Seed priming with Trichoderma harzianum isolates enhances plant growth and induces resistance against Plasmopara halstedii, an incitant of sunflower downy mildew disease

Three rhizosphere fungal isolates viz., PGPFYCM-2, PGPFYCM-8 and PGPFYCM-14 of Trichoderma harzianum, applied as seed treatment to a highly susceptible sunflower cultivar were evaluated for their ability to promote growth and induce resistance in sunflower against downy mildew disease caused by Plasmopara halstedii. Treatment of sunflower seeds with both conidial suspension (1 x 10(8) spores ml(-1)) and talc formulations (2.1 x 10(7) spores g(-1)) at 8 g kg(-1) seeds and 10 g kg(-1) seeds, significantly promoted growth and reduced disease incidence under both greenhouse and field conditions. Among the treatments, PGPFYCM-14 (1 x 10(8) spores ml(-1)) was highly significant (P = 0.05) in inducing resistance of 63 and 69 %, followed by PGPFYCM-2 which offered 41 and 42 % disease protection under greenhouse and field conditions respectively. Formulation treatments of PGPFYCM-14 also protected the plants significantly (P = 0.05) when compared to the untreated control. There was a significant increase in NPK macronutrients uptake in all the treated plants compared to the untreated control and maximum NPK uptake was observed with PGPFYCM-14 (1 x 10(8) spores ml(-1)). Under in vitro conditions, all the tested isolates expressed increase in seed germination and vigour index over the control. Tested plant growth promoting fungal (PGPF) isolates remain significant in enhancing vegetative and reproductive growth parameters, including plant height, early flowering, reduced crop duration, ear head size and crop yield under field conditions when compared to the untreated control.