Rice Germplasm Lines Research Articles

Evaluation of Germplasm for Seedling Stage Salinity Tolerance in Rice (Oryza Sativa L.)

Salinity affects rice growth and development. Mostly all growth stages from germination to maturity are affected by the salinity. Among all the stages, seedling and reproductive stages are the most sensitive stages to salinity, which results in considerable yield losses. Development of salt tolerant varieties is most feasible approach for improving the production of rice in salt affected soils as seedling stage is necessary for better crop improvement. Overall 76 rice germplasm lines were evaluated at RARS, Maruteru, West Godavari, A.P during Kharif 2020 for salinity tolerance at seedling stage. The different parameters like root length, shoot length, shoot Na+ content, shoot K+ content, Na+/K+ content and SIS (salt injury score) at 10th and 16th day were studied under hydroponics subjecting to electrical conductivity of 6 and 12 dSm-1, at a pH of 5.0. Salinity scoring during seedling stage was noted as per the modified standard evaluation score (SES) of IRRI, revealed that four genotypes FL478, MTU1290, MTU1061 and MCM109 as tolerant, 23 genotypes as moderately tolerant, 42 were susceptible and remaining seven genotypes namely BPT2848, BPT3140, Hallabhatta, MTU1271, MTU1121, BPT2846 and Krishnahamsa are highly susceptible. The phenotypic study signified that Na+/K+ ratio is the key note for salinity tolerance.

Molecular basis of distinct responses to drought between rice and wheat genotypes

The water-intensive cultivation of rice in flooded conditions poses a great challenge to global water resources, particularly in the face of climate change. Wheat requires significantly less water than rice with fairly high yields. A main research question is whether there are any drought adaptive mechanisms in rice similar to those existing in wheat. We report a study, where precise moisture stress was imposed at the vegetative stage using a high-throughput drought simulator phenomics facility. Variability in stress response was captured through untargeted metabolome analysis. In the first experiment, using two rice cultivars with contrasting drought responses (IR64 and Apo) and a wheat cultivar, Weebill, we found distinct variations in regulation of metabolite levels under well-watered or water-limited conditions, both between and within species. Several biosynthetic pathways, including those of polyamines, flavonoids, flavones, and specific metabolites like sphinganine-1-phosphate and anthranilate were enhanced under water-limited conditions. These metabolites were more abundant in wheat than in rice. Among the rice cultivars, Apo had higher abundance of metabolites than IR64. Regulatory patterns governing these metabolic pathways provided basis for stress responses of the tolerant rice cultivar and wheat. A second experiment was conducted to screen rice germplasm lines for acquired tolerance traits contrasting for drought responsiveness. Eight genotypes (four sensitive and four tolerant ones) were selected to validate the candidate metabolites from the first experiment. In the third experiment, an RT-PCR analysis of the key regulatory genes governing the metabolic pathways was conducted, using plant materials from both experiments. The results of this third experiment provided a strong validation for the relevance of these metabolic pathways under stress in rice. We identified promising rice genotypes that exhibited fold change levels of stress resistance metabolites comparable to those of the wheat cultivar Weebill. This study helped identify key candidate metabolites that can be either developed as markers or as elicitors, and genotypes that can be used as trait donor lines for rice improvement.

Genetic Assessment of Germplasms for Anaerobic Germination in Rice

The present study was planned using portray method to screen rice germplasm lines for anaerobic germination (AG) by assessing seedling parameters. Among 266 lines studies, 121 exhibited variable germination % of 100‒17 under AG condition. Germplasm lines viz., RDR 7555, WGL 915, CSR 27, RGP 103, IRTON 103, IET 23993, RGP 60 and MTU NS1 were with highest germination capability (100%). Longest seedling length was recorded in WGL 915 (33.1 cm), RGP 57 (31.8 cm) and CSR 27 (31.2 cm). Seedling vigour index was maximum in lines WGL 915 (3310), RGP 57 (3180) and CSR 27 (3120). Genotypes CSR 27 (22.5 cm), WGL 915 (23.3 cm), RGP 57 (23.1 cm), RGP 103 (21.5 cm) and IRTON 103 (20.7 cm) are possessing highest tolerance to AG conditions with elongated shoot length. Highest root length was recorded in WGL 915 (9.8 cm), CSR 27 (8.7 cm), RGP 57 (8.7 cm), Indursamba (8.5 cm) and RGP 103 (8.1 cm). Highest heritability, genetic advance, PCV and GCV were recorded for seedling vigour index clearly highlights the importance of trait for simple selection. Highest significant positive correlation was observed between the seedling length and seedling vigour index (0.93**) followed by germination % and seedling vigour index (0.88**). Seedling length and germination % are important traits for seedling establishment in direct seeded rice under AG conditions. The 121 Germplasm lines were grouped into four clusters, cluster 3 and 4 has genotypes with above standard germination % (80%), highest seedling length (33.1‒20.3 cm) and high vigour index (3310‒2030). Present day task for plant breeders is to identify rice germplasm lines tolerant for anaerobic germination and to introgress the trait into the superior variety for development of rice pre-breeding lines with tolerance to anaerobic conditions and high yield [1].

Multivariate Analysis to Study Genetic Diversity for Yield and its Attributing Traits in Rice (Oryza sativa L.)

The present investigation was carried out with 72 germplasm lines and three checks of rice (Oryza sativa L.) were grown at Crop Research Station, Masodha conducted in the GPB farm, Acharya Narendra Deva University of Agriculture and Technology, Kumarganj, Ayodhya (U.P.) during Kharif June 2022- February 2023. Data on 10 characters, including grain yield per plant focused on diversity and PCA analysis. This investigation involved the analysis of 72 rice germplasm lines alongside three checks, showcasing extensive variation in agronomic and morphological traits. The study utilized Non-hierarchical Euclidean cluster analysis to assess genetic diversity. The pseudo F-test determined the optimal grouping of 75 genotypes into six distinct clusters. Cluster distribution revealed varying genotype compositions, with Cluster V comprising the highest entries (20), followed by Clusters I, VI, and II. Intra- and inter-cluster distances illustrated significant variability among clusters, emphasizing genetic diversity. Examining agronomic traits across these clusters revealed noteworthy variations in days to 50% flowering, days to maturity, plant height, and productive tillers. Panicle length, flag leaf area, biological yield, harvest index, 1000-grain weight, and grain yield per plant also exhibited cluster-specific variations. These findings provide valuable insights for rice breeding programs, facilitating targeted enhancements of specific agronomic traits within the rice population, thus contributing to the development of more resilient and productive rice varieties.

Studies on PCV, GCV, heritability, and genetic advance for yield related traits in rice germplasm lines (Oryza sativa L.)

Studies on PCV, GCV, heritability, and genetic advance for yield related traits in rice germplasm lines (Oryza sativa L.)

Assessment of Genetic Variability for Yield & Its Contributing Traits in Rice (Oryza sativa L.)

The research work was executed Research cum Instructional Farm, Genetics and Plant Breeding department of IGKV Raipur (C.G.) during kharif 2021. The research material under research comprised of 50 rice germplasm lines including two checks namely Mahamaya and Rajeshwari, which were tested in RBD with two replications. The observation of research investigation were recorded for total eight characters viz. Days to 50% flowering, Number of tillers per plant, Panicle length(cm), Plant height(cm), 1000seed weight(g), Grain yield per plant(g), Biological yield per plant(g), Harvest index(%). The analysis of variance showed that there was a highly significant variation in genotypes for all of the studied characters. A small difference between PCV and GCV suggests that the environment has little impact on the concerning traits. The number of tillers per plant, 1000 seed weight, grain yield per plant, biological yield per plant and harvest index had high heritability along with high genetic advance as a percent of mean indicates that the heritability is most likely caused by additive gene action and selection may be effective.

Development of new aromatic rice lines with high eating and cooking qualities

Rice is the staple food of about half of the world’s population. Preferred by consumers, aromatic rice is special rice with great commercial value. Cooking and eating quality and aroma are major grain qualities favored by most consumers. Currently, most of the available aromatic varieties have low yield with some undesirable agronomic traits. Thus, there is an urgent need to develop better aromatic rice varieties. This work aims to identify rice germplasm lines having good grain quality and to develop new varieties with desirable traits. Thirty-six out of 188 germplasm lines were identified to have betaine aldehyde dehydrogenase 2 (badh2) controlling aroma and were determined for their 2-acetyl-1-pyrroline (2AP) contents. Then, 17 of these lines were identified to have alleles for low amylose content and low gelatinization temperature, controlled by waxy and starch synthase IIa (SSIIa) respectively, suggesting that they were aromatic rice lines with high cooking and eating quality. A total of 158 F7 recombinant inbred lines (RILs) generated from five crosses of selected germplasm lines were planted for phenotypic and yield observation, resulting in 27 F8 RILs selected for yield evaluation and genotyping. Finally, four out of the seven F9 aromatic RILs showed high yield, high 2AP production, and low amylose content, in agreement with their genotypes. The other 3 F9 RILs were aromatic rice lines with high amylose content and high yield. Because consumers’ preference for grain quality varies depending on regions and ethnic groups, the high-yielding aromatic RILs generated from this study can be used to increase yield of Thai rice and to raise market value and farm profit.

Identification of genomic regions governing moisture and heat stress tolerance employing association mapping in rice (Oryza sativa L.).

Rice crop is damaged extremely by abiotic stress world-wide. The best approach to enhance drought tolerance in rice varieties is to identify and introgress yield QTLs with major effects. The Association mapping approach helps in the identification of genomic regions governing physiological, yield and yield attributes under moisture and heat stress conditions in diverse collections of crop germplasm, based on historic recombination events and linkage disequilibrium across the genome. The association mapping panel of 110 rice germplasm lines exhibited significant variation for all the traits in both irrigated and moisture stress conditions. The extent of yield reduction ranged to 83% during rabi, 2018-19, 53% in rabi, 2019-20 and 68% in pooled analysis. The genotypes Badami, Badshabhog, Pankaj, Varalu, Vasundhara, Vivekdhan, Krishna and Minghui63 exhibited drought tolerance with least yield penalty under moisture stress conditions. The genotypes Konark, MTU3626, NLR33671, PR118 and Triguna exhibited minimal reduction in heat stress tolerance traits. Association mapping of germplasm using 37808 SNP markers detected a total of 10 major MTA (Marker-trait association) clusters distributed on chromosomes 1, 3, 4 and 11 through mixed linear model (MLM) governing multiple traits from individual data analysis which are consistent across the years and situations. The pooled data generated a total of five MTA clusters located on chromosome 6. In addition, several novel unique MTAs were also identified. Heat stress analysis generated a total of 23 MTAs distributed on chromosomes 1, 5, 6 and 11. Candidate gene analysis detected a total of 53 and 38 genes under individual and pooled data analysis for various yield and yield attributes under control and moisture stress conditions, respectively and a total of 11 candidate genes in heat stress Conditions. The major and novel MTAs identified in the present investigation for various drought and heat tolerant traits can be utilized for breeding climate-resilient rice varieties. The candidate genes predicted for key MTAs are of great value to deploy into the rice breeding after functional characterization.

Phenotyping Rice Germplasm Associated With Salinity Tolerance Under Hydroponics System

Screening of different rice (Oryza sativa L.) germplasms or breeding lines is a continuous effort to identify the promising source. A series of experiments (20) were undertaken to identify promising materials for five years of salinity screening from 2015 to 2019. The materials included total of 3,195 rice germplasm and breeding lines, out of which Bangladesh Rice Research Institute (BRRI) developped 2, 295 germplasms, 193 advanced breeding lines from BRRI, and 707 advanced breeding lines from International Rice Research Institute (IRRI), Philippines. From this study, the genotypes were categorized as 122 tolerant, 220 moderately tolerant, 1,207 sensetive, and 1,646 highly sensetive. Among the BRRI germplasms, most of the materials (61%) had sensitive responses against salinity, while only 2 and 3% of rice germplasm exhibited tolerant and moderately tolerant, respectively. BRRI lines comprised 44% sensetive and 35% highly sensetive rice genotypes. In the tolerance level, 4% appeared as tolerant and 17% moderately tolerant against salinity. Likewise, IRRI lines also showed relatively higher tolerance (9%) than the BRRI germplasm and lines. They were classified into 9 % tolerant and 16 % moderately tolerant rice genotypes.
 Bangladesh Agron. J. 2022, 25(1): 37-45

Identification of New Sources of Resistance to Rice Gall Midge Biotype 3 (GMB 3) Prevailing in Jagtial, Telangana, India

Aim: To screen different rice entries against rice gall midge, (Orseolia oryzae) biotype 3 under field conditions.
 Place and Duration of Study: A total of 84 rice germplasm lines along with resistant and susceptible checks were evaluated against rice the gall midge, (Orseolia oryzae) biotype 3. These studies were conducted during Kharif season (2021) under field conditions at the Regional Agricultural Research Station (RARS), Jagtial.
 Methodology: Data on the total number of plants and plants with silver shoots including the number of silver shoots per plant were also recorded on 30 and 50 days after transplantation. Gall midge incidence as silver shoot scored according to the standard evaluation system, International Rice Research Institute (IRRI) for gall midge [1].
 Results: Six entries viz., KAKAI, SINNA SIVAPPU, PTB-12, WGL-1145, WGL-1147 and WGL-1127 had shown high resistant (score 0) to gall midge. Four entries viz., IR72476-B-P-9-3-1-1, RP-5332-54-11-8-2-13, WGL-1143 and SUDD HONDARAWALA were found resistant (score 1) against gall midge.
 Conclusion: The entries KAKAI, SINNA SIVAPPU, PTB-12, WGL-1145, WGL-1147 and WGL-1127 exhibited the high resistance against gall midge. Hence, they can be developed as varieties or can be used in breeding programme as a source of gall midge resistance.

Comprehensive periodic evaluation of Oryza sativa germplasms for resistance against rice root-knot nematode, Meloidogyne graminicola

Rice root knot nematode, Meloidogyne graminicola is an important nematode pest with a devastating potential that causes serious damage to rice crop. There is an intensive search for eco-friendly, sustainable alternative to the existing nematode management practices. Host plant resistance offers propitious results in managing this minuscule crop enemy. Preliminary screening of 1731 Oryza sativa germplasms followed by periodic evaluation of nine resistant / tolerant germplasms shed new insights on nematode resistance. We observed seasonal inconsistency in the resistance in previously reported germplasms 'Ramakrishna', 'TKM6', 'Abhisek', 'Laxman sal', 'Ratna', and 'TKM1'. Hence, we strongly recommend repeated screening of identified resistant/tolerant rice germplasm lines against M. graminicola in both winter and summer season to confirm the consistency in resistance scale. Further investigation is needed to nullify other chance factors like nematode pathotypes.

Morphological characterization of red rice germplasm of Himachal Pradesh and identification of potential genotype for yield and biotic stress tolerance

The present investigation was carried out in Rice &Wheat Research Centre Malan of with thirty-five red rice germplasm lines collected across Himachal Pradesh Observations were recorded on twelve quantitative six grain quality traits. Analysis of variance showed presence of variability for all traits except flag leaf length, harvest index and grain breadth among the germplasm lines. Analysis of parameter of variability exhibited high heritability coupled with high genetic advance as percent of mean for biological yield per plant, thousand grain weight and L:B ratio which indicated the presence of high additive gene action and selection for such traits may be beneficial in future breeding programme. The mean performance of genotypes was compared with best check with particular trait and genotypes- Deval, HPR-2913, HPR-2908 were found to be promising for most of the traits including grain quality. The disease reaction for leaf and neck blast among genotypes indicated that, IC-12180, HPR-2800, HPR-2795, HPR-2913 and HPR-2914 were found to be resistance to both blast disease.

Diversity Analysis for Yield and Its Contributing Traits in Rice Germplasm (Oryza sativa L.) Using Principal Component Analysis Approach

The present study was aimed to assess genetic variation among rice germplasm lines employing a multivariate biometrical approach, viz., Principal Component Analysis. Analysis of variance as per Augmented Block Design indicated the presence of sufficient genetic variation among rice germplasm lines, while estimates of components of variation revealed a maximum contribution of genotypic variance to the phenotypic variance, suggesting its exploitation through selection and hybridization. Simultaneously, correlation estimates revealed a significant positive association of grain yield with panicle length, 1000 grain weight and grain length indicating suitability of these traits for indirect selection. D2 statistics grouped germplasm lines into sixteen clusters and among these cluster I consists of 67 germplasm lines forming the largest cluster followed by cluster III (26 lines), cluster II (18 lines), cluster IV (15 lines), cluster V (13 lines), cluster VI (5 lines), cluster VIII (3 lines), cluster VII and cluster IX (2 lines each), while clusters X, XI, XII, XIII, XIV, XV, XVI (1 line each). Inter cluster distances were found to be higher than intra cluster distances and the maximum inter cluster distance was observed between cluster IX and VI (73.47) followed by cluster IX and X (73.14). 
 Principal component analysis transformed eleven interrelated variables into four major principal components having an eigen value of more than 1, thereby, indicating that these components are responsible for a higher magnitude of variance in the population (76.60 per cent). Among these principal components, the first component accounted for 32.80 per cent of the total variation while, the second, third and fourth components explained 18.50 per cent, 13.90 per cent and 11.40 per cent of total variation, respectively. Factor loadings of the principal components revealed that principal component 1 had high positive loadings for grain length, panicle length, length/breadth ratio, 1000 grain weight and plant height whereas, principal component 2 had high positive loadings for total number of tillers per plant and number of effective tillers per plant indicating that the first two principal factors can be collectively designated as yield attributing factors. Principal component 3 had high positive loadings for grain breadth, 1000 grain weight and plant height, whereas, principal component 4 had high positive loadings for 1000 grain weight, days to maturity and days to 50% flowering. PCA biplots revealed that germplasm lines viz., GPL-1, GPL-4, GPL-131, GPL-128, GPL-20, GPL-127, GPL-135, GPL-100, GPL-130 were found to be superior performers for desirable traits and can be used as parents in hybridization programme.

Analyzing genetic variations for head rice recovery under heat stress in rice (Oryza sativa L.)

High temperature induces yield losses in rice, by affecting pollination, fertilization and also by affecting grain quality. High temperature stress coinciding with the grain filling period affects starch granule compaction thereby leading to reduced head rice recovery (HRR). The broken grains significantly reduce the price of rice by 50% in the market. Hence, the development of rice varieties that exhibit a lower reduction in grain quality coupled with higher head rice recovery under high temperature stress has become a major mandate in rice breeding programs. The present study was undertaken to survey the genetic variation for head rice recovery in rice under both normal (wet season) and high temperature (dry season) conditions. Evaluation of 50 diverse rice germplasm lines across different temperature regimes during grain filling viz. mean temperature of 30.8°C (wet season; May to Sep-Oct) and 35.8°C (Dry season 2017; January to May) and 36.2°C (Dry season 2018; Nov-Dec to May) identified huge genetic variation for HRR in rice. During the wet season, HRR ranged between 20.6 per cent and 90.9 per cent. During summer, rice genotypes exhibited a significant reduction in HRR from 3.6 to 82.7 per cent. Stability analysis revealed that the rice genotypes viz. CO 39, ChiemChanh, CO 18, Guan-Yin-Tsan, IR36, Teqing, ARC 10818 and Cimarron exhibited stable head rice recovery across all seasons. Keywords: Rice, heat stress, stability, head rice recovery

Phenotypic correlation between morphological and yield related traits of rice (Oryza sativa L.)

Rice is known as major staple food crop in India by providing food to more than 70 per cent population. An experiment was carried out in Alpha lattice design with two replications at ICAR-Indian Institute of Rice Research (ICAR-IIRR). An experiment was conducted during kharif season of year 2019 to study correlation and path coefficient analysis in 152 rice germplasm lines were collected. Analysis of variance showed significant differences among genotypes for all the 10 traits studied. Correlation studies revealed that grain yield per plant had positive and significant association plant height at both genotypic and phenotypic levels. Hence, these characters should be given due consideration while applying selection for increasing yield. Results of path analysis indicated that the maximum direct effects for plant height, tiller number per plant, no. of un filled grains per panicle, panicle weight as well as appreciable indirect effects were exerted by days to 50% flowering, effective number of tillers, test weight, towards grain yield per plant. Therefore, selection pressure imposed on these traits would bring improvement in grain yield of rice.

Assessment of genetic variability, correlation and path coefficient analysis for yield and its contributing traits in rice (Oryza sativa L.)

The entitled research work “Assessment of genetic variability, correlation and path coefficient analysis for yield & its contributing traits in rice (Oryza sativa L.)” was executed Research cum Intractional Farm, Genetics and Plant Breeding department of IGKV Raipur (C.G.) during kharif 2021. The research material under research comprised of 50 rice germplasm lines including two checks namely Mahamaya and Rajeshwari, which were tested in RBD with two replications with the objectives viz. (1) To estimate genetic variability for yield and quality traits. (2) To study the association analysis among yield and other traits. (3) To analyse the direct and indirect effects on trait under study on grain yield. The observation of research investigation were recorded for total 24 characters viz. Days to 50% flowering, Number of tillers per plant, Panicle length (cm), Plant height (cm), 1000seed weight (g), Grain yield per plant (g), Biological yield per plant(g), Harvest index(%), Paddy length(mm), Paddy breadth(mm), Paddy length breadth ratio, Hulling (%), Milling (%), Alkali spread value, Gel consistency (mm), Amylase content (%), Kernel length (mm), Kernel breadth (mm), Kernel length breadth ratio, Hulled rice length after cooking (mm), Hulled rice breadth after cooking(mm), Cooked rice length (mm), Cooked rice breadth (mm). The analysis of variance showed that there was a highly significant variation in genotypes for all of the studied characters. A small difference between PCV and GCV suggests that the environment has little impact on the concerning traits. The NTPP, TSW, GYPP, BYPP, HI, M, HRR, ASV, GC, AC, KL: B, HRBAC, CRL and CRB had high heritability along with high genetic advance as a percent of mean indicates that the heritability is most likely caused by additive gene action and selection may be effective. Positive significant correlation was showed GYPP with NTPP, TSW, BYPP and HRR with H, M. These characters would be beneficial for increasing yield and choosing superior genotypes among rice cultivars. Positive direct effect on GYPP showed by the HI, BYPP, PLN, DTFF, NTPP, TSW and on HRR showed by PL, M, ASV, GC, KB, KL:B, HRABC, CRL revealed true relationship between them and direct selection for these traits would be beneficial for increasing yield.

Genetic analysis of rice germplasm suitable for direct and transplanted establishments

Rice is the staple food crop for most of the population in the world especially in Asia. Due to climate change and labour shortage problems, there is a shift in rice cultivation practices in South Asia. The direct seeded rice cultivation is now preferred over transplanted rice owing to its greater advantage in mechanization and management practices. In the present study, 600 rice germplasm lines were evaluated in transplanted and direct seeded conditions (dry and wet). The principal component analysis revealed that, the first three principal components contributed for 76.54, 78.07 and 80.05 per cent for the total divergence in different establishments viz., dry seeding, wet seeding and transplanting, respectively. The traits viz., days to five per cent flowering, days to 50 per cent flowering, days to 100 per cent flowering and days to maturity contributed the maximum for the total divergence. Further, the genotypes were grouped into 10 clusters based on the dissimilarity coefficient. The clustering pattern of the different establishments was different from one another owing to the differential performance of genotypes in different establishments. The genotypes Tundus, Liu 19, Semiocho and Minchechinhsuthou were found to be very diverse from others in the current study as they were placed in the single solitary clusters in different crop establishments. The genotypes viz., White Ponni, La Hung Ku, IR 78875206B4B and Hsung Tieng 2 had performed better in all the three establishments. Hence, these lines can be used for both direct seeded and transplanted conditions. Key words: Dry seeded, Wet seeded, Transplanted, PCA, Rice, Cluster analysis

Field- and laboratory-based methods of screening salt tolerant genotypes in rice

Salinity is one of the major abiotic stresses that lead to loss of billions of dollars in crop production worldwide. The growth of rice plant is severely affected and subsequently the yield is generally low in salt affected areas. Salinity affects rice primarily at the early vegetative stage by interfering with biochemical and physiological processes governing its growth and development. This review aims at summarising various morphological, physiological, biochemical, and molecular-based methods that are currently used in screening salt-tolerant rice genotypes at different growth stages with particular emphasis on screening of breeding lines, and also the effectiveness of these methods. Field and laboratory-based methods are described including visual screening of salt-induced injuries as per the IRRI’s standard evaluation system, salt-induced accumulation of ions, changes in the levels of photosynthetic pigments, antioxidant, and image-based visual quantification of injuries, and molecular markers-based screening, which are lengthy and cumbersome. Among these methods currently available, this review highlights IC50 (50% inhibition concentration) estimation of shoot growth inhibition as a rapid and accurate method that can differentiate genotypes with the IC50 difference of only a few mm NaCl for the initial screening of a large number of rice germplasm and breeding lines.

Morphological and molecular screening of rice germplasm lines for low soil P tolerance

Phosphorus (P) is an essential macronutrient to all crops including rice and it plays a key role in various plant activities and development. Low availability of P in the soils negatively, influences rice crop growth and causes significant yield loss. In the present study, we characterized a set of 56 germplasm lines for their tolerance to low soil P by screening them at low soil P and optimum soil P levels along with low soil P tolerant and sensitive check varieties. These lines were genotyped for the presence/absence of tolerant allele with respect to the major low soil P tolerance QTL, Pup1, using a set of locus specific PCR-based markers, viz., K46-1, K46-2, K52 and K46CG-1. High genetic variability was observed for various traits associated with low soil P tolerance. The yield parameters from normal and low soil P conditions were used to calculate stress tolerance indices and classify the genotypes according to their tolerance level. Out of the total germplasm lines screened, 15 lines were found to be tolerant to low soil P condition based on the yield reduction in comparison to the tolerant check, but most of them harbored the complete or partial Pup1 locus. Interestingly, two tolerant germplasm lines, IC216831 and IC216903 were observed to be completely devoid of Pup1 and hence they can be explored for new loci underlying low soil P tolerance.

Screening for novel rice sheath blight resistant germplasm and their biochemical characterization

Rhizoctonia solani Kuhn causes sheath blight of rice which is a common and destructive disease. The present studies focus on screening of rice genotypes against R. solani to find out promising sheath blight resistant genotypes and the role of the defense-related biochemical enzymes in six different moderately resistance, moderately susceptible and susceptible germplasm lines. A total of 196 rice germplasm lines were used to conduct a field trial to screen sheath blight resistant germplasm during 2014–2015 and 2015–2016 crop seasons. The study identified 33.1% moderately resistant, 55.6% moderately susceptible and 11.2% susceptible genotypes to sheath blight in rice. Moderately resistant cultivar IC281785 recorded higher peroxidase activity (2.990) than moderately susceptible cultivar IC282450 (1.232). Higher PPO enzyme activity was observed in Tetep (1.729) followed by IC281785 (1.423) after 24 h of inoculation. Similarly, PAL activity was highest in moderately resistant cultivars than moderately susceptible and susceptible cultivars. The highest catalase activity was observed in moderately resistant cultivar Tetep (0.963) than susceptible cultivar PB1 (0.513) after 72 h of pathogen inoculation.