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  • ThesisItemOpen Access
    Diversity and bio-ecology of trichogrammatids in coastal Odisha
    (Department of Entomology, OUAT, Bhubaneswar, 2021-12-29) Balabantaray, Suchismita; Mandal, S. M. A.; Sarangi, P. K.; Mukherjee, S. K.; Samal, K. C.
    Field surveys were carried out in eight coastal districts of Odisha to study the diversity of trichogrammatids. Bio-ecology of trichogrammatids were studied in the Bio-control Laboratory, Department of Entomology, CA, OUAT, Bhubaneswar in addition to the Central Instrumentation Facility, OUAT, Bhubaneswar and the Experimental Laboratory, Department of Agricultural Biotechnology, CA, OUAT, Bhubaneswar. The studies were carried out during 2018-2021. Detailed morphological studies were carried out using stereo zoom trinocular microscope and scanning electron microscope. The morphological data and photographs were compared with the identification keys and four species of trichogrammatids i.e., Trichogramma chilonis (Ishii), Trichogramma japonicum Ashmead, Trichogramma pretiosum Riley and Trichogrammatoidea bactrae Nagaraja were identified. T. chilonis and T. japonicum were the predominant species among the four species recorded. T. chilonis was dominant in brinjal and sugarcane ecosystems while T. japonicum was dominant in rice ecosystem. Storage of egg of factitious host (Corcyra cephalonica Stainton) was found most suitable at 5°C for 5 and 10 days and at 7.5°C for 5 days on the basis of parasitization (86.67, 83.00 and 84.17 %, respectively by T. chilonis and 89.83, 88.33 and 87.50 %, respectively by T. japonicum) and adult emergence (96.53, 92.97 and 93.25 %, respectively of T. chilonis and 94.24, 90.00 and 91.24 %, respectively of T. japonicum). There were significant reductions in surface area, pH, water content, protein content and total carbohydrate content beyond 20 days of storage at 5°C and 10 days of storage at 7.5°C. These parameters contributed towards the significant reduction in pasitization and adult emergence beyond 20 days of storage at 5°C and 10 days of storage at 7.5°C. The food mixer, water: honey=20:80 was adjudged as the best in providing nutrition to the parasitoids recording the highest adult male longevity of 10.00 and 9.75 days, adult female longevity of 11.50 and 11.00 days, parasitization of host eggs registering 94.13 and 93 %, emergence of F1 adults of 93.97 and 92.26 % and sex ratio (F1 female: F1 male) of 3.70: I and 3.26:1 for T. chilonis and T. japonicum, respectively. This treatment was closely followed by water : honey : castor pollen =40:40:20 with the respective values of 9.75 and 9.50 days , 11.25 and 10.75 days, 92.88 and 91.13%, 90.01and 90.48 % and 3.69:1 and 3.15:1. The study on the effect of storage of parasitoid pupae on the adult emergence and parasitization revealed that the highest adult emergence of 94.27 % in T. chilonis and 93.07% in T. japonicum were observed at 7.5°C after 5 days of storage. The highest parasitization of 93.52 % in T. chilonis and 91.56% in T. japonicum were also observed at 7.5°C stored for 5 days. The adult emergence and parasitization gradually decreased with the increase ordecrease in storage temperature and increase in storage duration. However, the pupae of T. chilonis and T. japonicum stored at 7.5, 10 or 5°C up to 30 days exhibited higher rate of adult emergence (77.03,72.67, 70.32% and 76.48,71.65, 70.21%, respectively) and parasitization (73.76, 71.78, 70.35 % and 71.74, 70.22, 70.06%, respectively).
  • ThesisItemOpen Access
    Exploring novel pesticide mixtures to combat emerging pest complex in Rice (Oryza sativa L.)
    (Department of Entomology, OUAT, Bhubaneswar, 2022-03-07) Mishra, Ritesh; Sarangi, Pravat Kumar; Adak, Totan; Mukherjee, Sandeep Kumar; Mishra, Mihira Kumara; Das, Niranjan
    Two major pests, brown planthopper (BPH) and yellow stem borer (YSB) coexist in the late tillering stage of rice. Insecticide combinations are the most effective way to manage pest complex having different feeding behavior. This study investigated the compatibility of insecticide (chlorantraniliprole, triflumezopyrim, flonicamid and pymetrozine) formulations in mixtures. The insecticide mixtures were physically and chemically compatible and did not produce phytotoxic effects on rice plant. The experiment was conducted in laboratory and field of ICAR-National Rice Research Institute, Cuttack in two seasons of kharif 2019 and 2020. The toxicity of the insecticides in combination and alone against BPH and YSB was studied. The lethal doses (LD50) were 17.215, 0.059, 0.180 and 0.036 ng per insect for Chlorantraniliprole, Flonicamid, Pymetrozine and Triflumezopyrim against BPH, respectively. Similarly, LD50 were 2.737, 0.073, 0.313 and 0.061 ng per larva against YSB, respectively. The mixture of 17.215 ng Chlorantraniliprole + 0.059 ng Flonicamid per insect resulted in maximum mortality of BPH (86 %). The highest mortality of YSB was recorded in the treatment of 2.737 ng Chlorantraniliprole + 0.061 ng Triflumezopyrim per larva (86.67%). Two mixtures of Chlorantraniliprole + Triflumezopyrim (15 + 18.75 g a.i ha-1 and 22.5 g + 12.5 g a.i ha-1) were the most effective in managing BPH and YSB, respectively in field conditions. The residues of the insecticide mixtures in rice plant, soil, water, straw and grains were estimated using QuEChERs method in liquid chromatography-triple quadrupole tandem mass spectrometry. The dissipation pattern of all the mixtures (chlorantraniliprole + triflumezopyrim, chlorantraniliprole + flonicamid and chlorantraniliprole + pymetrozine) followed first order kinetics. Overall, the half-lives of chlorantraniliprole, triflumezopyrim, flonicamid and pymetrozine (both in single application and mixtures) ranged from 8.85-12.67 days in plant, 14.29-27.94 days in soil, 10.31-17.76 days in water. The residues of the mixtures in rice straw were below the detectable limit and in rice grains was below the Maximum Residue Limit (MRL). The insecticide mixtures at reduced doses were safe to the environment and the grains were safe for human consumption. Mixtures were safe to natural enemies (mirid bugs and spiders) in rice ecosystem. Pesticide combinations had increased toxicity and could reduce the quantities of individual pesticides and thereby, lowering the crop production costs. Pesticide mixtures could also be considered safe to the environment.
  • ThesisItemOpen Access
    Assessment of leaf folder, Cnaphalocrosis medinalis (Guenee) damage in rice using ground based hyperspectral remote sensing techniques
    (Department of Entomology, OUAT, Bhubaneswar, 2022-07-30) Adhikari, Bhubanananda; Mohapatra, L. N.; Mohapatra, S. D.; Padhi, J.; Rath, B. S.; Beura, S. K.
    Field and laboratory experiments on “Assessment of leaf folder, Cnaphalocrosis medinalis (Guenee) damage in rice using ground based hyperspectral remote sensing techniques” were undertaken during Rabi 2017-18, Kharif 2018-19 and Rabi 2018-19 at ICARNRRI, Cuttack. The spectral signature from the differentially infested canopy and leaves of rice var TN1 were assessed using ASD Field Spec hyperspectral spectroradiometer. The spectral curve obtained from the pre-processed data indicated higher reflectance of healthy vegetation than the rice plants infested by C. medinalis invisible and near infrared region. Derivative analysis was adopted to find out the particular spectral bands with maximum per cent change in first order derivatives. The continuum removed spectra were also obtained using ENVI software and the specific wavelengths with the absorption dips were identified. The central wavelengths identified from derivative analysis and continuum removal were subjected to unpaired ‘t’ test for testing of significance up to 100 nm interval. Seven spectral bands i.e., 515, 582, 673, 732, 815, 898 and 1131 nm were found most sensitive to infestation of C. medinalis from both canopy and leaf level. The healthy leaves had highest concentration of total chlorophyll (3.95 mg/g) and carotenoid (0.36 mg/g) whereas these concentrations were found lowest viz., 1.467, 0.207 mg/g in severely infested rice leaves (Grade 5). The phenol content was highest (4.79 mg/g) in severely infested rice leaves due to C. medinalis but it was lowest (3.25 mg/g) in the healthy leaves. The correlation between different biochemical components and identified sensitive bands revealed that four spectral bands viz., 515, 582, 597 and 672 nm were found sensitive due to chlorophyll absorption. Similarly, the spectral band of 1131 nm was found sensitive for phenol absorption whereas for the carotenoid absorption the spectral 515 and 582 nm bands was found sensitive. Feature selection study was carried out using MATLAB by the Random Forest Elimination tool to reduce the dimensionality of the spectral data. The spectral band combination of five bands viz., 515, 582, 673, 732 and 815 nm was found to be the best band combination with highest percentage of accuracy (86.33) which could differentiate the damage by C. medinalis. Studies on five spectral vegetation indices calculated based on spectral reflectance for detecting stress in rice infested by C. medinalis revealed that the values of Normalized Difference Vegetative Index (NDVI), Leaf Area Index (LAI) and Photochemical Reflectance Index (PRI) were highest in the healthy rice vegetation and were 0.77, 3.20 and 0.17, respectively. The values of these aforementioned indices were in a declining trend with increase in infestation of C. medinalis. A gradual increase in the value of Photochemical Senescence Reflectance Index (PSRI) was observed with subsequent rise in infestation level of C. medinalis. Severely infested rice plants recorded highest value of PSRI (0.18) whereas it was lowest (0.03) for the healthy vegetation. A gradual shifting of the red edge position towards the shorter wavelength (REPI) was observed with increase in infestation level of C. medinalis. Three new indices based on two spectral combinations {(R515/R732),(R732-R515) and (R732-R582/R732+R582)} as well as three other indices based on three spectral band combination {R732/(R515+R673), R815/(R568xR732), and R815/(R673+R582)} were derived which may be used for depicting the presence of C. medinalis using satellite imagery. Results on the spectral signature obtained from the differential infestation by C. medinalis in rice variety Naveen at farmer’s field (located at Aruha, Pipili block) and under controlled conditions at ICAR-NRRI, revealed that seven spectral bands i.e., 510, 583, 674, 762, 815, 897 and 1126 nm were confirmed as the pest sensitive spectral bands for infestation of C. medinalis. The ground truth spectral data were validated using Sentinel 2A image analysis with the satellite imagery. The analytical processing of both the ground truth data and data from satellite indicated the hotspots where infestation by C. medinalis were detected through the false colour composite map with the help of various colour codes.
  • ThesisItemOpen Access
    Genetic improvement of aromatic rice landraces through in vitro mutagenesis
    (Department of Plant Breeding and Genetics, OUAT, Bhubaneswar, 2022-05-17) Das, Subhashree; Pradhan, B.; Samantaray , S.; Sahu, Simanchal; Samal, K. C.
    Aromatic rice is a special group of rice with pleasant aroma and excellent taste. They have a consumer preference and generally fetch high price in domestic and international market. Around 18% of non basmati rice exported is traditional aromatic rice (USDA, 2020). There is steady increase in demand for milled quality rice from India in the international market as Indian aromatic rice varieties are best suitable for traditional dishes. There are a number of short and medium grain aromatic rice which includes aus type aromatic rice which is known as indigenous aromatic rice grown in India. The indigenous aromatic rice are characterized by tall plant stature, photoperiod sensitivity, susceptible to lodging and low yield. They possess unique genes tolerant to environmental stresses and high adaptability to low input conditions. In vitro mutagenesis using ethyl methane sulphonate (EMS) is being used in plant molecular biology as a tool to identify and isolate genes and to study their structure, function more precisely and utilize for crop improvement. Genetic improvement of crop plants through conventional breeding program can be made more effective if coupled with the current in vitro cell culture techniques of cellular and molecular biology. The present investigation was undertaken with 40 aromatic rice genotypes involving diversity study for selecting genotypes for in vitro culture, identifying responsive genotypes for in vitro mutagenesis using 0.2% EMS, macro mutants study, finding effectiveness and efficiency of the mutagen dose under different treatments in M2 generation, field observation and evaluation of M3 and M4 generations for identification of desirable mutant lines. High and moderate to high GCV, heritability and genetic advance was found in the characters like thousand grain weight, number of grains per panicle, effective tillers per plant, plant height, kernel length breadth ratio and single plant yield. 1000-grain weight, number of grains per panicle, kernel length breadth ratio, number of effective tillers per plant are found to be positively correlated while plant height, panicle length were found negatively correlated with yield, which have been used as criteria while selecting genotypes for genetic improvement of grain yield in indigenous aromatic rice. Both callus induction and shoot regeneration were found to be genotype dependent having specific media requirement for efficient callus induction and shoot regeneration. Murashige and Skoog (MS) medium with 2.0 mg/l 2,4-Dichlorophenoxyacetic acid (2,4-D) was most suitable for callus induction and half MS medium with 2.0 mg/l 6-Benzyl amino purine (BAP) gave more shoot regenerations in local aromatic rice genotypes. Genotype Basumati and Kalikati were found to be more responsive to mutagenesis by EMS than Gangabali and Karpurajeera. EMS (0.2%) at 4 hours treatment was found to be most effective. Higher mutation rate was recorded in the genotypes which showed diplontic selection (Basumati and Kalikati). Appreciable genotypic variation in the mutant population existed and 32 mutant lines with desirable traits were identified in the M3 generation by multireplicated trial and estimates of skewness and kurtosis. Eleven competitive mutant lines, showing higher grain yield in the replicated yield trial, having positive skewness and negative Kurtosis values were identified and selected in M4 generation to be utilized further to advance generations through selection to develop superior varieties.
  • ThesisItemOpen Access
    Effect of soil and foliar application of boron with ethrel on growth and yield of cucumber (Cucumis sativus L.)
    (Department of Plant Physiology, OUAT, Bhubaneswar, 2022-05-04) Thanh, Nguyen Viet; Panda, R.K.; Samal, K.C.; Sahu, G. S.; Nayak, R.K.
    The present investigation was carried out in two sets of experiment. At first, a net house study was done to identify a suitable cucumber variety to female flower induction by foliar application of ethrel @300 mg l-1 and secondly, to study further the chosen variety’s performance to ethrel and boron application on field experiment to improve the yield and yield attributes. The net house experiment was conducted in October, 2019 in the department of plant physiology, college of Agriculture, Bhubaneswar with completely randomized design (CRD) and replicated twice with twenty numbers of cucumber varieties. It was found that spray application of ethrel had improved vine length (133.50 cm), maximum number of leaves per plant (24.53), maximum leaves area (166.43 cm2), a greater number of primary nodes per plant (18), percentage of fruit set per plant (88.56), number of female flowers per plant (17.50), number of fruits per vine (15.50) and highest yield per vine (2.98 kg) in cultivar Rohan F1 than control (water spray) compared to other cultivars. The field experiment was conducted in two consecutive years in Central Farm of OUAT during 2020 and 2021 to observe the impact of ethrel and boron as soil and frequencies of foliar spray on cultivar Rohan F1 for its growth, yield and yield attributes. Cultivar Rohan F1 was used as planting material and was sown in rings of experimentally randomized block designed (RBD). Ethrel @300mg l-1 was applied twice to the crops at two true leaf stage with a gap of 7 days on all the treatments viz. T1- RDF (150-75-75):: N:P:K kg.ha-1 with zero boron (Control), T2- RDF+B @1.0 kg soil application, T3- RDF+ FS @ 0.25% borax once, T4- RDF+ FS@ 0.5% borax once, T5- RDF+ FS@ 0.75% borax once, T6- RDF+ FS @ 1.0% borax once, T7- RDF+ FS@ 0.25% borax twice, T8- RDF+ FS@ 0.5% borax twice, T9- RDF+ FS @ 0.75% borax twice, and T10- RDF+ FS @ 1.0% borax twice and B was also foliar sprayed twice at 30th and 37th days after sowing as per treatment need. We found that T8- RDF+ FS@ 0.5% borax twice was highest pooled performance in leaf area character with an increase of 47.11% and 18.44% compared to the control (T1) and soil application (T2), increase in number of nodes per plant up to 21.7% over control and 15.7% over soil application; vine length increased up to 30.68% and 14.21 %; Leaf area index increased to 40.93% and 17.54%; number of fruits per plant increased to 39.56% and 15.45%; yield per ha increased to 57.22 % and 40.92% in control and soil application respectively, where boron plays an important role in transporting carbohydrates and manufactured organic materials in the leaves and accelerating their transmission and accumulation in the fruits. Which leads to an increase in its weight, and the increase in the number of female flowers increases the yield of one plant (4.01 kg) and then an increase in the total yield (55.14-ton ha-1). Notably, T8 FS 0.5% twice resulted in increased flowering and fruit formation and tissue Fe, P, K, Mn, Mg, Ca, Zn and Mo contents, indicating B deficiency and its deficiency affects the translocation of sugar, starches, N, P and the synthesis of amino acids and proteins as recorded in control plant. We suggest that foliar spray of boron has more advantageous than soil application as boron applied through foliage are absorbed right at the site where they are needed as quickly as possible and B can be transported from leaves to roots via phloem in this species. The translocation of foliar supplied B to the roots is affected by plant B status and the synthesis of photosynthetic assimilates.
  • ThesisItemOpen Access
    Physiological and bio-chemical drought responsive mechanisms in rice genotypes
    (Department of Plant Physiology, OUAT, Bhubaneswar, 2021-07-30) Parida, Selukash; Swain, Padmini; Samal, K.C.; Panda, R.K.; Pradhan, S. K.
    Drought is a major abiotic threat that affects rice production. The experiment entitled “Physiological and bio-chemical drought responsive mechanisms in rice genotypes” was conducted during the dry season -2018 and dry season -2019 at Crop Physiology and Biochemistry Division, ICAR-National Rice Research Institute, Cuttack, India. Droughttolerance screening of 100 diversified rice genotypes including four controls (Sahabhagidhan,Vandana as tolerant control and IR 64, IR 20 as susceptible control) was conducted during the dry season -2018 at the vegetative stage based on physiological traits such as drought score (DS), drought recovery score (DRS), SPAD Chlorophyll Meter Reading (SCMR), Normalized Difference Vegetation Index (NDVI) value, Relative Water Content (RWC) and chlorophyll fluorescence (Fv/Fm) in the field condition. After screening, 14 genotypes were selected for drought tolerance capacity viz., five genotypes (Parijata, IC 516313, IC 516130, ARC 10376 and IC 516008) as tolerant, four genotypes (IC 516149, Pathara, Lalat and IR 36) as moderately tolerant, two genotypes (Satabdi and Naveen) as moderately susceptible and Prasad as susceptible genotype including two controls (Sahabhagidhan and IR 64 as tolerant and susceptible control). These fourteen genotypes were further grown in pot experiment during dry season -2019 for detailed physiological, biochemical and molecular assessments under control and water stress conditions and all data were recorded at flowering stage. Simultaneously, these genotypes were grown in the field for evaluation for reproductive stage drought tolerance. The genotypes Parijata, IC 516130, IC 516008, IC 516149 and Sahahagidhan showed higher values of leaf area, total root length, specific root length (SRL), leaf photosynthetic rate, stomatal conductance, transpiration rate, water use efficiency (WUE), photochemical efficiency of photosystem II (Fv/Fm) and membrane stability index compared to susceptible genotypes Prasad and IR 64. However, higher antioxidant activity (Superoxide dismutase (SOD), Catalase (CAT) and Peroxidase (POX)), higher proline accumulation with lesser malondialdehyde (MDA) content in tolerant genotypes was the well-adapted mechanism under water stress condition. Genes encoding antioxidant enzymes, such as OsCuSOD, OsFeSOD OsMnSOD, OsCATC, OsPOX1 and OsPOX2 had higher expression levels in the tolerant genotypes (IC 516130) compared to susceptible genotypes (Prasad) at flowering stage under water stress. At reproductive stage, the genotypes Parijata, IC 516130, IC 516008 and IC 516149 possessed the higher grain yield along with higher biomass accumulation, spikelet fertility percentage, panicle number per m2 with lesser relative yield reduction (below 50%) over susceptible genotypes. Based on these results, three genotypes Parijata, IC 516130 and IC 516008 were identified as tolerant to both vegetative and reproductive stage drought and can be used as parent donors in drought breeding programs of rice.
  • ThesisItemOpen Access
    Physiological basis of growth and yield of low land rice cultivars grown under low light environment
    (Department of Plant Physiology, OUAT, Bhubaneswar, 2021-11-15) Dey, Prajjal; Baig, M.J; Rout, G.R.; Samal, K.C.; Panda, R.K.; Pradhan, S.K.
    Rice is the major food crop in the world. It ensures livelihood security of millions of people around the world especially in economically weaker section people of Asia. Abiotic stress including salinity, drought, high and low temperature, high and low light majorly affect the yield of rice in plants. Among the abiotic stresses affecting rice productivity, low light stress is one of the most persistent in India, mostly in Eastern and North Eastern states, where it has a significant impact on agricultural productivity. Low light conditions damage rice production and strongly influences not only duration but physiological and agronomic traits of rice. Keeping in view the increasing threat, efforts have been made to understand the mechanism (molecular, biochemical and physiological) underlying low light stress. Against this background, the present investigation entitled “Physiological basis of growth and yield of low land rice cultivars grown under low light environment” was carried out with the major objectives of screening and characterization (physiological, biochemical and molecular) of rice genotypes under low light stress. The entire experiment was conducted at the National Rice Research Institute, Cuttack, Odisha. The experiment was laid out in randomized block design. Ten rice genotypes were selected out of the fifty genotypes screened in a previous experiment (Kharif 2016 and 2017) of the same lab under NASF funded project. Selected genotypes were grown during Kharif 2018 and 2019. Experiment was conducted with three replications during Kharif season under Normal Light, 75% light intensity (25% light cut off) and 50% light intensity (50% light cut off). The low light treatment was imposed by putting agro-shade net of different light intensities mounted on a hardwood frame. The treatment was imposed at 30 DAT. Swarnaprabha and IR-8 were used as tolerant and susceptible checks respectively. The observations for agronomic and morphological traits i.e. tiller m-2 , panicle m-2 , specific leaf area (SLA). Specific leaf weight (SLW), root length, root weight, plant height, shoot weight, yield attributing parameters were recorded during flowering and harvest stages. Correspondingly, physiological parameters (Net assimilation Rate, Stomatal Conductance, Transpiration rate, Fv/Fm, A/Ci, WUE) and biochemical parameters (total chlorophyll content, chl a, chl b, starch content, total Soluble Sugar content, Superoxide Dismutase, Catalase, Peroxidase) were recorded. Among the ten rice genotypes, Panindra, PS-3 along with Swarnaprabha performed better and were found to be tolerant than other genotypes for low light conditions. Swarnaprabha and Panindra performed better for yield attributing traits (grain yield, thousand grain weight, Harvest Index) among all the varieties. For studying the possible mechanism behind, we targeted and studied the expression of genes responsible for photosynthesis and starch synthesis i.e “SourceSink concept”. The expression analysis revealed non-significant down regulation of selected genes in Panindra and PS-3 along with Swarnaprabha whereas susceptible genotypes HKR-126 and IR-8 reported significant down regulation under low light stress. These results clearly indicate the light modulated activity of photosynthetic and starch biosynthetic genes. Though the exact pathway underlying is not clearly understood, the results indicate the potential of exploring the selected tolerant genotypes (Panindra, PS-3 and Swarnaprabha) as model plant for understanding low light stress in crop plants.
  • ThesisItemOpen Access
    Seed dormancy in rice: distribution, inheritance and effect on storability of seeds
    (Department of Seed Science and Technology, OUAT, Bhubaneswar, 2021-12-28) Kulkarni, Chiranjeevi C; Lenka, Devraj; Mohanty, S.; Bastia, D.N.; Samal, K.C.
    There is need for incorporating seed dormancy and improving storability of seed in rice crop for which information on the nature of variation and inheritance of these characters would be useful. The present study was undertaken to analyse the nature of variation of seed dormancy in different maturity groups (early, medium and late), study the inheritance of the character and examine the relationship between seed dormancy and storability. The material consisted of 54 rice varieties for screening in kharif season and later 30 varieties were selected and evaluated for seed dormancy and storability in kharif and summer seasons. A number of plants, panicle, seed and biochemical parameters like carbohydrate content, protein content, dehydrogenase activity and alpha amylase activity were also studied to examine the relationship of these characters with seed dormancy. Inheritance of seed dormancy was studied in 6 crosses involving 5 varieties. The efficacy of chemical treatment with maleic hydrazide (MH) in different concentrations for inducing seed dormancy was also studied to find out the most effective concentration for inducing dormancy in this crop. Dormancy periods (DG80) of the varieties ranged from 3 to 13 days in summer and 5 to 39 days in kharif seasons. Dormancy intensity (NGH0) ranged from 4% to 83.67% in summer and 9.67% to 95% in kharif seasons. These ranges indicated presence of varietal and seasonal differences for dormancy period and intensity. Most of the early varieties showed minimum dormancy period and weak intensity while most of the medium to late varieties possessed maximum dormancy with strong intensity of dormancy. Seeds of kharif season showed the highest degree of dormancy compared to summer grown seeds. Dormancy period and intensity showed high positive correlation between them and both showed strong positive association with days to flowering and maturity. Seed dormancy was found to have a digenic epistatic control with dormant nature is dominant over non-dormant. There were significant differences and wide range of variation among the varieties for different measures of storability of seed indicating presence of varietal differences for this trait. PG80 and PG50 were estimated by probit analysis which showed that seeds of different varieties in different seasons would maintain germinability above the minimum certification standard for periods of 8 and 9 months in summer and kharif seasons, respectively. All measures of storability showed that kharif seeds stored best than summer seeds. Storability of seed showed strong positive correlation with seed dormancy. The treatment with 15000 ppm maleic hydrazide (MH) was the most effective dormancy inducing dosage followed by 10000 ppm and 5000 ppm for rice varieties to prevent pre-harvest sprouting during monsoon seasons. This same trend was observed in these treatments for seed vigour parameters. The study brought out the existence of varietal and seasonal differences for seed dormancy and storability between and within different maturity groups and a strong positive relationship between the seed dormancy and storability traits. Several of the late varieties were found to have maximum seed dormancy, which can be used as such or as donors for transfer of dormancy to other early varieties to prevent yield losses due to viviparous germination. Seed dormancy was found to have a digenic epistatic control (complementary and inhibitory gene action) with dormant nature is dominant over non-dormant, which means that breeding manipulation of the character would be quite difficult. By incorporating seed dormancy into early varieties, the storability of the varieties can also be improved. The information obtained as the most effective dormancy inducing treatment is valuable for avoiding pre-harvest sprouting (PHS) and useful for preventing yield losses due to PHS during monsoon seasons.
  • ThesisItemOpen Access
    DUS characterization and assessment of seed dormancy and storage behaviour of aromatic short grain rice varieties
    (Department of Seed Science and Technology, OUAT, Bhubabneswar, 2021-08-26) M C, Muthu; Lenka, Devraj; Bastia, D.N.; Samal, K C; Mohanty, S
    Aromatic rice (Oryza sativa L.) varieties are preferred world-wide since ages because of the excellent aroma and palatability. More than hundreds of traditional land races of aromatic rice with pleasant aroma are being cultivated in different parts of Odisha. But the farmers are not growing these varieties because of low yield and lack of marketing facilities. Now, realising the demand in the market, to improve the economy of farmers, an investigation was carried out DUS characterization and assessment of seed dormancy and storage behaviour of aromatic short grain rice varieties for documentation and crop improvement. Thirty aromatic short grain rice varieties were selected from the rice germplasm of Rice Research Station, O.U.A.T, Bhubaneswar and were grown there during kharif 2016 and 2017 in RBD with three replications. The varieties were characterized by 57 (43qualitative+14quantitative) morphological descriptors adopted from the DUS guidelines of PPV and FR Authority, Govt. of India. Among the 43 qualitative traits the spectrum of variability in 30 aromatic short grain rice varieties indicated that traits were 22 monomorphic, 9 dimorphic and 12 polymorphic indicating their potential for varietal characterization and distinctiveness. No intra-varietal variation was observed for any of the visual characteristics. Among the 14 quantitative traits used for characterization 9 exhibited dimorphic and 5 polymorphic patterns of variation. Among the rapid chemical tests standard phenol test and modified phenol test with copper sulphate was found effective in differentiating aromatic short grain rice varieties. Further KOH and NaOH test were useful in identification of aromatic short grain rice varieties. However, not much significant response has been noticed due to added chemicals like GA3 and 2,4-D. Intensity of dormancy varied from 46 % (Dhanaprasad) to 96% (Dulhabhog) of non-germinated seeds on the day of harvest. The duration of dormancy in 30 aromatic short grain rice varieties ranged from 14 to 42 days with an initial germination percentage of 46 to 96, when they were tested immediately after harvest. Based on, this dormancy was classified as weak (7-14 days) 2 varieties (Dhanaprasad and Kanak champa), moderate(14-21days) 11 varieties, strong (21-28 days) 10 varieties, very strong (28-35 days) 6 varieties and extremely strong (35-42days) 1 variety (Dulahabhog). In storage studies among 30 aromatic short grain rice varieties Dulahabhog and Nua Kalajeera was showed highest seed quality parameters after 12 months of storage with minimum 82 per cent of germination up to seven months of storage.