Browsing by Author "Illangakoon, T.K."

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    Effect of Drought on Shoot, Root and Yield Parameters of Selected Rice Lines
    (Uva Wellassa University of Sri Lanka, 2020) Manurangi, D.D.M.; Illangakoon, T.K.; Kaliyadasa, P.E.; Jeewanthi, P.W.
    Rice (Oryza sativa L.) is the major food crop in Sri Lanka. That occupy 34 percent (0.77 /million ha) of the total cultivated area in Sri Lanka. Drought is one of the major environmental constraints severely reducing rice yields, making serious threat to global rice production. This study was conducted using eight rice lines including newly improved and exotic rice lines. Drought tolerant rice variety, Bg251 used as the control. The experiment was conducted inside a plant cage using Complete Randomized Design with three replicates for each rice variety and with 96 experimental pots. Seven days old seedlings were established in pots and drought condition were initiated after two weeks of planting. Growth parameters like plant height, chlorophyll content, shoot dry weight and flag leaf length were measured and Drought Tolerant Degree index was estimated. Root parameters were measured using WhinRHIZOpro root scanning machine. Further yield parameters like panicle weight, spikelet no per panicle, Yield and 1000 grain weight were measured. ANOVA process was conducted at 5% significant level for data analysis. Mean comparison was done by using Turkey’s comparison. And Pearson ’correlation was performed to investigate the relationship between the parameters. AERON 9-3, IRDTN 7- 11 and IRBBN dhana were identified as highly drought tolerant compared with BG 251. AERON 9-3 identified as a cultivar with good yield as well as good Drought Tolerant Degree value. And Drought Tolerant degree index was identified as simple and accurate drought screening method. Keywords: Drought Tolerant Degree, Drought Tolerance, Panicle weight, Spikelet no per panicle
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    Effect of High Temperature on Growth, Pollen Fertility and Yield Parameters of Selected Rice Varieties in Sri Lanka
    (Uva Wellassa University of Sri Lanka, 2019) Rajapaksha, R.M.C.Y.; Illangakoon, T.K.; Ranawana, S.R.W.M.C.J.K.; Jeewanthi, P.W.
    Temperature is one of the main environmental parameters affecting growth and development of rice. The mean surface air temperature has increased globally by ~0.74 °C in the last century and will further be increased by ~1.1- 6.4 °C by the end of this century. Therefore, identification and development of heat tolerant rice varieties is an urgent need. This study was conducted to screen twenty rice varieties including newly improved and traditional cultivars for high temperature tolerance based on their growth and yield parameters. Heat tolerant rice variety, N22 was used as the control. The experiment was conducted inside a temperature chamber (35-42 °C) using Randomized Complete Block Design with three replicates for each variety. Eighteen days old seedlings were established with the spacing of 15 x 20 cm as one plant per hill and 40 seedlings per replicate. Growth parameters, pollen fertility, days to 50% heading and 85% maturity, and yield were recorded. Cluster analysis was performed to group the varieties. Accordingly, Kalu heenati was grouped with N22 and was categorized as heat tolerant cultivar. The filled grain percentage and yield per plant of them were 53.5% and 2.19, respectively. Bg 300, Bg 304, Bg 305, Bg 310, Bg 94-1, Bg 352, Bg 357, Bg 358, Bg 359, Bg 360, Bg 366, Bg 369, Suwandal, Pachchaperumal and Pokkali were grouped together and categorized as moderately heat tolerant compared to N22. Sulai, Bg 370 and Madathawalu were grouped together and had the lowest pollen fertility, filled grain percentage and the yield per plant revealing its high susceptibility to elevated temperature. Since none of the tested improved rice varieties were tolerant to high temperature, further research is needed to develop heat tolerant rice varieties for changing future climate.
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    Effect of Storage Conditions on Seed Dormancy and Vigor of Newly Developed Rice Varieties
    (Uva Wellassa University of Sri Lanka, 2018) Rathnayaka, R.M.S.N.; Illangakoon, T.K.; Kaliyadasa, P.E.; Ranawana, S.R.W.M.C.J.K.
    Inappropriate storage conditions and seed dormancy affect the seed quality resulting poor germination and loss of vigor. A study was conducted to identify the effect of storage conditions on seed vigor and dormancy of newly developed rice varieties. The experiment was laid down in a split plot design with four replicates. Harvested seeds of 24 varieties were dried and stored at two storage conditions viz. cold storage (18-20 C) and ambient (30-32 C) separately. The duration for dormancy of each variety was considered as the period from harvest till germination reached up to 85% and determined using the germination test at one week interval. Seed vigor was investigated by electrical conductivity test and cold test. There was an interaction between storage condition and variety (P 0.05) for dormancy period. There was a significant effect of storage condition for seed vigor and dormancy. No significant differences (P > 0.05) in vigor index between two storage conditions were observed. Varietal variation was observed for dormancy, conductivity and vigor index. Bw12-574, Rathusuduru and Ld11-7-3-1 showed longer dormancy periods under cold (90-100 days) and ambient (48-83 days) storage. At13-3048, At373, Bg15-520 and Ld12-6-22-1 showed shorter dormancy periods under cold and ambient storage (32-62 and 20-27days, respectively). Bw272-6b, Rathusuduru and Ld12-6-22-1 showed less vigor due to high conductivity values (0.08-0.24 dS m-1) and Bw272-6b, Rathusuduru and Bw14-509 showed less vigor due to lower vigor indexes (18.5-22.2). At13-1543, At13-3791, WAS4-2-3 were considered as high vigor varieties due to lower conductivity value (0.05-0.12 dS m-I) and higher vigor indexes (27.2-25.5). Since cold storage increases dormancy period it can be recommended for rice seeds with shorter dormancy period to store them longer without breaking the dormancy. Results of this study revealed the importance of manipulating storage conditions to enhance seed vigor and lengthen the dormancy period.