Evaluation of Indigenous Fluorescent Pseudomonads for the Management of Newly Emerging Wilt of Pomegranate Caused by Ceratocystis fimbriata

Abstract

Pomegranate (Punica granatum L.) is a commercial fruit crop in India and regarded a vital cash crop in many states including Karnataka. Wilt disease (Ceratocystis fimbriata Elli. and Halst.) is a new devastating disease on pomegranate that caused losses estimated up to 30% and becoming a major threat leading to the destruction of several pomegranate orchards. Although suitable wilt management practices including cultural, sanitation, and chemical have been developed, there is still a need to develop more economical, feasible, and effective environmentally friendly alternative control methods. Recently, there is an increased interest for use of plant growth-promoting rhizobacteria (PGPR) for sustainable pomegranate cultivation. Thus, the present investigation is intended to evaluate indigenous fluorescent pseudomonad isolates for biocontrol, PGPR traits, and plant growth promotion. In the present investigation, 35 native isolates of fluorescent pseudomonads from wilt-affected pomegranate orchards were isolated, purified, and characterized. These were screened for their in vitro efficacy using standard dual culture plate culture technique for the inhibition of the growth of C. fimbriata. Out of 35 isolates, 11 isolates (PFP-1–PFP-11) significantly reduced the vegetative growth of C. fimbriata. These isolates were tested for PGPR traits such as the production of indoleacetic acid (IAA), hydrogen cyanide (HCN), hydrogen sulfide, and siderophore. All the 11 isolates showed bright fluorescence under UV light, and morphological and biochemical tests proved them as Pseudomonas fluorescens. The isolates were positive for siderophore production and plant growth-promoting activities. Two isolates PFP-11 and PFP-10 showed remarkable antifungal activity against C. fimbriata with the inhibition of 72.04% and 71.20%, respectively. These isolates showed significant producers of HCN, IAA, siderophore, and enzymes. Overall, our results suggest that these fluorescent pseudomonad isolates can be estimated as efficient bioagents for the sustainable management of newly emerging wilt of pomegranate caused by C. fimbriata and warrant further evaluations.