Journal of Pharmacognosy and Phytochemistry 2019; 8(6): 918-922

E-ISSN: 2278-4136 P-ISSN: 2349-8234 JPP 2019; 8(6): 918-922 Bacterial panicle blight of rice Received: 07-09-2019 Accepted: 09-10-2019 Sudha Nandni and Karuna Vishunavat Sudha Nandni Department of Plant Pathology, College of Agriculture Abstract G. B. Pant University of Climate change has led to the recurrence of certain diseases of minor incidence as major diseases. One Agriculture and Technology, such threat is Bacterial Panicle Blight of rice. This disease (B. glumae and B. gladioli) has emerged as a Pantnagar, Uttarakhand, India major bacterial disease covering different rice growing areas of northern India in recent past and has become a major threat to the paddy crop. This disease is seed-borne and therefore it’s important to Karuna Vishunavat monitor its dissemination in different geographical regions of major rice growing parts in the country Department of Plant Pathology, through infected seeds. Since, no genetically improved variety or biotechnological intervention presently College of Agriculture exist that help to control bacterial panicle blight. The use of chemical applications at appropriate doses G. B. Pant University of and at the right time is the only reliable method for the management of BPB to some extent. Agriculture and Technology, Pantnagar, Uttarakhand, India Keywords: Panicle, seed-borne, blight, major disease, minor disease

Introduction The name “panicle blight” has first been reported in The United States since more than 50 years ago (Chien and Chang, 1987; Sayler et al., 2006) [1, 2, 45]. The disease is called bacterial panicle blight but in other countries it is known as grain rot. In Japan, grain rot was initially observed as a minor disease. However, since the 1970s, the incidence and severity continued [3] to intensify in southern and central Japan (Uematsu et al., 1976) . In the early 1990s, bacterial panicle blight had been reported to be similar to grain rot in the southern United States. Initially, the symptoms were thought to be caused by an abiotic factors related to water stress, higher temperature and toxic chemicals but later it was confirmed that B. gladioli/B. glumae, caused the disease. The disease is identical to grain rot reported [4] in Japan (Shahjahan et al., 2000) . Subsequently, reports of BPB in Japan (Goto and Ohata, [5] [6] 1956) , Taiwan, Korea in 1995, and mainland China in 2007 (Luo et al., 2007) were there. The pathogen was reported to be seed-borne, and rice crops planted with infected seeds can suffer severe losses (Takeuchi et al., 1997) [7]. Infected seeds from the previous year, rice seeds stored at room temperature during the winter, or weeds in the field and in rice tissues

from the previous crop buried in soil serve as primary source of inoculum (Sogou and Tsuzaki, [8] 1983) . In the process of infection, host susceptibility, inoculum density, and climatic factors play the key roles (Tsushima et al., 1985) [9].

Economic impact of the disease

BPB of rice, the most severely emerging bacterial disease with rapid dissemination across the globe, has become severe recently. The disease causes substantial grain yield damage in the rice-cultivating areas of south eastern United States, Louisiana, Texas and Arkansas in 1996, 1997 and 2000. Most recently, in 2010, Ham et al. (2011) [10] and Jeong et al. (2003) [11] described the occurrence of this disease in the areas of Asia, Africa and South and North

America in the year 1980 and characterized the geographical or climate requirement of bacterial panicle blight pathogen (B. glumae). Losses include the reduced yields and poor milling quality. The loss estimates ranging from a trace to 70%. The bacterium is seed-borne and has caused seedling blights in many countries. The pathogen infects the plant at flowering stage and causes aborted and rotted chaffy grains (Gnanamanickam et al., 1999) [12]. In Taiwan

the disease was reported to be seed-borne. The BPB, caused by led yield losses [13] up to an extent of 75 per cent in the heavily infested paddy fields (Trung et al., 1993) . Shahjahan et al. (2000) [4] reported the epidemic occurrence of the bacterial panicle blight in Louisiana during 1995 and 1998 due to cultivation of local rice and found high night Corresponding Author: temperatures, were congenial for the pathogen multiplication and dissemination causing yield Sudha Nandni Department of Plant Pathology, losses. In some fields of Louisiana State of America, significant yield losses were estimated to College of Agriculture be as high as 40 per cent. G. B. Pant University of Agriculture and Technology, Pantnagar, Uttarakhand, India ~ 918 ~ Journal of Pharmacognosy and Phytochemistry http://www.phytojournal.com

Current status of the pathogen and disease panicles, due to failure of grain-filling and no seed With more and more scientific knowledge and understanding development is a characteristic phenomenon observed in a of genetic constitution and phylogenetics of the panicle blight field with severe infection. Continued high temperature pathogen has undergone re-organization in taxonomical terms during the panicle initiation is an important environmental in past few decades. Because of this rearrangement, condition that encourages the development of BPB. Severe plantarii was transferred to the genus epidemics of BPB caused up to 40 per cent yield damage. Burkholderia as Burkholderia plantarii causing seedling In the rice-producing states of North India, Mondal et al. blight of rice and later, based on DNA-DNA homology, (2015) [16] described the panicle blight symptoms in early cellular lipid and fatty acid compositions, and phenotypic planting stages as grain rotting and sterile spikelet. The characteristics, Pseudomonas glumae has also been infected panicle has light to light brown glumes, partially or transferred to Burkholderia as Burkholderia glumae (Azegami completely discolored. Grain filling of the diseased panicles is et al., 1987 and Uematsu et al., 1976) [14, 3]. Most importantly, altered with the development of chaffy grains. All of these the evidences of rapid evolution of B. glumae all over the signs are often regarded as an expression of a condition world are present because the pathogenically and genetically commonly referred to as panicle blight. Reports of B. glumae dissimilar strains of B. glumae have been isolated from as Pseudomonas glumae on rice was made by Goto and Ohata symptomless rice plants which produce symptoms, analogous (1956) [5] and Cottyn et al. (1996) [20], grain rot and grain with bacterial panicle blight (Seo et al., 2015) [15]. discoloration by Tsushima et al. (1985) [9] and Mew et al. Presently, the disease scenario witnesses that paddy crop in (1992) [24] and seedling rot by Uematsu et al. (1976) [3]. several countries is under arrest of Bacterial Panicle Blight (Cui Zhou et al., 2016) [17]. This disease presents an Pathogen: Burkholderia (Yabuuchi et al., 1992) [25]. emblematic illustration of the status shifting from minor to Taxonomic position major disease due to the climate change. Toxoflavin, lipases Kingdom: Bacteria and type III effectors have been identified as virulent factors Phylum: Beta-protebacteria of B. glumae (Zhou et al., 2011). Due to lack of strict Order: quarantine, non-availability of resistant cultivars and efficient Family: management practices and higher yield loss due to BPB has Genus: Burkholderia been observed at various locations (Nandakumar et al., 2009) [18]. The pathogen that causes bacterial grain rot was named earlier as Pseudomonas glumae in Japan. Due to rearrangement and Symptomatology shifting, of genus, the non-fluorescent bacteria in The pathogen produces wide-range of symptoms at different Pseudomonas are classified as genus Burkholderia. growth stages of plant starting from nursery stage causing Pseudomonas plantarii was transferred to the genus seedling blight, seedling rot, reduced growth of infected Burkholderia as Burkholderia plantarii and Pseudomonas leaves, roots and chlorotic symptoms on panicles (Cottyn et glumae has also been transferred to Burkholderia as al., 1996 [20]; Kim et al., 2004 and Suzuki et al., 2004) [19]. Burkholderia glumae (Azegami et al., 1987; Uematsu et al., Panicle emergence is characterized with distinctive symptoms 1976) [14, 3]. Yabuuchi et al. (1992) [25] established the genus pronounced at panicle stage, which may be confined up to Burkholderia from the seven species previously in the few florets or may infect the complete panicle (Rush, 1998) Pseudomonas homology group II to the new genus called [22]. Prominent feature of this disease is that, the rachis of the Burkholderia based on the 16S rDNA sequences, DNA-DNA infected panicle remains green while affected florets turn homology, cellular lipid and fatty acid compositions, and the brown or gray at their bases and abort the developing kernels. phenotypic characteristics. Until 2002, there were only 28 Infected florets are grey brown disoloured, usually on the half species in the genus Burkholderia. The important of the emerging panicle, with a clear, profound boundary characteristic features of the genus Burkholderia such as followed by sterility or partial filling of grains. In severe genomes are flexibility and plasticity, enables them to infection, panicle stands steadfast as the grain does not fill colonize in diverse environmental conditions such as human, (Shahjahan et al, 1998, 2000) [22, 4]. When symptoms upsurge plant, soil, and other animal hosts. (Chain et al., 2006) [27]. as panicle infection, may cause spikelet sterility, discolored Plant pathogenic Burkholderia sp. cause diseases in rice, and pale spikes and stained-kernels (Tsushima et al., 1996) tobacco, maize and other crops. [23]. Unusually hot night weather and high relative humidity The host range of B. glumae mainly includes Oryza sativa makes disease symptoms worse. Infection has been found to (L), Eleusine coracana (L) Lycopersicon esculentum (Mill), cause a decrease in weight of grain, inhibition of seed Solanum melongena (L). Sesamum indicum. In case of crop germination and a significant drop in yield in paddy plants plants, pathogen is reported to cause wilting symptoms, where (Jeong et al., 2003) [11]. In China, in 2007, the pathogen B. as in weed hosts such as Andropogon virginicus (L)., glumae was detected from the asymptomatic seeds and the Arundinella hirta (L)., Beckmannia syzigachne (Steud) isolated bacterial pathogen from such seeds on artificial Fernald, Chloris gayana (L.), Coix lacryma‐jobi (L)., Coix inoculation of paddy plant caused bacterial panicle blight lacryma (L)., Eleusine indica (L.)., Eragrostis curvula disease (Luo et al., 2014). (Schrad.)., Eragrostis pilosa (L.), Lolium multiflorum (Lam)., Symptoms of BPB include seedling blight in nursery, sheath Panicum coloratum (L), Panicum dichotomiflorum, Panicum rot and panicle blight symptoms in transplanted nursery. maximum (Jacq)., Paspalum dilatatum (L), Paspalum Infected panicles have discoloured florets, which initially distichum L., Pennisetum alopecuroides (L.), Phragmites show white or light gray basal portion and later become australis (Cav.), no distinguishing symptoms have been straw-colored. The florets become dark brown on the surface recorded on weed (Saddler, 1994) [26], and Jeong et al. (2003) due to secondary infection. Widespread incidence of standing [11].

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Isolation and Purification of the pathogen from medium, colonies are yellow, round, smooth, convex, and symptomatic seeds, asymptomatic seeds and infected plant swollen producing diffusible yellow pigment. parts Azegami et al. (1987) [14] studied that bacterium confirmed The pathogenically and genetically dissimilar strains of B. positive reaction for KOH, gelatin liquefaction, oxidase, glumae have been isolated from rice plants and the symptoms toxoflavin production and catalase test, negative reaction for and were analogous with bacterial panicle blight, which starch hydrolysis, levan production and H2S production test. shows the rapid evolution of B. glumae all over the world Similar biochemical tests were observed by Cottyn et al. (Seo et al., 2015) [15]. (1996) [20]; Jeong et al. (2003) [11]; Bassler, (2001) [37]; In paddy, the symptoms caused by Burkholderia spp. included Yabuuchi et al. (1992) [25]; Iiyama et al. (1995) [38]; Goto and upright panicles with stained and abortive grains, in samples Takikawa, (1984) [39] when the bacteria exhibited Gram from Daule and Palestina towns, the most important rice negative reaction, whereas positive gelatin liquefaction, KOH, producing areas in Ecuador (Riera-Ruiz, 2018) [28]. For the oxidase, catalase and negative starch hydrolysis, levan isolation of the bacterium, plant cut into 4-5 cm long pieces, production and sulphur production test. then surface-sterilized by immersion in 3 percent sodium Detection of plant pathogens involves pathogen isolation, hypochlorite or 70 percent ethanol for 1 min each. One gram cultivation, and confirmation on the basis of bacteriological of sterilized sample was ground in a mortar with 5 mL of characteristics, colony morphology, and conventional means sterile peptone water and 200 L of the suspension were are intense time process. The polymerase chain reaction plated onto SPG medium as described by Tsushima et al. (PCR) is mainly suitable for detecting plant pathogens quickly (1985) [9] and incubated for 48-96 hr at 37 ºC. Cultural growth and precisely. Different modifications of PCR (multiplex PCR thus obtained were transferred to potato dextrose agar (PDA) and SYBR Green real-time PCR) were developed to facilitate and incubated for 24-48 hr at 37 ºC. The colonies producing a the simultaneous detection of important seed borne rice fluorescent yellow pigment were selected for molecular pathogen like Burkholderia glumae (Lu et al, 2012) [40]. An identification. Pathogenicity of isolates was confirmed using effective multiplex PCR method was used to amplify 16S– Koch postulates as described by Riera-Ruiz et al. (2014) [29]. 23S ITS sites for rapid and accurate identification of Singh and Vishunavat (2015) [30] conducted the very first Burkholderia sp. Although, it is tough to distinct pathovars preliminary studies on Panicle Blight pathogen in Tarai region using 16S–23S and ITS sites for rice bacterial pathogens, of Uttarakhand. Rice plants exhibiting distinguished numerous other protocols based on DNA detection including- symptoms of bacterial panicle blight were collected from Southern blot hybridization and the Polymerase Chain Pantnagar and adjoining areas. Isolation of bacterial pathogen Reaction (PCR) - amplified DNA products analysis are being was done from infected seed samples on King’s B agar used presently for the identification of Burkholderia glumae . medium and purification was achieved on King’s B agar Several genus specific primers designed by Yamamoto et al. medium. Bacterium developed colonies within two days at 28 (2000) [42], Gee et al. (2003) [41] Yukiko et al., (2006) [44], °C. Hasibuan, (2018) [31] conducted a research to characterize Sayler et al. (2006) [2, 45] and Yuan et al. (2004) [21] are being the morphology of bacterial strains of B. glumae, isolated used for the identification up to genus level of pathogen. As from several symptom and symptomless rice seeds in North the methods based on PCR requires specific equipment along Sumatra using bacterial morphology as one aspect of bacterial with the skilled and trained personnel, may be for these identification. Rice seed samples were collected from several reasons, conventional techniques are still being followed in places in North Sumatra. Collected seed samples were surface some of the seed testing laboratories. The successful sterilized with 0.5 percent sodium hypochlorite to isolate the implication of PCR based techniques in the past years leaves bacterium on king’s B medium. The cultures were purified on no ground for not applying them in combined protocols, for semi-selective PPGA medium and maintained (Safni et al., the purpose of routine study. 2016) [32]. 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