GENETICAL STUDIES ON NO3- USE EFFICIENCY UNDER AEROBIC AND ANAEROBIC CONDITIONS IN RICE (ORYZA SATIVA L.)
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Date
2017
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Indira Gandhi Krishi Vishwavidhyalaya, Raipur
Abstract
Rice (Oryza sativa L.) is the world’s largest cultivated food crop and a main staple food for more than 50% of the world population. Faced with scarcity of water resources, soil moisture stress becomes most critical threat to rice production. Limited water that reduces nutrient availability to the plant. Presently water scarcity have been chased and breeders even developed a new plant type ‘‘aerobic rice’’ targeted at water limited rice environment but nutrient stress as a major constraints in most rice-based aerobic system in Asia. Among essential plant nutrients, nitrogen (N) is one of the most yield limiting nutrients for upland rice production. Nitrogen fertilizer applied in the form of urea as it is the main nitrogen carrier worldwide in annual crop production. Plant-useable N is consumed as nitrate (NO3-) from aerobic soils and as ammonium (NH4+) from flooded wetland, anaerobic soil. The current average nitrogen use efficiency (NUE) in the rice field is approximately 33%, poorest among cereals and a substantial proportion of the remaining 67% is lost into the environment. The complex nature of nitrogen fertilizer response particularly in the form of nitrate in aerobic soil, inefficient phenotypic selection and difficulty of effective low nitrogen tolerance screening methodology complicate the development of nitrogen responsive varieties. Therefore, the present study was undertaken to carry out the genetic analysis coupled with to identify efficient rice genotypes in response to grain yield and nitrogen use efficiency (in the form of nitrate) under aerobic cultivation.
123 rice lines including released varieties, advanced breeding lines, land races and checks were evaluated in augmented design with three treatment i.e. zero nitrogen, nitrogen in the form of calcium nitrate (NO3-) and nitrogen in the form of ammonium chloride (NH4+) with ratio of 80:60:40 NPK kg ha-1 under aerobic and anaerobic condition during wet season 2015, at Department of Genetics and Plant Breeding Research Cum Instructional Farm, IGKV, Raipur, to generate the phenotypic data. On the basis of grain yield and other important ancillary traits, 38 lines were selected and evaluated by using three way factorial designs with three treatments and two replication under both aerobic and anaerobic conditions during wet season, 2016. The genetic parameters studied namely, phenotypic coefficient of variation (PCV), genotypic coefficient of variation (GCV), heritability, genetic advance, association, path coeffient and stability analysis.
Three way analyses revealed significant differences among the genotypes for all the traits indicating the presence of sufficient amount of genetic variation among genotypes and possibility of manipulating these variations for rice improvement. The genotype by nitrogen (G×N) interaction component was found significant for all traits under study. The trend analysis of NH4+ and NO3- dynamics revealed that NH4+ concentration persisted more under anaerobic condition and NO3--N concentration under aerobic conditions. Mean performance of genotypes depicted higher values for agronomically important traits i.e. yield and NUE under NH4+ treatment as compared to NO3- and N0 treatment under all environments.
In aerobic condition highest grain yield and nitrogen use efficiency was reported by RP 5125-2-4 of 244.35, 278.82 and 310.76g/m2 under N0, NO3- and NH4+ respectively followed by IR-64 Drought (227.11, 268.17 and 300.62 g/m2) and RAU 1484-Aer-04 (200.75, 241.31 and 262.60 g/m2). This genotype gave stable performance under different form of nitrogen for both aerobic and anaerobic condition. RCPR 8, CR 3634-1-3 and RP 5125-2-4 were reported highest grain nitrogen and protein content under N0, NO3- and NH4+ for aerobic condition. Phenotypic coefficient of variation (PCV) were higher than genotypic coefficient of variation (GCV) for all the characters studied indicates that the apparent variation is not due to genotype but also due to the influence of environment.
High genetic advance coupled with high heritability was reported for plant height, biological yield, harvest index, grain nitrogen yield, straw nitrogen yield, biomass nitrogen yield, nitrogen harvest index, nitrogen uptake efficiency and nitrogen utilization efficiency under differential N regimes and environments. This indicated that these traits were predominantly controlled by additive gene action and more amenable for selection. These traits were exhibit positive correlation along as well as showed direct effect on grain yield it reveals true relationship between them and direct selection for these traits will be rewarding for yield and NUE improvement. The genotype CR Dhan 40 contains consistently stable Zn content (in brown and polished rice grain) under different nitrogen regimes for both aerobic and anaerobic environments.
In another set 32 out of 179 RILs (between Swarna x Basmati-370) were selected on the basis of grain yield. These 32 lines along with their parent are used for further single marker analysis. Result revealed that, 5 QTLs have been identified for the trait plant height at maturity, of which 3 minor genes on chromosome # 5 and 1 each minor gene on chromosome # 8 and # 9. The 4 QTLs have been identified for chlorophyll content at seedling stage. Two QTLs on chromosome # 1 and # 5 have been identified for grain yield. RM-18616 on chromosome # 5 was found significantly linked with grain yield under all nitrogen regimes for aerobic condition.
These results assist us to identify NH4+ and NO3- responsive cultivars which could be used for cultivation and/or used as parent’s in future breeding program to produce better nitrogen use efficiency varieties under aerobic and anaerobic conditions.
Description
GENETICAL STUDIES ON NO3- USE EFFICIENCY UNDER AEROBIC AND ANAEROBIC CONDITIONS IN RICE (ORYZA SATIVA L.)
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