Seedling Resistance Research Articles

Silicon enhances the drought resistance of peach seedlings by regulating hormone, amino acid, and sugar metabolism

BackgroundDrought is one of the main concerns worldwide and restricts the development of agriculture. Silicon improves the drought resistance of plants, but the underlying mechanism remains unclear.ResultsWe sequenced the transcriptomes of both control and silicon-treated peach seedlings under drought stress to identify genes or gene networks that could be managed to increase the drought tolerance of peach seedlings. Peach (Prunus persica) seedlings were used to analyse the effects of silicon on plant growth and physiological indexes related to drought resistance under drought stress. The results showed that silicon addition improved the water use efficiency, antioxidant capacity, and net photosynthetic rate, inhibition of stomatal closure, promoted the development of roots, and further regulated the synthesis of hormones, amino acids and sugars in peach seedlings. A comparative transcriptome analysis identified a total of 2275 genes that respond to silicon under drought stress. These genes were mainly involved in ion transport, hormone and signal transduction, biosynthetic and metabolic processes, stress and defence responses and other processes. We analysed the effects of silicon on the modulation of stress-related hormonal crosstalk and amino acid and sugar metabolism. The results showed that silicon promotes zeatin, gibberellin, and auxin biosynthesis, inhibits the synthesis of abscisic acid, then promote lateral root development and inhibit stomatal closure, and regulates the signal transduction of auxin, cytokinin, gibberellin and salicylic acid. Silicon also regulates the metabolism of various amino acids and promotes the accumulation of sucrose and glucose to improve drought resistance of peach seedlings.ConclusionsSilicon enhanced the drought resistance of peach seedlings by regulating stress-related hormone synthesis and signal transduction, and regulating amino acid and sugar metabolism.

Phenotypic characterization of the Hordeum bulbosum derived leaf rust resistance genes Rph22 and Rph26 in barley.

AimsTwo introgression lines (ILs), 182Q20 and 200A12, which had chromosomal segments introgressed from Hordeum bulbosum in H. vulgare backgrounds, were identified to show seedling resistance against Puccinia hordei, possibly attributed to two resistance genes, Rph22 and Rph26, respectively. This study characterized the phenotypic responses of the two genes against P. hordei over different plant development stages.Methods and ResultsUsing visual and fungal biomass assessments, responses of ILs 182Q20, 200A12 and four other barley cultivars against P. hordei were determined at seedling, tillering, stem elongation and booting stages. Plants carrying either Rph22 or Rph26 were found to confer gradually increasing resistance over the course of different development stages, with partial resistant phenotypes (i.e. prolonged rust latency periods, reduced uredinia numbers but with susceptible infection types) observed at seedling stage and adult plant resistance (APR) at booting stage. A definitive switch between the two types of resistance occurred at tillering stage.Conclusions Rph22 and Rph26 derived from H. bulbosum were well characterized and had typical APR phenotypes against P. hordei.Significance and Impact of the StudyThis study provides important insights on the effectiveness and expression of Rph22 and Rph26 against P. hordei during plant development and underpins future barley breeding programmes using non‐host as a genetic resource for leaf rust management.

Evaluation of Seedling Resistance and Marker Assisted Selection for Leaf Rust (Puccinia triticina) Resistance in Pakistani Wheat Landraces, Cultivars and Advanced Lines

Leaf rust is amongst major biotic constraints of wheat (Triticum aestivum L.) having ability to cause substantial yield reductions worldwide. A continuous exploration for novel sources of resistance is pre-requisite for its management. Objectives of study were to conduct resistance evaluation of 112 Pakistani landraces and 48 advanced lines/ cultivars at seedling stage with total 10 virulent pathotypes of leaf rust, 3 from Pakistan and 7 from U.S.A and to detect closely linked markers for Lr10, 16, 34 and 67 genes through marker-assisted selection (MAS). Findings revealed most of Pakistani landraces showed lack of resistance at seedling stage. Only 7 accessions of landraces and 11 advanced lines were found highly resistant against all pathotypes of Pakistan. Similarly, 10 advanced lines exhibited high resistance while variability in resistance was recorded for landraces against all pathotypes tested from USA. Marker-assisted selection revealed Lr genes i.e. Lr10, Lr16, Lr34 and Lr67 were present at various frequencies. Highest frequency was observed for Lr34 followed by Lr16 Lr67 while lowest was recorded for Lr10. These genetic resources and lines identified effective against Pakistan and USA pathotypes are potential sources for improvement of leaf rust (LR) resistance and can be utilized as valuable material for breeding resistant wheat cultivars.

Exogenous GABA improves the resistance of apple seedlings to long-term drought stress by enhancing GABA shunt and secondary cell wall biosynthesis.

Drought stress is an important factor limiting apple production. γ-Aminobutyric acid (GABA) exists widely in plants and participates in the response to abiotic stress as a metabolite or signaling molecule. The role of exogenous GABA in apple plants, response to long-term drought stress remains unclear. Our study confirmed that exogenous GABA affects the drought resistance of apple plants under long-term drought stress. We found that 1mM exogenous GABA improved the resistance of apple seedlings to long-term drought stress. The plants showed better growth, less reactive oxygen radical accumulation, less damage to cell membranes and greater active photosynthetic capacity. Under long-term drought stress, exogenous GABA facilitated GABA shunt, resulting in more accumulation of organic acids, namely citric acid, succinic acid and malic acid, in roots and stems of apple seedlings. In addition, exogenous GABA upregulated the expression of cellulose-related genes and lignin-related genes, and activated secondary cell wall-related transcription factors to synthesize more cellulose and lignin. A multiple factorial analysis confirmed that the GABA shunt and the biosynthesis of cellulose and lignin substantially contributed to the growth of apple seedlings with the application of exogenous GABA under long-term drought stress. Our results suggested that exogenous GABA improved the resistance of apple seedlings to long-term drought stress by enhancing GABA shunt and secondary cell wall biosynthesis.

The genetic basis and interaction of genes conferring resistance to Puccinia hordei in an ICARDA barley breeding line GID 5779743.

Leaf rust of barley causes significant losses in crops of susceptible cultivars. Deploying host resistance is the most cost-effective and eco-sustainable strategy to protect the harvest. However, most known leaf rust resistance genes have been overcome by the pathogen due to the pathogen’s evolution and adaptation. The discovery of novel sources of genetic resistance is vital to keep fighting against pathogen evolution. In this study, we investigated the genetic basis of resistance in barley breeding line GID 5779743 (GID) from ICARDA, found to carry high levels of seedling resistance to prevalent Australian pathotypes of Puccinia hordei. Multipathotype tests, genotyping, and marker-trait associations revealed that the resistance in GID is conferred by two independent genes. The first gene, Rph3, was detected using a linked CAPS marker and QTL analysis. The second gene was detected by QTL analysis and mapped to the same location as that of the Rph5 locus on the telomeric region of chromosome 3HS. The segregating ratio in F2 (conforming to 9 resistant: 7 susceptible genetic ratio; p > 0.8) and F3 (1 resistant: 8 segregating: 7 susceptible; p > 0.19) generations of the GID × Gus population, when challenged with pathotype 5477 P− (virulent on Rph3 and Rph5) suggested the interaction of two genes in a complementary fashion. This study demonstrated that Rph3 interacts with Rph5 or an additional locus closely linked to Rph5 (tentatively designated RphGID) in GID to produce an incompatible response when challenged with a pathotype virulent on Rph3+Rph5.

Molecular and Cytogenetic Identification of Stem Rust Resistant Wheat-Thinopyrum intermedium Introgression Lines.

Thinopyrum intermedium (JJJsJsStSt, 2n = 6x = 42), a wild relative of common wheat, possesses many desirable agronomic genes for wheat improvement. The production of wheat-Thinopyrum intermedium introgression lines is a key step for transferring these beneficial genes into wheat. In this study, we characterized three wheat-Thinopyrum intermedium introgression lines TA3681, TA5566, and TA5567 using non-denaturing fluorescence in situ hybridization, genomic in situ hybridization, PCR-based landmark unique gene, and intron targeting markers. Our results showed that TA3681 is a wheat-Thinopyrum intermedium 1Stdisomic addition line, TA5566 is a wheat-Thinopyrum intermedium non-Robertsonian translocation line carrying two pairs of 3A-7Js translocation chromosomes, and that TA5567 is a wheat-Thinopyrum intermedium non-Robertsonian translocation line carrying a pair of 3A-7Js translocation chromosomes. We developed 13, 36, and 15 Thinopyrum intermedium chromosome-specific markers for detecting the introgressed Thinopyrum chromosomes in TA3681, TA5566, and TA5567, respectively. Stem rust assessment revealed that TA3681 exhibited ahigh level of seedling resistance to Chinese-prevalent Puccinia graminis f. sp. tritici pathotypes, and both TA5566 and TA5567 were highly resistant to Australian P. graminis f. sp. tritici pathotypes, indicating that Thinopyrum intermedium chromosomes 1St and 7Js might carry new stem rust resistance genes. Therefore, the new identified introgression lines may be useful for improving wheat stem rust resistance.

Seedling resistance of wheat cultivars to Zymoseptoria tritici disease in Ethiopia

Seedling resistance of wheat cultivars to Zymoseptoria tritici disease in Ethiopia

Priming with the green leaf volatile (Z)-3-hexeny-1-yl acetate enhances drought resistance in wheat seedlings

Various studies showed that green leaf volatiles play vital roles in biotic and abiotic stresses. However, their role in drought resistance has never been studied. In order to investigate the possible role of (Z)-3-hexeny-1-yl acetate (Z-3-HAC, a type of green leaf volatile), various physiology experiments were performed to understand the physiological mechanisms of Z-3-HAC in alleviating wheat drought stress. Drought-resistant wheat seedlings were primed with 100 μM Z-3-HAC at the four-leaf stage before drought treatment. Morphological analysis showed that the primed seedlings grew better and showed higher biomass accumulation in both shoots and roots under drought stress. Additionally, exogenous Z-3-HAC significantly increased the total root length, total root surface area, and total root volume of the seedlings under drought stress. In primed seedlings, physiological measurements showed that the relative water content (RWC), net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), maximal photochemical efficiency of photosystem II (PSII) (Fv/Fm), photochemical activity of PSII (Fv′/Fm′), total chlorophyll content, activities of antioxidant enzymes, and osmolyte accumulation were higher than the control under drought conditions. Furthermore, relative electrolyte conductivity (REC), intercellular CO2 concentration (Ci), reactive oxygen species (ROS) accumulation, and malondialdehyde (MDA) content were significantly lower than the non-primed seedlings. Lastly, principal component analysis (PCA) indicated that Z-3-HAC protected wheat seedlings against damage from drought stress mainly through antioxidant and osmoregulatory systems. This study opens a new field of Z-3-HAC application, and provides a new opportunity to improve wheat drought resistance.

Involvement of MdWRKY40 in the defense of mycorrhizal apple against fusarium solani

BackgroundApple (Malus domestica Borkh.) is an important economic crop. The pathological effects of Fusarium solani, a species complex of soilborne pathogens, on the root systems of apple plants was unknown. It was unclear how mycorrhizal apple seedlings resist infection by F. solani. The transcriptional profiles of mycorrhizal and non-mycorrhizal plants infected by F. solani were compared using RNA-Seq.ResultsInfection with F. solani significantly reduced the dry weight of apple roots, and the roots of mycorrhizal apple plants were less damaged when the plants were infected with F. solani. They also had enhanced activity of antioxidant enzymes and a reduction in the oxidation of membrane lipids. A total of 1839 differentially expressed genes (DEGs) were obtained after mycorrhizal and non-mycorrhizal apple plants were infected with F. solani. A gene ontogeny (GO) analysis showed that most of the DEGs were involved in the binding of ADP and calcium ions. In addition, based on a MapMan analysis, a large number of DEGs were found to be involved in the response of mycorrhizal plants to stress. Among them, the overexpressed transcription factor MdWRKY40 significantly improved the resistance of the apple ‘Orin’ callus to F. solani and the expression of the resistance gene MdGLU by binding the promoter of MdGLU.ConclusionThis paper outlines how the inoculation of apple seedlings roots by arbuscular mycorrhizal fungi responded to infection with F. solani at the transcriptional level. In addition, MdWRKY40 played an important role in the resistance of mycorrhizal apple seedlings to infection with F. solani.

Unraveling the wheel of recruitment for salt-marsh seedlings: Resistance to and recovery after dislodgement

Elucidating bottlenecks at critical life stages and quantifying associated resilience (including resistance and recovery) to physical processes are central in inform restoration and attain sustainable development of coastal biogeomorphic ecosystems. Seedling establishment is a key life stage determines saltmarsh restoration potentials. However, the resilience of these recruits, especially through recovery, remains poorly understood. Here, two contrasting globally occurring saltmarsh species, namely Salicornia europaea and Spartina anglica, were employed to generate insights in i) seedling resistance against dislodgement, and ii) seedling recovery potential after dislodgement. Regarding resistance, we found that 1) root-shoot antagonism characterizes the growth rate of seedling resistance to dislodgement through hydraulic disturbance, 2) the root length determines seedling resistance to dislodgement through sheet erosion; 3) a 5 mm sedimentary setting amplifies seedling resistance without inhibiting their morphological evolution. Regarding recovery, we found that 4) dislodged seedlings have a high probability for achieving long-distance dispersal; 5) seedling age and the inundation-free period regulate the re-establishment potential of dislodged seedlings. Overall, S. anglica showed stronger resilience than S. europaea, characterized by stronger seedling resistance against dislodgement and higher re-establishment potential. Our results on seedling resilience suggest that seedling dislodgement is not an end-of-life cycle but a new spin on the “Wheel of Recruitment”, a proposed short-term cyclic behavior with alternating phases of seedling dislodgement, dispersal, and (re-)establishment. The Wheel of Recruitment concept is important for forecasting resilience and persistence of biogeomorphic systems such as salt marshes under global change and for guiding life cycle informed restoration.

Source Identification and Genome-Wide Association Analysis of Crown Rot Resistance in Wheat.

Crown rot (CR) is a soil-borne disease of wheat in arid and semiarid areas of the world. The incidence rate and severity of CR are increasing with each passing year, which seriously threatens the safety of world wheat production. Here, 522 wheat varieties/lines representing genetic diversity were used to identify and evaluate the resistance source to CR disease. Six varieties, including Zimai 12, Xinong 509, Mazhamai, Sifangmai, and Dawson, were classified as resistant ® to CR. Seventy-nine varieties were classified as moderately resistant (MR) to CR, accounting for 15.13% of the tested varieties. The wheat 660 K SNP array was used to identify resistance loci by genome-wide association analysis (GWAS). A total of 33 SNPs, located on chromosomes 1A, 1B, 1D, 4A, and 4D, were significantly correlated with seedling resistance to CR in two years. Among them, one SNP on chromosome 1A and nine SNPs on chromosome 1B showed most significant resistance to disease, phenotypic variance explained (PVE) by these SNPs were more than 8.45%. Except that significant locus AX-110436287 and AX109621209 on chromosome 1B and AX-94692276 on 1D are close to the already reported QTL, other SNPs are newly discovered resistance loci. These results could lay a strong theoretical foundation for the genetic improvement and breeding for CR resistance in wheat.

Genome-Wide Association Study of Leaf Rust and Stem Rust Seedling and Adult Resistances in Tetraploid Wheat Accessions Harvested in Kazakhstan.

Leaf rust (LR) and stem rust (SR) are diseases increasingly impacting wheat production worldwide. Fungal pathogens producing rust diseases in wheat may cause yield losses of up to 50–60%. One of the most effective methods for preventing such losses is the development of resistant cultivars with high yield potential. This goal can be achieved through complex breeding studies, including the identification of key genetic factors controlling rust disease resistance. The objective of this study was to identify sources of tetraploid wheat resistance to LR and SR races, both at the seedling growth stage in the greenhouse and at the adult plant stage in field experiments, under the conditions of the North Kazakhstan region. A panel consisting of 193 tetraploid wheat accessions was used in a genome-wide association study (GWAS) for the identification of quantitative trait loci (QTLs) associated with LR and SR resistance, using 16,425 polymorphic single-nucleotide polymorphism (SNP) markers in the seedling and adult stages of plant development. The investigated panel consisted of seven tetraploid subspecies (Triticum turgidum ssp. durum, ssp. turanicum, ssp. turgidum, ssp. polonicum, ssp. carthlicum, ssp. dicoccum, and ssp. dicoccoides). The GWAS, based on the phenotypic evaluation of the tetraploid collection’s reaction to the two rust species at the seedling (in the greenhouse) and adult (in the field) stages, revealed 38 QTLs (p < 0.001), comprising 17 for LR resistance and 21 for SR resistance. Ten QTLs were associated with the reaction to LR at the seedling stage, while six QTLs were at the adult plant stage and one QTL was at both the seedling and adult stages. Eleven QTLs were associated with SR response at the seedling stage, while nine QTLs were at the adult plant stage and one QTL was at both the seedling and adult stages. A comparison of these results with previous LR and SR studies indicated that 11 of the 38 QTLs are presumably novel loci. The QTLs identified in this work can potentially be used for marker-assisted selection of tetraploid and hexaploid wheat for the breeding of new LR- and SR-resistant cultivars.

Registration of ‘USDA Fortress’ winter feed barley with multiple aphid resistance

Abstract‘USDA Fortress’ (Reg. no. CV‐375, PI 696161), a multiple aphid‐resistant, high yielding, six‐rowed, mid‐season–maturing, winter feed barley (Hordeum vulgare L.) adapted to the Southern Plains, was developed and released by USDA‐ARS in Stillwater, OK. USDA Fortress is highly resistant to Russian wheat aphid [RWA; Diuraphis noxia (Kurdjumov)] and greenbug [Shizaphis graminum (Rondani)], with seedling resistance to the new invasive pest, hedgehog grain aphid [HGA; Sipha maydis (Passerini)]. USDA Fortress has the pedigree ‘Post 90’ *4/R012. Recurrent parent Post 90 has Rsg1 resistance to greenbug, and R012 is an unadapted RWA‐resistant germplasm line selected by USDA‐ARS Stillwater from PI 10706. Post 90 and USDA Fortress rate 2 on Starks’ greenbug resistance scale of 1–9, while USDA Fortress and R012 rate a 3 on Websters Russian wheat aphid resistance scale of 1–9, where 1 is immune and 9 is dead on both scales. Over 17 location‐years, in the absence of aphids, grain yield of USDA Fortress was 19 and 12% greater than ‘Thoroughbred’ and Post 90, respectively. USDA Fortress has average test weight of 60 kg hl–1 and has stable grain yield over state‐wide variability in climatic conditions. USDA Fortress is the first multiple‐aphid resistant barley cultivar in the United States.

Resistance of highland barley seedlings to alkaline salt and freeze-thaw stress with the addition of potassium fulvic acid

Crops are commonly subjected to freeze-thaw and salt stress factors simultaneously in Qinghai-Tibet Plateau. In the agricultural field, potassium fulvic acid can not only promote plant growth and increase crop yield but also enhance plant resistance to stress. In this study, the changes of osmotic adjustment substances, antioxidant enzyme activities and photosynthetic characteristics of barley seedlings under alkaline salt and freeze-thaw stress were investigated by laboratory simulation. The results showed that under single alkaline salt stress, the soluble protein content increased significantly (P &amp;lt; 0.05), and the malondialdehyde (MDA) content of seedlings increased by 63.1%; however, antioxidant enzymes activities and photosynthetic rate of barley seedlings decreased. Under combined stresses of alkaline salt and freeze-thaw, the soluble protein content, antioxidant enzyme activities, and photosynthetic rate of barley seedlings decreased; in contrast, the MDA content of seedlings increased. With the addition of potassium fulvic acid, the soluble protein content of seedlings increased, MDA content decreased significantly (P &amp;lt; 0.05), and enzyme activities tended to be stable. This study revealed that the addition of a proper amount of potassium fulvic acid could mitigate the damage of alkali salt and freeze-thaw stress on barley seedlings.

Transcriptome analysis and phenotyping of walnut seedling roots under nitrogen stresses

Nitrogen is an essential core element in walnut seedling growth and development. However, nitrogen starvation and excessive nitrogen stress can cause stunted growth and development of walnut seedlings, and environmental pollution is also of concern. Therefore, it is necessary to study the mechanism of walnut seedling resistance to nitrogen stress. In this study, morphological and physiological observations and transcriptome sequencing of walnut seedlings under nitrogen starvation and excess nitrogen stress were performed. The results showed that walnut seedlings under nitrogen starvation and excess stress could adapt to the changes in the nitrogen environment by changing the coordination of their root morphology and physiological indexes. Based on an analysis of transcriptome data, 4911 differential genes (DEGs) were obtained (2180 were upregulated and 2731 were downregulated) in a comparison of nitrogen starvation and control groups. A total of 9497 DEGs (5091 upregulated and 4406 downregulated) were obtained in the comparison between the nitrogen overdose and control groups. When these DEGs were analysed, the differential genes in both groups were found to be significantly enriched in the plant’s circadian pathway. Therefore, we selected the circadian rhythm as the focus for further analysis. We made some discoveries by analysing the gene co-expression network of nitrogen metabolism, circadian rhythm, and hormone signal transduction. (a) Nitrite nitrogen (NO2−) or Glu may act as a nitrogen signal to the circadian clock. (b) Nitrogen signalling may be input into the circadian clock by regulating changes in the abundance of the CRY1 gene. (c) After the nitrogen signal enters the circadian clock, the expression of the LHY gene is upregulated, which causes a phase shift in the circadian clock. (d) The RVE protein may send information about the circadian clock’s response to nitrogen stress back to the nitrogen metabolic pathway via the hormone transduction pathway. In conclusion, various metabolic pathways in the roots of walnut seedlings coordinated with one another to resist the ill effects of nitrogen stress on the root cells, and these coordination relationships were regulated by the circadian clock. This study is expected to provide valuable information on the circadian clock regulation of plant resistance to nitrogen stress.

Analysis of Transcriptome and Terpene Constituents of Scots Pine Genotypes Inherently Resistant or Susceptible to Heterobasidion annosum.

Root and stem rot caused by Heterobasidion annosum is a severe problem in boreal Scots pine. Dissecting the features of disease resistance is generally an essential step in resistance breeding in plants and forest trees. In this study, we explored inherent resistance factors of Scots pine against H. annosum. A total of 236 families consisting of 85 full-sib (FS), 35 half-sib population mix (HSpm), and 116 half-sib (HS) families of Scots pine seedlings were inoculated with a H. annosum isolate. We sampled needle tissues before inoculation for terpene measurements and RNA sequencing. Based on the lesion area, the extremes of 12 resistant and 12 susceptible families were selected for further analyses. Necrotic lesions resulting from fungal infection were in a weak to moderate relationship with the plant height. Monoterpenes were the principal terpene compounds observed in Scots pine seedlings. Concentrations of 3-carene were significantly higher in pine genotypes inherently resistant compared with susceptible seedlings. By contrast, susceptible genotypes had significantly higher proportions of α-pinene. Gene ontology analysis of differential expressed transcripts (DETs) revealed that response to biotic factors was enriched in resistant seedlings. Functional characterization of individual DETs revealed that higher expression of transcripts involved in response to abiotic stress was common in susceptible genotypes. This observation was supported by the annotation of hub genes in a key module that was significantly correlated with the lesion trait through weighted gene co-expression network analysis (WGCNA) of 16 HS and HSpm samples. These findings contribute to our understanding of constitutive resistance factors of Scots pine against Heterobasidion root and stem rot diseases.

Effects of nitrogen reduction combined with organic fertilizer on growth and nitrogen fate in banana at seedling stage

Nitrogen reduction combined with organic fertilizer is of considerable significance for the sustainable development of agriculture. A pot experiment using nitrogen reduction combined with organic fertilizer was conducted to explore the effects of different treatments on matter accumulation, physiological resistance, and fertilizer nitrogen fate in banana seedlings. Compared with conventional fertilization, a 20% reduction of nitrogen did not affect the dry weight, chlorophyll content, physiological resistance, and fertilizer utilization rate of banana seedlings, but significantly reduced the nitrogen leaching loss and increased the nitrogen soil residue. Compared with conventional fertilization, organic nitrogen substituting 20% or 30% of the nitrogen reduced by 20% significantly promoted dry matter accumulation and physiological resistance. Organic nitrogen substituting 30% of the 20% reduction of nitrogen increased the dry matter of the whole plant by 24.94%, the nitrogen uptake in the root by 30.87%, the chlorophyll content by 6.05%, the soluble sugar content by 16.88%, Peroxidase (POD) activity by 26.35%, Catalase (CAT) activity by 27.48%, and Super Oxide Dismutase (SOD) activity by 22.97%. Compared with conventional fertilization, all organic substitution treatments significantly reduced fertilizer nitrogen leaching loss, apparent loss, and increased nitrogen soil residue. Compared with the 20% reduction of nitrogen, organic nitrogen substituting 30% of the 20% reduction of nitrogen significantly increased nitrogen utilization by 16.34% and soil residue rate by 13.26%, and reduced nitrogen leaching loss by 35.46%. The results of the present study revealed that a 20% reduction of nitrogen fertilizer with a 30% organic substitution application promoted matter accumulation, enhanced the physiological resistance of banana seedlings, increased the utilization and residue of nitrogen fertilizer, and reduced nitrogen pollution.

Effect of Oligogalacturonides on Seed Germination and Disease Resistance of Sugar Beet Seedling and Root.

Oligogalacturonides (OGs) are a bioactive carbohydrate derived from homogalacturonan. The OGs synthesized in this study significantly inhibited the mycelial growth of Rhizoctonia solani AG-4HGI in vitro, even at a low concentration (10 mg/L). The seed vigor test demonstrated that the application of 50 mg/L OGs to sugar beet seeds significantly increased average germination percentage, germination energy, germination index, and seedling vigor index. The same concentration of OGs also improved the seedling emergence percentage of sugar beet when seeds were sown in soil inoculated with D2 and D31 isolates, respectively. The lesion diameter on mature sugar beet roots caused by R. solani AG-4HGI isolates D2 and D31 also decreased by 40.60% and 39.86%, respectively, in sugar beets roots first treated with 50 mg/mL OGs in the wound site, relative to lesion size in untreated/pathogen inoculated wounds. Sugar beet roots treated with 50 mg/mL OGs prior to inoculation with the D2 isolate exhibited up-regulation of the defense-related genes glutathione peroxidase (GPX) and superoxide dismutase (SOD) by 2.4- and 1.6-fold, respectively, relative to control roots. Sugar beet roots treated with 50 mg/mL OGs prior to inoculation with D31 exhibited a 2.0- and 1.6-fold up-regulation of GPX and SOD, respectively, relative to the control. Our results indicate that OGs have the potential to be used for the protection of sugar beet against R. solani AG-4HGI.

Bazı ekmeklik buğday genotiplerinin Fusarium pseudograminearum’a fide dönemi dayanıklılıkları

Fusarium pseudograminearum is one of the most damaging Fusarium species that causes root, crown, and foot rots in wheat. Identification of resistant germplasm is one of the most efficient and environmentally sound control methods. However, up to date, limited wheat genotypes with partial resistance are available. Therefore, in this study, the seedling resistance reaction of 200 bread wheat genotypes plus 6 control genotypes obtained from CIMMYT to Fusarium pseudograminearum was determined under growth room conditions. Out of the 200 tested genotypes; 1 (0.5%), 35 (17.5%), 112 (56%), 45 (22.5%), and 7 (3.5%) were resistant, moderately resistant, moderately susceptible, susceptible and very susceptible to Fusarium pseudograminearum, respectively. Resistant and moderately resistant genotypes could be used in breeding studies for developing crown rot-resistant cultivars.

Exogenous Application of GABA Alleviates Alkali Damage in Alfalfa by Increasing the Activities of Antioxidant Enzymes

Alfalfa (Medicago sativa L.) is a widely grown and important forage crop. However, alkali stress is detrimental to alfalfa yield and nutritional quality. Gamma-aminobutyric acid (GABA) is a signaling molecule, it participates in and responds to metabolic regulation related to plant growth and development and stress. In this study, we clarify the effect of spraying alfalfa seedlings with GABA on the alkali tolerance of the seedlings. We determined that exogenous application of GABA at 75 mmol/L improved the resistance of alfalfa seedlings to alkali stress caused by exposure to 100 mmol/L NaHCO3, pH 8.5. Exogenous GABA significantly increased the chlorophyll content, the accumulation of soluble sugars in the plants, significantly decreased their relative electrical conductivity, malondialdehyde (MDA), superoxide anion (O2−) and hydrogen peroxide (H2O2) contents, and significantly increased the activities of the antioxidant enzymes catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD). Exogenous GABA increased the activities of GAD and GABA-T, increased the content of glutamate and endogenous GABA, and regulated the expression of the genes MsGAD, MsGABA-T and MsGDH. In alfalfa plants that survived for a long time, compared to the control group, root length and fresh weight were significantly higher. Exogenous GABA had a positive effect on the resistance of alfalfa seedlings to alkali stress, and the effect was closely associated with GAD and GABA-T activity, glutamate content and the levels of endogenous GABA and antioxidants. This work provides a new method for the cultivation of early-stage alfalfa seedlings under low or moderate alkali stress conditions through the application of 75 mmol/L GABA.