Use of manganese oxide nanoparticle (MnO2 NPs) and Pseudomonas putida for the management of wilt disease complex of carrot

Abstract

Wilt disease complex of carrot is caused by Ralstonia solancearum and Meloidogyne incognita and is responsible for considerable yield loss. Manganese oxide nanoparticle (MnO₂ NPs) and Pseudomonas putida were used alone and in combination for the management of wilt disease complex. In vitro, MnO₂ NPs 0.10 g.L^-l caused 49.36% reduction in hatching and 14.23% mortality of second stage juveniles (J₂) of M. incognita while paper disc dipped in MnO₂ NPs suspension caused 0.51 mm inhibition zone around R. solanacearum in nutrient agar medium. Inoculation of P. putida to plants with pathogens caused a similar increase in plant growth, chlorophyll and carotenoid contents as caused by foliar spray with 0.10 g.L⁻¹ MnO₂ NPs. Use of P. putida with NPs foliar spray to plants with pathogens caused a greater increase in plant growth, chlorophyll and carotenoid contents than with P. putida or NPs foliar spray. Inoculation of M. incognita/R. solanacearum/M. incognita plus R. solanacearum/P. putida/MnO₂ NPs and MnO₂ NPs plus P. putida caused increase in proline contents. Root colonization by P. putida was reduced in plants with test pathogens. Foliar application of MnO₂ NPs and P. putida reduce wilt disease indices. Galling and populations of M. incognita was also reduced in plants co-inoculated with R. solanacearum. The greatest reduction in nematode populations and galling was observed in plants with NPs spray together with P. putida. Principal component analysis demonstrated a clear influence of NPS and P. putida and their combination on various studied parameters in diseased plants.