Quantitative Estimation of Rhizoctonia spp., the Organisms of Turfgrass Brown Patch and Their Control

• Main Authors: Huang, R. Z., 黃睿志
• Other Authors: S. P. Y. Hsieh
• Format: Others
• Language: zh-TW
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/68560047536041204847

碩士 === 國立中興大學 === 植物病理學系 === 84 === Rhizoctonia brown patch of turfgrasses caused by Rhizoctonia spp. is commonly and seriously occurring in Taiwan. The main causal agent is R. solani AG-4. Sixteen turfgrass seeds were screened for quantitative baiting of this causal organism. The criteria used to screen are conveniency of seed recovery from soil, baiting efficiency, stability, easy to handle and shorter time needed. Bahia grass seeds were found to be satisfied to these requirements. The suitable conditions for bahia grass seeds to bait R. solani are 12-15%(w/w) water content of the soil incubated at 25℃. Bahia grass seeds were buried in soil for 12 hr, and placed on tannic acid agar in dark for 12-16 hr. Positive baiting is shown by brown color appeared beneath and around the seeds. There is a good correlation between percent of bahia seed baiting at 12 hr and density of propagules of R. solani in soil assayed by multiple-pellet soil sampler method. Bahia grass seed baiting also does well on other anatomosis groups, i.e., AG-G(isolate WF2) and AG-F(TKS) but not WAG-O( NP18). Two methods can be used to estimate the popagule density of R. solani in soil by bahia grass seed baiting. Firstly equation Y=4.53+17.69X obtianed from correlation analysis of percent of bahia seed baiting and propagule density assayed by multiple-pellet soil sampler can be used. Secondly based on bahia grass seed could induce mycelial growth of R. solani in soil for 0.25 cm length within 12 hr, this means that a single bahia grass seed has ability to bait the pathogen in soil within a radius of 0.25 cm in 12 hr. The soil weight of baiting range of a single seed can be calculated from baiting range of soil volumn, 4/3r3 =4/3 x 3.1416 x 0.25=0.065 cm3. Density of propagules/g soil = number of positive baiting seeds/number of seeds assayed x a single seed baiting soil range in g. The second method can be used only when density of propagules is low, or soil has to be properly diluted. If density of propagules is too low, the sampling size of baiting seeds must increase.