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Development of Component Lines (CMS, Maintainer and Restorer lines) and their Maintenance Using Diversed Cytosources of Rice | OMICS International
ISSN: 2375-4338
Rice Research: Open Access
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Development of Component Lines (CMS, Maintainer and Restorer lines) and their Maintenance Using Diversed Cytosources of Rice

Ariful Islam1*, Mian MAK2, Rasul G2, Bashar K3 and Fatema-Tuj-Johora4
1Department of GPB, EXIM Bank Agricultural University, Bangladesh
2Department of Genetics and Plant Breeding, BSMRAU, Gazipur1706, Bangladesh
3International Potato Research Centre (CIP), Bangladesh
4Department of Crop Botany, EXIM Bank Agricultural University, Bangladesh
Corresponding Author : Dr. Ariful Islam M
Department of GPB, EXIM Bank Agricultural University, Bangladesh
Tel: +88-01711872774
Received February 24, 2015; Accepted March 31, 2015; Published April 03, 2015
Citation: Islam A, Mian MAK, Rasul G, Bashar K, Johora FT (2015) Development of Component Lines (CMS, Maintainer and Restorer lines) and their Maintenance Using Diversed Cytosources of Rice. J Rice Res 3:140. doi: 10.4172/2375-4338.1000140
Copyright: © 2015 Islam A, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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The practice of hybridization has greatly contributed to the increase in crop productivity. A major component that exploits heterosis in crops is the cytoplasmic male sterility (CMS)/nucleus-controlled fertility restoration (Rf) system. The development and use of hybrid rice varieties on commercial scale utilizing male sterility and fertility restoration system has proved to be one of the mile stones in the history of rice improvement. Pollen sterility status of 148 exotic rice germplasm was assessed at flowering stage. Sixteen genotypes showed 100% pollen sterility status which was considered as completely male sterile lines (A-line). Sixteen genotypes were also identified as completely fertile due to 80% and above pollen and spikelet fertility. For identification of proper maintainer lines, the identified 16 CMS lines chance crossed with established known maintainer lines viz. IR 58025B, IR 62829B, GAN46B, IR 68888B and BRRI1B. Based on pollen male sterility status of the F1s lines it was indicated that 10 out of 16 were maintained by IR 58025B line, 8 CMS lines were maintained by IR 62829B, three CMS were maintained by IR 68888B and one CMS line was maintained by GAN46B and BRRI1B. Restoration potentiality of identified 16 suspected restorer genotypes were assessed throgh judgement of pollen and spikelet fertility of F1s developed through crossing with five standard CMS lines. Based on 80% and above pollen and spikelet fertility of F1s, seven suspected restorers were identified as restoerer against IR 58025A, two against GAN 46A, five against IR 62829A and two against IR 68888A.

Pollen; Spikelet; Fertility; Sterility; Fertility restoration; CMS line; Maintainer line; Synthesized
The development and use of hybrid rice varieties on commercial scale utilizing male sterility and fertility restoration system has proved to be one of the mile stones in the history of rice improvement. The hybrid rice technology now in operation, aims at yield increment through higher exploitable heterosis levels [1]. In hybrid rice technology most usually two sterility systems viz., CMS and EGMS are used for commercial seed production. In three line system of hybrid rice variety development system, three lines, A, B and R are required. A line is the cytoplasm-genetic male sterile line where the male sterility is jointly controlled by recessive nuclear gene and sterile cytoplasm. B-line is isogenic line of A-line, only difference in male sterility and fertility. R-line possesses fertility restoration gene [2]. A commercial A-line is characterized by the absence of pollen grains or rudimentary pollens, argonomically superiority, stable sterility, wide regeneration spectrum, abortive anther and highly synchronized [3]. B line is the maintainer line characterized by normal anthers, functional pollens and seed setting on selfing. While normal anthers, functional pollens, abundant pollen producing capacity, strong restoring ability, good combining ability, high out crossing rate, and genetically diverse from CMS line [4,5] are the main characteristics of R-line. It is 30 years since the first commercial release of hybrid rice. Plant cytoplasmic male sterility (CMS), a maternally inherited trait that prevents plants from producing functional pollen, has been identified in many higher plants, including rice, cotton, maize, and sorghum. CMS restorer systems have been widely exploited to produce hybrids that outperform their inbred parents in yield, biomass, or other traits. CMS is usually attributed to an unusual chimeric gene in the mitochondrial genome. In many cases, a nuclear-encoded fertility restorer gene (Rf) can restore fertility of the cytoplasmic male-sterile plants. Therefore, the CMS/Rf system is an ideal model for dissecting the interaction between mitochondrial and nuclear genomes. A variety of mechanisms of fertility restoration by the Rf genes have been reported for different CMS systems. T-urf13, a mitochondrial gene encoding a 13 kDa protein, has been detected only in maize carrying T male-sterile cytoplasm. The first restorer allele cloned, the maize Rf2 gene, does not affect the expression of urf13 and encodes aldehyde dehydrogenase (ALDH), which is located in the mitochondrial matrix in a homotetrameric. Hybrid rice has spread such that now it commands about 50% of the total rice area in China but only 7% in Bangladesh [4]. New male sterile cytoplasm sources and inter-subspecies crosses have contributed to the development of super rice breeding. However, sustainable improvements of hybrid rice yield potential, grain quality, and tolerance to biotic and abiotic stresses continue to be a great challenge. Exploitation of new germplasm has always played a critical role in rice breeding, and this will continue [6]. Component lines development is considered as the backbone of any sustainable hybrid rice program. Successful and long lasting hybrid rice program depends on development of diversified component lines utilizing CMS source, local and exotic genetic resources. In this country rice hybrid programs mostly depend on the component lines developed by IRRI and China [7]. There is a shortage of research works in component line development of hybrid rice activities performing by different organizations of Bangladesh [8].
As a part of that program the present investigation was initiated with the following objectives:
1. Identification of male sterile (CMS) and fertile (B) lines from the exotic rice germplasm.
2. Identification of Restorer (R-lines) based on pollen and spike let fertility test.
Materials Used
A series of experiments were conducted from Winter (Boro) 2011 to Summer (Aman) 2013 in the experiment field of Department of Genetics and Plant Breeding, Bangabandhu Sheikh Mujubur Rahman Agricultural University, Gazipur Bangladesh using the following materials (germplasm) (Tables 1 and 2).
Methods of pollen fertility test
Pollen fertility test was done by Potassium Iodide solution (KI). At flowering stage young spikelets were collected early in the morning (7.30-8.50 AM) from the field and kept in the jar for opening the spikelets after about 2 hours. One or two anthers were kept on a glass slide and smashed with KI solution and covered with a cover slip and then observed under a compound Microscope. Records on fertile and sterile pollens from three microscopic focuses were noted. Round well developed stained pollens were considered as viable and non-stained irregular shaped pollens were counted as sterile pollens and then converted into percentage. At maturity stage filled spikelets per panicle were counted in each genotype and then converted into percentage.
Data Recorded on
• Pollen fertility
• Spikelet fertility
Identification of A and R lines
The plants having 100% pollens sterility were considered as male sterile (CMS) and the plants having 80% and above pollen fertility and spikelet fertility were initially suspected as restorer line.
Identification of B-lines and maintenance of CMS lines
The identified CMS lines from Chinese germplasm were chance crossed with the established maintainer lines, GAN 46B, BRRI 1B, viz., IR 58025B, IR 62820B and IR 68888B as the corresponding maintainer lines were not known to us. All the 16 CMS lines were crossed with each of the above five maintainer lines. F1 seeds from each cross were harvested separately and grown in next season along with their respective maintainer lines. At flowering stage pollen fertility status of each plant of each cross was recorded. If all the plants of a cross showed 100% pollen sterility then the corresponding male plant was considered as maintainer line.
Performance of restorer lines against established CMS lines
The identified sixteen restorer lines were crossed with five CMS lines viz. GAN46A, BRRI1A, IR58025A, IR62820A and IR68888A. The F1s were grown in the next rice growing season and performance based on pollen and spikelet fertility was analyzed. The F1(s) having above 80% pollen and spikelet fertility indicated that the male parent was an effective restorer.
Results and Discussion
Identification of A and R lines based on Pollen sterility and fertility status
Results of pollen sterility and fertility are shown in Tables 3 and 4. Among the 148 exotic rice genotypes different levels of pollen sterility and fertility were observed. Such variation in pollen fertility indicated the existence genetic variation in respect of these reproductive traits among the genotypes. Among one hundred and forty eight exotic rice germplasm sixteen genotypes (RG-BU 08-053, RG-BU 08-058, RGBU 08-061, RG-BU 08-066, RG-BU 08-069, RG-BU 08-084, RG-BU 08-086, RG-BU 08-087, RG-BU 08-107, RG-BU 08-125, RG-BU 08- 126, RG-BU 08-129, RG-BU 08-132, RG-BU 08-136, RG-BU 08-137 and RG-BU 08-141) showed 100% pollen sterility status which was considered as completely male sterile lines or A line. The amount is not so less but 10.81% of the total germplasm. Ten genotypes were found sterile having pollen fertility 0-9%. Miyagawa and Nakamura [9] classified 85 rice cultivars based on the regional differences in varietal characteristics and found some elite male fertile lines as well as their counterpart maintainer lines. Chetia et al. [10] evaluated five cytoplasmic male sterile (CMS) rice lines (PMS 2A, PMS 3A, PMS 10A, IR 58025A and IR 62829A) and observed that PMS 2A, PMS 10A and IR 62829A were recorded as complete pollen and spikelet sterility. Sun et al. [11] determined the genetic effects of male sterile cytoplasm on major characters of rice hybrids. Ramesha et al. [12] identified three new and diversified CMS sources and many CMS lines possessing sporophytic type of male sterility with a very high frequency of typically abortive pollen. The new CMS lines were compared with other CMS lines belonging to wild abortive. Besides stable sterility, the new CMS lines had very high panicle exertion rate (92-96%) and good stigma exertion (48-65%) ability. Twenty nine genotypes were recorded partially sterile which is 19.59% of total. But most of the genotypes were categorized in partially fertile based on pollen fertility test. About fifty one genotypes were found partially fertile which 36.46% of total. Such type of genotypes may open the scope of development of restorer lines of hybrid program. And sixteen genotypes (RG-BU 08-001, RG-BU 08-002, RG-BU 08-005, RG-BU 08-006, RG-BU 08-007, RG-BU 08- 013, RG-BU 08-016, RG-BU 08-018, RG-BU 08-025, RG-BU 08-034, RG-BU 08-038, RG-BU 08-046, RG-BU 08-057, RG-BU 08-063, RGBU 08-097 and RG-BU 08-105) were identified as completely fertile as these genotypes had above 80% pollen and spikelet fertility which is 10.81% of the total genotypes. Research results indicated that the frequency of restorer lines in Chinese rice germplasm was found very high as compared to local rice genotypes. Thus the above mentioned genotypes having restorer genes may be utilized as a good reservoir of restorer genes for development of efficient restorer lines. Abeysekera et al. [13] studied 53 cytoplasmic male sterile (CMS) lines of rice and observed that pollen fertility and spikelet fertility had significant effects on the out crossing rate (Tables 3 and 4).
Restorability of suspected restorer lines
Sixteen suspected restorer lines were used to test their restoration ability with four established CMS lines, IR 58025A, GAN 46A, IR 62820A and IR 68888A. Results of restoration ability based on pollen and spikelet fertility of F1s between CMS and restorer lines are shown in Tables 5 and 6. Out of sixteen F1 ten crosses (IR 58025A× RG-BU 08-001R, IR 58025A× RG-BU 08-006R, IR 58025A× RG-BU 08- 013R, IR 58025A× RG-BU 08-016R, IR 58025A× RG-BU 08-018R, IR 58025A× RG-BU 08-025R, IR 58025A× RG-BU 08-034R, IR 58025A× RG-BU 08-046R, IR 58025A× RG-BU 08-063R and IR 58025A× RGBU 08-0105R) showed above 80% pollen fertility but seven crosses showed 80% above both pollen and spikelet’s fertility (IR 58025A× RG-BU 08-001R, IR 58025A× RG-BU 08-006R, IR 58025A×RG-BU 08-018R, IR 58025A×RG-BU 08-034R, IR 58025A×RG-BU 08-046R, IR 58025A×RG-BU 08-063R and IR 58025A×RG-BU 08-0105R) which indicated that seven suspected restorers had desirable restoration ability with the above CMS line. When these sixteen suspected restorers were crossed with GAN 46A six F1s (GAN46A×RGBU 08-007R, GAN46A×RG-BU08-025R, GAN46A×RG-BU 08- 034R, GAN46A×RG-BU 08-038R, GAN46A×RG-BU 08-097R and GAN46A× RG-BU 08-105R) showed above 80% pollen fertility but only two crosses (GAN46A×RG-BU 08-007R and GAN46A×RGBU08- 025R) showed 80% above both pollen and spikelet’s fertility. Eight crosses of restorer lines with IR 62820A showed above 80% pollen fertility (IR 62820A×RG-BU 08-001R, IR 62820A×RG-BU 08-005R, IR 62820A×RG-BU 08-006R, IR 62820A×RG-BU 08- 007R, IR 62820A×RG-BU 08-013R, IR 62820A×RG-BU 08-025R, IR 62820A×RG-BU 08-038R and IR 62820A×RG-BU 08-057R) where as five F1s were found having 80% and above both pollen and spikelet’s fertility i.e., IR 62820A×RG-BU 08-005R, IR 62820A×RGBU 08-013R, IR 62820A×RG-BU 08-025R, IR 62820A×RG-BU 08- 038R and IR 62820A×RG-BU 08-057R. Five crosses of restorer lines with IR 68888A showed above 80% pollen fertility (IR 62820A×RGBU 08-001R, IR 62820A×RG-BU 08-002R, IR 62820A×RG-BU 08-007R, IR 62820A×RG-BU 08-097R and IR 62820A×RG-BU 08- 105R) where as only two F1s were found having 80% and above both pollen and spikelet’s fertility i.e., IR 62820A×RG-BU 08-002R and IR 62820A×RG-BU 08-007R. Li et al. [14] identified R899 as an earlymaturing restorer line. Its characteristics include desirable agronomic traits, strong restoring ability, strong resistance to rice blast, fine grain quality and high hybrid seed yield. The hybrid combinations displayed high and stable grain yield, fine grain quality, suitable growth period and wide adaptability. Five out of sixteen F1 crosses with IR 62820A showed above 80% pollen and spikelet fertility. Such results indicated that only five lines have desirable restoration ability in hybrids with IR 62820A. In case of IR 68888A only two restorers were found effective [15-17]. Further study on the performance of F1 hybrids obtained from crosses between IR 62820A and IR 68888A and the selected five and two restorer lines may done for identification of desirable rice hybrid.



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