Moderate Low Very low Overall phosphate solubilizing pea nodule endophytes Ammonia Good Moderate PNE9, PNE13, PNE18, PNE21, PNE23, Low
Narula et. al., : Beneficial traits of endophytic bacteria from field pea nodules and plant growth promotion of field pea 7 5
all the nodule endophytes were categorized in three groups i.e. 2.2 5, 5 10 and 10 15 cm root length as shown in Table
1. Root length of control was 2.2 cm. Out of 60 field pea nodule endophytes, 63.3 of isolates were promoting root growth of
field pea plant as the root length produced by them was more than that of control. PNE17, PNE26, PNE73 and PNE77 were
the highest root growth promoters. The root growth promotion is the consequence of phytohormone production,
mainly auxins and gibberellins. IAA is the main auxin produced by bacteria. Many researchers have reported that a good
producer of auxins or gibberellins is also a good growth
promoter Khan and Doty 2009; Sgroy et al. 2009 and Panchal and Ingle, 2011 and enhanced plant growth. Similarly,
elsewhere most of the endophytic isolates were reported to produce auxin specially IAA Hung and Annapurna, 2004; Li
et al.
and Selvakumar et al. 2008. Contrary to this, lesser number of auxin producers was found in the nodules of peanut
plant Taurian et al. 2010. Phosphate solubilization by bacteria increases the
availability of free phosphorus to the plant and therefore, is an important character of the endophytes for the plant growth
promotion. All pea nodule endophytes were screened for phosphate solubilization activity on Pikovskaya’s medium.
Depending upon the extent of P solubilization, the isolates were categoried as good, moderate, low and very low P
solubilizers so as to compare the different isolates among themselves and results showed that 38.3 bacterial isolates
were phosphate solubilizers Table 2. PNE15, PNE24 and PNE80C were good phosphate solubilizers and all other
isolates were low P-solubilizers Fig 2. Similarly, endophytic bacteria of alfalfa plant were also shown to solubilize insoluble
P Stajkovic et al. 2009 and all the isolates from the nodules of soyabean and kudzu were also reported to solubilize
phosphate Li et al. 2008 and Selvakumar et al. 2008.
Ammonia is an important metabolite produced by the endophytes as it fulfills the requirement of nitrogen for the
plants. All the pea nodule endophytes were screened for ammonia production. The isolates were grown in peptone
water and their ammonia producing activity was determined
Table 1.
Root growth promotion of field pea seeds Pisum sativum L. var. HFP4 on water agar plate assay by nodule endophytes
Root length of un-inoculated control = 2.2 cm
Table 2.
Phosphate solubilizing activity of field pea nodule endophytes
Phosphate solubilization
activity Pea nodule endophytes
Percent phosphate
solubilizers Good
PNE15