001 bacterial panicle blight, milton rush

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  • 1. BACTERIAL PANICLE BLIGHT:CAUSES AND SUGGESTED CONTROLL MEASURESMilton C. Rush, Donald E. Groth, Jong Ham,And R. Nandakumar Louisiana State University

2. RiceRi produced i th southernd d in the th United States has a long history of loss to panicle blighting of unknown etiology. Epidemics of panicle blight occurred during 1995 and 1998, years of record high temperatures, with y yield losses in some fields estimated to be as high as 40%. Significant losses were also experienced in Louisiana during d i 2000 and 2010 b th years ofd 2010, bothf unusually high temperature. 3. Panicle blighting had been attributed toggabiotic factors including hightemperatures, water stress, or toxicpchemicals near the root zone, but in1996-97 the bacterial plant p p pathogen gBurkholderia glumae (formerlyPseudomonas glumae) was identified g)as a cause of panicle blighting in thesouthern United States. Thisbacterium was first described fromJapan as the cause of gpgrain rottinggand seedling blighting in 1956. 4. PATHOGENS FURTHER STUDIES INDICATED THAT TWO PLANT PATHOGENIC BACTERIA CAUSED THE EPIDEMICS OF PANICLE BLIGHTING Burkholderia glumae SEEDBORNE Burkholderia gladiolig SEEDBORNE SOILBORNE 5. Bacterial Panicle Blight Inoculated Non inoculatedNon-inoculated 6. SEVERE BPB 7. More than 400 isolates of the two pathogens were isolated from diseased plants collected across the southern United States rice area.The two pathogens were identified by growth on selective media, BiologTM, Cellular fatty acidgy analysis, and PCR. The B. glumae pathogen was determined to be the same AS an ATTC isolate of the pathogen fh hfrom JJapan, which was fi reported hi hfirstd in 1956 as causing grain and seedling rot on rice. 8. Burkholderia glumae 9. PCR analysis of DNA isolated from B glumae (top) and B gladioliB. B.(bottom) strains with their respective species specific primers. Theexpected size of 400 and 300 bp fragments were indicated by arrows. Lane 1, 100 bp ladder; lane 2, positive control (top)-B. glumae (ATCC (top) B. 33617) and (bottom) B. gladioli (ATCC 19302); lane 3, negative control- (top) B. gladioli (ATCC 19302) and (bottom) B. glumae (ATCC 33617); lanes 3-12, B. glumae isolates from infected rice grains (top); lanes 4-12, B. gladioli strains from infected rice grains (bottom).1234 5 6 78 9 101112 10. Bacterial Panicle Blight in PanamaWe also observed the disease on rice in Panama in 2002 and 2005. I received samples in 2006 from which p we isolated both B. glumae and B. gladioli based on PCR and other identification procedures. 11. The disease was later reported from other Asian countries and Latin America. B. glumae p produces the p yphytotoxin, toxoflavin, which is, , essential for its virulence and strains that lack toxin production usually become avirulent. The Th symptoms of b t i l panicle blighttf bacterial i l bli ht include seedling blight, sheath rot lesions on the flag leaf flag-leaf sheath, and panicle blighting with significant yield losses. Specific leaf sheath symptoms include vertical lesions with gray centers surrounded b a d k reddish b t d d by dark ddi h brown margin. 12. This di Thi disease is characterized asi h t i d having upright, straw-colored panicles containing florets with a darker base and a reddish-brown line (margin of lesion) across the floret between the darker d k area and th straw-colored area, d the t l d resulting in abortion of the kernel before it fills. The severely affected y panicles remain upright, as the grain does not fill. The term panicle blight has been used in the United States for more than 50 years and BPB has been retained as the name for the disease in this country. 13. Bacterial Panicle Blight 14. BACTERIAL PANICLE BLIGHTSPRAY INOCULATED 106 CFU / ML (quorum sensing) 15. Effect of Temperature on Growth ofBPB pathogensEffect of temperature on the growth of B. glumae (A) and B. gladioli (B) strains. Each line represents gp growth of a single g strain after 48 h of incubation in KBB. Each strain was tested with three replicates. Ten strains were tested for each species (b d idf h i (based on PCR and fatty acid identification). Strains were isolated from rice panicle collections showing symptoms of bacterial panicle blight from Louisiana, Texas, and Louisiana Texas Arkansas. 16. EFFECT OF TEMPERATURE ON GROWTH OF Burkholderia glumae and Burkholderia gladioli STRAINS 1 .8 1 .81 .6 1 .61 .4 1 .4 nsity at 600 nm 1 .2 1 .211 Optical den 0 .8 0 .80 .6 0 .60 .4 0 .40 .2 0 .20030 3540 45 50303540 45 T e m p e r atu r e CT e m p e r atu r e C Burkholderia glumae strainsBurkholderia gladioli strains 17. The temperature optima ranged b td between 38 and 40C d ( (100-104F) for B. glumae and) g 35 and 37C (95-99F) for B. gladioli. Th l di li These results werelt confirmed with repeated experiments. 18. Bacterial Panicle Blight in theU.S. in 2010 TEMPERATURES were in the range of 90-100F (32-38C) during the day and in ()g y the 80s (27-29C) at night in Louisiana and Arkansas in 2010. These were new records for night temperature (37 states). Bacterial blighting was severe in ) gg both states according to Extension Specialists with y pyield losses to 50% in some fields. 19. NIGHT TEMPERATURESFrom our observations, itobservations appears that extended highppg temperatures at night seem to be b an iimportant factor in BPB t tf t i disease development. p 20. Quorum SensingThis is a type of decision-makingdecision making process used by decentralized groups to coordinate behavior. Many species of bacterial pathogens use quorum sensing to coordinate their gene expression according to the local i di t th l l density of their p p ypopulation. 21. A variety of diffi t f differentt molecules can be used as signals. A common class of signaling molecules in Gram-i lil l i G negative bacteria, such as B. glumae and B. gladioli, is N-Acyl Homoserine Lactones (AHL) 22. Activation of the receptor induces the up regulation of other specific gp gp genes,, causing all of the cells to begin transcription at approximately the same ppp y time. This includes the turning on of the p pathogen attack g g genes. Optimum p temperatures for growth means that the bacterial population reaches the p p threshold population to turn on these g genes more q quickly. y 23. Virulence Factors Produced By Burkholderiay glumae in Response to Quorum Sensing Known: toxoflavin toxin, lipase, flagella formation (QsmR), catalase (KatG) (Q),( ) Possible factors: type III secretion system, extracellular polysaccharides t ll l l h id 24. Temperature and Quorum Sensing: Relationship to BPB Disease Development It is known that the production of the major virulence factors of B glumae; toxoflavin lipaseB. toxoflavin, and flagella, are dependent on the quorum- sensing system mediated by AHL signal molecules. S Several virulent and avirulent B. ii glumae strains were tested for their ability to produce AHL signal molecules using an AHL- AHL biosensor strain, Chromobacterium violaceum CV026. Interestingly, all the strains that produce none of th virulence factors tested were d f ti f the i l f tt t ddefective in AHL-signal biosynthesis, while the strains that p produce at least one of the major virulence j factors showed AHL-positive phenotypes. 25. Effect of loss of quorum Sensing Signalsin Avirulent Strains of B. glumae Virulence of the B. glumae strains was closely related to their ability to produce various virulence factors Interestingly all factors. Interestingly, the confirmed avirulent strains were defective in multiple virulence factors and most of them lost their ability to produce acyl-homoserine lactone (AHL) quorum- sensing signals implying that mutation in global regulatory system(s) for the virulence factors is the major cause of the occurrence of avirulent B. glumae strains in naturef i li i 26. Testing for Virulence Onion scale inoculation Inoculation of rice 27. Flagella Production Virulent Avirulent 28. Toxoflavin Toxin Production No N toxoflavin fl i ToxoflavinT fl i (yellow) 29. Inoculating Entries in the BPB Nursery 30. Three Row Plot in the BPB Nursery Center Row Inoculated 31. Susceptible Breeding Line S tibl B di Li 32. LM-1: Resistance Source for BPB Developed byD.E.D E Groth using Cobalt Irradiation of VarVar. Lemont 33. Susceptible Commercial Var. Cocodrie 34. Crossing to Transfer Resistanceg Crosses with Resistant EntriesLM 1, AB 647, LR 2065Nipponbare,Nipponbare JupiterCrosses were made with the susceptible varieties CCDR, CPRS, and FRNS to study inheritance of the resistance in these materials. Results 35. SOURCES OF RESISTANCE TO BPB 1. 1 JUPITER U S MEDIUM GRAIN VARIETY U.S. VARIETY,STUDIES UNDERWAY BY DR. JONG HAMAND HIS GRADUATE STUDENTS, ,LOUISIANA STATE UNIVERSITY2. NIPPONBARRE, Teqing, LR 2065, LM-1, USHYBRED VARIETIES, OTHER MATERIALS 36. Effect of B. glumae on the Yield Potential of Rice B Difference between sprayed and unsprayed p p y p y plots 37. Effects of Panicle Blight on Selected Commercial Varieties - 2005 Yield (lb/A at 12% Moisture) DifferenceVarieties (lb/A at 12%Non- Inoculated moisture) inoculated i l t dYield Yield Rating RatingCocodrie8047 7001 - 1047ns 0.87.3 Jupiter10,168 9731 - 437ns 0.5 05 3.333Trenasse8338 6687 - 1651** 2.38.3 Bengal 8260 6262 - 1978** 2.78.7 38. Effects of Soilborne B. gladiolion Yield of Bengal Rice Soil strains sprayedYield (lb/A atRating12 % Moisture)Moist re) Non-inoculated (Healthy control) 2.7 8260 bcS-10 (Soil B. gladioli)3.7 7666 b223 gr-1 (Grain B. gladioli) 3.3 8659 bc3S4 (Soil B. gladioli) 2.7 8788 bc3S5 (Soil B gladioli) (S il B. l di li)373.7 8854 cS15 (Soil B. gladioli) 4.3 8822 bcATCC B. gladioli 4.3 8609 bc336gr-1 B. glumae8.7 6282 a 39. Chemical Control of BPBOxolinic acid (Starner) is the only effective chemical control available for this pathogen when used as a spray, however, o

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