Resistance Gene Pi9 Research Articles

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.

SSR Marker based Molecular Screening of Blast Resistant Genes in selected Rice genotypes

Rice blast caused by Magnaporthe oryzae is one of the most devastating disease causing major yield losses worldwide in every year. Use of resistant rice varieties is one of the most effective ways to control the disease and reduce yield loss. Molecular screening and allelic diversity of major rice blast resistant genes were determined in forty-eight (48) genotypes of rice germplasms of Bangladesh with ten (10) previously synthesized gene based SSR (Single Sequence Repeats) markers [RM 541, RM 224, RM21, RM527, RM 208, RM 247,RM 72, RM 259, RM 246 & RM 206]. The genetic frequencies of ten (10) major blast resistance genes (Pi-9, Pi-1, Pi-5(t), Piz-5, Pi-b, Pi-b, Pi-ta, Pi-33, Pi27(t), Pitp(t) and Pi-kh) were ranged from 2% to 93%. The blast resistance gene Pi-kh was widely (93%) and Pi5 (2%) was sparsely distributed among the studied genotypes. Nine (9) genotypes sonaanjana, jabedshail, karaja, pajon, IR-09, BAU 39, binni, katiabagdad and kataribhug, had maximum eight (8) blast resistance genes and only one BRRIdhan 46 had minimum two (2) blast resistance genes. Twelve genotypes possessed seven, twelve had six, seven had five and five had four resistant genes. Out of forty-eight (48) genotypes, forty-five (45) genotypes occupied at least five (5) positive fragments of expected product size. Allelic diversity was also found among the rice genotypes for different blast resistance genes.

Evaluation of blast resistance genes Pi9 and Pi54 in rice against local isolates of Tamil Nadu

Rice production system is greatly affected by blast disease caused by Magnaporthe grisea Barr which causes significant yield reduction throughout Asia and different parts of the globe. Developing resistant varieties has been most efficient and economical method for controlling blast disease in rice. Identification of broad spectrum resistance genes against prevailing isolates of the pathogen is a key determining success of developing resistant varieties. However, the blast resistance characterization and evaluation has not been well studied. In the current study, 3 parental lines namely CO 51 (Pi54), 562-4 (a NIL of CO 43x VRP1 harboring Pi 9) and a susceptible genotype Improved White Ponni (IWP) were evaluated against local isolates of blast pathogen. Presence of Pi9 and Pi54 blast resistance genes in the parental lines was confirmed by using functional markers such as NBS4 and Pi54MAS respectively. All the three genotypes were evaluated against blast disease in a hot spot environment. Both CO51 and 562-4 carrying the Pi54 and Pi9 genes respectively showed moderate resistance against blast disease whereas IWP showed a susceptibility reaction against blast disease. Results indicated that pyramiding of these genes would improve resistance against blast disease. The present study has favored the selection of blast resistant parental lines which can be utilized as donor in breeding programs.

Marker-Assisted Breeding of Thermo-Sensitive Genic Male Sterile Line 1892S for Disease Resistance and Submergence Tolerance

Rice line 1892S is an elite thermo-sensitive genic male sterile (TGMS) line for two-line hybrid rice production. However, 1892S is susceptible to rice blast, bacterial blight and submergence. Here we reported the introduction of blast resistance (R) gene Pi9, bacterial blight R gene Xa21 and submergence tolerance gene Sub1A into 1892S genetic background through backcrossing and marker-assisted selection. The improved TGMS line 31892S and its hybrids conferred disease resistance to rice blast and bacterial blight, and showed submergence tolerance for over 14 d without significant loss of viability. The sterility- fertility conversion of 31892S was similar to that of 1892S. 31892S and its derived hybrid rice had similar agronomic traits and grain quality with 1892S and the control hybrid rice, respectively. The newly developed 31892S provided an improved TGMS line for two-line hybrid rice production with disease resistance to rice blast and bacterial blight, and submergence tolerance with no yield penalty or change in grain quality.

Rice Breeding in Russia Using Genetic Markers.

The article concentrates on studying tolerance to soil salinization, water flooding, and blast in Russian and Asian rice varieties, as well as hybrids of the second and third generations from their crossing in order to obtain sustainable paddy crops based on domestic varieties using DNA markers. Samples IR 52713-2B-8-2B-1-2, IR 74099-3R-3-3, and NSIC Rc 106 were used as donors of the SalTol tolerance gene. Varieties with the Sub1A locus were used as donors of the flood resistance gene: Br-11, CR-1009, Inbara-3, TDK-1, and Khan Dan. The lines C101-A-51 (Pi-2), C101-Lac (Pi-1, Pi-33), IR-58 (Pi-ta), and Moroberekan (Pi-b) were used to transfer blast resistance genes. Hybridization of the stress-sensitive domestic varieties Novator, Flagman, Virazh, and Boyarin with donor lines of the genes of interest was carried out. As a result of the studies carried out using molecular marking based on PCR in combination with traditional breeding, early-maturing rice lines with genes for resistance to salinity (SalTol) and flooding (Sub1A), suitable for cultivation in southern Russia, were obtained. Introgression and pyramiding of the blast resistance genes Pi-1, Pi-2, Pi-33, Pi-ta, and Pi-b into the genotypes of domestic rice varieties were carried out. DNA marker analysis revealed disease-resistant rice samples carrying 5 target genes in a homozygous state. The created rice varieties that carry the genes for blast resistance (Pentagen, Magnate, Pirouette, Argamac, Kapitan, and Lenaris) were submitted for state variety testing. The introduction of such varieties into production will allow us to avoid epiphytotic development of the disease, preserving the biological productivity of rice and obtaining environmentally friendly agricultural products.

Development of blast-resistant rice varieties based on application of DNA technologies

Diseases of crops are the main reason for the decrease in yield and product quality. Blast is the most dangerous disease in all areas of world rice cultivation. The most effective, economically viable, and environmentally friendly strategy to combat it is the development of resistant varieties. The use of molecular genetic markers (DNA markers) linked to the loci of blast resistance is relevant in this direction. The objective of the study was to introgress and pyramid genes effective in the south of Russia for race-specific resistance to blast Pi ta, Pi-b, Pi-1, Pi-2, Pi-33, Pi-40 into the genotypes of highly productive rice varieties of domestic breeding to obtain new forms resistant to P. oryzae. To achieve this, varieties Flagman and Boyarin were hybridized with the donors of resistance to blast IR-36, Bl-1, C101-Lac, C101Lac-A-51, IR 83260-2-10-5-2-1-B, which have the genes Pi-ta, Ρi-b, Pi-1 + Pi-33, Pi-2, Pi-40, respectively, with a growing season of more than 150 days. Three backcrosses were carried out and the breeding material was obtained. Several samples with high rates of milled rice quality and blast resistance, productivity, and other economically valuable traits were identified. The program for combining the genes of resistance to blast was performed. The hybridization of the obtained genotypes with the integrated Pi genes between themselves in their various combinations was carried out. The result was a breeding variety with three resistance genes (Pi-1; Pi-2; Pi-33). The cultivation of such varieties in production will reduce the use of chemical protective equipment and avoid pollution of grain ecosystems.

Marker Assisted Gene Pyramiding (MAGP) for bacterial blight and blast resistance into mega rice variety "Tellahamsa".

Bacterial blight (BB) and fungal blast diseases are the major biotic constraints that limit rice productivity. To sustain yield improvement in rice, it is necessary to developed yield potential of the rice varieties by incorporation of biotic stress resistance genes. Tellahamsa is a well-adapted popular high yielding rice variety in Telangana state, India. However, the variety is highly susceptible to BB and blast. In this study, simultaneous stepwise transfer of genes through marker-assisted backcross breeding (MABB) strategy was used to introgress two major BB (Xa21 and xa13) and two major blast resistance genes (Pi54 and Pi1) into Tellahamsa. In each generation (from F1 to ICF3) foreground selection was done using gene-specific markers viz., pTA248 (Xa21), xa13prom (xa13), Pi54MAS (Pi54) and RM224 (Pi1). Two independent BC2F1 lines of Tellahamsa/ISM (Cross-I) and Tellahamsa/NLR145 (Cross-II) possessing 92% and 94% recurrent parent genome (RPG) respectively were intercrossed to develop ICF1—ICF3 generations. These gene pyramided lines were evaluated for key agro-morphological traits, quality, and resistance against blast at three different hotspot locations as well as BB at two locations. Two ICF3 gene pyramided lines viz., TH-625-159 and TH-625-491 possessing four genes exhibited a high level of resistance to BB and blast. In the future, these improved Tellahamsa lines could be developed as mega varieties for different agro-climatic zones and also as potential donors for different pre-breeding rice research.

Improvement of rice blast and brown planthopper resistance of PTGMS line C815S in two-line hybrid rice through marker-assisted selection

Two-line hybrid rice breeding, which plays an important role in ensuring food security in China, is one of important approaches to utilize the heterosis in rice. Breeding of photo-thermo-sensitive genic male sterile (PTGMS) lines of two-line hybrid rice with high resistance to diseases and pests is vital for enhancing rice yield stability, reducing environmental pollution, and increasing rice production efficiency. To breed PTGMS rice with resistance to both rice blast and brown planthopper (BPH), four broad-spectrum blast resistance genes Pi9, Pi47, Pi48, and Pi49 and two BPH resistance genes Bph14 and Bph15 were introgressed into a PTGMS line C815S through backcrossing and gene pyramiding coupled with molecular marker-assisted selection (MAS) in this study. Finally, several improved PTGMS lines of C815S which pyramided 1–3 homozygous rice blast resistance genes and two BPH resistance genes were developed. Evaluation of rice blast resistance showed that the improved PTGMS lines were resistant, while C815S was susceptible or only moderately resistant. Assessment of the BPH resistance showed that C815S was highly susceptible, while the improved lines were resistant. The improved lines had similar major agronomic traits and temperature of fertility transition to C815S, and several traits were even better. The newly developed PTGMS lines can be used for breeding of superior two-line hybrid rice or advanced PTGMS lines.

Marker assisted rice breeding for resistance to biotic and abiotic stressors

Due to the fact that blast (causative agent – Pyricularia oryzae Cav.) is considered to be one of the harmful diseases of rice around the world, weeds compete with the crop for light, mineral nutrition and space, the accelerated development of resistant genotypes for these stressors is very relevant. The use of modern biotechnological approaches (molecular marking) is promising and especially in demand in breeding rice varieties of a new generation. This article presents the results on the introduction and pyramiding in the same genotype blast resistance genes Pi-1, Pi-2, Pi-33, Pi-ta, Pi-b, Pi-40 and the gene for tolerance to prolonged flooding Sub 1A, as a weed control factor, based on domestic rice varieties Flagman, Snezhinka, Novator, Boyarin, as well as large-grain lines, with a short growing season VNIIR5242, KP-25-14, KP-163 and VNIIR9678. As a result of the volumetric work using marker control of target genes in the genotypes of hybrid plants, 4 modern varietal samples and more than 400 backcross self-pollinated rice lines with introduced and pyramided blast resistance genes, as well as backcross self-pollinated lines with Pi and Sub1A genes, were obtained. These plants are adapted for cultivation in the south of Russia, have a duration of 115-117 days, a height of 87-100 cm, a mass of 1000 grains – 30 or more grams, a yield of 8.5 – 11 t/ha, which is significantly higher than that of the standard variety Flagman.

Deciphering signalling network in broad spectrum Near Isogenic Lines of rice resistant to Magnaporthe oryzae

Disease resistance (R) genes like Pi9, Pita, Pi21, Pi54 are playing important role for broad spectrum blast resistance in rice. Development of near isogenic lines (NILs) using these type of broad spectrum genes and understanding their signalling networks is essential to cope up with highly evolving Magnaporthe oryzae strains for longer duration. Here, transcriptional-level changes were studied in three near-isogenic lines (PB1 + Pi1, PB1 + Pi9 and PB1 + Pi54) of rice resistant to blast infection, to find the loci that are unique to resistant lines developed in the background of Pusa Basmati 1 (PB1). The pathway analysis of loci, unique to resistant NILs compared to susceptible control revealed that plant secondary metabolite synthesis was the common mechanism among all NILs to counter against M. oryzae infection. Comparative transcriptome analysis helped to find out common clusters of co-expressed significant differentially expressed loci (SDEL) in both PB1 + Pi9 and PB1 + Pi54 NILs. SDELs from these clusters were involved in the synthesis and degradation of starch; synthesis and elongation of fatty acids; hydrolysis of phospholipids; synthesis of phenylpropanoid; and metabolism of ethylene and jasmonic acid. Through detailed analysis of loci specific to each resistant NIL, we identified a network of signalling pathways mediated by each blast resistance gene. The study also offers insights into transcriptomic dynamics, points to a set of important candidate genes that serve as module to regulate the changes in resistant NILs. We suggest that pyramiding of the blast resistance gene Pi9 with Pi54 will lead to maximum broad spectrum resistance to M. oryzae.

Improving rice blast resistance of Feng39S through molecular marker-assisted backcrossing

BackgroundRice blast caused by Magnaporthe oryzae is one of the most widespread biotic constraints that threaten rice production. Using major resistance genes for rice blast resistance improvement is considered to be an efficient and technically feasible approach to achieve optimal grain yield.ResultsWe report here the introgression of the broad-spectrum blast resistance gene Pi2 into the genetic background of an elite PTGMS line, Feng39S, for enhancing it and its derived hybrid blast resistance through marker-assisted backcrossing (MABC) coupled with genomics-based background selection. Two PTGMS lines, designated as DB16206–34 and DB16206–38, stacking homozygous Pi2 were selected, and their genetic background had recurrent parent genome recovery of 99.67% detected by the SNP array RICE6K. DB16206–34 and DB16206–38 had high resistance frequency, with an average of 94.7%, when infected with 57 blast isolates over 2 years, and the resistance frequency of their derived hybrids ranged from 68.2% to 95.5% under inoculation of 22 blast isolates. The evaluation of results under natural blast epidemic field conditions showed that the selected PTGMS lines and their derived hybrids were resistant against leaf and neck blast. The characterizations of the critical temperature point of fertility-sterility alternation of the selected PTGMS lines, yield, main agronomic traits, and rice quality of the selected PTGMS lines and their hybrids were identical to those of the recurrent parent and its hybrids. DB16206–34/9311 or DB16206–38/9311 can be used as a blast-resistant version to replace the popular hybrid Fengliangyou 4. Likewise, DB16206–34/FXH No.1 or DB16206–38/FXH No.1 can also be used as a blast-resistant version to replace another popular hybrid Fengliangyou Xiang 1.ConclusionsOur evaluation is the first successful case to apply MABC with genomics-based background selection to improve the blast resistance of PTGMS lines for two-line hybrid rice breeding.

Pyramiding of 3-resistant-gene to improve rice blast resistance of a restorer line, Fuhui 673

To improve the blast resistance of elite rice restorer line Fuhui 673, 3 blast resistance genes Pi-1, Pi-9 and Pi-kh were introduced into Fuhui 673 from a good-quality restorer line Jinhui 1059 through 3 successive backcrosses followed by one selfing using the technique of marker-assisted selection. Ten near-isogenic lines (NILs) of Fuhui 673 carrying the 3 introduced resistance genes were created. Genotype analysis using 68 SSR markers evenly distributed in the genome indicated that 92.96%-98.59% of the NILs' genetic background had been recovered to Fuhui 673. Both indoor and field resistance tests indicated that the NILs and their hybrids with sterile line Yixiang A were all resistant to rice blast, with resistance levels significantly higher than those of controls Fuhui 673 and hybrid Yiyou 673 (Yixiang A  Fuhui 673). In addition, among the 10 hybrids between the NILs and Yixiang A, 2 showed significantly higher yield than and 4 displayed similar yield to that of control Yiyou 673, suggesting that most of the NILs retained the elite characteristics of Fuhui 673. Two new hybrid rice cultivars Liangyou 7283 and Jintaiyou 683 from NIL Line 9 showed high yield, good resistance to blast and moderate growth period in regional trial, suggesting that the NIL Line 9 has a good prospect for application.

Development of InDel marker for rice blast resistance gene Pi9

Pi9 is one of the major blast resistance genes which encodes a nucleotide-binding site-leucine-rich repeat (NBS-LRR) domain-containing protein. This gene was observed to show resistance against many pathotypes of the blast pathogen in Malaysia. Resistance allele Pi9 from rice variety 75-1-127 had previously been cloned using map-based cloning strategy. The gene sequence was used to design specific primers to amplify susceptible Pi9 allele from MR219 rice variety prior to cloning. The resistance and susceptible allele of Pi9 were 8.587kb and 8.785kb in length respectively. Allele mining was carried out by comparing between the susceptible and resistance allele of Pi9. One potential InDels polymorphism at position 590bp and 920bp was identified. Primer named as Pi9_InDel was designed targeting this region in such a way that the resistance and susceptible genotypes yielded 327 bp and 438 bp amplicon respectively.

Improving blast resistance of the rice restorer line, Hui 316, by introducing Pi9 or Pi2 with marker-assisted selection

Introducing resistance (R) genes into a susceptible rice cultivar is an effective strategy to achieve broad-spectrum and durable disease resistance. During the breeding process, marker-assisted selection (MAS) provides an efficient approach for direct screening of the progeny containing the R gene in a population. In this study, we designed an optimized polymerase chain reaction marker, Pi9/2, targeting the same polymorphic region of our previously developed Pi9-Pro and demonstrated that Pi9/2 is more specific than Pi9-Pro for the blast resistance genes Pi9 and Pi2 in MAS. With the assistance of Pi9/2, Pi9 and Pi2, from donor lines 75-1-127 and C101A51, respectively, were separately introgressed into the strong rice restorer line, Hui 316, by backcrossing. The two improved representative Hui 316 lines, Hui 316-Pi9 and Hui 316-Pi2, displayed similar agronomic traits to Hui 316. Inoculation tests for blast resistance revealed that Hui 316-Pi9 and Hui 316-Pi2 showed markedly enhanced resistance to blast fungi compared with Hui 316. Investigation of agronomic traits for yield and rice quality indicated that the hybrid combinations from Hui 316-Pi9 or Hui 316-Pi2 crossed with male sterility lines were similar to those derived from Hui 316. Therefore, introgression of Pi9 or Pi2 into with Hui 316 could improve its resistance to blast with little influence on its restoring ability, which will facilitate the application of Hui 316 in rice production. These results also indicate that the optimized marker, Pi9/2, is effective in introducing Pi9 or Pi2 by MAS to improve blast resistance of rice cultivars.

Gene diagnosis and targeted breeding for blast-resistant Kongyu 131 without changing regional adaptability

The fungus Magnaporthe oryzae threatens the rice production of Kongyu 131 (KY131), a leading japonica variety in Northeast China. In this study, two rice lines, KP1 and KP2-Hd1, were obtained by introgressing the blast resistance genes Pi1 and Pi2 into KY131, respectively. However, both lines headed later than KY131. RICE60K SNP array analysis showed that Hd1 closely linked to Pi2 was introgressed into KP2-Hd1, and the linkage drag of Hd1 was broken by recombination. On the other hand, no known flowering genes were introgressed into KP1. Gene diagnosis by resequencing six flowering genes showed that KP1 carried functional Hd16 and Ghd8 alleles. Due to its suppression role in heading under long-day conditions, Ghd8 was chosen as the target for gene editing to disrupt its function. Four sgRNAs targeting different sites within Ghd8 were utilized to induce large-deletion mutations, which were easy to detect via agarose gel electrophoresis. All the ghd8-mutated KP1 lines were resistant to rice blast disease and headed earlier than the control KP1, even than KY131, under natural long-day conditions, which ensures its growth in Northeast China. This study confirmed that a combination of gene diagnosis and targeted gene editing is a highly efficient way to quickly eliminate undesired traits in a breeding line.

Virulence structure of Magnaporthe oryzae populations from Fujian Province, China

Rice blast, caused by Magnaporthe oryzae, is one of the most devastating diseases of rice worldwide. The aim of the present study was to elucidate the virulence structure of M. oryzae populations in Fujian Province, China, over the period 2006–2015. For this purpose, 456 M. oryzae isolates collected from diverse cultivars from eight rice cropping regions in Fujian were screened for the presence of 11 known avirulence genes: Avr-Pik, Avr-Pita1, Avr-Pita2, Avr-Pita3, PWL2, Avr1-CO39, ACE1, Avr-Piz-t, Avr-Pia, Avr-Pii and Avr-Pikm, with gene-specific molecular markers. The results showed that Avr-Pik and Avr-Pita3 occurred at the highest frequency (94.5% and 91.7%, respectively), while Avr1-CO39 and Avr-Pii were not detected. Further, the remaining avirulence genes occurred at frequencies ranging from 5.9% to 89.0%. Temporal population dynamics revealed that Avr-Pik was uniformly distributed in all 10 years, at frequencies of more than 87.5%. Spatial distribution analysis showed avirulence genes were present at different frequencies among the geographic regions. In addition, 24 rice monogenic lines of IRRI-Japan with known blast resistance genes were inoculated to assess the virulence of 60 isolates. The results revealed that the resistance gene Pik showed the broadest resistance spectrum to the isolates tested and therefore would be the most useful in rice blast resistance breeding. The resistance genes Pi-z5, Pi-1(1), Pi-kp, Pi-9(t), Pi-ta(1) and Pi-kh also were effective and would therefore also be of value to resistance breeding programmes. The present study provides information that should be useful for the development and deployment of rice blast resistant cultivars in Fujian Province.

Genetic structure of Magnaporthe oryzae populations in three island groups in the Philippines

Genetic structure of the rice blast pathogen, Magnaporthe oryzae was characterized using 453 monoconidial isolates collected from different rice agroecosystems from Luzon, Visayas and Mindanao, the three island groups in the Philippines in experimental plots and in farmer fields. Using 12 microsatellite markers, a total of 93 new multi-locus genotypes (MLGs) were determined when compared to the reference isolates representing the genotypes previously published. Analysis revealed a weak geographic structuring of pathogen genotypes, with some of those collected from Luzon clustering with those from Visayas or Mindanao. Nevertheless, none of the strains from Mindanao clustered with those from the Visayas and none from Visayas clustered with those from Mindanao. This structure likely results from limited natural migration and from some events of long distance migration, probably through the transport of infected seeds. Significant genetic differences were noted on isolates collected from distinct rice agroecosystems. A subset of 30 isolates, representative of MLGs, were tested for fertility status. Of these, eight induced the production of perithecia, of which six were male-fertile and two were also female-fertile. In addition, MAT1.1 isolates represented 36% of our sample whereas it represented only 5% in the collection of reference strains. Pathogenicity test of a subset of 24 isolates inoculated to 16 differential rice varieties demonstrated that most isolates were avirulent to varieties which carry the resistance genes Pi1, Pi33 Pi9, Pikm, and the combination of Piz and Pish.

Marker-assisted introgression of three dominant blast resistance genes into an aromatic rice cultivar Mushk Budji

Modern high yielding rice varieties have replaced most of the traditional cultivars in recent past. Mushk Budji, is one such short grained landrace known for its aroma and exquisite quality, however, is highly susceptible to blast disease that has led to considerable decline in its area. Mushk Budji was crossed to a triple-gene donor line, DHMAS 70Q 164-1b and followed through marker-assisted foreground and background selection in first and second backcross generations that helped to incorporate blast resistance genes Pi54, Pi1 and Pita. Marker-assisted background selection was carried out using 78 SSR and STS markers that helped to reduce linkage drag around the genes Pi54, Pi1 and Pita to 2.74, 4.60 and 2.03 Mb, respectively. The three-gene lines in BC2F2:3 were genotyped using 50 K SNP chip and revealed more than 92% genome similarity to the RP. 2-D gel assay detected differentially expressing 171 protein spots among a set of backcross derived lines, of which 38 spots showing match score of 4 helped us to calculate the proteome recovery. MALDI-TOF analysis helped to detect four significant proteins that were linked to quality and disease resistance. The improved lines expressed resistance to blast under artificial and natural field conditions.

The Race Structure of the Rice Blast Pathogen Across Southern and Northeastern China

BackgroundRice blast, caused by the ascomycete Magnaporthe oryzae (Mo), imposes a major constraint on rice productivity. Managing the disease through the deployment of host resistance requires a close understanding of race structure of the pathogen population.ResultsThe host/pathogen interaction between isolates sampled from four Mo populations collected across the rice-producing regions of China was tested using two established panels of differential cultivars. The clearest picture was obtained from the Chinese cultivar panel, for which the frequency of the various races, the race diversity index, the specific race isolate frequency, and the frequency of the three predominant races gave a consistent result, from which it was concluded that the pathogen population present in the southern production region was more diverse than that in the northeastern region. The four blast resistance genes Pi1, Pik, Pik-m, and Piz all still remain effective in the southern China rice production area, as does Pi1 in the northeastern region. The effectiveness of Pita, Pik-p, Piz, and Pib is restricted to single provinces. The distinctive resistance profile shown by the Chinese differential cultivar set implied the presence of at least five as yet unidentified blast resistance genes.ConclusionsThe Chinese differential cultivar set proved to be more informative than the Japanese one for characterizing the race structure of the rice blast pathogen in China. A number of well characterized host resistance genes, in addition to some as yet uncharacterized ones, remain effective across the major rice production regions in China.

Diverse Rice Landraces of North-East India Enables the Identification of Novel Genetic Resources for Magnaporthe Resistance.

North-East (NE) India, the probable origin of rice has diverse genetic resources. Many rice landraces of NE India were not yet characterized for blast resistance. A set of 232 landraces of NE India, were screened for field resistance at two different hotspots of rice blast, viz., IIRR-UBN, Hyderabad and ICAR-NEH, Manipur in two consecutive seasons. The phenotypic evaluation as well as gene profiling for 12 major blast resistance genes (Pitp, Pi33, Pi54, Pib, Pi20, Pi38, Pita2, Pi1, Piz, Pi9, Pizt, and Pi40) with linked as well as gene-specific markers, identified 84 resistant landraces possessing different gene(s) either in singly or in combinations and also identified seven resistant landraces which do not have the tested genes, indicating the valuable genetic resources for blast resistance. To understand the molecular diversity existing in the population, distance and model based analysis were performed using 120 SSR markers. Results of both analyses are highly correlated by forming two distinct subgroups and the existence of high diversity (24.9% among the subgroups; 75.1% among individuals of each subgroup) was observed. To practically utilize the diversity in the breeding program, a robust core set having an efficiency index of 0.82 which consists of 33 landraces were identified through data of molecular, blast phenotyping, and important agro-morphological traits. The association of eight novel SSR markers for important agronomic traits which includes leaf and neck blast resistance was determined using genome-wide association analysis. The current study focuses on identifying novel resources having field resistance to blast as well as markers which can be explored in rice improvement programs. It also entails the development of a core set which can aid in representing the entire diversity for efficiently harnessing its properties to broaden the gene pool of rice.