Central Rice Research Institute Annual report...2011-12

Physiological basis of salt tolerance in rice
with reference to coastal saline ecosystem
Physiological basis of salt tolerance was studied in
eight landraces from Odisha and West Bengal found
tolerant in earlier studies. After 10 days of salt stress
(EC 12 dS m -1 ), Kamini with 90% plant survival was
comparable to Pokkali and Saltol donor FL478. The three
cultivars survived under salt stress for 16 days while
the remaining entries died completely between 10 and
16 days. Salinity significantly reduced the area and
fresh weight of the 2 nd top most leaf seven days after
stress in all the genotypes, but the reduction over the
control was lowest (22.0 & 30.7%) in Kamini and highest
(71.8% & 71.2%) in IR29. In FL478, the corresponding
reduction in the leaf area and leaf weight was 41.1%
and 44.5%, respectively. Total chlorophyll content per
unit leaf area in 2 nd leaf at seven days after the stress
increased under salinity for all the genotypes, except
Marisal. The increase was lowest in IR29 and highest
in Ravana followed by Kamini. The increase in chlorophyll
content was generally due to an increase in chlorophyll
b content. Total dry matter production at seven
days after salt stress was also lowered by salinity in all
the genotypes, but again the reduction was lowest
(24.5%) in Kamini and highest (56.6%) in IR 29. Distribution
of dry matter in different plant parts (root, leaf
and stem) was also affected by salt stress and the response
varied with the genotypes. While Kamini and
IR29 showed similar reduction in root dry matter, reduction
in leaf and stem dry matter was relatively much
lower for Kamini. As a result, shoot:root ratio in salt
stress treatment was significantly increased in Kamini
but decreased in IR29. For the remaining genotypes,
shoot: root ratio was either maintained to the same level
as in the control or decreased. After seven days of salt
stress, tolerant genotypes recorded significantly higher
K content in leaf (22.7-27.9 mg g -1 dry weight) and stem
(15.2-29.9 mg g -1 dry weight) compared to IR29 (18.5 &
11.1 mg g -1 dry weight) while reverse was true for Na
content. The Na content in leaf and stem was 24.9 and
31.0 mg/g dry weight for IR29, as against 11.3-21.5 and
19.7-27.9 mg g -1 dry weight for the remaining cultivars.
The Na:K ratio in leaf and stem was much higher in
IR29 (1.35 & 2.79) than in tolerant varieties (0.44-1.02 &
0.66-1.80). Among the tolerant cultivars, Marisal and
Talmugra recorded higher Na:K ratio both in leaf and
stem.
Identification of rice varieties tolerant to
different growth stage drought stress
Seedling stage
Thirty two entries out of 100 genotypes for seedling
stage drought stress recorded SES score ‘1’ at Soil Moisture
Content (SMC) 10-12%, while under severe stress
(SMC 1.2-2.0 %), nine entries IC568024, IC-568009,
IC568114, IC568060, IC568016, IC568030, IC568083,
IC568112 and IC568065 survived having more than 50%
RWC and recovered fast after re-irrigation.
Vegetative stage
Two hundred eighty seven entries out of 970 genotypes
for vegetative stage drought stress recorded SES
score ‘1’ at SMC 12-14%. Promising entries R-RF-45
(1.79 t ha -1 ), IR72667-16-1-B-B-3 (1.56 t ha -1 ), IR84882-
B-120-CRA-1-1-1 (1.51 t ha -1 ); CB5-754 (3.5 t ha -1 ), Lalat
(3.20 t ha -1 ) and IR83388-B-B-108-3 (2.80 t ha -1 ); IR83614-
643-B (2.90 t ha -1 ) and IR36 (2.60 t ha -1 ) under vegetative
stage stress recorded higher grain yield compared
to other entries.
Reproductive stage
Thirty four entries out of 56 genotypes for reproductive
stage stress were observed to be tolerant with SES
score’1’. Under reproductive stage stress (10 days before
flowering to 10 days after flowering), RR345-2 recorded
highest grain yield of 2.50 t ha -1 followed by
RR2-6 (2.30 t ha -1 ), CR143-2-2 (1.80 t ha -1 ) and IET 18817
(1.15 t ha -1 ) with high moisture retention capacity (>
80%) and low DSI (drought susceptibility index) values
(about 0.60) with high grain filling percentage
(>70%).
Evaluation of drought tolerant genotypes for
yield potential under control and rainfed
upland condition (along with AICRIP entries)
Forty entries including 14 entries from AICRIP were
evaluated under rainfed upland condition at KVK,
Santhpur and controlled irrigated condition at CRRI,
Cuttack for their yield potential. The crop experienced
two mild stresses of six days duration in seedling stage
and of 15 days duration during reproductive stage (54
days old seedling) at KVK Santhpur. Out of 40 entries
tested, RR 270-5, RR345-2, Kalakeri and IET 18717, IET
20859, IET 21620, IET 21627, IET 22020, IET 22051, IET
22026, Anjali and Sahabhagidhan had yield potential
of more than 4.0 t ha -1 under controlled irrigated condition
at CRRI farm, while RR383-2, RR 2-6, CR143-2-2,
Zhu11-16, RR443-2, IET 21620, IET 22026, IET 22032,
Kalakeri and Sahabhagidhan had yield potential of >
1.50 t ha -1 with > 50% grain filling percentage under
rainfed condition even after getting exposed to stress at
both the stages.
Physiological basis of drought stress tolerance
Six rice varieties viz., Bala, Peta, Dular, Mahsuri,
Safri17 and IR20 grown in pots were exposed to veg-
46 CRRI ANNUAL REPORT 2011-12