Head Rice Recovery Research Articles

Correlation and Path Coefficient Studies for Grain Yield and Yield Components in Rice (Oryza sativa L.)

The current research was conducted with an objective to study the correlation between different traits and path coefficient analysis in rice. Four CMS lines were crossed with eight elite restorers in a Line × Tester design and the resultant 32 hybrids were evaluated along with the parents and two checks in a randomized block design with three replications during the rabi season of 2022. The data was collected on 13 quantitative characters. The results revealed that there is a significant variability in the material studied. The character association studies indicated that the trait, grain yield per plant had significant positive genotypic correlation with panicle length, number of productive tillers per plant, number of grains per panicle, 1000 grain weight, 50% flowering, plant height, kernel length, kernel breadth and head rice recovery. The path analysis studies revealed that panicle length was the major contributor for grain yield per plant followed by plant height, number of grains per panicle, days to 50% flowering, 1000-grain weight, kernel length, number of productive tillers per plant, head rice recovery and kernel breadth. These characters showed direct positive effects for grain yield per plant. The above characters can be used directly as the selection criteria in rice yield improvement programmes.

Study of Combining Ability in Association with Heterosis in Rice (Oryza sativa L.)

In the current investigation, eight lines KNM 12444, KNM 12469, KNM 12472, KNM 13449, KNM 13555, KNM 13568, KNM 14913 and KNM 14985 were crossed with four testers namely Aganni, IBT MRR 24, INRC 3021 and WGL 1119 in Line by Tester mating design during rabi season of 2021-22. The resultant 32 F1’stogether with parents and two commercial checks, KNM 118 and KNM 1638 were evaluated for their combining ability and heterosis at Agricultural Research Station, Kunaram during kharif season, 2022.The analysis of variance for combining ability specified that significant differences were observed due to lines, testers, F1’ hybrids and various interactions indicating the existence of wider adaptability in the material examined. The ratio of gca to sca variances showed that non-additive gene action was predominant in the inheritance of panicle length, plant height, number of productive tillers/plants, grain yield per plant, kernel length, kernel L/B ratio and incidence of gall midge, whereas, preponderance of additive gene action was noticed for 1000 grain weight, days to 50% flowering, number of filled grains per panicle, kernel breadth, hulling percentage, milling percentage and head rice recovery. The gca effects of the parents revealed that, the line KNM 13555 and the testers Aganni, IBT MRR 24 were found to be the best general combiners for single plant yield and its components. Based on the significant sca effects, per se performance, standard heterosis and gall midge incidence, KNM 12469/Aganni followed by KNM 13555/INRC 3021, KNM 13568/IBT MRR 24, KNM 12472/Aganni and KNM 13449/Aganni were identified as promising for single plant yield, its components, quality traits and gall midge incidence. Hence, these parents and F1 hybrids may be further tested for future crop improvement programme.

Correlation and Path Analysis for Yield and Yield Attributes in Maintainer Lines of Rice (Oryza sativa L.)

The study was conducted during kharif season (June–October) of 2016 at the Regional Agricultural Research Station, Agriculture College, Professor Jayashankar Telangana State Agricultural University (PJTSAU), Jagtial, Telangana, India. Forty (40) maintainer lines of rice (Oryza sativa L.) were grown in randomized block design replicated twice to find the relationships between the yield and its components, as well as their direct and indirect effects on the rice grain yield. Observations were recorded for yield, yield attributing characters and quality traits on five randomly selected competitive plants for each entry in each replication for 15 characters. The results revealed that the analysis of variance was significant for all the characters investigated. Grain yield was significantly correlated with its component characters like number of tillers plant-1 (0.9191**), panicle length (0.3339**), milling percentage (0.3214**) and hulling percentage (0.2873**) whereas it showed a negligible positive correlation with days to 50% flowering, days to maturity, plant height, panicle length, number of grains per panicle, kernel length, kernel breadth, L/B ratio, test weight, hulling percentage, and head rice recovery percentage. Path coefficient analysis revealed that number of tillers plant-1 (0.9439) exerted maximum positive direct effect on plant yield followed by kernel breadth, L/B ratio, panicle length, milling percentage, days to flowering and head rice recovery percentage indicated their importance in determining the complex character and therefore should be kept in mind while practicing selection aimed at improving the grain yield.

NLR 3186: A Long Duration Blast Resistant Rice Culture Suitable for Irrigated Ecology of Andhra Pradesh

The culture NLR 3186 was derived from a cross of NLR 28523 / Secandro Brazelio (5720-11-1-3-1) through Pedigree method of breeding at Agricultural Research Station, Nellore. It recorded an average yield increase of 19.97% over the check NLR 33892 in the station trials. In Multi Location Trial conducted for 2 years, it recorded 11.26% increase over the checks used for testing MTU 1061.I n 3 years of minikit testing the entry NLR 186 recorded 8.3% higher grain yield than the check varieties tested. In AICRIP trial during 2012-13, it recorded on par with the national check MTU 7029 (4249 kg/ha). It has non-lodging nature, high yielding, nitrogen responsive, with medium green foliage, low shattering and complete exertion of panicle. It was tolerant to leaf blast, neck blast and sheath rot. It has good cooking and chemical quality as it exhibits intermediate and desired values of ASV, gel consistency, good linear elongation ratio and amylase content. It also possesses good head rice recovery with translucent grains which is very much desired for marketing.

Characterization of morpho-phenological traits in the traditional landraces of rice

The landraces of rice provide a wide range of genetic variations and environmental adaptation and act as excellent genetic resources for crop improvement. Natural germplasm that has been maintained through conservation is in desperate need of rigorous investigation in order to uncover new genes or alleles to introduce into rice breeding programmes. Given this context, an investigation was done to determine the degree of genetic divergence and variability across 31 rice landraces for various productivity, physiological, and grain quality traits. On evaluation of the mean performance of landraces and the influence of characters in genetic divergence resulted in the identification of better landraces viz., Vellaikuruvikar, Karupu Kavuni, Kichidi Samba and Athur Kichadi which are better for both grain yield and quality traits that can be used to create better recombinants, by hybridization. These gene pools could be used in selective breeding to significantly enhance the agronomic characters. Out of 20 traits that were investigated,15 traits viz., height of the plant, productive tillers per plant, length of panicle, spikelets per panicle, filled grains per panicle, grain yield per plant, seedling root to shoot ratio, harvest index, head rice recovery, length of the kernel, length to breadth ratio of kernel, breadth of kernel after cooking, length to breadth ratio of kernel after cooking, gelatinization temperature and aroma were noted for high heritability and genetic advancement suggesting that additive gene action predominates, there by opening up a wide range of opportunities for these traits to be improved through simple phenotypic selection. Keywords: Rice, landraces, GCV, PCV, heritability, PCA

Long-term impact of biofertilization on soil health and nutritional quality of organic basmati rice in a typic ustchrept soil of India

Healthy soils are the foundation for producing healthy food and creating a healthy environment. Therefore, we assessed the changes in the physical and chemical properties of soil, and their long-term impact on yield, quality, and nutritional status of rice grains in an organic basmati rice-based cropping system in a typic Ustchrept Soil of India. The experiment was laid out in a strip plot design with three replications. The vertical strips consisted of two rice-based cropping systems, namely, basmati rice-wheat-mung bean (RWM) and basmati rice-wheat-sesbania (RWS), whereas seven combinations of different organic materials and biofertilizers (BF) were assigned to horizontal strips, viz., control (no manure application), farmyard manure (FYM), vermicompost (VC), FYM + crop residues (CR), VC + CR, FYM + CR + BF, and VC + CR + BF. The results revealed that soil moisture content (SMC), soil organic carbon (SOC), soil total N, and soil available P, Fe, Zn, Mn, and Cu were significantly higher under the RWS system than in RWM. The application of organic manures either alone or in conjunction with CR and BF significantly lowered the soil pH (∼3.0%), EC (43.1%–45.8%), and BD (3.3%–9.2%) as compared to the control. Water holding capacity (WHC), SMC, and SOC were increased by 5.7%–14.7%, 8.7%–49.3%, and 35.3%–76.5%, respectively under single or co-application of FYM/VC with CRs and BFs as compared to control. Similarly, sole or conjoint application of organic manures, CR, and BF significantly enhanced the soil available macro (N, P, and K) and micro (Fe, Zn, Mn, and Cu) nutrients over the control. Grain yield, protein content, N uptake, and cooking quality parameters were significantly higher under the RWS system than under RWM. However, the Zn concentration and its uptake by grains were significantly higher under the RWM system over RWS. The grain yield was significantly increased by 25.8%–49.2% under different organic nutrient management options over control. The single or conjoint application of FYM/VC with CR and BF increased the hulling, milling, head rice recovery, and protein concentration in grain by 9.4%–9.8%, 23.2%–28.4%, 22.7%–25.5%, and 9.6%–10.7%, respectively over control. The concentration of N, P, K, Fe, Zn, Mn, and Cu was significantly improved by 9.7%–11.3%, 45.5%–63.6%, 16.7%–20.8%, 66.9%–74.1%, 72.9%–81.9%, 87.1%–97.0%, and 48.9%–67.2%, respectively under co-application of FYM/VC with CR and BF compared to control. Thus, our results indicate that improved soil properties could significantly increase the physical and nutritional quality of basmati rice grain. Therefore, adopting basmati rice-based cropping systems with different organic nutrient sources can sustain soil health, end global hunger, produce nutritious food, and create a healthy environment.

Meta-QTL and haplo-pheno analysis reveal superior haplotype combinations associated with low grain chalkiness under high temperature in rice.

Chalk, an undesirable grain quality trait in rice, is primarily formed due to high temperatures during the grain-filling process. Owing to the disordered starch granule structure, air spaces and low amylose content, chalky grains are easily breakable during milling thereby lowering head rice recovery and its market price. Availability of multiple QTLs associated with grain chalkiness and associated attributes, provided us an opportunity to perform a meta-analysis and identify candidate genes and their alleles contributing to enhanced grain quality. From the 403 previously reported QTLs, 64 Meta-QTLs encompassing 5262 non-redundant genes were identified. MQTL analysis reduced the genetic and physical intervals and nearly 73% meta-QTLs were narrower than 5cM and 2Mb, revealing the hotspot genomic regions. By investigating expression profiles of 5262 genes in previously published datasets, 49 candidate genes were shortlisted on the basis of their differential regulation in at least two of the datasets. We identified non-synonymous allelic variations and haplotypes in 39 candidate genes across the 3K rice genome panel. Further, we phenotyped a subset panel of 60 rice accessions by exposing them to high temperature stress under natural field conditions over two Rabi cropping seasons. Haplo-pheno analysis uncovered haplotype combinations of two starch synthesis genes, GBSSI and SSIIa, significantly contributing towards the formation of grain chalk in rice. We, therefore, report not only markers and pre-breeding material, but also propose superior haplotype combinations which can be introduced using either marker-assisted breeding or CRISPR-Cas based prime editing to generate elite rice varieties with low grain chalkiness and high HRY traits.

Exploration of Genetic Variability and Trait Association in High Protein Landraces of Rice (Oryza sativa L.)

The present investigation was carried out at the Indian Institute of Rice Research farm, ICRISAT, Hyderabad with 31 genotypes of rice in a randomized block design with three replications, and observations were recorded on grain yield, yield components and quality characters. Analysis of variance revealed significant differences among the genotypes for all characters studied. The studies on variability, heritability and genetic advance as per cent mean thus revealed high GCV and PCV for grains panicle-1 and iron content. High heritability coupled with high genetic advance as per cent mean was recorded for plant height, ear bearing tillers plant-1, grains panicle-1, grain yield plant-1 and iron content indicating, the effectiveness of simple selection for improvement of these traits. The results on character associations and path analysis revealed positive and significant association coupled with high positive direct effect for ear bearing tillers plant-1, panicle length, grains panicle-1, and amylose content indicating the effectiveness of direct selection for these traits in the improvement of grain yield plant-1. However, for test weight, days to 50 percent flowering, plant height, head rice recovery (%), and zinc content, indirect effects seemed to be the cause of correlation, while for days to maturity, protein and iron content, the use of restricted simultaneous selection model is suggested with restrictions imposed for nullifying the undesirable indirect effects in order to make use of the high positive direct effect observed for these traits on grain yield plant-1.

Study of Physicochemical, Cooking and Nutritional Properties of Selected Traditional Rice Varieties of Tamil Nadu

The study has been undertaken to investigate the physico-chemical, cooking and nutritional qualities of selected traditional rice varieties of Tamil Nadu. Significant variations (p<0.05) were observed among the twelve traditional rice varieties for all the characters except hulling percentage. Among the varieties, the highest hulling out-turn was found in Poonkar (90.0 %) and the lowest was found in Anaikomban (84.0 %). The milling out-turn was ranged from 74.0 % to 80.0 %. Head Rice Recovery (HRR) varied from 50.0 % to 75.0 %. The kernel length was highest in Kullakar (6.3 mm) and lowest (4.2 mm) in Milagu samba and Thulasi vasa samba. Kernel breadth was ranged between 1.4 – 2.5 mm. Based on length/breadth ratio, the variety Thanga samba obtained slender grain type whereas all other varieties obtained medium grain type. The Kernel length after cooking ranged from 6.5 mm (Thulasi vasa samba) to 9.8 mm (Poonkar). The volume expansion ratio ranged from 4.6 in Sorna masuri to 3.7 in Poonkar and Kullakar. Gel consistency ranged from 46.0 - 135.0 mm. The Gelatinization Temperature (GT) was determined based on alkali spreading value and the rice varieties Milagu samba, Kuzhiadichan and Thulasi vasa samba have obtained intermediate GT values whereas other varieties evaluated showed high to intermediate GT. Intermediate amylose content is considered to be the best from the cooking point of view. Varieties Anaikomban (20.1 %), Garudan samba (20.4 %), Poonkar (20.7 %) and Sorna masuri (23.2 %) were identified with intermediate amylose content. Highest protein (10.40 %), iron (15.8 mg kg-1) and zinc (20.5 mg kg-1) content were recorded in the varieties Poonkar, Thuaiya malli samba and Kullakar respectively, making them nutritionally superior among the tested varieties. There is a growing global demand for rice varieties with good quality characteristics. This study provides immense information on varieties with superior physico-chemical, cooking and nutritional characteristics which could be used to meet those demands.

Effect of zinc application on yield, nutrients uptake and biochemical properties of rice under Inceptisols

A field experiment was conducted in a randomized block design at Regional Agricultural Research Station, Karjat during kharif 2016-2019 to study the effect of zinc on soil fertility, yield, nutrients uptake and biochemical properties of rice under Inceptisols. Results revealed that the grain (50.65 q ha-1) and straw (56.74 q ha-1) yield of rice was significantly improved with application of zinc in the form of zinc sulphate @ 15 kg ha-1 at the time of transplanting through soil application (T7) which was better than foliar spray and root dipping methods. Significantly highest values of DTPA-extractable Zn (0.45 mg kg-1) and SO4-S (32.40 kg ha-1) were registered in the treatment T8. The zinc supplied plots led to significant enhancement in total N (93.38 kg ha-1), P (15.55 kg ha-1), K (96.80 kg ha-1) and S (35.54 kg ha-1) uptake in the treatment T7 and Zn (183.40 g ha-1) in the treatment T8. The treatment T7 showed higher hulling (74.28%), milling (63.32%), gel consistency (81mm), alkali spreading value (4.0) as well as the head rice recovery (57.80%), protein (8.96%) and amylose (24.40%) content which was acceptable.Overall, Zn-fertilization assumes great significance in improving soil properties, productivity and quality of rice.

Correlation and Path Analysis Studies for Yield and Quality Traits of Rice Landraces and Mutants of Chhattisgarh, India

Background: The production of rice needs to grow as this is one of the major objective in plant improvement program to fulfill the requirement of the rapidly growing population.
 Objective and Methods: The field experiment was conducted to study character association among yield and its attributes among 58 rice genotypes at Indira Gandhi Krishi Vishwavidyalaya, College of Agriculture, Raipur (C.G.) to know the relationship among characters.
 Results: it is found out that Traits like panicle weight per plant, filled spikelets per panicle, harvest index, and biological yield per plant are having a high direct effect and significant correlation with grain yield per plant, and traits like milled grain length-width ratio, hulling %, and alkali spreading value are having a high direct effect and significant correlation with head rice recovery.
 Conclusions: Direct selection based on these traits for improvement of rice grain yield and grain quality can be effective.

PHYSICO-CHEMICAL AND COOKING QUALITY TRAITS OF SELECTED BLACK RICE (Oryza sativa L.) VARIETIES

In this research, six black rice varieties cultivated in Kharif 2021 namely BPT 2841, BPT 2848, BPT 3136, BPT 3137, BPT 3145 and Burma Black (control) were studied for different quality traits such as physical, chemical and cooking quality traits. All the parameters showed significant variance. Thousand grains weight showed positive correlation with hulling per cent (r=0.748), milling percent (r=0.981), head rice recovery (r=0.594), kernel length (r=0.947) and kernel breadth(r=0.932). In terms of physical quality, 1000 grain weight of Burma black showed greater value due to its large grain size which is treated as undesirable. In terms of chemical quality traits, all the rice varieties except control had intermediate amylose content (20-25%) and intermediate alkali spreading value (4-5). These were considered as key characteristics to improve rice grain quality.

Studies on gene action and combining ability in rice (Oryza sativa. L) hybrids

The study was carried out to learn about the nature of gene action and combining ability in rice hybrids for grain yield and its component traits. For this, eight lines were crossed with four testers in an L x T mating design. The analysis of variance revealed significant variance for all the characters studied among the parents and hybrids. GCA variances were higher than SCA variances for most of the characters, indicating the predominance of additive gene action, while SCA variances were higher than GCA variances for number of productive tillers per plant, pollen fertility, hulling, milling, head rice recovery and grain yield per plant, indicating the predominance of non-additive gene action. The testers JMS 13A (3.91) and CMS 59A (2.46), as well as the lines MTU 1153 (9.52), RNR 28355 (3.26) and RNR 26085 (3.09), were the best combiners for grain yield and important yield components due to positive GCA effects. Based on SCA effects and corresponding mean performance for grain yield and its component traits, the hybrids CMS 59Ax RNR 26015, CMS 23A x JGL 25960, CMS 64Ax RNR 26015 and JMS 13Ax MTU 1153 were identified as the best specific combiners. These hybrids could be tested in multi-environment trials for commercial use. Keywords:  CMS lines, Gene action, Combining ability, GCA, SCA, Line x Tester &nbsp

Indigenous storage structures for paddy in North East region

The effect of different indigenous storage methods on the quality of rice during the storage period was studied. Four different varieties of paddy were stored in different storage structures as indigenous types, such as Kot (small bamboo structures), Kei (large size storage structure), wooden structures and metal bins separately, and the total head rice recovery of rice during storage period was studied. The maximum head rice yield was found in the KD cultivar and the minimum in the Huikap cultivar. The different physical dimensions and characteristics of paddy influenced the breakage of paddy, affecting the total head rice recovery during storage. Long, slender grains are more susceptible to breakage, affecting the head yield.

Effect of microwave drying of paddy on milling characteristics, cooking quality, and microstructure of rice

AbstractEffect of microwave drying on milling, cooking, and microstructure characteristic of paddy rice in comparison to hot air drying was assessed in the present study. Results revealed that modified microwave drying significantly (P < 0.05) affected the milling quality of paddy. Raw paddy had head rice recovery of 49.63%, while after microwave drying, the head rice recovery increased by 6.73% in comparison to hot air drying. Microwave drying brought significant changes in the colour characteristic of rice as it had total colour change of 13.50 in comparison to 10.93 by hot air drying. Cooking time and water uptake ratio after microwave drying increased to 31.46 min and 3.16%, in comparison to 27.05 min and 2.65% for hot air dried samples, respectively. Scanning Electron Microscope images revealed that both hot air and microwave dried rice had a coarse surface and large starch particles, while starch structure was more damaged in hot air drying, however, agglomeration of protein-starch matrix was more uniform in microwave dried samples due to modification of the microwave applicator that prevented thermal decomposition. It was recommended that paddy may be dried using a modified microwave applicator with a shorter duration and a better quality.

The effect of drying temperature on the physical and antioxidant qualities of MARDI Warna 98 rice

Drying is an important activity after the rice is harvested in order to minimize quality deterioration. Generally, drying temperature ranging from 42-45°C is known worldwide to preserve rice physical quality, mainly for white rice and it is widely practised by all rice millers. A study was conducted to determine the optimum drying temperature of the new coloured rice variety, MARDI Warna 98 (MW 98) in the preservation of physical as well as antioxidant qualities. The rice was dried at ambient temperature as control and ovendried at 40-45°C, 46-50°C and 51-55°C until moisture content reached 13-14%. Physical qualities that have been determined were head rice and broken rice, while the antioxidant properties evaluation measured were total phenolic content (TPC), total flavonoid content (TFC), total anthocyanin content (TAC) and 2, 2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activities. Antioxidant parameters were measured spectrophotometrically. The results showed that the head rice recovery was significantly lower at ambient temperature and 51-55°C drying temperature (90.59% and 91.23%, respectively) and this was directly proportional to a higher percentage of broken rice (9.41% and 8.77%, respectively). The results also showed no significant difference in head rice recovery either drying at 40-45° or 46-50°C, which were 95.50% and 95.93%, respectively. The rice was then evaluated for its antioxidant activities and results showed there was no significant difference in the content of total phenolic, total flavonoid, total anthocyanins and DPPH radical scavenging activities at different drying temperatures except for ambient temperature. Rice dried at ambient temperature showed significantly lower content of total phenolic, total flavonoid, total anthocyanins and DPPH inhibition. In conclusion, drying temperature does affect the physical and antioxidant qualities of MW 98. Therefore, we suggested that drying at 46-50°C was the best for MW98 to preserve rice’s physical and antioxidant qualities.

Introgression of tsv1 improves tungro disease resistance of a rice variety BRRI dhan71

Rice Tungro disease poses a threat to rice production in Asia. Marker assisted backcross breeding is the most feasible approach to address the tungro disease. We targeted to introgress tungro resistance locus tsv1 from Matatag 1 into a popular but tungro susceptible rice variety of Bangladesh, BRRI dhan71. The tsv1 locus was traced using two tightly linked markers RM336 and RM21801, and background genotyping was carried out using 7 K SNPs. A series of three back crosses followed by selfing resulted in identification of plants similar to BRRI dhan71. The background recovery varied at 91–95% with most of the lines having 95%. The disease screening of the lines showed moderate to high level of tungro resistance with a disease index score of ≤ 5. Introgression Lines (ILs) had medium slender grain type, and head rice recovery (59.2%), amylose content (20.1%), gel consistency (40.1 mm) and gelatinization temperature were within the acceptable range. AMMI and Kang’s stability analysis based on multi-location data revealed that multiple selected ILs outperformed BRRI dhan71 across the locations. IR144480-2-2-5, IR144483-1-2-4, IR144484-1-2-2 and IR144484-1-2-5 are the most promising lines. These lines will be further evaluated and nominated for varietal testing in Bangladesh.

Genetic Variability, Heritability and Genetic Advance Studies on Yield, Its Components, Quality Traits and Gall Midge Incidence in Rice (Oryza sativa L.)

Twenty-eight lines including 18 F1 plants, 9 parents, and one commercial were studied for estimation of genetic variability, heritability, and genetic advance at Agricultural Research Station, Kunaram. Analysis of variance revealed highly significant differences among the genotypes for all the traits studied indicating the presence of a considerable amount of variability among the genotypes for yield and its components, quality traits and gall midge incidence. PCV values for the number of productive tillers per plant were significantly greater than GCV indicating highly sensitive to environmental changes. The GCV and PCV were high for the percentage of gall midge incidence, the number of productive tillers per plant, the number of filled grains per panicle, and grain yield per plant, whereas, low for hulling percentage, head rice recovery, milling percentage, and kernel length. Additive gene action was predominant for Gall midge incidence, number of productive tillers per plant, number of filled grains per panicle, grain yield per plant and grain weight per 1000 grains as they registered high heritability coupled with high genetic advance values.

Quality Deterioration of Rice Grains under High Temperature Stress

High temperatures, which cause a decline in grain weight and quality, are one of the most significant environmental concerns checking productivity of rice in tropical areas. To combat these problems, understanding the consequences of high temperature stress on nutritional qualities of rice is imperative. An experiment was conducted at Regional Agricultural Research Station, Pattambi during 2019-2020 with rice variety Jyothi cultivated during five dates of planting [June 1st (D1), June 30th (D2), October 1st (D3), October 30th (D4) and January 1st (D5)] under open condition (O) and climate-controlled green house (GH). Grains obtained from different treatments were analyzed for different quality parameters like milling percentage, head rice recovery, starch, amylose, protein, fat and mineral (Ca, Fe, Zn, P) content. Highest milling percentage, head rice recovery, starch, amylose, protein, fat and mineral (Ca, Fe, Zn, P) content were observed during June 1st planting and lowest during January 1st planting. When comparing the two growing conditions, grains obtained from open condition had high milling percentage, head rice recovery, starch, amylose, protein, fat and mineral (Ca, Fe, Zn, P) content than that under climate-controlled greenhouse. The study shows that high temperature stress on plants can be managed by early sowing of rice cultivars in all the three seasons viz. virippu, mundakan and puncha and rice grains obtained from virippu sowing gives good quality grains as compared to that of mundakan and puncha planted grains.

Rice CO 53: A high yielding drought tolerant rice variety for drought prone districts of Tamil Nadu

Early duration drought tolerant rice culture CB 06803, a derivative of the cross PMK (R ) 3 x Norungan was released as Rice CO 53 during the year 2020 as an alternate variety for Anna(R)4, with 115 -120 days duration. It possesses desirable features like high yield, drought tolerance and better physiological efficiency. This culture with semi dwarf stature has efficient tillering capacity, long droopy panicles with a highly acceptable plant characters and is a replacement for the rice variety Anna (R) 4 due to its grain yield and pest and disease resistance. In the overall yield analysis, the culture CB06803 recorded an overall mean grain yield of 3718 kg/ha which was 12.19 per cent increase over TKM (R) 12 and 14.08 per cent over Anna (R) 4 under dry condition. Under semi dry condition, it recorded 3866 kg/ha with 18.40 per cent increase over TKM (R) 12 and 8.67 per cent over Anna (R) 4. It is moderately resistant to WBPH, leaf blast, neck blast, sheath rot, brown spot and RTD under artificial condition. It has white short bold rice with high milling percentage (69.6), head rice recovery (59.6%) and suitable for idly making. The culture, CB 06803 had better  agronomic efficiency than TKM (R)12 and Anna (R) 4 by recording more number of productive tillers per plant and grain yield under control and drought. The culture CB 06803 had better physiological efficiency under drought than TKM (R) 12 and Anna (R) 4  having higher RWC, total chlorophyll content, chlorophyll stability index, photosynthetic rate, stomatal conductance and photo chemical efficiency. The culture had higher proline content than TKM (R) 12 and was on par with Anna (R) 4. It had higher catalase activity than Anna (R) 4. CB 06803 had better physiological efficiency under drought by showing partial closure of stomata as that of Sahbagidhan. CO 53 with higher grain yield under drought, disease resistance and short bold grains and suitable for cultivation in drought prone districts of Tamil Nadu as direct seeded rainfed or semi dry rice ecosystem. Keywords: Rice CO 53, bold grain rice, short duration, drought tolerance