Ice nucleation active bacteria and its mitigation on tomato (Solanum lycopersicum)

Abstract

Microbes play a vital role in ice nucleation, supporting bio-precipitation, and allowing plants to live in low-water environments. A field experiment was conducted during December 2018 with two phyllosphere microorganisms’ spraying viz., Pseudomonas aeruginosa and pink-pigmented facultative methylotrophs (PPFM) and under three moisture regimes (0.6, 0.8, 1.0 IW/CPE (irrigation water/ cumulative pan evaporation) ratio) on tomato (PKM 1) in Tamil Nadu Agricultural University, Coimbatore (Tamil Nadu). A laboratory experiment was conducted to confirm ice nucleation using two phyllosphere microorganisms’ P. aeruginosa and PPFM. The bioprecipitation impacts on tomatoes were assessed using a set of physiological parameters such as photosynthetic rate, average chlorophyll Index and the ice nucleation activity (INA) assessed using tube nucleation test and scanning electron microscope (SEM). The results showed that the mean photosynthetic rate of PPFM sprayed tomato (Solanum lycopersicum) (PKM 1) plants (40.7 μmol CO2/m2/s) at 10 DAS was significantly higher than P. aeruginosa sprayed plant (38.7 μmol CO2/m2/s) under different irrigation regimes. The average chlorophyll Index value of the P. aeruginosa sprayed tomato plants (58.1) was higher than PPFM sprayed plants (56.4). The tube nucleation tests were proved that ice crystallization induced by P. aeruginosa in super-cooled buffer at - 2 to -10°C while PPFM not catalyze the buffer even after 3hours. The scanning electron microscope (SEM) indicated the P. aeruginosa growth at the upper surface of the leaf and PPFM growth more at the lower surface of the leaf compared to without inoculation of microbes on leaves. Overall, the result revealed that P. aeruginosa may assist in ice nucleation activity that will help to make artificial rain in the near future.