Search Results (28)

Diseases and weeds occupy a leading place among the factors limiting the yield of agricultural crops, including rice. These factors can be overcome through the use of chemical protective agents, as well as through the creation and introduction into agricultural production of rice varieties resistant to these stressors. The use of DNA marking technologies for target genes of economically valuable traits in the creation of promising varieties allows not only for the identification of genes but also the monitoring of their transmission during crosses and the selection of breeding-valuable genotypes with genes of interest. In addition, this ensures a reduction in the volume of breeding nurseries, as well as time and material costs during variety modeling, and rapid rotation of new high-yield varieties with specified characteristics. We have selected effective marker systems based on the use of DNA marking technologies for target genes for resistance to blast (Pi) and submergence tolerance (Sub1A). These systems allow for precise targeted selection of hybrid plants with these genes in the breeding process. In addition, we have automated the detection of transferred Pi-ta and Pi-b genes, which greatly relieves the DNA analysis during mass screening of breeding material. The final result of this work is the created rice varieties Al’yans, Lenaris and Kapitan with the Pi-ta blast resistance gene and the Pirouette rice variety with the Pi-1, Pi-2, and Pi-33 genes. These varieties exceed the standards by 0.64–2.2 t/ha, and their involvement in production makes it possible to obtain additional products by increasing yields in the amount of about RUB 80 thousand/ha. Full article

Rice blast caused by the ascomycete fungus Magnaporthe oryzea is one of the most widespread and destructive rice diseases worldwide. The most economical and effective strategy for controlling rice blast is the rational use and promotion of disease-resistant varieties. To enhance disease resistance, it is essential to analyze the resistance levels of rice varieties and the role of resistance (R) genes. To investigate blast resistance, R gene distribution, and their contributions in japonica rice, 287 varieties were evaluated through artificial inoculation. PCR detection was also performed using specific primers for eleven R genes. The results showed that 24.4% of the varieties exhibited moderate resistance (MR), indicating an overall moderate resistance level. The frequency of R genes varied significantly: Pib was the most prevalent (89.2%), followed by Pi5 (73.5%), Pita (62.4%), Pia (54.4%), Pikh (48.4%), Pik (41.1%), Pi9 (35.5%), Pizt (23.7%), Pit (10.8%), and Pi1 (10.5%). No Pigm was detected. Among these, Pik, Pi9, Pizt, and Pita contributed most significantly to disease resistance, with contributions of 42.4%, 38.2%, 38.2%, and 33.5%, respectively. The number of R genes detected in the tested varieties ranged from 0 to 9, with most varieties containing more than three genes. The highest proportion of resistant varieties was observed in those carrying six genes. The most common R gene combinations in resistant varieties were ‘Pib + Pita + Pi5 + Pikh + Pik + Pi9’ and ‘Pizt + Pib + Pita + Pia + Pi5 + Pik + Pi9’. In conclusion, these findings provide valuable insights into the breeding and utilizing blast-resistant japonica rice varieties in Anhui Province. Full article

The avirulence (AVR) genes of the filamentous ascomycete fungus Magnaporthe oryzae (M. oryzae) are known to mutate rapidly under a higher selection pressure, allowing the pathogen to evade recognition by rice resistance (R) genes. Understanding the geographic distribution and natural variation of AVR genes is critical for the rational utilization and prolonging of the effectiveness of R genes. In this study, a total of 1060 M. oryzae strains collected from 19 rice blast nurseries in 13 provinces across southern China were subjected to presence/absence variation (PAV), genetic variation, and virulence analyses of the AVR-Pita1 gene. PCR amplification results indicated that AVR-Pita1 was present in only 57.45% of the blast strains, with significant geographic variation in distribution frequency. Specifically, the highest frequency (100%) was observed in strains from Chengmai, Hainan, while the lowest (1.79%) was observed in strains from Baoshan, Yunnan. A sequencing analysis identified 29 haplotypes of AVR-Pita1, characterized by insertions, deletions, and base substitutions. A phylogenetic analysis indicated that haplotypes of AVR-Pita1 identified in this study were clustered into one clade. A further amino acid sequence analysis of these haplotypes led to the identification of 25 protein variants. Notably, four haplotypes of AVR-Pita1 exhibited pathogenicity toward its corresponding rice R gene, PtrA. Additionally, we performed allele profiling of Ptr in a collection of elite parental lines that are widely used in rice breeding in southern China and found that the functional Ptr alleles (PtrA, PtrB, and PtrC) accounted for over 70%. Full article

Identifying major blast resistance genes in Oryza sativa L. genotypes is key to enhancing and maintaining the resistance. Observing rice varieties with durable resistance to blast has become a potential target in rice breeding programs. In this study, an evaluation was conducted during 2020 and 2021 on ten Egyptian and introduced varieties. First, a field experiment was conducted in a randomized complete block design with three replications, and it was found that the Egyptian cultivar Sakha 101 had the highest crop grain yields (53.27 g). The Spanish varieties Hispagrán and Puebla were the earliest (110 and 108 days, respectively) as well as the highest in 1000-grain yield, giving them priority as donors for these traits; however, they had the lowest mean values in the number of panicles. Second, these cultivars were subjected to eighteen isolates from five strains of Pyricularia oryzae (IH, IC, ID, IE, and II). The Egyptian varieties Giza 177, Giza 179, Sakha 106, Giza 182, GZ1368-5-5-4, and GZ6296 were 100% resistant, while Hispagrán’s resistance was 16.6%, followed by Sakha 101 with 27.8%. To gain insight into the ten varieties, we used STS, SCAR, and CAPS markers to detect and mine alleles for major blast broad-spectrum resistance genes Pi2, Pi9, and Pita2. In the context of considering gene pyramiding as an effective strategy for achieving broad durable spectrum resistance to blast, molecular profiling was also conducted on eighteen F2 single plants obtained from the hybridization of Giza 177 (resistant) × Puebla (susceptible) varieties. Also, eighteen F2 single plants were obtained from Giza 177 × Hispagrán (highly susceptible) varieties. Conducting a molecular scan with STS dominant marker YL153/YL154 was performed on ten cultivars to detect the presence of the Pita2 gene, which conferred a unique band in Puebla. By doing a scan of the 18 second-generation plants derived from Giza 177 × Puebla, 11 individual plants of the 18 plants obtained a band, which was transferred from Puebla. F2 plants obtained from Giza 177 × Puebla amplified with CAPS marker RG64-431/RG64-432 had higher numbers of Pi2 alleles, while F2 plants of Giza 177 × Hispagrán cross-amplified with SCAR marker linked to Pi9 exceeded their parents more. Our results have revealed that molecular markers played an essential role in determining the direction of evolution for blast resistance traits. Full article

Barnyard grass is one of the most serious rice weeds, often growing near paddy fields and therefore potentially serving as a bridging host for the rice blast fungus. In this study, we isolated three fungal strains from diseased barnyard grass leaves in a rice field. Using a pathogenicity assay, we confirmed that they were capable of causing blast symptoms on barnyard grass and rice leaves to various extents. Based on morphology characterization and genome sequence analyses, we confirmed that these three strains were Epicoccum sorghinum (SCAU-1), Pyricularia grisea (SCAU-2), and Exserohilum rostratum (SCAU-6). The established Avirulence (Avr) genes Avr-Pia, Avr-Pita2, and ACE1 were detected by PCR amplification in SCAU-2, but not in SCAU-1 or SCAU-6. Furthermore, the whole-genome sequence analysis helped to reveal the genetic variations and potential virulence factors relating to the host specificity of these three fungal pathogens. Based on the evolutionary analysis of single-copy orthologous proteins, we found that the genes encoding glycoside hydrolases, carbohydrate esterases, oxidoreductase, and multidrug transporters in SCAU-1 and SCAU-6 were expanded, while expansion in SCAU-2 was mainly related to carbohydrate esterases. In summary, our study provides clues to understand the pathogenic mechanisms of fungal isolates from barnyard grass with the potential to cause rice blast. Full article

The objective of this study was to examine whether fucosterol, a phytosterol of marine algae, could ameliorate skeletal muscle atrophy in tumor necrosis factor-alpha (TNF-α)-treated C2C12 myotubes and in immobilization-induced C57BL/6J mice. Male C57BL6J mice were immobilized for 1 week to induce skeletal muscle atrophy. Following immobilization, the mice were administrated orally with saline or fucosterol (10 or 30 mg/kg/day) for 1 week. Fucosterol significantly attenuated immobilization-induced muscle atrophy by enhancing muscle strength, with a concomitant increase in muscle volume, mass, and myofiber cross-sectional area in the tibialis anterior (TA) muscle in mice. In both the TNF-α-treated C2C12 myotubes and the TA muscle of immobilized mice, fucosterol significantly prevented muscle protein degradation, which was attributed to a reduction in atrogin-1 and muscle ring finger 1 gene expression through an increase in forkhead box O3α (FoxO3α) phosphorylation. Continuously, fucosterol stimulated muscle protein synthesis by increasing the phosphorylation of the mammalian target of the rapamycin (mTOR), 70 kDa ribosomal protein S6 kinase, and 4E binding protein 1, which was mediated through the stimulation of the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway. Thus, fucosterol alleviated skeletal muscle atrophy in TNF-α-treated C2C12 myotubes and immobilized C57BL/6J mice through the regulation of the Akt/mTOR/FoxO3α signaling pathway. Full article

Background: Rice blast, caused by Magnaporthe oryzae, seriously damages the yield and quality of rice worldwide. Pi-ta is a durable resistance gene that combats M. oryzae carrying AVR-Pita1. However, the distribution of the Pi-ta gene in rice germplasms in Yunnan Province has been inadequately studied. Methods: We analyzed the potential molecular evolution pattern of Pi-ta alleles by examining the diversity in the coding sequence (CDS) among rice varieties. Results: The results revealed that 95% of 405 rice landraces collected from different ecological regions in Yunnan Province carry Pi-ta alleles. We identified 17 nucleotide variation sites in the CDS regions of the Pi-ta gene across 385 rice landraces. These variations led to the identification of 28 Pi-ta haplotypes, encoding 12 novel variants. Among these, 5 Pi-ta haplotypes (62 rice landraces) carried R alleles. The evolutionary cluster and network of the Pi-ta haplotypes suggested that the Pi-ta S alleles were the ancestral alleles, which could potentially evolve into R variants through base substitution. Conclusions: This study suggests that Pi-ta alleles are diverse in the rice landraces in Yunnan, and the Pi-ta sites resistant to blast evolved from the susceptible plants of the rice landraces. These results provide the basis for breeding resistant varieties. Full article

Rice blast caused by the pathogenic fungus Magnaporthe oryzae poses a significant threat to rice cultivation. The identification of robust resistance germplasm is crucial for breeding resistant varieties. In this study, we employed functional molecular markers for 10 rice blast resistance genes, namely Pi1, Pi2, Pi5, Pi9, Pia, Pid2, Pid3, Pigm, Pikh, and Pita, to assess blast resistance across 91 indica rice backbone varieties in South China. The results showed a spectrum of resistance levels ranging from highly resistant (HR) to highly susceptible (HS), with corresponding frequencies of 0, 19, 40, 27, 5, and 0, respectively. Yearly correlations in blast resistance genes among the 91 key indica rice progenitors revealed Pid2 (60.44%), Pia (50.55%), Pita (45.05%), Pi2 (32.97%), Pikh (4.4%), Pigm (2.2%), Pi9 (2.2%), and Pi1 (1.1%). Significant variations were observed in the distribution frequencies of these 10 resistance genes among these progenitors across different provinces. Furthermore, as the number of aggregated resistance genes increased, parental resistance levels correspondingly improved, though the efficacy of different gene combinations varied significantly. This study provides the initial steps toward strategically distributing varieties of resistant indica rice genotypes across South China. Full article

The increased use of chemicals in rice farming poses significant issues regarding the emergence of pesticide/fungicide resistance and environmental sustainability concerns. This study was aimed at the genetic improvement of blast, bacterial leaf blight (BB) and gall midge resistance in a popular rice variety CO 51 which already harbours a blast resistance gene Pi54. Efforts were made to pyramid an additional blast resistance gene Pi9 along with two BB resistance genes (xa13 and Xa21) and two gall midge resistance genes (Gm1 and Gm4) into an elite rice variety CO 51 to enhance the resistance level to biotic stresses. The superior lines were selected using functional markers conferring resistance to blast (NBS4 and Pi54MAS linked to Pi9 and Pi54 genes, respectively) and BB [(xa13Prom (xa13) and pTA248 (Xa21)] and SSR markers linked to Gm1 (RM1328) and Gm4 (RM22550) for phenotypic screening and agronomic evaluation. The genotyping and phenotyping of F₆ and BC₂F₆ progenies of CO 51 X 562-4, for agronomic traits and resistance to BB and blast, identified ten superior progenies in F₆ and five superior progenies in BC₂F₆. The breeding lines harbouring both xa13+Xa21 exhibited high levels of resistance to BB (score ≤ 1 cm) and Pi9+Pi54 exhibited strong resistance to blast (score ≤ 2). Identified lines can be evaluated further for varietal improvement or utilised as genetic stocks in breeding programs. Full article

In order to understand the pathogenicity differentiation of rice blast fungus (Pyricularia oryzae Cavara), a total of 206 isolates of P. oryzae were collected from three Japonica rice regions in Jilin Province, northeast China. Pathogenicity test showed that the reaction pattern of 25 monogenic differential varieties (MDVs) of rice (Oryza sativa L.) demonstrated a wide pathogenic diversity among the isolates. Those MDVs harbor 23 resistance (R) genes with the susceptible variety Lijiangxintuanheigu (LTH) as control. Virulent isolates of MDVs harboring R genes Pish, Pit, Pia, Pii, Pik-s, Pik, Pita (two lines), and Pita-2 (two lines) had high frequencies ranging from 80 to 100%, to MDVs harboring R genes Pib, Pi5(t), Pik-m, Pi1, Pik-h, Pik-p, Pi7(t), Piz, Piz-5, and Piz-t showed intermediate frequencies ranging from 40 to 80%, and to MDVs with R genes Pi3, Pi9(t), Pi12(t), Pi19(t) and Pi20(t) presented low frequencies ranging only from 0 to 40%. The U-i-k-z-ta pattern of race-named criteria categorized the 206 isolates into 175 races. Sub-unit U73 for Pib, i7 for Pi3 and Pi5(t), k177 for Pik-m/Pik-h/Pik-p, z17 for Pi9(t), and ta332 for Pi20(t) were crucial on pathogenic differences in regions. Twenty-seven standard differential blast isolates (SDBIs) were selected to characterize resistance in rice accessions. This study could help to build a durable identification system against blast in the Japonica rice area of northeast China and enhance our understanding of the differentiation and diversity of blast races in the world. Full article

Pusa Basmati 1509 (PB1509) is one of the major foreign-exchange-earning varieties of Basmati rice; it is semi-dwarf and early maturing with exceptional cooking quality and strong aroma. However, it is highly susceptible to various biotic stresses including bacterial blight and blast. Therefore, bacterial blight resistance genes, namely, xa13 + Xa21 and Xa38, and fungal blast resistance genes Pi9 + Pib and Pita were incorporated into the genetic background of recurrent parent (RP) PB1509 using donor parents, namely, Pusa Basmati 1718 (PB1718), Pusa 1927 (P1927), Pusa 1929 (P1929) and Tetep, respectively. Foreground selection was carried out with respective gene-linked markers, stringent phenotypic selection for recurrent parent phenotype, early generation background selection with Simple sequence repeat (SSR) markers, and background analysis at advanced generations with Rice Pan Genome Array comprising 80K SNPs. This has led to the development of Near isogenic lines (NILs), namely, Pusa 3037, Pusa 3054, Pusa 3060 and Pusa 3066 carrying genes xa13 + Xa21, Xa38, Pi9 + Pib and Pita with genomic similarity of 98.25%, 98.92%, 97.38% and 97.69%, respectively, as compared to the RP. Based on GGE-biplot analysis, Pusa 3037-1-44-3-164-20-249-2 carrying xa13 + Xa21, Pusa 3054-2-47-7-166-24-261-3 carrying Xa38, Pusa 3060-3-55-17-157-4-124-1 carrying Pi9 + Pib, and Pusa 3066-4-56-20-159-8-174-1 carrying Pita were identified to be relatively stable and better-performing individuals in the tested environments. Intercrossing between the best BC₃F₁s has led to the generation of Pusa 3122 (xa13 + Xa21 + Xa38), Pusa 3124 (Xa38 + Pi9 + Pib) and Pusa 3123 (Pi9 + Pib + Pita) with agronomy, grain and cooking quality parameters at par with PB1509. Cultivation of such improved varieties will help farmers reduce the cost of cultivation with decreased pesticide use and improve productivity with ensured safety to consumers. Full article

Rice blast is a fungal disease that seriously threatens rice production. It is of great significance to identify blast resistance genes and clarify their functions in rice varieties. In this study, 11 rice blast resistance genes in 80 Japonica rice varieties in northern China were investigated, including their resistance to rice blast. The results demonstrated that Pita, Ptr, Pib, Pik, and Piks were most widely found, accounting for 48.8, 48.8, 41.3, 20.0, and 18.8% of the tested varieties, respectively. Pi5-G2 at the Pi5 locus and Pik-G5 and Pik-G8 at the Pik locus were also commonly found, and these alleles accounted for 30.0, 10.0, and 3.8% of all the tested varieties, respectively. Pizt was identified only in two cultivars, and alleles Pi2, Pi9, and Pigm at the Piz locus on chromosome 6 were not detected. We found that Pi5 and Pita were relatively conserved, but the alleles of Pik were abundant. Besides Pik, Pikm, and Piks, we also found 10 new haplotypes, and Pikp and Pikh were not found in the japonica rice varieties in northern China. Among the tested varieties, 5 did not carry any of the tested genes, 30 carried only one blast resistance gene, 27 carried two, 14 carried three, and 4 carried four. The resistance of varieties carrying three or four resistance genes was better than those carrying none of the resistance genes or only one or two. There were no significant differences in the resistance characteristics among varieties from different provinces. Our study provided a reference for the molecular breeding of rice blast resistance. Full article

Aim: EBV encodes at least 44 miRNAs involved in immune regulation and disease progression. Exosomes can be used as carriers of EBV-miRNA-BART intercellular transmission and affect the biological behavior of cells. We characterized exosomes and established a co-culture experiment of exosomes to explore the mechanism of miR-BART1-3p transmission through the exosome pathway and its influence on tumor cell proliferation and invasion. Materials and methods: Exosomes of EBV-positive and EBV-negative gastric cancer cells were characterized by transmission electron microscopy. NanoSight and Western blotting, and miRNA expression profiles in exosomes were sequenced with high throughput. Exosomes with high or low expression of miR-BART1-3p were co-cultured with AGS cells to study the effects on proliferation, invasion, and migration of gastric cancer cells. The target genes of EBV-miR-BART1-3p were screened and predicted by PITA, miRanda, RNAhybrid, virBase, and DIANA-TarBase v.8 databases, and the expression of the target genes after co-culture was detected by qPCR. Results: The exosomes secreted by EBV-positive and negative gastric cancer cells range in diameter from 30 nm to 150 nm and express the exosomal signature proteins CD9 and CD63. Small RNA sequencing showed that exosomes expressed some human miRNAs, among which hsa-miR-23b-3p, hsa-miR-320a-3p, and hsa-miR-4521 were highly expressed in AGS-exo; hsa-miR-21-5p, hsa-miR-148a-3p, and hsa-miR-7-5p were highly expressed in SNU-719-exo. All EBV miRNAs were expressed in SNU-719 cells and their exosomes, among which EBV-miR-BART1-5p, EBV-miR-BART22, and EBV-miR-BART16 were the highest in SNU-719 cells; EBV-miR-BART1-5p, EBV-miR-BART10-3p, and EBV-miR-BART16 were the highest in SNU-719-exo. After miR-BART1-3p silencing in gastric cancer cells, the proliferation, healing, migration, and invasion of tumor cells were significantly improved. Laser confocal microscopy showed that exosomes could carry miRNA into recipient cells. After co-culture with miR-BART1-3p silenced exosomes, the proliferation, healing, migration, and invasion of gastric cancer cells were significantly improved. The target gene of miR-BART1-3p was FAM168A, MACC1, CPEB3, ANKRD28, and USP37 after screening by a targeted database. CPEB3 was not expressed in all exosome co-cultured cells, while ANKRD28, USP37, MACC1, and FAM168A were all expressed to varying degrees. USP37 and MACC1 were down-regulated after up-regulation of miR-BART1-3p, which may be the key target genes for miR-BART1-3p to regulate the proliferation of gastric cancer cells through exosomes. Conclusions: miR-BART1-3p can affect the growth of tumor cells through the exosome pathway. The proliferation, healing, migration, and invasion of gastric cancer cells were significantly improved after co-culture with exosomes of miR-BART1-3p silenced expression. USP37 and MACC1 may be potential target genes of miR-BART1-3p in regulating cell proliferation. Full article

Rice blast, caused by the Magnaporthe oryzae fungus, is one of the most devastating rice diseases worldwide. Developing resistant varieties by pyramiding different blast resistance (R) genes is an effective approach to control the disease. However, due to complex interactions among R genes and crop genetic backgrounds, different R-gene combinations may have varying effects on resistance. Here, we report the identification of two core R-gene combinations that will benefit the improvement of Geng (Japonica) rice blast resistance. We first evaluated 68 Geng rice cultivars at seedling stage by challenging with 58 M. oryzae isolates. To evaluate panicle blast resistance, we inoculated 190 Geng rice cultivars at boosting stage with five groups of mixed conidial suspensions (MCSs), with each containing 5–6 isolates. More than 60% cultivars displayed moderate or lower levels of susceptibility to panicle blast against the five MCSs. Most cultivars contained two to six R genes detected by the functional markers corresponding to 18 known R genes. Through multinomial logistics regression analysis, we found that Pi-zt, Pita, Pi3/5/I, and Pikh loci contributed significantly to seedling blast resistance, and Pita, Pi3/5/i, Pia, and Pit contributed significantly to panicle blast resistance. For gene combinations, Pita+Pi3/5/i and Pita+Pia yielded more stable pyramiding effects on panicle blast resistance against all five MCSs and were designated as core R-gene combinations. Up to 51.6% Geng cultivars in the Jiangsu area contained Pita, but less than 30% harbored either Pia or Pi3/5/i, leading to less cultivars containing Pita+Pia (15.8%) or Pita+Pi3/5/i (5.8%). Only a few varieties simultaneously contained Pia and Pi3/5/i, implying the opportunity to use hybrid breeding procedures to efficiently generate varieties with either Pita+Pia or Pita+Pi3/5/i. This study provides valuable information for breeders to develop Geng rice cultivars with high resistance to blast, especially panicle blast. Full article

Rice blast, caused by Pyricularia oryzae, is one of the main rice diseases worldwide. The pyramiding of blast-resistance (Pi) genes, coupled to Marker-Assisted BackCrossing (MABC), provides broad-spectrum and potentially durable resistance while limiting the donor genome in the background of an elite cultivar. In this work, MABC coupled to foreground and background selections based on KASP marker assays has been applied to introgress four Pi genes (Piz, Pib, Pita, and Pik) in a renowned japonica Italian rice variety, highly susceptible to blast. Molecular analyses on the backcross (BC) lines highlighted the presence of an additional blast-resistance gene, the Pita-linked Pita2/Ptr gene, therefore increasing the number of blast-resistance introgressed genes to five. The recurrent genome was recovered up to 95.65%. Several lines carrying four (including Pita2) Pi genes with high recovery percentage levels were also obtained. Phenotypic evaluations confirmed the effectiveness of the pyramided lines against multivirulent strains, which also had broad patterns of resistance in comparison to those expected based on the pyramided Pi genes. The developed blast-resistant japonica lines represent useful donors of multiple blast-resistance genes for future rice-breeding programs related to the japonica group. Full article