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The study entitled ‘Mitigating water stress in summer rice using beneficial root
endophytic fungus Piriformospora indica’ was undertaken at College of Agriculture, Vellayani
during 2019 - 2021. The objective of the study was to assess the performance of P. indica
colonized rice under different levels of moisture stress during summer.
The field experiment was laid out in randomized block design with 2 x 3 x 2 treatments,
replicated thrice in the low land paddy fields during February to May 2021, using variety
Prathyasa. The treatments included colonizing with P. indica [p1- P. indica colonized rice and
p2- non-colonized rice(control)], three irrigation intervals[i1- 30 mm CPE (cumulative pan
evaporation), i2- 35 mm CPE and i3- 40mm CPE] and two irrigation depths(d1- to a depth of
1.5 cm and d2- to a depth of 3 cm). P. indica colonized/ non-colonized rice seedlings raised in
trays were transplanted at 14 days after sowing at 15 cm x 10 cm and uniformly irrigated till
10 days after transplanting (DAT). The crop was raised as per the KAU package of practices
recommendation for short duration rice (KAU, 2016).
The results of the study revealed that colonization and irrigation to 3 cm depth improved
the growth and growth attributes viz., plant height, tiller number m-2
, leaf area index and dry
matter production of summer rice. Colonization with P.indica significantly influenced the
number of tillers m-2 with 10.64, 16 and 15.69 per cent increase in tiller production at 30, 45
and 60 DAT respectively, compared to non-colonized plants. Colonized plants irrigated at 30
mm CPE to a depth of 3 cm evinced the maximum leaf area index (4.54) at 60 DAT and dry
matter production (4559.26 kg ha-1
) at harvest.
Yield attributes and yield of rice were significantly affected by P. indica colonization,
irrigation interval and depth of irrigation. Superior number of productive tillers m-2
(222.84),
filled grains per panicle (81.11) and the lowest sterility percentage (13.37) were recorded with
colonization. Colonized plants irrigated at 30 mm CPE to a depth of 3 cm produced
significantly superior productive tillers m-2
(275.00), filled grains per panicle (111.33) and the
lowest sterility percentage (8.80). Among second order interactions, p1i1d2 produced
significantly superior grain yield (2698.56 kg ha-1
) and straw yield (2848.13kg ha-1
).
P. indica colonization, irrigation interval and depth of irrigation had significant effect
on root parameters of rice at all stages of observation. P. indica colonized plants showed
significantly superior rooting depth at all stages. Colonized rice plants irrigated at 35 mm CPE
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to a depth of 3 cm revealed superior rooting depth viz., 19.4, 29.86 and 30.00 cm and average
root length of 23.36, 34.87 and 36.20 cm at 30, 60 DAT and harvest respectively. Significantly
superior root volume and root dry weight at 30, 45, 60 DAT and harvest respectively were
recorded in colonized plants irrigated at 30 mm CPE to a depth of 3 cm.
Among the physiological parameters studied, proline content declined in the order of
decreasing CPE, 40 mm >35 mm > 30 mm. P. indica colonized plants irrigated at 40 mm CPE
to a depth of 1.5 cm produced significantly greater proline (115.33 and 106.00 μmole g-1
at
panicle initiation and flowering respectively). Colonized rice plants at 30 mm CPE to a depth
of 3 cm observed the maximum relative leaf water content, cell membrane stability and
chlorophyll stability index at panicle initiation and flowering respectively. P x I x D remained
significant with the highest water use efficiency (WUE) of 3.47 kg ha-1mm-1
for P. indica
colonized plants irrigated at 30 mm CPE to a depth of 3 cm.
P. indica, irrigation interval and depth of irrigation could significantly influence the
available nitrogen, phosphorus and potassium status of soil after experiment. Colonized plants
irrigated at 40 mm CPE to a depth of 1.5 cm resulted in significantly superior available
phosphorus (179.93 kg ha-1
). Considering the economics, P. indica colonized plants irrigated
at 30 mm CPE to a depth of 3 cm brought about the highest gross income (₹ 88951 ha-1
), net
income (₹ 30351 ha-1
) and B: C ratio (1.51).
Based on the above findings, it could be inferred that rice plants colonized with P. indica
significantly enhanced the growth and yield attributes, root biomass, nutrient uptake and WUE,
irrespective of interval and depth of irrigation.Yield and WUE of P. indica colonized plants
subjected to severe stress, were observed to be equivalent to those of non-colonized plants under
moderate stress. Colonization resulted in saving of 30 mm water or 3 irrigations and could help
rice to combat drought stress by enhanced root biomass, nutrient uptake and water use
efficiency during summer.