Analysis and design for the comprehensive ballistic and blast resistance of polyurea-coated steel plate

Fragments and blast waves generated by explosions pose a serious threat to protective structures.In this paper,the impact resistance of polyurea-coated steel plate under complex dynamic loading is analyzed and designed for improving comprehensive ballistic and blast resistance using the newly established computational evaluating model.Firstly,according to the thickness and placement effects of the coating on the impact resistance,the steel-core sandwich plates are designed,which are proved to own outstanding comprehensive ballistic and blast resistance.Besides,the distribution diagram of ballistic and blast resistance for different polyurea-coated steel plates is given to guide the design of protective structures applying in different explosion scenarios.Furthermore,the dynamic response of designed plates under two scenarios with combined fragments and blast loading is studied.The results show that the synergistic effect of the combined loading reduces both the ballistic and blast resistance of the polyurea-coated steel plate.Besides,the acting sequence of the fragments and blast affects the structural protective performance heavily.It is found that the first loading inducing structural large deformation or damage is dominant.When fragments impact first,the excellent unit-thickness ballistic performance of the structural front part is strongly needed for improving the comprehensive ballistic and blast resistance.

Effects of Nitrogen Rate on Blast Resistance and Grain Yield of Super Early Hybrid Rice Luliangyou 996

Super early hybrid rice Luliangyou 996 was the materials for this experiment. This paper focused on the influences of different nitrogen rates on blast resistance and grain yield. Studies suggested that with the increase of nitrogen rate,there were no distinct changes in the sick grain rate and sickness index, but the fifth grade of panicle blast rate rose gradually. When the nitrogen was too much（270 kg/hm^2）, the sick grain rate and sickness index were the highest. The yield rose along with the addition of nitrogen if the amount of applied nitrogen was within the range of 0 to 180 kg/hm^2, and the yield would decrease with the addition of nitrogen if the amount of applied nitrogen was over 180 kg/hm^2. Considering the sickness, output and economic benefit of rice, it is better to applied 90 to 135 kg/hm^2 of nitrogen for Luliangyou 996.

Avoidance of Linkage Drag Between Blast Resistance Gene and the QTL Conditioning Spikelet Fertility Based on Genotype Selection Against Heading Date in Rice

Previous study showed that a linkage drag between a blast resistance gene Pi25（t） and QTLs conditioning spikelet fertility （qSF-6） and number of filled grains per panicle （qNFGP-6） was detected on the short arm of chromosome 6. A larger population was used for further verification, and the results confirmed the linkage drag between the blast resistance gene and QTL conditioning spikelet fertility, other than QTL conditioning number of filled grains per panicle. Breakdown or avoidance of the linkage drag could be achieved by selection against the genotype background of a heading-date gene （qHD-7） that resided in the region between RM2 and RM214 on chromosome 7. For further validation, two lines with almost identical genotypes on all chromosomal regions except the Pi25（t） region on chromosome 6 were chosen to develop a new population The results showed that qSF-6 could be further subdivided into qSF-6-1 and qSF-6-2. When the genotype of the region between RM2 and RM214 was from rice variety Zhong 156, the linkage drag between Pi25（t） and qSF-6-2 was detected and the allele of qSF-6-2 from rice variety Gumei 2 reduced the spikelet fertility. When the genotype of the region between RM2 and RM214 was from Gumei 2, no linkage drag was detected. This indicates that the linkage drag between the blast resistance gene and the QTL conditioning spikelet fertility could be broken down or avoided under a certain background genotype selection against heading-date and provides a marker aided solution for high level of blast resistance and yield breeding in rice and other crops as well.

Clustering of Major Genes Conferring Blast Resistance in a Durable Resistance Rice Cultivar Gumei 2

By using 304 recombinant inbred lines derived from indica rice cross Zhong 156/Gumei 2, a linkage map consisting of 177 marker loci and covering 12 rice chromosomes was constructed and employed for mapping genes conferring blast resistance in rice. Genomic location of gene Pi25(t) conferring neck blast resistance to the Chinese isolate 92-183 (race ZC15) was verified to be located between markers A7 and RG456 on chromosome 6, with genetic distances of 1.7 cM and 1.5 cM to A7 and RG456, respectively. Leaf blast resistance of Gumei 2 to the Philippine isolate Ca89 (lineage 4) was found to be controlled by a single gene. The gene tentatively designated as Pi26(\) was located between makers B10 and R674 on chromosome 6, with genetic distances of 5.7 cM and 25.8 cM to B10 and R674 respectively. Resistant alleles at both gene loci were derived from Gumei 2, indicating an existence of resistance gene cluster in Gumei 2.

Development of elite restoring lines by integrating blast resistance and low amylose content using MAS

Blast resistance and grain quality are major problems in hybrid rice production in China. In this study, two resistance （R） genes, Pi46 and Pita, along with the gene Wxb, which mainly affects rice endosperm amylose content （AC）, were introgressed into an elite indica restoring line, R8166, which has little blast resistance and poor grain quality through marker-assisted selection （MAS）. Eight improved lines were found to have recurrent genome recovery ratios ranging from 88.68 to 96.23%. Two improved lines, R163 and R167, were selected for subsequent studies. R167, which has the highest recovery ratio （96.23%）, showed no significant differences in multiple agronomic traits. In contrast, R163 with the lowest recovery ratio （88.68%） exhibited significant differences in heading date and yield per plant compared with the recurrent parent. At two developmental stages, R163 and R167 had greatly enhanced resistance to blast over the recurrent parent. Similar trends were also observed for agronomic traits and blast resistance in R163- and R167-derived hybrids when compared with the counterparts from R8166. In addition, R163, R167, and their derived hybrids significantly improved the grain quality traits, including amylose content （AC）, gel consistency （GC）, chalky grain rate （CGR）, and degree of endosperm chalkiness （DEC）. It confirmed the success of efficiently developing elite restoring lines using MAS in this study.

Analysis of the Relationship between Blast Resistance Genes and Disease Resistance of Rice Germplasm via Functional Molecular Markers

Rice blast disease is one of the most devastating diseases of rice(Oryza sativa L.)caused by the fungus Magnaporthe oryzae(M.oryzae),and neck blast is the most destructive phase of this illness.The underlying molecular mechanisms of rice blast resistance are not well known.Thus,we collected 150 rice varieties from different ecotypes in China and assessed the rice blast resistances under the natural conditions that favoured disease development in Jining,Shandong Province,China in 2017.Results showed that 92(61.3%)and 58(38.7%)rice varieties were resistant and susceptible to M.oryzae,respectively.Among the 150 rice varieties screened for the presence of 13 major blast resistance(R)genes against M.oryzae by using functional markers,147 contained one to eight R genes.The relationship between R genes and disease response was discussed by analysing the phenotype and genotype of functional markers.The results showed that the rice blast resistance gene Pita was significantly correlated with rice blast resistance.Our results provided a basis for the further understanding of the distribution of 13 major R genes of rice blast in the germplasm resources of the tested rice varieties,and were meaningful for rice disease resistance breeding.

Pyramiding of Pi46 and Pita to improve blast resistance and to evaluate the resistance effect of the two R genes

Utilization of R（resistance） genes to develop resistant cultivars is an effective strategy to combat against rice blast disease. In this study, R genes Pi46 and Pita in a resistant accession H4 were introgressed into an elite restorer line Hang-Hui-179（HH179） using the marker-assisted backcross breeding（MABB） procedure. As a result, three improved lines（e.g., R1791 carrying Pi46 alone, R1792 carrying Pita alone and R1793 carrying both Pi46 and Pita） were developed. The three improved lines had significant genetic similarities with the recurrent parent HH179. Thus, they and HH179 could be recognized as near isogenic lines（NILs）. The resistance spectrum of the three improved lines, which was tested at seedling stage, reached 91.1, 64.7 and 97.1%, respectively. This was markedly broader than that of HH179（23.5%）. Interestingly, R1793 showed resistance to panicle blast but neither R1791 nor R1792 exhibited resistance at two natural blast nurseries. The results implied that the stacking of Pi46 and Pita resulted in enhanced resistance, which was unachievable by either R gene alone. Further comparison indicated that the three improved lines were similar to HH179 in multiple agronomic traits; including plant height, tillers per plant, panicle length, spikelet fertility, and 1 000-grain weight. Thus, the three improved lines with different R genes can be used as new sources of resistance for developing variety. There is a complementary effect between the two R genes Pi46 and Pita.

Improvement of Upland Rice Variety by Pyramiding Drought Tolerance QTL with Two Major Blast Resistance Genes for Sustainable Rice Production

Varalu is an early maturing rice variety widely grown in the rainfed ecosystem preferred for its grain type and cooking quality.However,the yield of Varalu is substantially low since it is being affected by reproductive drought stress along with the blast disease.The genetic improvement of Varalu was done by introgressing a major yield QTL,qDTY_(12.1),along with two major blast resistance genes i.e.Pi54 and Pi1 through marker-assisted backcross breeding.Both traits were transferred till BC_(2) generation and intercrossing was followed to pyramid the two traits.Stringent foreground selection was carried out using linked markers as well as peak markers(RM28099,RM28130,RM511 and RM28163)for the targeted QTL(qDTY_(12.1)),RM206 for Pi54 and RM224 for Pi1.Extensive background selection was done using genome-wide SSR markers.Six best lines(MSM-36,MSM-49,MSM-53,MSM-57,MSM-60 and MSM-63)having qDTY_(12.1) and two blast resistance genes in homozygous condition with recurrent parent genome of 95.0%-96.5% having minimal linkage drag of about 0.1 to 0.7 Mb were identified.These lines showed yield advantage under drought stress as well as irrigated conditions.MSM-36 showed better performance in the national coordinated trials conducted across India,which indicated that improved lines of Varalu expected to replace Varalu and may have an important role in sustaining rice production.The present study demonstrated the successful marker-assisted pyramiding strategy for introgression of genes/QTLs conferring biotic stress resistance and yield under abiotic stress in rice.

Relationship Between Resistance Gene Analogue and Blast Resistance in Rice

DNA fragments of 43 rice varieties were amplified with 11 pairs of primers designed based on resistance gene analogue （RGA） of plants, and the blast resistance of the varieties was identified by inoculation with 33 isolates of Magnaporthe grisea collected from Yunnan Province, China. Clustering results revealed a significant correlation between the blast resistance and DNA bands with a correlation coefficient of 0.6117 （α=0.01）, indicating that the resistance analysis based on RGA-PCR clustering analysis coincided with that based on inoculation. The correlation coefficients, ranging from 0.1701 to 0.535, however, depended on the primers. Five pairs of primers, S1/AS3, S1 INV/S2 INV, XLRR For/XLRR Rev, Pto-Kinl IN/Pto-Kin2 IN, and NLRR For/NLRR Rev might be applied for blast resistance identification in consideration of their band numbers and polymorphisms, and their correlation coefficients with blast resistance were 0.5305, 0.4898, 0.4059, 0.3719 and 0.3524, respectively. Besides, indica and japonica rice except two highly susceptible varieties, CO39 and Lijiangxintuanheigu could be well classified by the 11 pairs of primers.

Improving Blast Resistance of a Thermo-Sensitive Genic Male Sterile Rice Line GD-8S by Molecular Marker-Assisted Selection

The broad-spectrum blast resistance gene Pi-1, from donor line BL122, was introduced into a thermo-sensitive genic male sterile rice line GD-8S, which possessed good grain quality but high susceptibility to rice blast, by using backcross breeding and molecular marker-assisted selection. Five elite improved male sterile lines, RGD8S-1, RGD8S-2, RGD8S-3, RGD8S-4 and RGD8S-5, were selected based on the results of molecular marker analysis, spikelet sterility, recovery rate of genetic background and agronomic traits. Thirty-three representative blast isolates collected from Guangdong Province, China were used to inoculate the improved lines and the original line GD-8S artificially. The resistance frequencies of the improved lines ranged from 76.47% to 100%, much higher than that of the original line GD-8S （9.09%）. On the agronomic characters, there were no significant differences between the improved lines and GD-8S except for flag leaf length and panicle number per plant. The improved lines could be used for breeding hybrid rice with high blast resistance.

Development of Hybrid Rice Variety FY7206 with Blast Resistance Gene Pid3 and Cold Tolerance Gene Ctb1

Hybrid rice Fanyou 7206（FY7206）, derived from the cross between a sterile line Fanyuan A and a restorer line Fuhui 7206, was bred by the Rice Research Institute, Fujian Academy of Agricultural Sciences, China. FY7206 was characterized by moderate blast resistance, cold tolerance, as well as wide adaptability, and high yields. The blast resistance results indicated that the frequencies of blast races in race B, race C and the total resistance frequency for FY7206 were 95.5%, 100.0% and 97.2%, respectively. The disease resistance results showed that the leaf blast grade for FY7206 was level 1 and panicle blast was level 5. The indoor spray results indicated that FY7206 was resistant to 11 isolates of Magnorpathe oryzae. The blast resistance of FY7206 might be derived from the high expression of blast resistance gene Pid3. The results for simulated cold resistance in an artificial climate chamber indicated that the cold tolerance for FY7206 was moderate at the booting and flowering stages. The cold tolerance results also indicated that FY7206 could be tolerant to temperatures as low as 10 °C at the seedling stage. The q RT-PCR results showed that the expression of cold tolerance gene Ctb1 in FY7206 was relatively high. These results suggested that FY7206 is a hybrid indica rice variety with good comprehensive characteristics, including blast resistance and cold tolerance.

Blast Resistance of Rice Induced by Ag-antibiotic 702

To explore rice blast resistance induced by Ag-antibiotic 702, different concentrations of Ag-antibiotic 702 were spayed on susceptible variety Luliangyou 996 at three-leaf and one-heart stage, to screen the optimal concentration for inducing rice blast resistance. Ag-antibiotic 702 was sprayed at seven different growth stages of rice, to determine the best growth stage for induced blast resistance and duration of blast resistance. Various treatments were inoculated with spore fluid of Magnaporthe grisea at 4 d post spraying, and disease index and incidence rate as well as induction effect of different treatments were investigated after 7 d. The results showed that six concentrations of Ag-antibiotic 702 could induce rice resistance against blast, and 15 μg/mL led to the highest blast resistance; spraying 15 μg/mL Ag-antibiotic 702 at seven different growth stages could induce rice resistance against blast ; the three-leaf and one-heart stage was the best growth stage for inducing rice blast resistance, and the relative induction effect reached 56.56% ; rice blast resistance was the highest at 48 -96 h post spraying, and duration of induced rice blast resistance exceeded 144 h. The study will provide useful experimental data for further development of Ag-antibiotic 702 and application of pre- vention and control methods against rice blast.

Improvement of Rice Blast Resistance of High-Quality Rice Variety Xiangwanxian 13 by Molecular Marker-Assisted Selection

At present, most of high-quality rice varieties are susceptible to blast diseases. In this study, Gumei 2, a rice variety carrying broad-spectrum resistant Pi25 gene, was used as the donor, with Xiangwanxian 13 taken as the receptor and recurrent parent which is also of good quality but highly susceptible to rice blast, to improve the rice blast resistance of Xiangwanxian 13 by crossing and backcrossing based on molecular marker-assisted selection. The results showed that the resistance of the improved strains （i.e. Xiang C72, Xiang C76 and Xiang C77） to blast diseases had been enhanced signifcantly through feld resistance identifcation, equaling the resistance level of Gumei 2, and the main agronomic and quality-related traits of these improved strains had been restored to the level of Xiangwanxian 13, except the chalkiness and cooking-related traits, which suggested similar genomic loci of Xiang C72, Xiang C76 and Xiang C77 to those of Xiangwanxian 13. These three improved strains （i.e. Xiang C72, Xiang C76 and Xiang C77） can provide good intermediate materials for breeding elite varieties with high grain yields and superior blast resistance.

Promising blast resistance entries from 20th-23rd IRBN in Hangzhou

Evaluation for blast resistances of rice entries of 20th to 23rd International Rice Blast Nursery (IRBN) was conducted at CNRRI during 1990-1993. The resistance to seedling blast (SB) was evaluated in a greenhouse at 3-4 leaf stage with artificial inoculation while resistance to leaf blast (LB) and neck blast (NB) were evaluated in the natural field as instructed by the International Network of Genetic Evaluation for Rice (INGER). Materials with high level of blast resistance and good agronomic traits were selected and

Identification of a RAPD marker linked to a blast resistance gene in Oryza sativa L

Marker-aided selection has received more attention in recent years. This relies on the exploitation of dose linkage between molecular markers and target gene(s). We report here a randomly amplified polymorphic DNA (RAPD) marker tightly linked to the blast resistance gene Pi-ll(t) derived from Hongjiaozhan, which confers the resistance to race ZB1 of Pyricularia oryzae Cav.

The rice miR171b–SCL6-IIs module controls blast resistance,grain yield,and flowering

Micro RNAs(mi RNAs)act as regulators of plant development and multiple stress responses.Here we demonstrate that the rice mi R171 b-SCL6-IIs module regulates the balance between blast resistance,grain yield,and flowering.mi R171 b-overexpressing rice plants(OX171 b)displayed increased rice blast resistance accompanied with enhanced defense responses and late heading,whereas blocking mi R171 b expression in rice(MIM171)led to greater susceptibility to blast disease,associated with compromised defense responses and early heading.Either overexpressing or silencing of mi R171 b significantly affected plant height and number of filled seeds per panicle(seed-setting rate),resulting in decreased grain yield.mi R171 b targets SCL6-IIa,SCL6-IIb,and SCL6-IIc,whose expression was suppressed in OX171 b but increased in MIM171.Mutants of SCL6-IIa,SCL6-IIb,and SCL6-IIc all displayed phenotypes like that of OX171 b,including markedly increased blast disease resistance,slightly decreased grain yield,and delayed flowering.Amounts of mi R171 b increased gradually in leaves during the vegetative stage but decreased gradually in panicles during the reproductive stage,whereas SCL6-IIs displayed the reverse expression pattern.Together,these results suggest that the expression of mi R171 b was time-and space-dependent during the rice growth period and regulated the balance between rice blast disease resistance,grain yield,and flowering via SCL6-IIs,and that appropriate accumulation of mi R171 b is essential for rice development.

Experimental investigation of engineered geopolymer composite for structural strengthening against blast loads

The recent increase in blast/bombing incidents all over the world has pushed the development of effective strengthening approaches to enhance the blast resistance of existing civil infrastructures.Engineered geopolymer composite(EGC)is a promising material featured by eco-friendly,fast-setting and strain-hardening characteristics for emergent strengthening and construction.However,the fiber optimization for preparing EGC and its protective effect on structural elements under blast scenarios are uncertain.In this study,laboratory tests were firstly conducted to evaluate the effects of fiber types on the properties of EGC in terms of workability,dry shrinkage,and mechanical properties in compression,tension and flexure.The experimental results showed that EGC containing PE fiber exhibited suitable workability,acceptable dry shrinkage and superior mechanical properties compared with other types of fibers.After that,a series of field tests were carried out to evaluate the effectiveness of EGC retrofitting layer on the enhancement of blast performance of typical elements.The tests include autoclaved aerated concrete(AAC)masonry walls subjected to vented gas explosion,reinforced AAC panels subjected to TNT explosion and plain concrete slabs subjected to contact explosion.It was found that EGC could effectively enhance the blast resistance of structural elements in different scenarios.For AAC masonry walls and panels,with the existence of EGC,the integrity of specimens could be maintained,and their deflections and damage were significantly reduced.For plain concrete slabs,the EGC overlay could reduce the diameter and depth of the crater and spallation of specimens.

Improving the resistance of the rice PTGMS line Feng39S by pyramiding blast,bacterial blight,and brown planthopper resistance genes

Knowledge of rice(Oryza sativa L.)genes and various DNA markers can be used in genomic breeding programs aimed at developing improved elite rice cultivars.We used an efficient genomic breeding approach to pyramid four resistance genes(Pi2,Xa23,Bph14,and Bph15)in the popular photoperiod-and thermosensitive genic male sterile(PTGMS)rice line Feng39S.We performed foreground selection for the target genes,followed by recombinant selection and background selection.This process reduced the sizes of the genomic segments harboring the target genes(566.8 kb for Pi2,1143.9 kb for Xa23,774.7 kb for Bph14,and 1574.9 kb for Bph15)and accelerated the recovery of the recurrent parent genome to proportions ranging from 98.77%to 99.16%,thus resulting in four near-isogenic lines.To assemble the four resistance genes in Feng39S,we performed a double-way cross combined with foreground and background selection to generate two improved lines of Feng39S(Pi2+Xa23+Bph14+Bph15)with a recurrent parent genome recovery of 98.98%.The two lines showed agronomic performance,grain quality,and fertility–sterility transition characteristics similar to those of the original Feng39S line.The newly developed PTGMS lines and corresponding hybrid combinations were resistant to various field blast isolates and seven representative isolates of bacterial blight.At the seedling stage,the lines also showed resistance against brown planthopper.This study provides an efficient and accurate genomic breeding approach for introducing desirable traits into PTGMS lines.

Marker-Assisted Pyramiding of Genes Conferring ResistanceAgainst Bacterial Blight and Blast Diseases into Indian RiceVariety MTU1010

Two major bacterial blight （BB） resistance genes （Xa21 and xa13） and a major gene for blastresistance （Pi54） were introgressed into an Indian rice variety MTU1010 through marker-assistedbackcross breeding. Improved Samba Mahsuri （possessing Xa21 and xa13） and NLR145 （possessingPi54） were used as donor parents. Marker-assisted backcrossing was continued till BC2 generationwherein PCR based functional markers specific for the resistance genes were used for foregroundselection and a set of parental polymorphic microsatellite markers were used for background selectionat each stage of backcrossing. Selected BC2F1 plants from both crosses, having the highest recoveriesof MTU1010 genome （90% and 92%, respectively）, were intercrossed to obtain intercross F1 （ICF1） plants,which were then selfed to generate 880 ICF2 plants possessing different combinations of the BB andblast resistance genes. Among the ICF2 plants, seven triple homozygous plants （xa13xa13Xa21Xa21Pi54Pi54）with recurrent parent genome recovery ranging from 82% to 92% were identified. All the seven ICF2plants showed high resistance against the bacterial blight disease with a lesion lengths of only 0.53–2.28 cm, 1%–5% disease leaf areas and disease scoring values of ‘1’ or ‘3’. The seven ICF2 plants wereselfed to generate ICF3, which were then screened for blast resistance, and all were observed to behighly resistant to the diseases. Several ICF3 lines possessing high level of resistance against BB andblast, coupled with yield, grain quality and plant type on par with MTU1010 were identified and advanced forfurther selection and evaluation.

Identification of blast-resistance loci through genome-wide association analysis in foxtail millet(Setaria italica (L.)Beauv.)

Blast disease caused by the fungus Magnaporthe grisea results in significant yield losses of cereal crops across the world.To date,very few regulatory genes contributing to blast resistance in grass species have been identified and the genetic basis of blast resistance in cereals remains elusive.Here,a core collection of foxtail millet(Setaria italica)containing 888 accessions was evaluated through inoculation with the blast strain HN-1 and a genome-wide association study(GWAS)was performed to detect regulators responsible for blast disease resistance in foxtail millet.The phenotypic variation of foxtail millet accessions inoculated with the blast strain HN-1 indicated that less than 1.60% of the samples were highly resistant,35.25% were moderately resistant,57.09% were moderately susceptible,and 6.08% were highly susceptible.The geographical pattern of blast-resistant samples revealed that a high proportion of resistant accessions were located in lower latitude regions where the foxtail millet growing season has higher rain precipitation.Using 720000 SNP markers covering the Setaria genome,GWAS showed that two genomic loci from chromosomes 2 and 9 were significantly associated with blast disease resistance in foxtail millet.Finally,eight putative genes were identified using rice blast-related transcriptomic data.The results of this work lay a foundation for the foxtail millet blast resistance biology and provide guidance for breeding practices in this promising crop species and other cereals.