Symbiotic effectiveness of abiotic stress tolerant pigeon pea [Cajanus cajan (L.) millspaugh] rhizobia
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Date
2016
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
CCSHAU
Abstract
Pigeon pea [Cajanus cajan (L.) Millsp.], is a plant of Fabaceae family grown in semi-arid tropics in Asia
and Africa. Pigeon pea is a versatile, stress-tolerant, and nutritious grain legume, possessing traits of value
for enhancing the sustainability of dry sub-tropical and tropical agricultural systems. Environmental stress is
a major component of natural selection in soil ecosystem. Among several environmental conditions, the most
prominent problematic abiotic factors in the arid regions are drought, salinity and high temperature. Unlike
legumes, rhizobia have high affinity to tolerate stress conditions. Hence, inoculation of stress tolerant strains
of rhizobia may enhance the nodulation and nitrogen fixation ability of plants under stress conditions. So in
the present study, 54 abiotic stress tolerant pigeon pea rhizobial isolates already existing in the department
were checked for their purity on YEMA media and maintained on same medium for further studies. All these
isolates were able to form nodules, when tested in cups under sterilized condition, however, 10 pigeon pea
isolates showed better nodulation as compared to commercial rhizobial strain, 1021. Nitrogenase activity of
these isolates was tested by using acetylene reduction assay (ARA) and only 9 isolates showed good
nitrogenase activity, which ranged between 11- 208 nmoles ethylene h
-1
tube
-1
. Most of the rhizobial isolates
were able to solubilize P and their P-solubilization index (P-SI) varied from 1.1 to 2.1 and 13-49µg TCP ml
-1
on solid and liquid Pikovskaya’s medium, respectively. Ammonia excretion was also observed in most of the
isolates, which varied from 0.5 to 4.53 µg ml
-1
ammonia after 4 days of incubation, while bacteriocin
production was observed only in 12 isolates. These isolates showed resistance towards ampicillin, nalidixic
acid, chloramphenicol, neomycin and streptomycin up to a concentration of 100µg ml
-1
, while some of the
isolates were found to be sensitive to streptomycin and neomycin antibiotics even at a concentration of 10µg
ml
-1
. On the basis of nodulation efficiency under sterilized conditions and different agricultural useful traits,
10 multi-trait rhizobial isolates were selected to check their efficacy in pigeon pea under field conditions.
The nodulation efficiency of all these rhizobial isolates in Micro plots under field conditions also found to be
better than reference strain 1021 and un-inoculated control. These isolates also performed better in terms of
shoot length, shoot dry weight, no. of branches, no. of pods, seed weight per plant, grain and straw yield as
well as N & P uptake, when compared with control and reference strain, 1021 in Drought plots after harvest.
Some of the pigeon pea rhizobial isolates like PPM37D, PPH8C, PPH10B and PPM33B, which performed
better as compared to commercial strain, 1021 under field conditions, can be used as potential candidates for
biofertilizer production in pigeon pea crop under rain-fed conditions.
Description
Keywords
Planting, Peas, Livestock, Antibiotics, Bacteria, Biological development, Root nodulation, Nitrogen, Biological phenomena, Crops