Fungal Disease Of Rice Research Articles

Efficacy of bioinoculants to control of bacterial and fungal diseases of rice (Oryza sativa L.) in northwestern Himalaya.

Biological control holds great promise for environmentally friendly and sustainable management of the phytopathogens. The multi-function features of plant growth-promoting rhizobacteria (PGPR) enable to protect the plants from disease infections by replacing the chemical inputs. The interaction between the plant root exudates and the microbes stimulates the production of secondary metabolism and enzymes and induces systemic resistance in the plants. The aim was to identify the potential PGPR which would show an antagonistic effect against basmati rice fungal and bacterial diseases. In the study, native originating microbes have been isolated, characterized using 16S rRNA sequencing, and used as potential antagonistic microbial isolates against diseases of rice plants. Rhizobacteria isolated from rhizosphere, endo-rhizosphere, and bulk soil samples of Basmati 370 exhibited promising inhibitory activity against rice pathogens. Molecular characterization of bacterial isolates based on 16S rRNA sequencing classified the bacterial isolates into different genera such as Bacillus, Pseudomonas, Streptomyces, Exiguobacterium, Aeromonas, Chryseobacterium, Enterobacter, and Stenotrophomonas. PGPRs exhibited biocontrol activities against various rice diseases like bacterial leaf blight, leaf blast, brown spot, and sheath blight and boost the plant growth traits. In the study, the potentially identified PGPRs isolates could be used as efficient bioinoculants as bio-fertilizers and biocontrol agents for sustainable rice crop production.

Mapping of a Major QTL, qBK1Z, for Bakanae Disease Resistance in Rice.

Bakanae disease is a fungal disease of rice (Oryza sativa L.) caused by the pathogen Gibberella fujikuroi (also known as Fusarium fujikuroi). This study was carried out to identify novel quantitative trait loci (QTLs) from an indica variety Zenith. We performed a QTL mapping using 180 F2:9 recombinant inbred lines (RILs) derived from a cross between the resistant variety, Zenith, and the susceptible variety, Ilpum. A primary QTL study using the genotypes and phenotypes of the RILs indicated that the locus qBK1z conferring bakanae disease resistance from the Zenith was located in a 2.8 Mb region bordered by the two RM (Rice Microsatellite) markers, RM1331 and RM3530 on chromosome 1. The log of odds (LOD) score of qBK1z was 13.43, accounting for 30.9% of the total phenotypic variation. A finer localization of qBK1z was delimited at an approximate 730 kb interval in the physical map between Chr01_1435908 (1.43 Mbp) and RM10116 (2.16 Mbp). Introducing qBK1z or pyramiding with other previously identified QTLs could provide effective genetic control of bakanae disease in rice.

Innovative trends in breeding disease resistant rice varieties

Rice has become widespread in world agriculture due to its high adaptation to growing conditions and the selection of many different types of varieties. The creation of new varieties of rice in Russia has been carried out using the methods of complex multistage hybridization and marker selection with close cooperation of breeders and biotechnologists. The result of this work is a mid-season variety Utyos that combines high yields with resistance to blast, the main fungal disease of rice that affects leaves, stems and panicles of the plant. The late-ripening rice variety IR-36, which has complex resistance to fungal and bacterial diseases and viruses, was used as a donor. Variety Utyos was created by selecting an elite plant from the F2 BC4 Flagship / IR-36 population, with repeated selection and verification by offspring. Starting from the first backcrossing, marker control was carried out for the presence of transferred donor alleles in the hybrid offspring. In parallel, phytopathological control was carried out against an infectious background. In 2019, in environmental tests, Utyos formed the maximum grain yield of 11.95 t / ha with winter wheat as the predecessor. At the same time, the variety showed high resistance to blast.

Monitoring and analysis of rice pathogen Ustilaginoidea virens isolates with resistance to sterol demethylation inhibitors in China

Rice false smut (RFS), caused by Ustilaginoidea virens (Cooke) Takah, is an important fungal disease of rice. In China, sterol demethylation inhibitors (DMIs) are common fungicides used to control RFS. In a previous study, we detected two propiconazole-resistant U. virens isolates in 2015 in Huai’an city, Jiangsu Province, China. In the current study, we detected six propiconazole-resistant isolates out of 180 U. virens isolates collected from rice fields in Jiangsu Province in 2017, and found they were from three different places (Xuzhou, Huai’an and Jintan). All these six propiconazole-resistant isolates were cross-resistant to three other sterol demethylation inhibitor (DMI) fungicides, i.e. difenoconazole, tebuconazole, and epoxiconazole. Among them, two isolates (2017–61 and 2017–170) had high fitness. Through sequencing and RT-qPCR analysis, we found that the expression levels of CYP51 and its encoded protein were significantly increased in the propiconazole-resistant isolates with a “CC” insertion mutation upstream of the CYP51 coding region compared to the propiconazole-sensitive isolates. In addition, propiconazole stimulated CYP51 expression in all isolates. Propiconazole also stimulated the accumulation of CYP51 protein in propiconazole-sensitive isolates and propiconazole-resistant isolates without mutation, but not in propiconazole-resistant isolates with the “CC” mutation. According to JASPAR database analysis, the predicated functional binding sites for propiconazole-resistant isolates with a “CC” insertion mutation and propiconazole-sensitive isolates were different. Given the high fitness of the propiconazole-resistant isolates, the development of resistance to DMIs in U. virens should be monitored. Furthermore, we speculated that the over-expression of CYP51 may contribute to DMI resistance in U. virens with the “CC” insertion mutation.

Screening and Biochemical Characterization of Wheat Cultivars Resistance to Magnaporthe oryzae pv Triticum (MoT)

Global food security is seriously threatened due to increased frequency and occurrence of fungal diseases. One example is wheat blast caused by Magnaporthe oryzae is a fungal diseases of rice, wheat, and other grasses, that can destroy the whole food production to sustain millions of people. Wheat blast was first detected in february 2016 with a serious outbreak in Asia. Assessment of the available germplasms to stress tolerant/resistant is one of the best options for developing stress tolerant crop varieties. In this study, a total of sixteen wheat cultivars were collected and test their disease severity to blast pathogen Magnaporthe oryzae pv. Triticum (MoT). Among the varieties, BARI Gom 33 exhibited partially resistance against blast pathogen, whereas all other genotypes become susceptible to MoT. Different yield and yield contributing characters of both resistant and susceptible cultivars were also evaluated and found no significant differences among them. To understand the underlying mechanism of resistance in BARI Gom 33, antioxidant enzyme activity, concentration of reactive oxygen species and cellular damage after fungal infection were also evaluated and found that activities of ascorbate peroxidase (APX), catalase (CAT) and peroxidase (POD) were higher in BARI Gom 33 than BARI Gom 25 and BARI Gom 31. The hydrogen peroxide (H2O2) and malondealdehyde (MDA) content in BARI Gom 33 was low compare to BARI Gom 25 and BARI Gom 31, which may due to greater increase of the APX, CAT and POD in resistant genotypes. Thus, it may suggest that a more efficient antioxidative defense system in BARI Gom 33 during the infection process of M. oryzae restricts the cell damage caused by the fungus. The identified genotypes can either be used directly in the blast prone area or as a source of resistance to further development of blast resistance high yielding wheat variety.

Rice Blast: A Disease with Implications for Global Food Security

Rice blast is a serious fungal disease of rice (Oryza sativa L.) that is threatening global food security. It has been extensively studied due to the importance of rice production and consumption, and because of its vast distribution and destructiveness across the world. Rice blast, caused by Pyricularia oryzae Cavara 1892 (A), can infect aboveground tissues of rice plants at any growth stage and cause total crop failure. The pathogen produces lesions on leaves (leaf blast), leaf collars (collar blast), culms, culm nodes, panicle neck nodes (neck rot), and panicles (panicle blast), which vary in color and shape depending on varietal resistance, environmental conditions, and age. Understanding how rice blast is affected by environmental conditions at the cellular and genetic level will provide critical insight into incidence of the disease in future climates for effective decision-making and management. Integrative strategies are required for successful control of rice blast, including chemical use, biocontrol, selection of advanced breeding lines and cultivars with resistance genes, investigating genetic diversity and virulence of the pathogen, forecasting and mapping distribution of the disease and pathogen races, and examining the role of wild rice and weeds in rice blast epidemics. These tactics should be integrated with agronomic practices including the removal of crop residues to decrease pathogen survival, crop and land rotations, avoiding broadcast planting and double cropping, water management, and removal of yield-limiting factors for rice production. Such an approach, where chemical use is based on crop injury and estimated yield and economic losses, is fundamental for the sustainable control of rice blast to improve rice production for global food security.

Conservation agriculture cropping systems reduce blast disease in upland rice by affecting plant nitrogen nutrition

In the central highlands of Madagascar, blast, a serious fungal disease of rice caused by Magnaporthe oryzae, was shown to be less severe in conservation agriculture (CA) than in conventional tillage (CT) cropping systems. To assess the effects of CA cropping systems on rice susceptibility to blast and to understand the mechanisms involved, an experiment was conducted over three growing seasons in two sites (at high and mid-altitude). Two fertilization treatments, one with mineral nitrogen (N) fertilizer, and one without, were studied in interaction with two different cropping systems (CA/CT) and two rice varieties that differ in their susceptibility to blast. The performances of the two cropping systems were assessed, and results showed that yields were no higher in the CA or were lower than in CT cropping systems. The effects of the treatments on upland rice crop growth were measured by leaf N content as an indicator of N crop status, and leaf area index (LAI) as an indicator of canopy density. In all years at both sites, leaf N content during early growth stages was higher in the CT than in the CA cropping system. The LAI was lower in the CA than in the CT cropping system at the high altitude site in all three years, and in two out of three seasons at the middle altitude site. Overall, when the level of blast was high, blast was less severe in the CA cropping system and with no N fertilizer. Leaf N content and LAI were used as intermediate explanatory variables in the statistical analyses, and one or the other or both always masked the effect of the cropping system or of N fertilization. Our results show that leaf N content during early growth stages masks the effect of the cropping system on leaf blast severity. When the LAI is strongly affected by the cropping system, it also masks the effect of the cropping system on the severity of leaf and panicle blast. Very often both variables masked the effects of the cropping system and of N fertilization. These findings should help improve disease management by modifying fertilization practices and crop nutrition in conservation agriculture cropping systems.

English

Environmentally friendly technologies, such as the use of bacteria (e.g. Bacillus spp.) to control fungal diseases of rice (Oryza sativa L.), represent a promising alternative for the sustainability of agricultural ecosystems. The present work aimed to isolate, identify, and evaluate (in vitro) various Bacillus spp. from the rice phylloplane for their potential to control the rice fungus Magnaporthe oryzae. Samples were taken from the phylloplane of healthy young rice plants growing in commercial fields in ten municipalities of Maranhao (Brazil), and Bacillus spp. were subsequently isolated and molecularly identified. Both experiments utilized a randomized design, and data were submitted to analysis of variance as well as means comparison by the Tukey test. Twelve bacterial isolates were obtained and identified. Using a control isolate (B25), four in vitro M. oryzae-inhibition methods were compared, with the ‘circle’ method ultimately providing the highest mycelium growth inhibition. The most promising experimental isolates for biological control were then identified as B. methylotrophicus isolates B41, B31, and B22, which achieved 90.41, 69.47, and 67.55% inhibition, respectively. This study demonstrates the potential of Maranhao Bacillus spp. isolates for use as biological fungal-control agents. Key words: biological control, pathogen, rice.

Mining of Blast Resistance Gene, Pi2 and Its Novel Allelic Variant from Landraces of Rice from Karnataka

Rice blast is one of the important fungal diseases of rice, caused by Magnaporthe oryzae. Rice blast can be effectively managed by the deployment of R-genes. Pi2 (Piz-5) is one of the major blast resistant genes effective against pathogen populations in various parts of India. In the present study, Pi2 gene was mined from 83 native landraces of rice from Karnataka state, India which revealed the presence of Pi2 in 60 landraces with the frequency of 72.28 %. Further, by using sequencing based allele mining approach, allelic variants of Pi2 from 16 landraces were analysed. High nucleotide variations (InDels) in the middle region of the conserved domain sequence of Pi2 in all variants were obtained. 469 polymorphic sites were observed with a total 570 mutations and 191 InDels among 16 Pi2 variants. Among Pi2 resistant and susceptible variants, 206 mutations with 29 InDel events were observed. Comparative modeling and Ramachandran plot of Pi2 protein variants from resistant and susceptible landraces were studied which revealed the significant differences among them. One potential novel Pi2 allelic variant from landrace Vanasurya was identified for the first time. This novel effective allelic variant can be used in rice breeding programmes to enhance blast resistance.

English

False smut of rice (Oryza sativa L.) caused by Ustilaginoidea virens (Cooke) Takahashi (teleomorph Villosiclava virens) is one of the most common fungal diseases of rice in China. The objectives of the research were: 1) to study the biology of Ustilaginoidea virens, 2) to develop suitable media for inoculum production of U. virens, and 3) to develop an artificial inoculation technique for the study of false smut resistance in rice. Seventy diseased rice samples were collected from seven districts of Guizhou province, China during 2007-2008 and 138 single-spore isolates of U. virens were isolated. Among two inoculation methods applied at 3 rice growth stages of rice variety Gangxiang 707 using spore suspension of U. virens isolate 2008-33-1, conidia injection at late booting stage produced the highest false smut incidence of 50.43%, while conidia spraying during the same stage gave only 34.75% disease incidence. Pathogenicity test of selected eight U. virens isolates on rice variety Zhongyou 177 using the conidia injection at late booting stage, showed that the isolates were different in their aggressiveness in which isolate 2008-11-1 gave the highest virulence score of 9 with the disease incidence of 81.66%, while isolate 2007-48-1 gave the lowest score of 5 with only 15.57% disease incidence. These eight U. virens isolates were further tested on six rice varieties using the same inoculation technique. Most of the rice varieties were either susceptible or moderately susceptible except Fengyouxiangzhan that was highly susceptible to U. virens isolate 2007 -79-1 and Nongfengyou 256 was moderately resistant. When the evaluation was done across all the U. virens isolates, Gangyou 827, Jixiangyou 830 and Fengyouxiangzhan were among the most susceptible varieties with disease incidence of 55.06, 54.79 and 53.50%, respectively, while Nongfengyou 256 varieties showed the lowest disease severity as 23.85%. For the pathogen strain, 2008-33-1 was the most aggressive giving 58.09% disease incidence while the fungal pathogen strain 2008-2-2 gave the lowest of 28.17%. Key words: False smut, rice, colony morphology, fungal characterization, Ustilaginoidea virens.

Enhancement of MAMP signaling by chimeric receptors improves disease resistance in plants

Plants activate defense responses through the recognition of microbe-associated molecular patterns (MAMPs). Recently, several pattern-recognition receptors (PRRs) have been identified in plants, paving the way for manipulating MAMP signaling. CEBiP is a receptor for the chitin elicitor (CE) identified in the rice plasma membrane and XA21 is a member of the receptor-like protein kinase (RLK) family that confers disease resistance to rice bacterial leaf blight expressing the sulfated protein Ax21. To improve resistance to rice blast, the most serious fungal disease of rice, we aimed to create a defense system that combines high affinity of CEBiP for CE and the ability of XA21 to confer disease resistance. Cultured rice cells expressing the chimeric receptor CRXA, which consists of CEBiP and the intracellular region of XA21, induced cell death accompanied by an increased production of reactive oxygen and nitrogen species after exposure to CE. Rice plants expressing the chimeric receptor exhibited more resistance to rice blast. Engineering PRRs may be a new strategy in molecular breeding for achieving disease resistance.

STRAW AND WINTER FLOODING BENEFIT MOSQUITOES AND OTHER INSECTS IN A RICE AGROECOSYSTEM

Rice fields are widespread agroecosystems that provide wetland habitat for many species, including pests like mosquitoes and beneficial insects. They can be used as models to understand how basal resources affect food web dynamics in seasonal wetlands. Rice field management may also influence adjacent communities by affecting mosquitoes, wildlife, and air quality. Rice straw incorporation and winter flooding have become common methods used to prepare seedbeds, largely replacing burning of straw. These methods could affect aquatic insects, including mosquitoes, because they increase nutrient availability during the growing season. We studied 16 fields where straw was either burned or incorporated into soil after the previous growing season; these treatments were crossed with either winter flooding or no winter flooding. Algae, mosquitoes, other herbivorous insects and predatory insects all responded positively to one or both treatments that increased nutrients (straw incorporation and winter flooding). While the overall increase in insect production could benefit wildlife, mosquito abatement personnel may need to monitor unburned fields more closely. The issue of mosquito production adds to the complexity of agricultural and environmental concerns bearing on rice field management. Straw incorporation and winter flooding reduce particulate pollutants caused by burning, reduce fertilizer needs, and increase densities of beneficial insects. However, these techniques may increase mosquitoes, methane production, and fungal diseases of rice. Further improvement of straw management practices could minimize these problems.

Studies on the behaviour of some fungal diseases of rice in the mangrove swamp ecology at Warri, south eastern Nigeria

Studies on the ecological behaviour of Cochliobolus miyabeanus (Ito et Kurib.) Drechsl. ex Dast., syn. Bipolaris oryzae (Breda de Haan Shoem.), the causal agent of brown spot in rice (Oryza sativa L.), were carried out in the tidal mangrove swamp at Warri Experimental Farm, Southeastern Nigeria. A split randomised complete block design with four replications was used. Monthly transplantings from July to September formed the main plot, which was subdivided into control and N-treated subplots. Disease incidence increased when transplanting was delayed. This was probably due to the fact that flowering coincided with environmental conditions favourable for disease development from November to February. Nitrogen fertilization at 40 kg N/ha significantly (P=0.05) reduced C. miyabeanus incidence in 1997/1998, but not in the 1998/1999 and 1999/2000 cropping seasons at the same site. The grain yields of ROK 5, a medium-duration improved rice variety (approx. 150 days), were significantly (P=0.05) reduced in late-transplanted crops (September to November) in spite of adequate N fertilization. Mangrove mud was not an important source of C. miyabeanus propagules. The incidence of leaf scald caused by Monographella albescens (Thum) Parkinson, Sivanesan and Booth syn. Microdochium oryzae (Hashioka and Yokogi) Samuels and Hallet, and of leaf smut caused by Etyloma oryzae Miyake was generally stimulated by N application.

Induced systemic resistance to rice blast fungus in rice plants infested by white‐backed planthopper

Many of the studies on herbivorous insects and also on pathogens have been conducted to clarify the relationship of insects to plants and of pathogens to plants. Studies on the relationship between insects and pathogens via host plants, however, have seldom been conducted (Karban et al., 1987). The white-backed planthopper, Sogatella furcifera Horvas (Homoptera: Delphacidae), and the rice blast disease caused by Pyricularia grisea Cooke, are an economically important insect pest and fungal disease of rice throughout south-east and far-east Asia, including Japan. In general, S. furcifera does not hibernate in Japan. The entire original S. furcifera population emigrates from mainland China into Japan during the rainy season from early June to early July. The population of the next generation of S. furcifera then increases rapidly in rice fields, and the highest peak of the population appears around late July or early August (Watanabe et al., 1991; Watanabe, 1996). At the same time, the rice blast disease caused by P. grisea develops commonly in rice fields in Japan and occasionally causes serious damage to the rice plants (Iwano, 1999). The authors therefore were interested in the interspecific relationships between S. furcifera and P. grisea via the host plants. In this paper, the results of experiments elucidating such interspecific relationships are discussed, in particular the effect of S. furcifera infestation in rice on the incidence of rice blast disease caused by P. grisea . Materials and methods

Rice Blast Disease

Blast continues to be the most destructive fungal disease of rice despite decades of research devoted to its control. This text has been developed from a conference held in Madison, Wisconsin, in August 1993, and presents a review of the status of knowledge of the disease and its management. It should be useful for plant pathologists as well as agronomists and plant breeders concerned with rice production.

Current concepts on fungal diseases of rice

Current concepts on fungal diseases of rice