Comparison of three methods (leaf, soil and stem) of inoculation for stem rot jute (Corchorus olitorius L. and C. capsularis L.) caused by Macrophomina phaseolina (Tassi) Goid.

Abstract

In order to devise a suitable method of inoculation of jute (Corchorus olitorius L. and C. capsularis L.) stem rot caused by Macrophomina phaseolina (Tassi) Goid. for large scale use, three methods (leaf, soil and stem) were compared. Among four leaf inoculation methods, tip cut and cotton swab method was better than inoculating floating leaf disc (8 mm), floating leaf and cotton swabbed detached leaf with typical symptom with light to dark brown spots in 100 % inoculated leaves within 48 hours on susceptible line JRC 412 which enlarged on further incubation. Among three different times of soil inoculation, 7 days before sowing was more effective in causing infection in JRO 524 and JRO 8432 with 26.6 and 23.3% stem rot than soil inoculated during sowing (15%) and 7 days after sowing (10%). Resistant reaction of four lines (OIN 125, OIN 154, OIN 651 and OIN 853) was confirmed by these three soil inoculation methods with JRO 524 as check. Stem inoculation technique was highly efficient and caused 100% infection with typical stem rot symptoms with brown spots of different length and intensity encircling the stem in JRO 524 compared to earlier methods. The variation in virulence pattern of isolates was evident, as more virulent isolate (from Sorbhog, Assam) produced distinctly clear, longer and darker brown stem rot lesion than less virulent ones (from Barrackpore, West Bengal).