, GR and CAT activities in conjunction with SOD seem to play an essential protective role in the O2^- and H2O2 scavenging process. Lipid peroxidation was enhanced significantly only in K12 （P 〈 0.001） and there was no difference （P 〉 0.05） in HZ32 up to 6 d after waterlogging stress. These results indicated that oxidative stress may play an important role in waterlogging-stressed maize plants and that the greater protection of HZ32 leaves and roots from waterlogging-induced oxidative damage results, at least in part, through the maintenance of increased antioxidant enzyme activity.

Genetic Analysis on Characteristics to Measure Drought Resistance Using Dongxiang Wild Rice(Oryza rufupogon Griff.) and Its Derived Backcross Inbred Lines Population at Seedling Stage

Drought stress is one of the major constraints to rice （Oryza sativa L.） production and yield stability especially in rainfed ecosystems and is getting worse as the climate changes worldwide. Dongxiang wild rice （DXWR） Oryza rufipogon Griff., contains drought resistant gene. Improving drought resistance of cultivars is crucial to increase and stabilize rice grain yield via transferring resistant gene from species related to rice. In this paper, four upland rice, sixty backcross inbred lines （BILs） derived from BC1F5 of R974//DXWR/R974, and their parents were employed to evaluate drought-resistance at seedling stage in the greenhouse. Nine traits were recorded for assessment of drought resistance, including maximum root length （MRL）, number of roots （NR）, shoot length （SL）, dry root weight （DRW）, fresh root weight （FRW）, root relative water content （RRWC）, leaf relative water content （LRWC）, level for rolling leaf （LRL）, and seedling survivability under repeat drought （SSRD）. Using more than 88% of accumulative contribution resulted from the principal component analysis （PCA）, the nine traits were classified into five independent principal components and the line 1949 showed the highest resistance. Analysis on the stepwise regression equation and correlation demonstrated that MRL, RN, FRW, and RRWC significantly influenced the drought resistance, thus could be used as comprehensive index for drought resistance at the seedling stage. Using the major gene plus polygene mixed inheritance model of quantitative traits, the inheritance of drought-resistance of BIL population at seedling stage was mostly controlled by two independent genes plus polygene. As a result, the DXWR could be precious resources for genetic improvement of drought resistance in cultivated rice.

Effects of seedling age on the growth stage and yield formation of hydroponically grown long-mat rice seedlings

Understanding the characteristics of rice productivity is of great importance for achieving high yield formation.However,such traits have not yet been studied for different ages of hydroponically grown long-mat rice seedlings(HLMS),which constitutes a new method of seedling cultivation.Field experiments were conducted to evaluate the effects of seedling age on the growth stage,photosynthesis characteristics,dry matter production,and yield of HLMS.A conventional japonica rice cultivar(Wuyunjing 24)and an indica hybrid rice cultivar(6 Liangyou 9368)were used as test materials.The results showed that the whole phase was shortened by 13-15 days for young seedlings(13-day-old)compared with old seedlings(27-day-old),which occurred because the growth process accelerated with the transplantation of young seedlings.As seedling age increased,the dry matter weight of stems of individual plants and of the population increased at the transplanting stage but decreased at the maturity stage(MS).Compared with that of 27-day-old seedlings,the average ratio of panicle weight to total plant dry weight of 13-day-old seedlings during a 2-year period increased by 3.71%for Wuyunjing 24 and by 3.78%for 6 Liangyou 9368 at the MS.Moreover,as seedling age increased,the leaf area index and photosynthetic potential decreased for both cultivars,and the photosynthetic rate markedly decreased at the heading stage(HS).With the exception of that of Wuyunjing 24 from the jointing stage to the HS in 2014,the crop growth rate was higher for young seedlings than for old seedlings.Grain yield significantly decreased with seedling age,but no significant difference was detected between the 13-and 20-day-old seedlings for either cultivar.Therefore,equilibrious and high biological yield formation,vigorous growth in the late stages,and high photosynthetic production capacity are important characteristics and causes of the efficient and sustainable output of photosynthetic systems and for achieving high yield formation in young transplanted seedlings(13-20-day-old).

Wheat genotypes tolerant to heat at seedling stage tend to be also tolerant at adult stage:The possibility of early selection for heat tolerance breeding

Wheat production is seriously influenced by extreme hot weather,which has attracted increasing attention.It is important to compare wheat responses to heat at seedling and reproductive stages,to explore the potential relationship between the performances at different growing stages and the possibility of early selection to accelerate heat tolerance breeding.In this study,forty wheat genotypes were screened under heat stress at both seedling and adult stages.It was found that root lengths at seedling stage were severely reduced by heat stress with significant variations among wheat genotypes.Heat-tolerant genotypes at seedling stage showed less root length decrease than susceptible ones.Wheat genotypes tolerant at seedling stage showed higher yield at adult stage after heat treatment.The performances of wheat genotypes screened under heat stress at seedling and adult stages were ranked by seedling damage index and adult damage index.A significant positive relationship was found between heat tolerance at seedling stage and at adult stage(r=0.6930),suggesting a similar tolerant/susceptible mechanism at different plant growth stages and the possibility of early selection at seedling stage for breeding heat tolerance.Extremely tolerant and susceptible genotypes with consistent performances at seedling and adult stages were genetically compared and associated SNP markers and linked candidate genes were identified.

Identification Cold Tolerance of Pineapple Germplasms at Seedling Stage

Pineapple plant was always injured due to low temperature. Breeding varieties with high cold tolerance was the supreme way to resolve this problem and identifying cold tolerance of germplasms collected was necessary. In this study, SSR locus around homologous sequences of cold-tolerant genes was searched and screened using MD-2 (cold-tolerant variety) and Tainong 17 (cold-sensitive variety). Seventy three pairs of primers of which PCR results were different between these two varieties were gotten. PCRs were performed using these as primers and genomic DNA of germplasms collected as templates. Six pairs of primers were found that their PCR results were in good consistent with cold tolerance. Using GLM (General linear model) association mapping analysis, two SSR markers linked to cold tolerance were found. Their efficiency was verified further using pineapple germplasms with high cold tolerance which had been validated in field by cold wave. They will be used in cold-tolerant breeding of pineapple in the future.

Drought Resistance of Eight Maize Varieties at Seedling Stage in Yunnan Province

Using eight maize varieties （Tiannuo 888, Yunnuo 6, Yunrui 999, Yunrui 6, Yunrui 47, Yunrui 88, Yunyou 105, Yuntianyun 2） as the research ma- terials, this paper aimed to figure out the possible influence caused by repeated drought treatment. A pot experiment was conducted to investigate the changes in 13 phenotypic characters and physiological and biochemical indexes （plant height, fresh mass, root shoot ratio, POD activity, SOD activity） related to drought resist- ante, under two levels of water supply （repeated drought treatment and CK） at seedling stage of maize varieties, and evaluated drought resistanee comprehensively by standard deviation coefficient allocation weighed method. The results showed that the survival rate, leaf area, plant height, shoot fresh mass, root fresh mass, shoot dry mass and root dry mass of seedling maize decreased at varying degrees after repeated drought stress. However, the MDA molality, root shoot ratio, Pro content and soluble protein content increased under repeated drought stress. There were significant difference in morphological, physiological and biochemical inde- xes among different maize varieties. The drought resistances of different maize varieties successively were Yunrui 47 〉 Yuntianyu 2 〉 Yunyou 105 〉 Yunnuo 6 〉 Tianuo 888 〉 Yunrui 6 〉 Yunrui 999 〉 Yunrui 88. These results provide references for maize drought-resistant breeding and maize production.

Screening and identification of soybean varieties with high phosphorus efficiency at seedling stage

In order to simplify the workload and find a reliable method for screening soybeans with different phosphorus(P)efficiencies,47 soybean varieties were screened from 90 varieties according to yield under normal phosphorus,and 10 indicators including root phenotype,phosphorus utilization efficiency at the seedling stage and yield were measured.Through single-index cluster analysis,the performance value and relative value of the abovementioned indexes under low-phosphorus conditions were analyzed,and then,the combined indexes were analyzed by principal components method.The membership function method and the cluster analysis method was used to calculate and analyze the comprehensive score value.Three indexes of root P utilization efficiency(X_(1)),relative value of root P utilization efficiency(X_(2)),and root volume(X_(3))under low P at the seedling stage were selected as the most consistent with the yield screening results under low P condition,and the mathematical model of the comprehensive score value was obtained:D=1.218X_(1)t 0.320X_(2)t 0.007X_(3)-0.664(P=0.000,R^(2)=1.000).The comprehensive score can screen and identify the P efficiency of soybeans with fewer indexes in the early growth stages,which provides a more rapid and reliable mathematical model for screening and identifying a larger number of germplasm resources for P efficiency.