Seed priming induced blast disease resistance in finger millet plants through phenylpropanoid metabolic pathway

Abstract

Phenylpropanoids contribute to all aspects of plant responses to biotic and abiotic stimuli. The lignin biosynthesis by phenylpropanoid pathway induces cell wall strengthening, a barrier against fungal penetration and progression. In the present study, two fluorescent Pseudomonas isolates JUPC113 and JUPW121 from cotton and wheat rhizospheres respectively were used for seed priming in greenhouse studies along with the unprimed seeds as control. Plants were assessed for disease symptoms from 10 to 20d of challenge inoculation with the blast pathogen Magnaporthe grisea (MTCC-1477). Pronounced increase in disease resistance was seen in primed plants; JUPW121 (0.21 ± 0.04) and JUPC113 (0.27 ± 0.02) compared with the mock control plants with maximum disease incidence rate of 2.67 ± 0.33. Spectrophotometric estimation of the different enzymes involved in lignin biosynthesis, viz., phenylalanine ammonia lyase (PAL; EC 4.3.1.24) and tyrosine ammonia lyase (TAL; EC 4.3.1.25) showed an increased activity in JUPC113-primed plants at the initial 6 and 12 hpi in comparison with the control. The biochemical studies were validated by the histochemical (lignin) and metabolomic (phenolic compounds and amino acids) studies. The disease incidence rate was also low when compared to the primed and mock control plants which was validated by biochemical estimation of the enzyme activities. The present study presented the experimental evidence on induction of disease resistance in finger millet against the pathogen by accumulation of host defense compounds during early hours post challenge. Hence these isolates can be used in further studies of seed priming for disease resistance against different plant pathogens.