Asymmetric Somatic Plant Hybridization: Status and Applications

To create asymmetric somatic hybrids, the genome of the so-called donor protoplast is fragmented prior to protoplast fusion. As a result, only a limited amount of the donor genome is transferred to the fusion product. This technique can circumvent some commonly observed problems related to symmetric fusion and offers a practical breeding tool for asexual hybridization. Genomes are typically fragmented by irradiation, microprotoplast production or application of metabolic inhibitors such as iodoacetamide. Irradiation and microprotoplast production fragment the nuclear genome, whereas iodoacetamide inactivates the cytoplasmic genome. It can therefore be used to introduce cytoplasmic male sterility, an important practical application. For hybrid verification and genome characterization, molecular markers and cytogenetic techniques are applied. This review highlights and discusses progress made during the last decade in spermatophytes asymmetric protoplast fusion.

Evaluation of a Subset of Ethiopia Sorghum Collection Germplasm from the National Genetic Resources Program of the United States Department of Agriculture for Anthracnose Resistance

Globally, one of the most devastating diseases of sorghum is anthracnose incited by Colletotrichum sublineola. During the 2019 and 2020 growing seasons, 94 and 64 accessions from the Ethiopian sorghum germplasm collection maintained by the National Genetic Resources Program of the United States Department of Agriculture were evaluated for anthracnose resistance. Seeds were planted in 1.8 m rows with 0.9 m row spacing in a randomized complete block design. The accessions and checks were replicated three times and 30 days after planting, inoculated by placing C. sublineola-colonized grains in the plant whorls. A total of 30 accessions, including PI533918, PI533923, PI534131 and PI534151 were resistant to the disease in both years. These identified resistant sources can be used in breeding programs to develop anthracnose-resistant lines and hybrids.

Controlled drainage in the Nile River delta of Egypt:a promising approach for decreasing drainage off-site effects and enhancing yield and water use efficiency of wheat

North Africa is one of the most regions impacted by water shortage.The implementation of controlled drainage(CD)in the northern Nile River delta of Egypt is one strategy to decrease irrigation,thus alleviating the negative impact of water shortage.This study investigated the impacts of CD at different levels on drainage outflow,water table level,nitrate loss,grain yield,and water use efficiency(WUE)of various wheat cultivars.Two levels of CD,i.e.,0.4 m below the soil surface(CD-0.4)and 0.8 m below the soil surface(CD-0.8),were compared with subsurface free drainage(SFD)at 1.2 m below the soil surface(SFD-1.2).Under each drainage treatment,four wheat cultivars were grown for two growing seasons(November 2018–April 2019 and November 2019–April 2020).Compared with SFD-1.2,CD-0.4 and CD-0.8 decreased irrigation water by 42.0%and 19.9%,drainage outflow by 40.3%and 27.3%,and nitrate loss by 35.3%and 20.8%,respectively.Under CD treatments,plants absorbed a significant portion of their evapotranspiration from shallow groundwater(22.0%and 8.0%for CD-0.4 and CD-0.8,respectively).All wheat cultivars positively responded to CD treatments,and the highest grain yield and straw yield were obtained under CD-0.4 treatment.Using the initial soil salinity as a reference,the soil salinity under CD-0.4 treatment increased two-fold by the end of the second growing season without negative impacts on wheat yield.Modifying the drainage system by raising the outlet elevation and considering shallow groundwater contribution to crop evapotranspiration promoted water-saving and WUE.Different responses could be obtained based on the different plant tolerance to salinity and water stress,crop characteristics,and growth stage.Site-specific soil salinity management practices will be required to avoid soil salinization due to the adoption of long-term shallow groundwater in Egypt and other similar agroecosystems.

一个与甘蓝显性雄性不育基因连锁的RFLP标记

运用RFLP技术 ,采用集群分析 (BSA)法进行了甘蓝显性雄性不育基因连锁的分子标记研究 ,结果表明 ,该显性不育基因与RFLP标记pBN11连锁 ,经两个回交群体检测 ,其遗传距离分别为 5 189和 1 787cM ,首次将该不育基因被定位于第 1和第

Identification and substrate prediction of new Fragaria x ananassa aquaporins and expression in different tissues and during strawberry fruit development

The newly identified aquaporin coding sequences presented here pave the way for further insights into the plant–water relations in the commercial strawberry(Fragaria x ananassa).Aquaporins are water channel proteins that allow water to cross(intra)cellular membranes.In Fragaria x ananassa,few of them have been identified hitherto,hampering the exploration of the water transport regulation at cellular level.Here,we present new aquaporin coding sequences belonging to different subclasses:plasma membrane intrinsic proteins subtype 1 and subtype 2(PIP1 and PIP2)and tonoplast intrinsic proteins(TIP).The classification is based on phylogenetic analysis and is confirmed by the presence of conserved residues.Substrate-specific signature sequences(SSSSs)and specificity-determining positions(SDPs)predict the substrate specificity of each new aquaporin.Expression profiling in leaves,petioles and developing fruits reveals distinct patterns,even within the same(sub)class.Expression profiles range from leaf-specific expression over constitutive expression to fruit-specific expression.Both upregulation and downregulation during fruit ripening occur.Substrate specificity and expression profiles suggest that functional specialization exists among aquaporins belonging to a different but also to the same(sub)class.

In the name of the rose:a roadmap for rose research in the genome era

The recent completion of the rose genome sequence is not the end of a process,but rather a starting point that opens up a whole set of new and exciting activities.Next to a high-quality genome sequence other genomic tools have also become available for rose,including transcriptomics data,a high-density single-nucleotide polymorphism array and software to perform linkage and quantitative trait locus mapping in polyploids.Rose cultivars are highly heterogeneous and diverse.This vast diversity in cultivated roses can be explained through the genetic potential of the genus,introgressions from wild species into commercial tetraploid germplasm and the inimitable efforts of historical breeders.We can now investigate how this diversity can best be exploited and refined in future breeding work,given the rich molecular toolbox now available to the rose breeding community.This paper presents possible lines of research now that rose has entered the genomics era,and attempts to partially answer the question that arises after the completion of any draft genome sequence:‘Now that we have“the”genome,what’s next?’.Having access to a genome sequence will allow both(fundamental)scientific and(applied)breeding-orientated questions to be addressed.We outline possible approaches for a number of these questions.

Identification of powdery mildew resistance loci in wheat by integrating genome-wide association study(GWAS) and linkage mapping

Wheat powdery mildew(Blumeria graminis f.sp.tritici, Bgt) is a disease of increasing importance globally due to the adoption of high yielding varieties and modern sustainable farming technologies.Growing resistant cultivars is a preferred approach to managing this disease, and novel powdery mildew resistance genes are urgently needed for new cultivar development.A genome-wide association study was performed on a panel of 1292 wheat landraces and historical cultivars using 5011 single nucleotide polymorphism(SNP)markers.The association panel was evaluated for reactions to three Bgt inoculants, OKS(14)-B-3-1, OKS(14)-C-2-1, and Bgt15.Linkage disequilibrum(LD) analysis indicated that genome-wide LD decayed to 0.1 at 23 Mb, and population structure analysis revealed seven subgroups in the panel.Association analysis using a mixed linear model(MLM) identified three loci for powdery mildew resistance on chromosome 2 B, designated QPm.stars-2BL1,QPm.stars-2BL2, and QPm.stars-2BL3.To evaluate the efficacy of GWAS in gene discovery,QPm.stars-2BL2 was validated using F2 and F2:3 populations derived from PI420646 × OK1059060-126135-3.Linkage analysis delimited the powdery mildew resistance gene in PI 420646 to an interval where QPm.stars-2BL2 was located, lending credence to the GWAS results.QPm.stars-2BL1 and QPm.stars-2BL3, which were associated with four SNPs located at 457.7–461.7 Mb and two SNPs located at 696.6–715.9 Mb in the Chinese Spring reference IWGSC RefSeq v1.0, respectively, are likely novel loci for powdery mildew resistance and can be used in wheat breeding to improve powdery mildew resistance.

Character Association Studies in Groundnut (<i>Arachis hypogaea</i>L.)

The aim of this study was to evaluate the degree of relationship and association amongst morphological characters of groundnut as an important food crop in Nigeria. 118 cultivars were planted in a completely randomized design structure. Characterization was based on qualitative and quantitative evaluations of 62 characters. Data were analysed on the SPSS software (20.0 versions). Correlation tools were applied using Spearman, Kendall and Pearson methods. Level of relationship was determined based on the strength of coefficients R. Dependence among traits was tested using the Chi square. Multiple regression analysis was carried out in a predictive model. As a result, many of the traits are very weakly correlated. Day to emergence has no effect on Day to 50% flowering (R = 0.237, p < 0.05) and number of flower (R = 0.221, p < 0.05). Day to first flowering weakly correlates with maturity time of the plant (R = 0.39, p < 0.01) but no effect on the yield. Also, number of flower correlates moderately with number of pods (R = 0.535, p < 0.01) and seeds (R = 0.409, p Plant height also moderately affects leaflet sizes (R = 0.354, p < 0.01) with a low R2 of 13%. Plant biomass moderately affects number of pod (R = 0.494, p < 0.01), pod length (R = 0.395, p < 0.01), pod width (R = 0.473, p < 0.05), number of seed (R = 0.468, p < 0.01) and seed weight (R = 0.548, p < 0.01). Most of the high positive correlations recorded (R > 0.6, p < 0.9) were observed amongst pod and seed parameters. Pod sizes significantly affect the number of seeds present (R = 0.551, p 2 of 30%. Qualitative traits have no effect on each other as all coefficients are very low. Pod constriction and sizes have no relationship (R = -0.029). Tolerance to diseases is not affected by any qualitative trait. Also, no trait determines seed colour. Pubescence of young and mature leaflets recorded the only high positive correlation among all qualitative traits (R = 0.837, p = 0.01). However, leaf and stem pubescence have no relationship. The following traits significantly depend on cultivar type: disease tolerance (χ2 = 17.93, p = 0.000), plant survivorship (χ2 = 39.97, p = 0.000) and pod yield (χ2 = 69.695, p = 0.008). Seed yield has been predicted in a fit model with R2 of 51% and significant p values (p < 0.05) among some predictors. When appropriately applied, the information provided in this report may be useful to groundnut growers and breeders as well those interested in systematic studies of the crop.

Seed Germination and Effects of Three Watering Regimes on the Growth of <i>Dialium guineense</i>(Wild) Seedlings

The effectiveness of three pre-germination treatments in breaking dormancy of the seeds of Dialum guineense and effects of three watering regimes on the growth performance of the seedlings were investigated. The pre-germination treatments were: soaking in hot water for 10 seconds and cooling down in cold water (T1), soaking in cold water for 24 hours (T2), soaking in running water for 48 hours (T3) and control (T4), while watering regimes include: watering once daily in the morning (W1), watering once every two days in the morning (W2) and watering once every three days in the morning (W3). The results showed that germination occurred first at 5 days after sowing (5 DAS) among the seeds soaked in cold water for 24 hours before sowing (T2), while the untreated seeds (control) took the longest period of 12 days before germination occurred. T1 had the highest germination value of 49.6% while T3 had the least of 31.2%. The effects of watering regimes were found to be significantly different on stem-collar diameter, leaf area and total dry weight (P < 0.05). The least significant difference (LSD) test showed that W2 and W3 supported the best growth performance. It is concluded from the results that T2 should be adopted for breaking the dormancy of Dialium guineense seeds and watering interval of three days would not dispose the seedlings to water-stress.

Cell Wall Characteristics of a Maize Mutant Selected for Decreased Ferulates

The cross-linked nature of plant cell walls provides structural integrity for continued growth and development, but limits degradation and utilization by ruminants. In grasses a major cross-linking component is ferulic acid that is incorporated into cell walls as an ester linked residue on arabinoxylans. Ferulates can become coupled to each other and to lignin forming a highly cross-linked matrix of carbohydrates and lignin. Seedling ferulate ester mutants (sfe) were produced in maize using the transposon system and evaluated in feeding trials. The work described here was undertaken to characterize changes in the ferulate cross-linked nature as well as other components of the corn cell wall matrix in leaf, sheath and stem tissues. Total ferulates decreased modestly due to the mutation and were more apparent in leaf tissue (16% - 18%) compared to sheath (+5 to?-6% change) and stem (8% - 9% decrease). The most significant changes were in the ether linked ferulates to lignin, both monomer and dehydrodiferulates (14% to 38% decrease). Other characteristics of the cell wall (lignin, neutral sugar composition) also showed modest changes. The change in total ferulates was modest, but led to improved animal performance. These findings suggest that relatively small changes can have a significant impact upon how well plant materials can be broken down and utilized by ruminants such as dairy cows.

Quantitative disease resistance:Multifaceted players in plant defense

In contrast to large-effect qualitative disease resistance,quantitative disease resistance(QDR)exhibits partial and generally durable resistance and has been extensively utilized in crop breeding.The molecular mechanisms underlying QDR remain largely unknown but considerable progress has been made in this area in recent years.In this review,we summarize the genes that have been associated with plant QDR and their biological functions.Many QDR genes belong to the canonical resistance gene categories with predicted functions in pathogen perception,signal transduction,phytohormone homeostasis,metabolite transport and biosynthesis,and epigenetic regulation.However,other"atypical"QDR genes are predicted to be involved in processes that are not commonly associated with disease resistance,such as vesicle trafficking,molecular chaperones,and others.This diversity of function for QDR genes contrasts with qualitative resistance,which is often based on the actions of nucleotidebinding leucine-rich repeat(NLR)resistance proteins.An understanding of the diversity of QDR mechanisms and of which mechanisms are effective against which classes of pathogens will enable the more effective deployment of QDR to produce more durably resistant,resilient crops.

The Ozone Component of Global Change:Potential Effects on Agricultural and Horticultural Plant Yield,Product Quality and Interactions with Invasive Species

The productivity, product quality and competitive ability of important agricultural and horticultural plants in many regions of the world may be adversely affected by current and anticipated concentrations of ground-level ozone （O_3）. Exposure to elevated O_3 typically results in suppressed photosynthesis, accelerated senescence, decreased growth and lower yields. Various approaches used to evaluate O_3 effects generally concur that current yield losses range from 5% to 15% among sensitive plants. There is, however, considerable genetic variability in plant responses to O_3.

Ethylenediurea（EDU） pretreatment alleviated the adverse effects of elevated O3 on Populus alba "Berolinensis" in an urban area

Ethylenediurea(EDU)has been used as a chemical protectant against ozone(O3).However,its protective effect and physiological mechanisms are still uncertain.The present study aimed to investigate the changes of foliar visible injury,physiological characteristics and emission rates of volatile organic compounds(VOCs)in one-year-old Populus alba"Berolinensis"saplings pretreated with EDU and exposed to elevated O3(EO,120μg/m3).The results showed that foliar visible injury symptoms under EO were significantly alleviated in plants with EDU application(p<0.05).Under EO,net photosynthetic rate,the maximum photochemical efficiency of PSII and the photochemical efficiency of PSII of plants pretreated with 300 and600 mg/L EDU were similar to unexposed controls and significantly higher compared to EOstressed plants without EDU pretreatment,respectively.Malondialdehyde content was highest in EO without EDU and decreased significantly by 14.9%and 21.3%with 300 and600 mg/L EDU pretreatment,respectively.EDU pretreatment alone increased superoxide dismutase activity by 10-fold in unexposed plants with further increases of 88.4%and 37.5%in EO plants pretreated with 300 and 600 mg/L EDU pretreatment,respectively(p<0.05).Abscisic acid content declined under EO relative to unexposed controls with the effect partially reversed by EDU pretreatments.Similarly,VOCs emission rate declined under EO relative to unexposed plants with a recovery of emission rate observed with 300 and 600 mg/L EDU pretreatment.These findings provided significant evidence that EDU exerted a beneficial effect and protection on the tested plants against O3 stress.

Quantitative Disease Resistance： Dissection and Adoption in Maize

Maize is the world＇s most produced crop, providing food, feed, and biofuel. Maize production is constantly threatened by the presence of devastating pathogens worldwide. Characterization of the genetic compo- nents underlying disease resistance is a major research area in maize which is highly relevant for resistance breeding programs. Quantitative disease resistance （QDR） is the type of resistance most widely used by maize breeders. The past decade has witnessed significant progress in fine-mapping and cloning of genes controlling QDR. The molecular mechanisms underlying QDR remain poorly understood and exploited. In this review we discuss recent advances in maize QDR research and strategy for resistance breeding.

Quantitative trait loci associated with soybean seed weight and composition under different phosphorus levels

Seed size and composition are important traits in food crops and can be affected by nutrient availability in the soil. Phosphorus （P） is a non-renewable, essential macronutrient, and P deficiency limits soybean （G1ycine max） yield and quality. To investigate the associations of seed traits in low- and high-P environ- ments, soybean recombinant inbred lines （RILs） from a cross of cultivars Fiskeby III and Mandarin （Ottawa） were grown under contrasting P availability environments. Traits including individual seed weight, seed number, and intact mature pod weight were significantly affected by soil P levels and showed transgressive segregation among the RILs. Surprisingly, P treatments did not affect seed composition or weight, suggesting that soybeanmaintains sufficient P in seeds even in Iow-P soil. Quantitative trait loci （QTLs） were detected for seed weight, intact pods, seed volume, and seed protein, with five significant QTLs identified in Iow-P environments and one significant QTL found in the optimaI-P environment. Broad-sense heritability estimates were 0.78 （individual seed weight）, o.go （seed protein）, 0.34 （seed oil）, and 0.98 （seed number）. The QTLs identified under low P point to genetic regions that may be useful to improve soybean performance under limiting P conditions.

Protecting the photosynthetic performance of snap bean under free air ozone exposure

Tropospheric ozone（O3） is a major air pollutant and causes serious injury to vegetation. To protect sensitive plants from O3 damage, several agrochemicals have been assessed,including cytokinin（e.g., kinetin, KIN） and ethylenediurea（EDU） with cytokinin-like activity.In higher plant, leaves are primarily injured by O3 and protective agrochemicals are often applied by leaf spraying. To our knowledge, the mitigating abilities of EDU and KIN have not been compared directly in a realistic setup. In the present research, impacts of elevated O3（2 × ambient O3, 24 hr per day, for 8 days） on an O3 sensitive line（S156） of snap bean（Phaseolus vulgaris）, which is often used for biomonitoring O3 pollution, were studied in a free air controlled exposure system. The day before starting the O3 exposure, plants were sprayed with a solution of EDU（300 ppm）, KIN（1 mmol/L） or distilled water, to compare their protective abilities. The results demonstrated that 2 × ambient O3 inhibited net photosynthetic rate and stomatal conductance, increased the minimal fluorescence yield of the dark-adapted state, decreased the maximal quantum yield of PSII photochemistry, and led to visible injury. KIN and EDU alleviated the reduction of the photosynthetic performance, and visible injury under O3 fumigation. The plants sprayed with EDU showed greater ability to mitigate the O3 damage than those sprayed with KIN. Chlorophyll fluorescence imaging may have detected more precisely the differences in O3 response across the leaf than the conventional fluorometer.

Objective Phenotyping of Root System Architecture Using Image Augmentation and Machine Learning in Alfalfa (Medicago sativa L.)

Active breeding programs specifically for root system architecture(RSA)phenotypes remain rare;however,breeding for branch and taproot types in the perennial crop alfalfa is ongoing.Phenotyping in this and other crops for active RSA breeding has mostly used visual scoring of specific traits or subjective classification into different root types.While image-based methods have been developed,translation to applied breeding is limited.

Close encounters in the corn field

Plants defend themselves against microbial pathogens in several ways.Among the most important of these mechanisms are cyto-plasmic nucleotide-binding,leucine-rich repeat(NLR)resistance(R)proteins that are activated by direct or indirect interaction with pathogen-derived effector proteins introduced into the plant cell as part of the pathogenesis process.