Evaluation of Diacetylphloroglucinol Producing Pseudomonads for Their Biocontrol Potential Against Ralstonia Wilt in Brinjal

Abstract

Diacetylphloroglucinol (DAPG) producing isolates of pseudomonads were screened against bacterial wilt in brinjal caused by Ralstonia solanacearum under greenhouse conditions. Thirty Pseudomonas isolates were obtained from the culture collection of NBAII, Bangalore that include seven isolates of Pseudomonas putida (CK8C, CK24E, Pf4K, RPF9, RPF13, OTN5E2, GR1ARS1), one P. mosselli (CK24C) isolate, three isolates of P. fluorescens (GR3ARS3, Pf-DWD, CHAO), three isolates of P. plecoglossicida (BA11D1, BA16-2, BA3-D1) and sixteen isolates of P. aeruginosa (CK13C, CK19E, AFP3, AFP4, AFP6, RFP7, OTN8, AFP9, AFP8, PDB8, PDB1, AFP7, AFP5, AFP13, ND4-IARIB, RPF8). Bacterial wilt susceptible brinjal variety MEBH- 9 was used in the screening. The brinjal seedlings were dipped in Pseudomonas suspension for five minutes before transplantation and plants were observed for wilt symptoms like stunted growth, drooping of leaves, loss of rigidity and eventually death of the plant. Four weeks later, the plants were uprooted and length and weight of both roots and shoots were recorded. The highest percentage of wilt disease reduction was observed in seedlings treated with P. plecoglossicida BA11D1 (95.8%), P. putida CK24E (62.5%) and P. plecoglossicida BA3D1 (41.7%). Average shoot length, root length and shoot weight, root weight were comparatively lesser in most of the pseudomonads treated plants than the control plants.