Induction of resistance against downy mildew on sunflower by rhizobacteria

Abstract

Induction of resistance to downy mildew caused by Plasmopara halstedii in sunflower was studied after treatment with PGPR (plant growth promoting rhizobacteria) strain INR7 (Bacillus spp). Treatment of sunflower seeds with 1 )10 8 cfu/ml of PGPR strain INR7 resulted in decreased disease severity and offered 51 and 54% protection under green house and field conditions, respectively. The induction of resistance to P. halstedii by PGPR strain INR7 was accompanied by the accumulation of various host defense-related enzymes in susceptible sunflower seedlings. Enhanced activation of catalase (CAT), phenylalanine ammonia-lyase (PAL), peroxidase (POX), polyphenol oxidase (PPO) and chitinase (CHI) was evident at 6, 9, 12, 12 and 12 h post inoculation, respectively, in sunflower seedlings raised from seeds treated with PGPR strain INR7. This enhanced and early activation of defense-related responses in the susceptible cultivar after treatment with PGPR strain INR7 was comparable to that in the resistant cultivar. The results indicate that PGPR strain INR7 induced resistance against P. halstedii in sunflower is mediated through enhanced expression of defense mechanism.

Induction of Polyphenol Oxidase in Walnut and Its Relationship to the Pathogenic Response to Bacterial Blight

“…Strong induction of PPO has been reported in diverse plant species after wounding, application of MeJA (Constabel and Ryan, 1998), or inoculation with pathogens (Constabel et al, 1995;Sarwar et al, 2003;Thipyapong et al, 1995). Enhanced activation of PPO was evident in sunflower (Helianthus annuus) at 12 h after inoculation of plant growthpromoting rhizobacteria to induce resistance to Plasmopara halstedii (Nandeeshkumar et al, 2008). Moreover, in this study, presence of the JrPPO-1 gene in 'Chandler' was detected, which is in agreement with previous work by Escobar et al (2008).…”

The Significance of Bacillus spp. in Disease Suppression and Growth Promotion of Field and Vegetable Crops

“…The induction of resistance to Plasmopara halstedii by Bacillus sp. strain was accompanied by the accumulation of defense-related enzymes (PAL, POX, PPO) in sunflower [ 89 ].…”

Trichoderma harzianum antagonistic activity and competition for seed colonization against seedborne pathogenic fungi of sunflower

“…Disinfested seeds were treated with a conidial suspension of antagonist mixed with each pathogen in addition to Tween 20 (0·1%) in 50‐ml conical flasks, which were then gently rotated on a reciprocating shaker (Elecro‐Mag) for 6 h (NandeeshKumar et al . 2008; Nagaraju et al . 2012a, 2012b; Özer et al .…”

“…Seeds of 13 TR 009 were surface disinfested in a 1% solution of sodium hypochlorite for 1 min, then rinsed in sterile distilled water and air-dried on sterile filter paper. Disinfested seeds were treated with a conidial suspension of antagonist mixed with each pathogen in addition to Tween 20 (0Á1%) in 50-ml conical flasks, which were then gently rotated on a reciprocating shaker (Elecro-Mag) for 6 h (NandeeshKumar et al 2008;Nagaraju et al 2012aNagaraju et al , 2012b€ Ozer et al 2021) at 40 rev min À1 . Control seeds were separately inoculated with each pathogen only.…”