STUDY ON DIVERSITY OF RICE IN NAGALAND AND THEIR SUITABILITY TO CHANGING CLIMATE
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Date
2022
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Publisher
AAU, Jorhat
Abstract
The present investigation was carried out during the year 2018 to 2020 to
evaluate the performance of some rice (Oryza sativa L.) genotypes from Nagaland
under different CO2 and temperature regimes viz., Treatment I = Field (control),
treatment II = (CO2 (550±20ppm) + Temp. of 40 C > ambient) and Treatment III = CO2
(750±20ppm) + Temp. of 60 C > ambient) under fully automated bioreactors with CO2
and temperature control facilities in Stress Physiology Laboratory, Department of Crop
Physiology, Assam Agricultural University, Jorhat-13. In the first experiment, 75 rice
genotypes collected from different locations of Nagaland were subjected for initial
screening for tolerance against elevated CO2 and temperature out of which 7 genotypes
were selected for further study on their response mechanism of tolerance by comparing
with the national check variety N22. The results revealed that treatment II had a positive
impact on the various morpho-physiological parameter viz., plant height, number of
leaves, leaf area index, root volume and length, membrane stability index, total leaf
chlorophyll content, leaf nitrate reductase activity, proline in all the genotypes whereas
a declining trend indicating the deleterious effect of high temperature, at a higher CO2
and temperature in treatment III was observed in all these parameters. Similarly,
significant variation in photosynthesis and its related parameters (viz. stomatal
conductance, internal CO2, transpiration) affected the photosynthetic rate and their
partitioning to root, shoot and reproductive organ under both the treatments as
compared to field condition. These factors ultimately contributed to growth efficiency
and yield of the plant. Amongst the treatments, significant increase of H2O2, MDA
content was recorded in treatment III as compared to treatment III. Kohima Special and
N22 recorded lower H2O2 and MDA when compared to other local genotypes. Hence
these two genotypes could maintain their plant water status as evidenced by their higher
MSI under both the treatments. The maintenance of higher plant water status in Kohima
Special and N22 could be attributed to their higher RLWC and increased compatible
solutes viz. proline content and non structural carbohydrate contents. Further, studies in
tolerance indices indicated that among the tested local genotypes, Kohima Special and
Lisem were tolerant whereas Tatza and Tzumma showed to be most susceptible under
high temperature. In the molecular analysis, using SCoT molecular markers out of 77
bands amplified, 55 were found to be polymorphic with 68.99 per cent polymorphism.
Only four primers SCoT28 and SCoT34 not found to be polymorphic alleles, while
remaining 23 SCoT primers showed both polymorphic alleles. Yield and yield
attributing characters are governed by all the morphological, physiological and
biochemical processes. Among yield parameters, 1000-grain weight, spikelets per
panicle and total grain weight per plant were significantly higher due to elevated CO2 at
treatment II since the genotypes could maintain a higher photosynthetic rate and had a
superior plant defence mechanisms but were significantly decreased under high
temperature at treatment III which was negatively influenced by all the processes
resulting in decrease in yield and yield attributing characters in all the genotypes.