PJB-2013-266
EFFECTS OF HOST GROWTH STAGE, RE-ISOLATION AND CULTURE MEDIUM ON SCREENING FOR RESISTANCE TO STEM ROT DISEASE CAUSED BY SCLEROTIUM ROLFSII SACC. IN JERUSALEM ARTICHOKE
R. SENNOI, S. JOGLOY, W. SAKSIRIRAT, T. KESMALA AND A. PATANOTHAI
Abstract
Consistently replicable methods of inoculation are necessary to efficiently screen Jerusalem artichoke (Helianthus tuberosus L.) genotypes for resistance to the soilborne fungal pathogen Sclerotium rolfsii Sacc. The fact that plant age, type of inoculum and source of inoculum can affect severity and incidence of stem rot disease caused by S. rolfsii are factors that must be assessed and controlled in seeking disease-resistant accessions The objective of this work was to investigate the effects of seedling stage, source of S. rolfsii inoculum (serial In vitro subculture and re-isolation of S. rolfsii from infected plants), and culture medium used to prepare inoculum on stem rot disease. Seedlings of Jerusalem artichoke (Kaen Tawan # 2) at 6-, 8- and 10-leaf stages were inoculated with sorghum seed that had been infested with S. rolfsii derived from different sources (serial In vitro subculture or re-isolated from symptomatic host tissue, and cultured in either potato dextrose agar (PDA) or a sorghum-based medium; the infested seed were placed in wounds made at the base of the stem). In a greenhouse, the experiment was set up as a 3 x 2 x 2 factorial in a randomized complete block design with six replications; the experiment was repeated once. Plants at the 6-leaf stage were more susceptible than those at the 8- or 10-leaf stages. S. rolfsii inoculum derived from serial In vitro subculture caused more severe stem rot symptoms than inoculum derived by re-isolation from symptomatic host plants, but the difference was not significant for disease incidence. Inoculum culture on the sorghum-based medium resulted in a higher incidence of stem rot than PDA. The highest incidence of disease was observed with inoculum grown on PDA from serial In vitro subculture and on the sorghum-based medium that had been re-isolated from symptomatic host tissue. In addition, disease severity was higher when inoculum was grown on PDA from serial In vitro subculture than from sorghum-based medium that had been sub-cultured In vitro.
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