Pathogenic effects of <i>Salmonella enterica </i>subspecies <i>enterica </i>serovar Typhimurium on sprouting and growth of maize

Abstract

The study was undertaken to understand effects and survival of <i>S</i>. <i>enterica </i>subspecies <i>enterica </i>serovar Typhimurium (<i>S</i>. Typhimurium), a zoonotic serovar, on maize seed germination and plant growth. All the four strains of <i>S. enteric</i> subspecies <i>enterica </i>serovar Typhimurium significantly reduced germination of maize seeds in sprouting plates as well as in soil. About ≥2.7×10³ <i>Salmonella </i>cfu ml^-1 of soaking water, while ≥2.7×10⁷ <i>Salmonella </i>cfu g^-1 soil were required to significantly inhibit germination of maize. Similar inhibition of germination could be observed using ≥16 mg of bacteria free <i>Salmonella </i>cell lysate (CL) protein per g of soil or ≥0.5 mg of CL protein per ml of soaking water in sprouting plates.

At the constant dose of 3.6×10⁷ to 3.8×10⁷ <i>Salmonella </i>cfu or 5 mg cell lysate protein ml^-1 of soaking water, four strains of <i>Salmonella </i>significantly reduced germination, however difference between strains was insignificant. After germination too, maize growth was affected both by <i>Salmonella </i>organism and CL with little strain-to-strain variation. All <i>Salmonella</i> persisted in growing plants from 15 to 35 days of plant age and up to 190 days in soil. Maize plants once grown for a week in sterile soil were resistant to invasion of <i>S</i>. <i>enterica </i>subspecies <i>enterica </i>serovar Typhimurium in their leaves even in doses as high as 7.6×10⁹ cfu g^-1 of soil. <i>Salmonella </i>persisted better and longer in plants grown from contaminated seed sown in loam soil, but rarely in plants grew in sandy soil. All maize plants had <i>Salmonella </i>in their stumps even after 35 days of sowing irrespective of kind of soil, primary source of infection (soil or seed) and type of <i>S</i>. <i>enterica </i>subspecies <i>enterica</i>

serovar Typhimurium strain. The study revealed that <i>Salmonella </i>is not only zoonotic but a phytopathogen also.