74 research outputs found
Mapping of quantitative trait loci for thermosensitive genic male sterility in indica rice
Progress and Prospects of Two Line Rice Breeding in India
Increasing the yield potential through hybrid rice technology was very well proved in nearby countries. Three line hybrid rice technology is encounted with some of the difficulties in seed production. Identification of Environmentally influenced male sterility overcomes the problem encountered in seed production since it is regulated by the temperature it is called temperature regulated male sterility and hybrids produced using this line is called two line rice hybrids. Types of male sterility and methods to identify the new TGMS lines and breeding methods employed for producing the tgms lines were described. Characterization of tgms lines by both conventional method and molecular tools has been enumerated. Seed multiplication of tgms under fertility inducing environment and seed production of two line hybrids has been explained. Seed production location was exclusively identified for seed multiplication of tgms lines. Heterotic potential of two line rice hybrids has been studied. Future prospectes in tgms research and two line heterotic potential was explained for increasing the yield potential in rice
Mapping of quantitative trait loci for thermosensitive genic male sterility in indica rice
O objetivo deste estudo foi selecionar e utilizar marcadores microssatélites, para mapear as regiões genômicas associadas ao controle genético de macho-esterilidade termossensÃvel (TGMS) em arroz. Uma população F2, derivada do cruzamento entre linhagens indica fértil e TGMS, foi usada para construir um mapa genético de arroz, baseado em marcadores microssatélites. O fenótipo TGMS analisado apresentou uma variação contÃnua na população segregante. Um baixo nÃvel de distorção da segregação foi detectado na população segregante (14,65%), e a seleção zigótica foi apontada como causa da distorção. Não houve evidência de relação de causa-efeito entre a seleção zigótica e o controle de TGMS nesse cruzamento. Um mapa de ligação com 1.213,3 cM foi construÃdo, baseado nos dados de segregação da população F2. Noventa e cinco marcadores microssatélites, de um total de 116 marcadores polimórficos, foram reunidos em 11 grupos de ligação, com uma média de 12,77 cM entre os locos marcadores adjacentes. Os dados fenotÃpicos e genotÃpicos permitiram a identificação de três novos locos controladores de caracteres quantitativos (QTL) para a macho-esterilidade gênica termossensÃvel em arroz indica. Dois dos QTLs foram mapeados em cromossomos que não tinham, ainda, sido associados ao controle genético da caracterÃstica TGMS (cromossomos 1 e 12). O terceiro QTL foi mapeado no cromossomo 7, onde um loco TGMS (tms2) foi recentemente mapeado. Testes alélicos deverão ser realizados para verificar se as regiões mapeadas são as mesmas.The objective of this work was to select and use microsatellite markers, to map genomic regions associated with the genetic control of thermosensitive genic male sterility (TGMS) in rice. An F2 population, derived from the cross between fertile and TGMS indica lines, was used to construct a microsatellite-based genetic map of rice. The TGMS phenotype showed a continuous variation in the segregant population. A low level of segregation distortion was detected in the F2 (14.65%), whose cause was found to be zygotic selection. There was no evidence suggesting a cause-effect relationship between zygotic selection and the control of TGMS in this cross. A linkage map comprising 1,213.3 cM was constructed based on the segregation data of the F2 population. Ninety-five out of 116 microsatellite polymorphic markers were assembled into 11 linkage groups, with an average of 12.77 cM between two adjacent marker loci. The phenotypic and genotypic data allowed for the identification of three new quantitative trait loci (QTL) for thermosensitive genic male sterility in indica rice. Two of the QTL were mapped on chromosomes that, so far, have not been associated with the genetic control of the TGMS trait (chromosomes 1 and 12). The third QTL was mapped on chromosome 7, where a TGMS locus (tms2) has recently been mapped. Allelic tests will have to be developed, in order to clarify if the two regions are the same or not
Genetics, fertility behaviour and molecular marker analysis of a new TGMS line, TS6, in rice
The thermosensitive genic male sterility (TGMS) system has great
potential for revolutionizing hybrid rice production through simple,
less expensive and more efficient seed production technology. For the
successful utilization of this novel male sterility system, knowledge of
the breeding and fertility behaviour of a TGMS line is essential. In this
study, the fertility transformation behaviour, the critical fertility and
sterility temperatures and the mode of inheritance of male sterility were
studied for a new TGMS line, TS6, identified at Tamil Nadu
Agricultural University, Coimbatore, India. The pollen and spikelet
fertilities recorded on plants raised at fortnightly intervals revealed
that this line was completely sterile for 78 consecutive days (35/22 to
32/23�C, maximum/minimum temperatures) and reverted to fertile
when the temperature was 30/18�C. It remained fertile continuously
for 69 days and the maximum pollen and spikelet fertilities recorded
were 75 and 70%, respectively. The fertility was highly influenced by
daily maximum temperature followed by average and minimum
temperatures. It was not influenced by relative humidity, sunshine
hours or photoperiod. The critical temperature inducing sterility and
fertility was 26.7 and 25.5�C, respectively. The male sterility in TS6 was
inherited as a monogenic recessive in the F2 and BC1 populations of
TS6 · MRST9 as well as TS6 · IR68281B. Using bulked segregant
analysis on an F2 population of TS6 · MRST9, an RAPD marker,
OPC052962, was identified to be associated with TGMS in TS6
Genetics of salt tolerance in rice
Experimental procedures viz., line x tester analysis, diallel analysis and stability analysis have been utilized in rice breeding programs to study combining ability, heterosis, gene action and stress tolerance capacity of various genotypes based on yield related traits. The results have helped in development of good varieties and hybrids. Excessive work is available in the particular area of research as many plant breeders in Asia work towards improving the yield of rice. A review on gene action studies in rice has been attempted with emphasis on the research progress made in India
Current insights and advances into plant male sterility: new precision breeding technology based on genome editing applications
Plant male sterility (MS) represents the inability of the plant to generate functional anthers, pollen, or male gametes. Developing MS lines represents one of the most important challenges in plant breeding programs, since the establishment of MS lines is a major goal in F1 hybrid production. For these reasons, MS lines have been developed in several species of economic interest, particularly in horticultural crops and ornamental plants. Over the years, MS has been accomplished through many different techniques ranging from approaches based on cross-mediated conventional breeding methods, to advanced devices based on knowledge of genetics and genomics to the most advanced molecular technologies based on genome editing (GE). GE methods, in particular gene knockout mediated by CRISPR/Cas-related tools, have resulted in flexible and successful strategic ideas used to alter the function of key genes, regulating numerous biological processes including MS. These precision breeding technologies are less time-consuming and can accelerate the creation of new genetic variability with the accumulation of favorable alleles, able to dramatically change the biological process and resulting in a potential efficiency of cultivar development bypassing sexual crosses. The main goal of this manuscript is to provide a general overview of insights and advances into plant male sterility, focusing the attention on the recent new breeding GE-based applications capable of inducing MS by targeting specific nuclear genic loci. A summary of the mechanisms underlying the recent CRISPR technology and relative success applications are described for the main crop and ornamental species. The future challenges and new potential applications of CRISPR/Cas systems in MS mutant production and other potential opportunities will be discussed, as generating CRISPR-edited DNA-free by transient transformation system and transgenerational gene editing for introducing desirable alleles and for precision breeding strategies
Genetic Improvement Strategies for Increasing Rice Yield: A Review Article
A review article was aimed to summarize various conventional and biotechnological breeding strategies that increased rice yield in major rice producing counties having strong breeding programs. An increase in productivity is always one of the main goals of any crop breeding program including rice. Even though there was a series of breakthroughs the main breeding goals in most international programs remain similar since a long time ago: increasing grain yield potential, resistance to blast disease, grain quality, and drought tolerance. Increase in grain yield potential is the major goal of almost all rice breeding programs. The major impacts are related to the development of new strategies to increase the genetic grain yield potential of the varieties. Rice breeders have been very successful in improving the crop. The main breeding method used to improve rice is the pedigree, but development of hybrids, new plant types and mutation breeding are added to the breeder’s portfolio. Breeders have been taking advantage of biotechnology tools in order to accelerate rice improvement programs as the main additional tool to conventional rice breeding strategies; however, many programs are still struggling on how to integrate them into the breeding programs especially in developing countries
Genetic Analyses of Male Sterility and Wide Compatibility in U.S. Hybrid Rice Breeding Lines
Two line hybrid rice breeding is widely used in Asia and involves the use of environmentally-sensitive male sterile lines to achieve high grain yields compared to pure line varieties. Currently, there is limited information concerning the performance and inheritance of two indica male sterile lines 2008S and 2009S under U.S. field conditions. The first objective of the research herein was to characterize genetic male sterility of lines 2009S and 2008S under controlled environment conditions. Results showed that 2009S exhibited a thermosensitive response whereas little or no response was observed with changes in daylength. Furthermore, high pollen fertility was achieved at the proper developmental stage (flag leaf not fully exposed) under low temperature treatment for 10 days. On the other hand, 2008S showed partial fertility when subjected to short daylength and high temperature conditions. Both lines were completely male sterile at high temperature and long daylength under Louisiana field conditions. The second objective was two-fold: to investigate the inheritance of photoperiod, thermosensitive genetic male sterility (PTGMS) under field conditions and to evaluate SNP-based markers for male sterility. A three-year study of 2008S F2 and BC1F2 populations from 2012 to 2014 revealed a two-locus segregation model indicating two recessive genes acting on male sterility. Inheritance of 2009S in a two-year study from 2013 and 2014 displayed single locus segregation using F2 and BC1F2 populations demonstrating that male sterility was controlled by a single recessive gene. SNP markers at LOC_Os07g12130 and LOC_Os12g36030 in the 2008S background showed significant interactions with up to 65% variance explained in one population, while a SNP marker at LOC_Os02g12290 identified 90-100% of male sterile lines segregating in F2 and BC1F2 populations derived from 2009S. The third objective was to conduct QTL mapping for male sterility in populations derived from 2008S using a selective genotyping approach. A total of five major QTLs including those previously identified in LOC_Os07g12130 and LOC_Os12g36030 and eight new minor QTLs were detected using single marker analysis. Four QTL intervals were detected with a LOD score of greater than 3.0 using inclusive composite interval mapping (ICIM). QTLs identified will be useful in future studies to fine-map additional markers associated with male sterility and increase prediction accuracy for marker assisted selection. The fourth objective was to investigate the effect of the S5n wide compatibility gene on grain yield and spikelet fertility in hybrids derived from the SB5 RIL mapping population. Results from this study revealed that heterozygous S5n S5j hybrids produced significantly higher spikelet fertility and yield versus the hybrids carrying S5i S5j genotypes. Indel and SNP markers developed for the S5 locus successfully differentiated the three unique genotypes (S5n, S5i and S5j). Overall results from this study demonstrated that male sterile lines 2008S and 2009S were useful for two-line hybrid rice breeding under Louisiana conditions. New QTLs discovered and markers developed for male sterility and wide compatibility will help facilitate marker assisted breeding in developing male sterile lines for the LSU hybrid rice breeding program
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