Differential Response of Inoculation with Indole Acetic Acid Producing Pseudomonas Sp. In Green Gram ( Vigna radiata L.) and Black Gram ( Vigna mungo L.)

摘要

Rhizosphere bacteria promote plant growth by improving the availability of nutrients, suppressing the growth of plant pathogens or by production of hormones such as auxins. Influence of indole acetic acid (IAA) producing bacterial mutants was studied on nodulation and plant growth promotion in green gram ( Vigna radiata L.) and black gram ( Vigna mungo L.) in the present studies. IAA producing Pseudomonas strain MPS90 was mutagenized with transposon Tn5 to obtain mutants with variation in IAA production ability. Low amount of IAA production was observed in 35.14% mutants whereas, 3.43% mutants produced higher amount of IAA in comparison to parent strain. Seed inoculation of three mutants i.e., MPS90-14, MPS90-106 and MPS90-150 caused slight stimulation of root growth of green gram seedlings at both 5 and 10 days of observation whereas four mutants i.e., MPS90-39, MPS90-133, MPS90-145 and MPS90-157 caused stimulation of shoot growth at 5 days. In black gram, majority of the Pseudomonas mutants enhanced the root growth of seedlings at 5 days of observation whereas at 10 days, only four mutants i.e., MPS90-39, MPS90-157, MPS90-102 and MPS90-106 caused stimulation of root growth. The shoot growth of black gram seedlings at 5 days observation was retarded with most of the mutants except the mutants MPS90-14, MPS90-51, MPS90-133 and MPS90-280. Coinoculation studies of Pseudomonas mutants with Bradyrhizobium sp. strain S24 caused increase in shoot dry weight that varied from 110 to 137 per cent in green gram and from 105 to 198 per cent in black gram in comparison to Bradyrhizobium -inoculated plants at 60 days of growth. The stimulation effect varied from 280-390% in green gram and 179-357% in black gram in comparison to uninoculated control treatment. Mutants MPS90-133, MPS90-145 and MPS90-51 showed more nodule formation by Bradyrhizobium strain S24 in green gram whereas mutants MPS90-102, MPS90-39 and MPS90-280 caused more stimulation for nodule formation in black gram at 60 days of plant growth. Thus, mutants altered in IAA production ability showed differential responses on nodulation and plant shoot weight in the two hosts.