Chitosan has been reported to have antimicrobial property to some pathogen species as well as an elicitor of resistance in plants , particularly Systemic Acquired Resistance (SAR). A bioassay of chitosan against Xanthomonas oryzae pv. oryzae (Xoo) was conducted to determine its antimicrobial property against bacterial blight pathogen and the optimum concentration that is most inhibitory to the pathogen. Chitosan was also tested as foliar spray to rice plants to evaluate its potential to induce SAR against bacterial blight disease.
Chitosan treatments (300 ppm, 400 ppm, and 500 ppm) possessed antimicrobial property against Xoo in vitro, producing zones of inhibition which were generally significantly bigger than those of the control (streptomycin, acetic acid, and sterile distilled water) at 2, 4, and 6 days after inoculation. Chitosan-sprayed plants showed significantly shorter bacterial blight lesions which were comparable to the plants sprayed with streptomycin, and Boost, a commercial plant defense activator and a known inducer of SAR. Chitosan is found effective in reducing bacterial blight lesions in rice plants due to its antimicrobial property and also most likely due to the induction of SAR.
Fusarium wilt caused by Fusarium oxysporum f.sp. cubense (FOC) is one of the problem diseases attacking abaca. The most effective way of minimizing the damage is through the use of resistant varieties. The levels of resistance of different abaca varieties/accessions, however, have not been determined yet so this study was conducted to: 1) evaluate the reaction of eight recommended abaca varieties to fusarium wilt, 2) evaluate the reaction of abaca varieties/accessions and abaca relatives from the National Abaca Research Center (NARC) germplasm collection and production area to fusarium wilt, and 3) confirm the reaction of the identified resistant varieties/accessions in a naturally infested field.
Among the 8 recommended abaca varieties, Linino showed resistance to FOC having the lowest infection, foliage yellowing and internal vascular discoloration ratings in a pot experiment. This variety was also proven resistant in the field plot screening together with 6 other accessions, namely: Alman No.2, Alman No.4, Tinawagan Puti #.2, Pakol, CES x Pacol and Pakil #1. Of the six, Alman No.4, Tinawagan Puti #2, Linino and Pakil also showed resistance to FOC, when planted in a naturally infested field in Polahongon, Mahaplag, Leyte.
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