Brown Planthopper Resistance Genes Research Articles

Molecular mapping and transfer of a novel brown planthopper resistance gene bph42 from Oryza rufipogon (Griff.) To cultivated rice (Oryza sativa L.).

Brown planthopper (BPH), Nilaparvata lugens (Stål), is one of the most destructive pests of rice accounting for 52% of annual yield loss. The breakdown of resistance against known BPH biotypes necessitates the identification and deployment of new genes from diverse sources. The current study aimed at mapping and transfer of a novel BPH resistance gene from the wild species of rice O. rufipogon accession CR100441 to the elite rice cultivar against BPH biotype 4. The phenotypic screening against BPH biotype 4 was conducted using the standard seedbox screening technique (SSST). Inheritance study using damage score caused by BPH infestation at the seedling stage indicated the presence of a single major recessive gene with the segregation ratio of susceptible to resistant plants in 3:1 (210:66, χ2c = 0.17 ≤ χ20.05,1 = 3.84). The genotyping of the mapping population was done using polymorphic microsatellite markers between PR122 and O.rufipogon acc.CR100441 spanning all the 12 chromosomes of rice. A total of 537 SSR markers were used to map a BPH resistance gene (designated as bph42) on the short arm of chromosome 4 between RM16282 and RM6659. QTL analysis identified a peak marker RM16335 contributing 29% of the phenotypic variance at 40.76 LOD. The identified marker co-segregates with the bph42 and hence could be efficiently used for marker-assisted selection (MAS) for the transfer of resistance into elite rice cultivars. The introgression lines with higher yield and BPH resistance were identified and are under advanced yield trails for further varietal release.

Molecular identification and efficacy assessment of a glufosinate-tolerant and brown planthopper-resistant transgenic rice line

Insect pests and weeds are the two major biotic factors affecting crop yield in the modern agricultural system. In this study, a brown planthopper (BPH) resistance gene (BPH9) and glufosinate tolerance gene (bar) were stacked into a single T-DNA cassette and transformed into an indica rice (Oryza sativa L.) line Guangzhan 63-4S. A stable transgenic line H23 with a single T-DNA insert was generated, with the T-DNA cassette located on chromosome 3. Field resistance trial using H23 revealed high tolerance to glufosinate and excellent resistance to BPH. These results propose H23 as valuable germplasm for BPH-resistance and glufosinate-tolerance breeding in rice.

Wild Rice Species in Sri Lanka as Genetic Resources for Breeding for Brown Plant Hopper (<em>Nilaparvata lugens</em> (Stål)) Resistance in Rice

Brown pl anthopper (BPH) Nilaparvata lugens (Stål.) is considered the most destructive rice pest in rice-growing countries including Sri Lanka. Resistance breeding considered the most e conomical management strategy, starts by identifying new genetic resources for BPH resistance and comparative analysis wi th existing donors. So far, scientists have identified 38 genes/QTLs responsible for BPH resistance. This study explored the BPH resistance in five wild rice species in Sri Lanka, inc luding the endemic species Oryza rhizomatis. One recommended rice variety; Bg 352, fourteen O. rhizomatis accessions, and one accession from Oryza nivara, Oryza rufipogon, Oryza granulata and Oryza eichingeri screened by the honeydew test. The experiment was arranged in a complete randomize d design with fifteen replicates with Bg 380 and Ptb 33 as susc eptible and resistant checks respectively. The lower amount of honeydew excretion recorded in all tested O. rhizomatis accessions, O. nivara, O. granulata, and O. eichingeri accessions suggested BPH resistance. Both Ptb 33 and O. rufipogon showed a similar level of resistance with low honeydew excretion. The varieties Bg 352 and Bg 380 showed a high amount of honeydew excretions confirming higher susceptibility to the BPH. Therefore, all fourteen accessions of O. rhizomatis and the selected accessions of O. nivara and O. eichingeri are potential donors for rice breeding programs. Further, th e coding sequences (CDS) of known BPH genes of O. sativa were used as queries to search similar genes in wild rice genomes. The CDS coverage and phylogenetic analysis suggest, of known BPH resistance genes, at least BPH6, BPH9, BPH14-1, and BPH18 are present in O. rhizomatis, O. eichingeri, O. nivara, and O. rufipogon genomes. This information will assist in marker-as sisted breeding attempts.

Molecular Mapping of a New Brown Planthopper Resistance Gene Bph43 in Rice (Oryza sativa L.)

Brown planthopper (BPH) has become the most devastating insect pests of rice and a serious threat to rice production. To combat newly occurring virulent BPH populations, it is still urgent to explore more new broad-spectrum BPH resistance genes and integrate them into rice cultivars. In the present study, we explored the genetic basis of BPH resistance in IRGC 8678. We identified and mapped a new resistance gene Bph43 to a region of ~380 kb on chromosome 11. Genes encoding nucleotide-binding domain leucine-rich repeat-containing (NBS-LRR)-type disease resistance proteins or Leucine Rich Repeat family proteins annotated in this region were predicted as the possible candidates for Bph43. Meanwhile, we developed near isogenic lines of Bph43 (NIL-Bph43-9311) in an elite restorer line 9311 background using marker-assisted selection (MAS). The further characterization of NIL-Bph43-9311 demonstrated that Bph43 confers strong antibiosis and antixenosis effects on BPH. Comparative transcriptome analysis revealed that genes related to the defense response and resistance gene-dependent signaling pathway were significantly and uniquely enriched in BPH-infested NIL-Bph43-9311. Our work demonstrated that Bph43 can be deployed as a valuable donor in BPH resistance breeding programs.

Genetics, Mechanisms and Deployment of Brown Planthopper Resistance Genes in Rice

Among the rice insects, brown planthopper (BPH), (Nilaparvata lugens Stål) is a monophagous migratory phloem-sucking insect causing severe loss in Asiatic countries. High nitrogen and willful insecticide application coupled with an increase in temperature have created havoc by this pest during the last few years in certain parts of India, Indonesia, China, Japan, Taiwan, Vietnam, and the Philippines. Though chemical control measures are advocated to mitigate this insect, yet, the incorporation of host-plant resistance factor is the preferred approach to manage this insect attack owing to the high cost of chemical control and adverse effects on the environment. To date, more than 40 major resistance genes and 22 minor genes or quantitative trait loci (QTLs) are identified. Cloning of 11 BPH resistance genes has been completed to date. Majority of the cloned genes produced coiled-coil nucleotide-binding and leucine-rich repeat protein for the defense response in the host plant. Salicylic acid, jasmonic acid, ethylene, mitogen-activated protein kinases, Ca2+, OsRac1, and other signaling molecules play a definite role in the defense response. Signal transduction may lead to sieve tube sealing, production of metabolites, and induction of proteinase inhibitor for defense response against BPH attack. Plants have intrinsic mechanisms for recognition of damage-associated and herbivore-associated molecular patterns and elicitors for host defense response. This review provides an update on the sources of resistance, identification of resistance genes, gene maps, (QTL) detection, cloning, insights into the molecular mechanisms of resistance, and deployment of resistance genes for durable and broad-spectrum resistance in the cultivars against BPH.

Multiparent-Derived, Marker-Assisted Introgression Lines of the Elite Indian Rice Cultivar, 'Krishna Hamsa' Show Resistance against Bacterial Blight and Blast and Tolerance to Drought.

Major biotic stresses viz., bacterial blight (BB) and blast and brown plant hopper (BPH) coupled with abiotic stresses like drought stress, significantly affect rice yields. To address this, marker-assisted intercross (IC) breeding involving multiple donors was used to combine three BB resistance genes—xa5, xa13 and Xa21, two blast resistance genes—Pi9 and Pi54, two BPH resistance genes—Bph20 and Bph21, and four drought tolerant quantitative trait loci (QTL)—qDTY1.1, qDTY2.1, qDTY3.1 and qDTY12.1—in the genetic background of the elite Indian rice cultivar ‘Krishna Hamsa’. Three cycles of selective intercrossing followed by selfing coupled with foreground selection and phenotyping for the target traits resulted in the development of 196 introgression lines (ILs) with a myriad of gene/QTL combinations. Based on the phenotypic reaction, the ILs were classified into seven phenotypic classes of resistance/tolerance to the following: (1) BB, blast and drought—5 ILs; (2) BB and blast—10 ILs; (3) BB and drought—9 ILs; (4) blast and drought—42 ILs; (5) BB—3 ILs; (6) blast—84 ILs; and (7) drought—43 ILs; none of the ILs were resistant to BPH. Positive phenotypic response (resistance) was observed to both BB and blast in 2 ILs, BB in 9 ILs and blast in 64 ILs despite the absence of corresponding R genes. Inheritance of resistance to BB and/or blast in such ILs could be due to the unknown genes from other parents used in the breeding scheme. Negative phenotypic response (susceptibility) was observed in 67 ILs possessing BB-R genes, 9 ILs with blast-R genes and 9 ILs harboring QTLs for drought tolerance. Complex genic interactions and recombination events due to the involvement of multiple donors explain susceptibility in some of the marker positive ILs. The present investigation successfully demonstrates the possibility of rapid development of multiple stress-tolerant/resistant ILs in the elite cultivar background involving multiple donors through selective intercrossing and stringent phenotyping. The 196 ILs in seven phenotypic classes with myriad of gene/QTL combinations will serve as a useful genetic resource in combining multiple biotic and abiotic stress resistance in future breeding programs.

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 thermo-sensitive 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.

Development of New Rice (Oryza. sativa L.) Breeding Lines through Marker-Assisted Introgression and Pyramiding of Brown Planthopper, Blast, Bacterial Leaf Blight Resistance, and Aroma Genes

Brown planthopper, blast, and bacterial blight are the main biotic stressors of rice and can cause a massive loss in rice production. Aroma is an important character of rice quality. It is of far-reaching significance to breed resistant and high-quality varieties using germplasms with objective genes. In this study, the introgression and pyramiding of brown planthopper (BPH), blast, and bacterial leaf blight (BLB) resistance genes and aroma genes into elite rice maintainers and restorers were conducted through conventional cross-breeding coupled with the marker-assisted selection (MAS) breeding method. Single-plant selection was performed from F2 onwards to select desirable recombinants possessing alleles of interest with suitable phenotypes. Respective linked markers were used in each generation from intercrossing to the F7 generation for tracking the presence of targeted genes. A total of 74 improved lines (ILs) have been developed which possess a combination of 1 to 4 genes for BPH, blast, and BLB resistance and aroma. These ILs showed moderate to high resistance to multiple biotic stresses (BPH, blast and BLB) or aromatic fragrance without obvious negative effects on agronomic traits. As multiple resistance and aromatic traits have become significant objectives in rice breeding, these resistance and/or aroma gene introgressed or pyramided lines have important application prospects. Core ideas: (1) marker-assisted breeding was used to pyramid multiple genes for an elite breeding line; (2) improved lines with the introgression of 1–4 genes were developed to achieve high resistance against various biotic stresses and aroma; (3) new lines were used as donor parents to introgress multiple genes in other genetic backgrounds.

Metatranscriptomic Sequencing Suggests the Presence of Novel RNA Viruses in Rice Transmitted by Brown Planthopper.

Viral pathogens are a major threat to stable crop production. Using a backcross strategy, we find that integrating a dominant brown planthopper (BPH) resistance gene Bph3 into a high-yield and BPH-susceptible indica rice variety significantly enhances BPH resistance. However, when Bph3-carrying backcross lines are infested with BPH, these BPH-resistant lines exhibit sterile characteristics, displaying panicle enclosure and failure of seed production at their mature stage. As we suspected, BPH-mediated viral infections could cause the observed sterile symptoms, and we characterized rice-infecting viruses using deep metatranscriptomic sequencing. Our analyses revealed eight novel virus species and five known viruses, including a highly divergent virus clustered within a currently unclassified family. Additionally, we characterized rice plant antiviral responses using small RNA sequencing. The results revealed abundant virus-derived small interfering RNAs in sterile rice plants, providing evidence for Dicer-like and Argonaute-mediated immune responses in rice plants. Together, our results provide insights into the diversity of viruses in rice plants, and our findings suggest that multiple virus infections occur in rice plants.

The Impact of Climate Change on the Resistance of Rice Near-Isogenic Lines with Resistance Genes Against Brown Planthopper

BackgroundThe impact of climate change on insect resistance genes is elusive. Hence, we investigated the responses of rice near-isogenic lines (NILs) that carry resistance genes against brown planthopper (BPH) under different environmental conditions.ResultsWe tested these NILs under three environmental settings (the atmospheric temperature with corresponding carbon dioxide at the ambient, year 2050 and year 2100) based on the Intergovernmental Panel on Climate Change prediction. Comparing between different environments, two of nine NILs that carried a single BPH-resistant gene maintained their resistance under the environmental changes, whereas two of three NILs showed gene pyramiding with two maintained BPH resistance genes despite the environmental changes. In addition, two NILs (NIL-BPH17 and NIL-BPH20) were examined in their antibiosis and antixenosis effects under these environmental changes. BPH showed different responses to these two NILs, where the inhibitory effect of NIL-BPH17 on the BPH growth and development was unaffected, while NIL-BPH20 may have lost its resistance during the environmental changes.ConclusionOur results indicate that BPH resistance genes could be affected by climate change. NIL-BPH17 has a strong inhibitory effect on BPH feeding on phloem and would be unaffected by environmental changes, while NIL-BPH20 would lose its ability during the environmental changes.

Bph30 confers resistance to brown planthopper by fortifying sclerenchyma in rice leaf sheaths

Phloem-feeding insects cause massive losses in agriculture and horticulture. Host plant resistance to phloem-feeding insects is often mediated by changes in phloem composition, which deter insect settling and feeding and decrease viability. Here, we report that rice plant resistance to the phloem-feeding brown planthopper (BPH) is associated with fortification of the sclerenchyma tissue, which is located just beneath the epidermis and a cell layer or two away from the vascular bundle in the rice leaf sheath. We found that BPHs prefer to feed on the smooth and soft region on the surface of rice leaf sheaths called the long-cell block. We identified Bph30 as a rice BPH resistance gene that prevents BPH stylets from reaching the phloem due to the fortified sclerenchyma. Bph30 is strongly expressed in sclerenchyma cells and enhances cellulose and hemicellulose synthesis, making the cell walls stiffer and sclerenchyma thicker. The structurally fortified sclerenchyma is a formidable barrier preventing BPH stylets from penetrating the leaf sheath tissues and arriving at the phloem to feed. Bph30 belongs to a novel gene family, encoding a protein with two leucine-rich domains. Another member of the family, Bph40, also conferred resistance to BPH. Collectively, the fortified sclerenchyma-mediated resistance mechanism revealed in this study expands our understanding of plant-insect interactions and opens a new path for controlling planthoppers in rice.

A new source of resistance in rice against Brown planthopper, Nilaparvata lugens Stal (Homoptera: Delphacidae) and elucidation of its inheritance using phenotypic selections under artificial infestations at seedling and reproductive stages of the crop

Genetic resistance in rice through native traits is an important tactic to manage Brown planthopper (BPH), Nilaparvata lugens Staal (Homoptera: Delphacidae) which is one of the most dreaded pests in the farmer’s field causing serious crop losses. Many sources of resistance, both from cultivated and wild accessions, are known with almost 36 resistance genes mapped to different chromosomes through phenotypic and genotypic selections. A majority of resistance genes identified are effective for BPH biotypes prevailing in Southeast Asia and China. For South Asia, very few BPH resistance genes are effective but without their utilization for the development of commercial hybrids and varieties. A new source of resistance HSPP 6417 has been identified in the present paper, which displayed resistance to 11 populations of BPH collected from different rice ecologies of India. The new source HSPP 6417 had an adverse effect on the population dynamics of BPH by inhibiting the population build-up on the plants. The resistance of HSPP 6417 was equivalent to the only source of resistance in India, G7253 used to develop a commercial rice hybrid AZ8433 DT. On crossing HSPP 6417 with other prolific restorer lines of the commercial hybrids, the major genes were found to control its modes of inheritance. Field trials with F4 generation revealed that resistance was stable with good agronomic performance under infestations. The implications of using such a source of resistance for developing BPH resistant hybrids are discussed in the paper.

Development of a multiplex PCR system to discriminate the alleles of the brown planthopper resistance locus BPH1 in rice (Oryza sativa L.)

The brown planthopper, Nilaparvata lugens Stal (Hemiptera: Delphacidae), is a serious insect pest of rice (Oryza sativa L.). It is known that several wild rice and some Indica Group rice cultivars carry brown planthopper resistance genes. The brown planthopper resistance locus BPH1 has been used for the development of brown planthopper resistance rice in Southeast Asia. Bph1 and Bph2 are considered to be different resistance alleles in the same BPH1 locus, and each resistance allele has a different specificity against different brown planthopper biotypes. The first and second intronic DNA sequences in the BPH1 locus, which are derived from the Indica Group rice cultivar ADR52, wild rice Oryza officinalis and the Japonica Group rice cultivar Nipponbare, were analyzed to find insertion and deletion (InDel) polymorphisms. Based on this InDel polymorphisms information, we developed a multiplex polymerase chain reaction (PCR) method that enables the simultaneous identification of three alleles from the BPH1 locus: Bph1, Bph2 and a Japonica-type allele. Our method will be useful for future breeding research because it facilitates the classification of allele types in the BPH1 locus.

Development of 'multiresistance rice' by an assembly of herbicide, insect and disease resistance genes with a transgene stacking system.

Weeds, diseases and pests pose serious threats to rice production and cause significant economic losses. Cultivation of rice varieties with resistance to herbicides, diseases and pests is believed to be the most economical and environmentally friendly method to deal with these problems. In this study, a highly efficient transgene stacking system was used to assembly the synthetic glyphosate-tolerance gene (I. variabilis-EPSPS*), lepidopteran pest resistance gene (Cry1C*), brown planthopper resistance genes (Bph14* and OsLecRK1*), bacterial blight resistance gene (Xa23*) and rice blast resistance gene (Pi9*) onto a transformable artificial chromosome vector. The construct was transferred into ZH11 (a widely used japonica rice cultivar Zhonghua 11) via Agrobacterium-mediated transformation and 'multiresistance rice' (MRR) with desirable agronomic traits was obtained. The results showed that MRR had significantly improved resistance to glyphosate, borers, brown planthopper, bacterial blight and rice blast relative to the recipient cultivar ZH11. Besides, under the natural occurrence of pests and diseases in the field, the yield of MRR was significantly higher than that of ZH11. A multigene transformation strategy was employed to successfully develop rice lines with multiresistance to glyphosate, borers, brown planthopper, bacterial blight and rice blast, and the obtained MRR is expected to have great application potential. © 2020 Society of Chemical Industry.

Substitution mapping and characterization of brown planthopper resistance genes from indica rice variety, 'PTB33' (Oryza sativa L.).

Rice (Oryza sativa L.) yield is severely reduced by the brown planthopper (BPH), Nilaparvata lugens Stål, in Asian countries. Increasing resistance in rice against BPH can mitigate yield loss. Previous reports indicated the presence of three BPH resistance genes, BPH2, BPH17-ptb, and BPH32, in durable resistant indica rice cultivar ‘PTB33’. However, several important questions remain unclear; the genetic locations of BPH resistance genes on rice chromosomes and how these genes confer resistance, especially with relationship to three major categories of resistance mechanisms; antibiosis, antixenosis or tolerance. In this study, locations of BPH2, BPH17-ptb, and BPH32 were delimited using chromosome segment substitution lines derived from crosses between ‘Taichung 65’ and near-isogenic lines for BPH2 (BPH2-NIL), BPH17-ptb (BPH17-ptb-NIL), and BPH32 (BPH32-NIL). BPH2 was delimited as approximately 247.5 kbp between RM28449 and ID-161-2 on chromosome 12. BPH17-ptb and BPH32 were located between RM1305 and RM6156 on chromosome 4 and RM508 and RM19341 on chromosome 6, respectively. The antibiosis, antixenosis, and tolerance were estimated by several tests using BPH2-NIL, BPH17-ptb-NIL, and BPH32-NIL. BPH2 and BPH17-ptb showed resistance to antibiosis and antixenosis, while BPH17-ptb and BPH32 showed tolerance. These results contribute to the development of durable BPH resistance lines using three resistance genes from ‘PTB33’.

Molecular and functional analysis of a brown planthopper resistance protein with two nucleotide-binding site domains.

The brown planthopper (Nilaparvata lugens Stål, BPH) resistance gene BPH9 encodes an unusual coiled-coil (CC) nucleotide-binding leucine-rich repeat (LRR) protein with two nucleotide-binding site (NBS) domains. To understand how this CC-NBS-NBS-LRR (CNNL) protein regulates defense signaling and BPH resistance, we dissected each domain's functions. The CC domain of BPH9 self-associated and was sufficient to induce cell death. The region of 97-115 residues in the CC domain is crucial for self-association and activation. NBS2, which contains a complete set of NBS function motifs and inhibits CC domain activation, rather than NBS1, acts as a molecular switch to regulate the activity of BPH9. We demonstrated that the CC domain, the NBS domain, and the LRR domain of BPH9 associate with each other and themselves in planta. Further domain swapping experiments revealed that the CC domains of BPH9 and susceptible alleles were similarly competent to induce resistance and the hypersensitive response, while the LRR domain of BPH9 confers resistance specificity to BPH. These findings provide new insights into the regulatory mechanisms governing the activity of CNNL proteins.

Gene Pyramiding for Brown Planthopper Resistance-related Traits, Early Maturity and Aroma of Rice Assisted by Molecular and Phenotypic Markers

The brown planthopper (BPH)-resistant rice, early maturity, and aromatic are expected by both farmers and consumers. The traits have been combined through gene pyramiding and some promising rice genotypes obtained. However the genetic control of BPH resistance and maturity is quantitatively inherited, it is therefore both molecular and phenotypic assessments would be tremendously helpful in selecting promising genotypes. The study aimed to obtain genotypes with such valuable traits. Rice lines were analyzed using molecular markers i.e., RM586, RM589, RM8213 (BPH resistant gene markers); RM7610 and RM19414 (early maturity markers), and IFAP (Internal Fragrant Antisense Primer) for detecting aromatic, and INSP (Internal Non-fragrant Sense Primer) for non-aromatic rice. Phenotypic assessment was performed for brown planthopper resistant-related traits, such as chlorophyll content, stomatal conductance, and trichome density. Other evaluations were heading date and aroma (using 1.7% KOH solution). Results showed that molecular markers for evaluating BPH resistance genes (Bph3, Bph4, Qbph4, and Bph17), aroma (fgr gene), and heading date (Hd2 and Hd3 genes) could differentiate genotypes, and they serve as perfect markers, except for heading date markers. Seven genotypes i.e., #2, #3, #4, #5, #6, #10, and #11 were related to all traits expected based on molecular marker analysis. Meanwhile, genotypes #1, #2, #4, #6, and #11 were similar to their parents based on phenotypic analysis. Pyramiding program based on molecular and phenotypic markers enables us to combine three valuable traits into one rice genotype as presented in this study

Screening and Identification of Brown Planthopper Resistance Genes OsCM9 in Rice

The brown planthopper (BPH) is a major pest that causes serious damage to rice in countries with mild climates, including Korea, Japan, China, and Vietnam. Although a large number of BPH-resistant genes have been reported, BPH has recently evolved rapidly and in a variable manner due to rapid climate change and an unpredictable environment. The synthesis of secondary metabolites in plants is essential, as it provides resistance to various stressors, including pests such as BPH. For QTL mapping, a Samgang/Nagdong double haploid (SNDH) 113 population was used. The BPH resistance gene was screening by measure the resistance score using the phenotype that appeared after BPH inoculation in the 113 SNDH population. QTL mapping was used, and SSR marker RM584-RM225 of chromosome 6 and SSR marker RM331-S8024 of chromosome 8 were commonly identified. These locations contained transcription factors, phytohormones, signaling molecules, kinases, and secondary metabolites that defend plants from stressors in the environment. This region of chromosome 8 also contained a sequence similar to that of rice Choristmate mutase (OsCM9). CM is a gene that is not only found in rice, but also in thale cress (Arabidopsis thaliana (L.) Heynh.), maize (Zea mays L.), and soybean (Glycine max (L.) Merr.). After inoculation with BPH, the relative expression levels of OsCM9 were greater in the line resistant to BPH than in the line susceptible to BPH. The newly identified BPH-resistant gene OsCM9 can be used for the development of rice varieties that are capable of resisting sudden damage due to BPH, as the evolution of BPH due to climate change has had negative impacts on rice crops.

Genetic and molecular understanding of host rice resistance and Nilaparvata lugens adaptation.

The variability of brown planthopper (BPH) populations and diversity of the host rice germplasm provide an ideal model for exploring the genetic and molecular basis of insect-plant interactions. During the long-term evolutionary arms race, complicated feeding and defense strategies have developed in BPH and rice. Nine major BPH resistance genes have been cloned and the exploration of BPH resistance genes medicated mechanism against BPH shed a light on the molecular basis of the rice-BPH interaction. This short review provides an update on our current understanding of the genetic and molecular mechanism for rice resistance and BPH adaptation. Understanding the interactions between BPH and rice will provide novel insights for sustainable control of this pest.

Development of InDel markers of Bph3 and pyramiding of four brown planthopper resistance genes into an elite rice variety

Brown planthopper (BPH) is one of the most destructive pests in rice. Breeding resistant cultivars is the most effective strategy to control BPH. Bph3 is a broad-spectrum and durable BPH resistance locus spanning ~ 50 kb on the short arm of rice chromosome 4. Using the genomic variation data of 4726 rice varieties from public database, we developed 8 InDel markers within the Bph3 locus. By analyzing 563 rice varieties, we demonstrated that these markers could effectively identify Bph3-carriers, with an accuracy rate near to 90%. Through marker-assisted backcross breeding (MABC), we introduced four BPH resistance genes (Bph3/14/18/32) into an elite rice variety, Guang 8B. The results showed that Bph3 had the biggest effect, followed by Bph14 and Bph32, and Bph18 had the smallest effect. In addition, the level of BPH resistance increased with the number of genes pyramided. However, in the case of only two genes being pyramided, the resistance increase was not significant in comparison with the larger effect of the two genes. This suggests that the resistance effects are not simply additive, but epistasis may be involved. The InDel markers and pyramiding lines developed in this study will facilitate Bph3-carrier identification and BPH resistance breeding in rice.