| This paper explores the occurrence of cotton bacterial rot boll--a new disease in Xinjiang, inspects itsinfluence on cotton yield and fibre quality, identifies primary causes for disease, the invasion channel ofand genetic differentiation of pathogens, determines major mode of pathogen transmission in the cottonfields of Xinjiang. It provides the basis for effective prevention and reasonable disease control.A rudimentary disease paradigm for seed and boll rot of cotton includes in field:(i) asymptomaticouter carpels of infected bolls;(ii) incomplete maturity of fibre and seed; and(iii) brown necroticcoloration of both fibre and seed tissue.All of 53 isolates were obtained from diseased cotton bolls in Xinjiang. Pathogenicity of isolates wasdetermined through puncturing and rejecting cotton boll, and symptoms of boll rot were discovered ininoculated cotton bolls. Pathogens were identified basing on morphological characterizations, physiologicaland biochemical reactions and 16 S ribosomal DNA sequence analysis. The pathogen causing cotton bolland seed rot was confirmed Pantoea agglomerans. This is the first report that P. agglomerans is thepathogen of cotton roll rot in China.Incidence and influence on cotton yield and fibre quality of cotton bacterial boll rot was investigated infield and plot. The results showed that all the tested cotton varieties could be infested P.agglomerans,average incidence of 20.6%, and incidence among varieties was significant difference in field. The singleboll weight and lint percentage of infested cotton bolls reduced 27.6% and 5.3%, respectively, the immatureseeds increased 160%, and the length of velveteen, fiber breaking tenacity, fibre elongation of bacteriainfesting fibre was inferior normal. Most importantly, seed and boll rot of cotton(Gossypium hirsutum) beresponsible for losses of 10–15% of yield in Xinjiang. Germination rate of seeds was reduced in laboratoryand field.Invading cotton boll pathway of P. agglomerans was explored using bacterial suspension inoculatingseed, irrigating cotton, spraying seedling, flower, boll, bruising boll, puncturing and injecting bolls duringgrowth period of bolls. Infected bolls only were observed when bacterial injections breached the endocarpof the boll either through the carpel wall or a suture between carpel sections. P. agglomerans is nottransmitted through contaminated bacteria seeds, soil, flower, rain and bruising boll. The wound penetratingboll carpel wall is obligatory to infesting cotton.All kinds of pest were catched during cotton flowering in field, and pest endophytic bacteria wereisolated and indentified using P. agglomerans specific primer PCR. The results show that pest endophyticP. agglomerans were isolated from Frankliniella.formosae, Lygus pratensis, Adelphocoris suturalis,Geocoris.spp, Orius.spp, Leptocorisa.spp, Adonia variegate, Coccinella septempunctata and Heliothisarmigera, but nothing Aphis gossypii. P. agglomerans isolating from Frankliniella.formosae, Lyguspratensis and Adelphocoris suturalis was higher than other pests. Furthermore, populations of P.agglomerans harbored the single of L. pratensis and A. suturalis were 0.08-5.14*103CFU/bug, and F.formosae was 44 CFU/bug.The differences of 33 Pantoea agglomerans isolates from boll and pest were determined through theindoor sensitivity of antibiotics and rep-PCR fingerprinting. The results showed that 33 strains havedifferent sensitivity to different antibiotic. 33 strains were clustered at the level of 20.12%,5 clusters wereobtained at the differences of 15.0%, among 33 strains, 14 are in A group, 16 are in B group, and otherthree are in three groups respectively. And groups of A and B is the total number of 91.0%. Most of strainsin A group were from isolates of cotton bacterial boll rot and endophytic bacteria of bug. Rep-PCRfingerprinting showed that six groups were obtained. 21 of 31 strains belong to B groups. Strains from ofcotton boll rot and endophytic bacteria of bug revealed near genetic relationship.P. agglomerans mutants resistant to chloroamphenicol(CM)(strain Cx21-R) and express greenfluorescent protein(GFP)(strain Cx21-GFP) was used to location of P.agglomerans colonization in L.pratensis and A. suturalis after ingestion of soaked in a suspension of strain CX21-R sterile green beans inlaboratory. The insect rostrum, head, and alimentary canal were subsequently processed the presence of P.agglomerans strain Cx21-R. Overall, the alimentary canal exhibited significantly more bacterial colonythan than the head and rostrum. Ggreen fluorescent was observed in midgut and hindgut bug alimentarycanal.In laboratory, adult L. pratensis and A. suturalis were individually feeded by green beans that weresterilized and then soaked in either sterile water or in a suspension of strain Cx21-R. Insects wereindividually caged with an unopened cotton bolls for 2 days. The result showed that evidence of insectfeeding on the exterior wall of the carpel was not always apparent, whereas feeding was always observed(100%) on the interior wall in association with bacterial infections of seed and lint. Bolls rot were occuredingestion of soaked in a suspension of strain Cx21-R sterile green beans, incidence 47.1%(2013) and56.25%(2014), respectively. Research reported immature boll responses various stages of boll maturity(10,20, and 30 d post-anthesis [DPA]) to insect injury and to infection by the vectored cotton P. agglomerans bydemonstrating the progression of effects. Bolls at a maturity of 10 or 20 DPA showed similar susceptibilitywhen exposed to insect that vectored Cx21-R, incidence 71.88% and 66.67%(2013), 67.86% and64.28%(2014), At 30 DPA, incidence of the fruit was 33.33% and 30.77%. Qiantity of insect harboring thepathogenic organisms contributed to cotton bolls infested. 2,5,10 bug feed, incidence 13.79%, 30.00% and52.9%, respectively.L. pratensis and A. suturalis harboring the P. agglomerans(Cx21-R) were reared into cage cottonplant. Rot bolls were observed in field plant, incidence 31.87%, non-insect control 6.8%. The Cx21-Rstrain was isolated only from insects exposed to the marked strain and from seed and lint of respective bollsshowing signs of insect feeding.L. pratensis and Ad. suturalis readily ingested the opportunistic P. agglomerans and transmitted it intounopened cotton bolls. Infections by the transmitted XC21-R strain caused rotting of the entire locule thatmasked internal carpel wounds incurred by insect feeding. it is the first study that the ability of L. pratensisand Ad. suturalis could acquire and transmit plant pathogenic bacteria into cotton bolls in Xinjiang. |
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