A field experiment was conducted at the Agricultural College and Research Institute, Killikulam, Tamil Nadu during the year to Dry seeds were irradiated with 10, 20, 25, 30, 40 and 50 kR dose of gamma rays from 60 Co source at Tamil Nadu Agricultural University, Coimbatore.
In the present study, from M 2 progenies, 10 salt tolerant single plants from each treatment Gamma rays 10, 20, 25, 30, 40 and 50 kR were selected by artificially inducing salt stress EC 12 ds m -1 under field conditions and M 3 generation were raised subsequently. In M 3 , 10 single plants were selected. The seeds of the individual plants were sown in progeny rows in Randomized Block Design with three replications.
Observations were made on 15 randomly selected plants at the rate of five plants per replications. The single plants with increased yield were selected for M 4 generation. Selection on individual plant was practised in M 4 generation based on increased plot yield.
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The seeds of selected plants in M 4 were forwarded to M 5 generation. Each mutant line and control was grown in uniform size plots. Statistical analysis: The estimates of the intercomponent correlations were calculated in both M 3 and M 4 generations as per the standard method for correlation analysis suggested by Goulden Using data on M 5 generation, analysis of variance was done following the method suggested by Singh and Chaudhary, Genotypic variance was determined by the formula suggested by Burton Heritability in broad sense was computed by the formula suggested by Johnson et al.
Correlation studies: Significance was observed in association between panicle length and yield in M 3 population at 30 and 40 kR 0. Association of yield with productive tiller was significant in 50 kR of ADT 43 0. In ASD 16 of M 3 population, significance was noted at 10 0. Association was significant between plant height and yield at 10 0. Kole et al. Association reversal was noted between boot leaf length and yield at 10 0. Significance between chlorophyll content a chla and yield was found in 25kR 0.
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Similarly, Chl b also show significance with yield in 10 kR 0. Chlorophyll content was found to be increased with an increase in radiation dose under saline conditions Shereen et al. This supports our study where we have observed an increase in chlorophyll contents with an increase in yield in some mutants. The non significant association of seed weight and seed yield in control population of ASD 16 0.
Besides, ADT 43 also shows a significant association at 30 kR The association of yield with number of productive tillers was non significant in the irradiated population at all the doses except 40 kR of ASD 16 0. Negative significance was found between plant height and yield at 30 kR In irradiated population the association was non significant at all the other doses.
The nature of alternation in the association varied with the mutagenic doses, genotypes and the character pairs Rafi, These results in dicate that the situation can be exploited by selection for positively associated traits for improving yield in rice. Based on the above, selection was practiced for decrease in plant height as negative association was noticed.
Similarly the other characters were also selected. Variability studies: The application of mutation breeding in identifying abiotic stress resistant mutants has been successful in some crop plants including rice Ahloowalia et al. In the present study, salt tolerant mutants isolated from 20, 30, 40 and 50 kR treatment showed significant increase in yield as compared to the other treatments and parental varieties In this 20 kR of ADT 43 Plant height was found to be significantly higher in all the treatments when compared with the control varieties All the treatments showed significant increase in number of tillers as compared to control varieties.
The control mean of ADT 43 was The mean of the control variety ASD 16 was 5. Plant height, panicle length and No.
Since yield is a quantitatively inherited character and is subject to different degree of non heritable variability and more particularly its genetic components are the most important factor in any breeding material. This has a close bearing on the response to selection. The results obtained in our study on yield and its associated parameters Table 3 , 5 are highly heritable which can be effectively used in developing salt tolerant rice. In the present study, heritability estimates were high for all the three traits under study.
High heritability indicates that the induced variability in mutant lines was fixed by selection. Johnson et al. This is because heritability estimates are subject to genotype environment interactions.
Mutations, In Vitro and Molecular Techniques for Environmentally Sustainable Crop Improvement
Furthermore, genetic advance gives the extent of stability and genetic progress for a particular trait under a suitable selection system. Results on yield and contributing characters possesses sufficiently high values of heritability and genetic advance which can be utilised for further improvement in rice and in evolving a high yielding saline tolerant variety. Lee et al. Gamma ray treatment resulted in generation of high genetic variability in both the varieties used for this study.
The mutants differs significantly for all yield related parameters assessed, thereby providing a wide genetic base for selection.
The mutagenic treatment also results in alternation of character association, hence correlation was worked out and selection was based on the characters identified. Estimated variations of segregating generations increased depending on the character investigated and the mutagenic dose used. The high heritability estimates in response to selection shows that the treatment has generated inheritable variability. As expected genetic advance is high in M 5 generation saline tolerable plants with higher yield can be obtained. Abdullah, Z. Khan and T. Flowers, Causes of sterility in seed set of rice under salinity stress.
Crop Sci. Malusznyski and K. Nichterlin, Global impact of mutation derived varieties. Euphytica, Principles of Plant Breeding. Burton, G. Quantitative inheritance in grasses. Figure 4. Locations of , genotyped animals. Figure 5. It measures the marginal economic value of improvement in customer profitability.
Figure 6. Genetic improvement in a nucleus herd translates into visible gains on commercial farms.
Figure 7. Figure 8. Genomic selection in rainbow trout doubles selection accuracy in a single generation compared with traditional pedigree-based predictions. This figure is reproduced and modified from Additional file 2 of Figure S1 in Vallejo and Leeds Genome-based analyses that increase knowledge of the genetic basis of production traits will lead to the development of new technologies that optimize animal breeding strategies and inform management decisions to realize the maximum production potential of animals across environments.
The primary use of genome-enabled technologies is the identification of large numbers of single nucleotide polymorphism markers that represent genetic diversity at the molecular level. These are associated with economically important traits. High-throughput platforms for genotyping large numbers of these markers in a single assay has led to their widespread use in research that seeks to determine the genetic basis of traits and improve predictions of performance in offspring.
Creating successful genome-enabled applications for commercial breeding industries was facilitated by many factors:. Progress in commercial breeding attributed to genomics has been primarily achieved through four practices: 1 identifying and selecting for one or a few alleles having significant effects on phenotype; 2 using large numbers of genetic marker combinations to more correctly define relatedness between animals in a population and therefore increase selection accuracies; 3 identifying and eliminating deleterious recessive alleles that reside in populations because they lay dormant when inherited from a single parent but are fully expressed when inherited from both; and 4 identifying animals with higher genome estimated breeding values e.
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The technologies that enable these advances in breeding have just begun to unlock the potential of genomic techniques to improve animal production. Improving the use of genome information in commercial animal production will require the efforts described here. Access to species-specific genome information, including well-annotated genome reference assemblies, characterization of genetic diversity within and across breeds, and developing cost-effective methods to carry out genome analyses, are critical if we are to make improvements over contemporary strategies.
Cost-effectiveness is partially dependent on data sharing and reproducibility.
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Genome-enabled parentage and traceability are used to address questions associated with species management and product quality. For another example, cultured and wild aquaculture species are often at risk for mixing. As offshore aquaculture develops [for example, in the Gulf of Mexico where 18 species are being considered for farming Florida Atlantic University, ], genome analyses are needed to verify broodfish region of origin. This would minimize the risks to wild fish if cultured fish escape and provide traceability tools if a sizable escapement episode occurs 8.
Genomic-scale genotyping of broodstock populations is attractive for some aquaculture species in which breeding candidates are limited to variant selection from wild-caught or F1 brood individuals in an effort to mitigate escapement concerns. Genome-enabled technologies have been developed for a few species with high economic value and research investments. However, it is possible to make further improvements in many of these species and employing these technologies in additional species and industries has great potential to improve animal production. For instance, although the United States contributed to the development of genome tools for sheep, the use of genome information has been limited compared with New Zealand, for example, which has large sheep populations and where genomic information is used extensively van der Werf et al.
Similarly, the use of genome information to improve goat genetics is not currently practiced in the United States, but it is used in Europe to improve dairy goat populations Carillier et al.
Since genome-enabled technologies have been applied where there is a clear economic gain, then there is rationale to be made for similar investments in other species. Consumers and producers are also poised to benefit by applying genome-enabled technologies to aquaculture species whose domestic production was only recently initiated, such as oysters and the California Yellowtail marine fish.
To implement improvements in genome-enabled selection in more animal species, scientists must do the following:. Researchers must have access to large integrated data sets of easily searchable phenotypic, environmental, and genomic information. Ideally, comprehensive phenotypes representing a wide range of production, reproduction, fitness, metabolic, welfare, disease susceptibility, and immune responsiveness traits would be collected on every commercial animal to allow precision breeding see below. Phenotype and trait ontologies exist in animal genomics, however their utilization must increase to maximize the value of data sets.