CMS Lines Research Articles

Combining ability studies in sunflower (Helianthus annuus L.)

Combining ability studies were made in sunflower using line x tester analysis with three CMS lines and ten testers. Ten important yield traits viz., days to 50% flowering, number of leaves/plant, plant height, stem girth, head diameter, number ofseeds/head, autogamy per cent, 100-seed weight, seed yield/plant and oil content were studied. Non-additive gene action was predominant for all the traits. Based on general combining ability of parents, the line 234 A was found to be good general combiner for days to 50% flowering, stem girth, head diameter, number of seeds/head, 100-seed weight, seed yield/plant and oil content. Three testers viz., RHA 83R6, RHA 17 and DRSF 110 R exhibited higher gca effects for most of the yield traits and these parents can be considered as good general combiners. The hybrid NDCMS 1A x RHA 6D-5-3-6 possessed superior sca effects for six traits viz., days to 50% flowering, head diameter, number of seeds/head, autogamy per cent, 100-seed weight and seed yield/plant. Three hybrids viz., 234 A x DRSF 111 R, NDCMS 1A x RHA 83R6 and 234 A x RHA 859-2 can be considered as good specific combiners for exploitation of yield and its components. Hybrid 234 A x RHA RR 2 was the best for stem girth, head diameter, 100-seed weight and seed yield/plant. These above mentioned hybrids can be considered as good specific combiners.

Heterosis studies in rice for the identification of better hybrids for Telangana, India

In the present study, 23 elite rice genotypes were test crossed with IR 58025A and based on which, 12 restorer lines viz., Rajendra, MTU 1010, IR 64, KNM 118, NLR 33358, Satya, Varalu, RNR 15048, RNR 15038, Tel- lahamsa, RNR(RK) 28 and RNR(RK) 53 were identified during Kharif- Rabi 2013-14. Then, three CMS lines viz., IR 58025A, IR 68902A and IR 72081A were crossed with these identified 12 restorer lines to produce 36 hybrids in line × tester mating design and were evaluated along with standard hybrid check, PA 6129 at Rice Research Centre, Rajendranagar, during Kharif 2014 to find out the best heterotic combinations in terms of grain yield and yield component characters. The degree of heterosis varied from trait to trait. Out of 36 hybrids studied, the significant standard heterosis for grain yield is observed in 3 hybrids, over best check PA 6129, viz., IR 58025A × MTU 1010 (18.25), IR 68902A × RNR 15038 (14.59) and IR 72081A × RNR 15038 (9.57). The best experimental hybrid IR58025A × MTU 1010 recorded average heterosis (78.26) and heterobeltiosis (64.37). These three experimental hybrids can be further evaluated over locations for large scale commercialization in Telangana.

Identification of fertility restorers and maintainers in sunflower (Helianthus annuus L.) from gene pools and exotic material

Diversification of parental base in any hybrid breeding programme is an important step to sustain the crop. For considering above was taken up to explore the possibilities of finding out good restorers and maintainers of sunflower based on sterility and pollen fertility. Thirty two inbreds of sunflower from gene pool (GP lines) and fourteen exotic collection (EC lines) inbreds of economic importance were crossed with six cytoplasmic male sterile lines viz., CMS-17A, CMS-2A, CMS-10A, CMS-234A, CMS-852A and CMS-7-1A in a Line x Tester fashion to study their maintainer or restorer reaction during kharif -2014. The accessions from gene pool, GP 6 -1051 acted as restorers for all six CMS lines. GP 6 -46 and GP 6 -236 were acted as restorers for CMS-10A, CMS-234A, CMS-852A and CMS-7-1A. It was found that GP 6 -54 of the restorer for CMS-10A and CMS-852A and maintainer for other CMS lines. From exotic collection EC-601622, EC-601664, EC-601666, EC-601672, EC-601691, EC-601726, EC-601821, EC-601848 and EC-601711-1 were acted as restorers for all six CMS lines. Majority of the gene pool lines and exotic collection were behaved as maintainer for all the CMS. The range of fertility restoration in different cross combinations was between 93.1 and 97.8 per cent. In the present study maximum frequency of pollen fertility restoration was reported for CMS-7-1A (41.3%) followed by CMS-852 (36.95%), CMS-234A (36.95%) and CMS-10A (34.78%). However, lowest frequency of pollen fertility restoration was observed for CMS-17A (28.26%).From the study it was evident that among the six CMS lines, restorers for CMS-17A are rather scarce. Efforts should be made to locate restorers for CMS-17A for its utilization in breeding of more productive sunflower hybrids.

Combining Ability Analysis and Gene Action Studies of Different Quantitative Traits in Sunflower by Line x Tester

Four CMS lines and four restorers were crossed in a line x tester fashion to elucidate the information on the combining ability of seed yield, yield components and also to know the nature of gene action involved in inheritance of important quantitative traits. A total of 16 crosses were evaluated for eight different quantitative traits. Line CMS-HA-03 and CMS-HA-54 exhibited maximum GCA effects for most of the characters studied and were found to be the good general combiners. Likewise, tester RHP-73 was the good general combiners for most of the traits under study. Similarly cross combinations viz., CMS-HA-111 × RHP-71 and CMS-HA-03 × RHP- 76 were observed as potential cross having desirable SCA values.The estimates of variance components revealed predominance of non-additive gene action for all characters studied except days tomaturity.

Identification of restorers and maintainers among the locally adapted genotypes for hybrid development in rice (Oryza sativa L.)

Two cytoplasmic genic male sterile lines of rice viz., CO MS 24A and TNAU CMS 2A having wild abortive source were crossed with 20 testers to identify their restorer/maintainer nature. Total of 40 hybrids were subjected to pollen and spikelet fertility analysis along with their parents. Six effective restorers and eight maintainers were identified among the 20 genotypes. TKM 9 was found to be a common maintainer for CGMS lines TNAU CMS 2A and COMS 24A and the genotype ADT 37 was identified as restorer for both the CGMS lines COMS 24A and TNAU CMS 2A. The identified restorers and maintainers could be utilized for development of new rice hybrids and CMS lines in future.

Combining Ability Studies in Rice Hybrids Involving New CMS Lines in Bangladesh

Combining Ability Studies in Rice Hybrids Involving New CMS Lines in Bangladesh

Estimation of heterosis in pearl millet [Pennisetum glaucum (L.)] for yield and quality traits

Five CMS lines were crossed with nine testers in a line x tester design to study the extent of heterosis in pearl millet for yield and quality traits. Heterosis was observed in both directions for most of the characters. High magnitude of heterosis was observed for plant height, ear head girth, ear head weight, grain yield per plant and harvest index. The heterosis was moderate for Fe content, Zn content and test weight. The heterobeltiosis for grain yield per plant ranged from -26.50 to 200.00 per cent, while the standard heterosis ranged from -53.38 to 37.79 per cent. The highest heterobeltiosis was recorded by cross JMSA 1 20141 x 149-SB-14 and JMSA 5 20142 x J-2340 followed by JMSA 1 20141 x 81-SB-14, ICMA 4 10444 x 149-SB-14. The cross JMSA 5 20142 x J-2340, ICMA 4 10444 x J-2340 and ICMA 4 10444 x 149-SB-14 recorded the highest standard heterosis for grain yield per plant. These crosses also exhibited desirable heterosis for important yield attributes suggesting that the heterosis for grain yield per plant was associated with heterosis for component character. Thus, these hybrids can be commercially exploited through heterosis breeding programme after testing in multilocational trial to work out its stability and in diseases screening trial to find out its resistance capacity against major pearl millet diseases in order to achieve hybrids with high grain yield in pearl millet.

Total Antioxidant Potential of Pearl Millet Genotypes: Inbreds and Designated B-lines

Antioxidant potential was measured by estimation of total antioxidant activity (TAA) of 92 pearl millet genotypes comprising 46 each of inbreds and designated B-lines (maintainer of CMS lines) grown during kharif-2013 and those of the 27 genotypes (9 inbreds and 18 designated B-lines) selected during kharif-2013 further grown during kharif-2014. TAA was estimated by 2, 2-diphenyl-1-picrylhydrazyl (DPPH) method as well as by 2, 2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS+) method. All the genotypes showed appreciable amount of TAA irrespective of the method used. Average TAA of total genotypes screened during kharif-2013 was 1032 ig Vit. C equi./g with a wide significant variation from 332 to 1529 μg Vit. C equi./g. The designated B-lines had higher average TAA (1127 μg Vit. C equi./g) than that of inbred lines. During kharif-2014 the average TAA of selected lines varied from 549 to 1880 μg Vit. C equi./g with an average value of 1087 μg Vit. C equi./g (DPPH method) and from 3970 to 6804 μg Trolox equi./g with an average value of 5360 μg Trolox equi./g (ABTS+ method). The average TAA of pearl millet genotypes (DPPH method) was significantly higher than that of commercial samples of wheat (550 μg Vit. C equi./g) and maize (680 μg Vit. C equi./g) procured from local market and tested along with.

Identification of fertility restorers among Assam rice cultivars by phenotyping and molecular screening approaches

In three line hybrid rice seed production the combination of a CMS line, maintainer line and restorer line are involved in the development of hybrids. The wild abortive CMS is extensively used in commercial hybrid seed production. The fertility restoration of wild abortive CMS is governed by two independent dominant Rf genes viz., Rf4 and Rf3. The present study was conducted with the objective of molecular characterization rice genotypes from Assam, India and to identify restorers for hybrid rice breeding programme. A total one hundred and eleven hybrids were generated and evaluated for their pollen and spikelet fertility. Based on molecular screening twenty five genotypes were identified to carry only Rf4 gene and three genotypes identified to carry both Rf3 and Rf4 genes. These identified restorers in the present study would be a usable restores for hybrid rice breeding in north east India. Molecular diversity for fertility restoration using NTSYS package formed two clusters among the tested genotypes, cluster A represented a landrace Terabali from Assam and cluster B with all other genotypes.

Components of Variance Analysis in Pearl Millet (Pennisetum glaucumL.)

One hundred germplasm lines (83 inbreds and 17 CMS lines) were evaluated for morpho-physiological traits of pearl millet and were sown in randomized complete block design with two replications at Forage and Millet Research Farm, Punjab Agricultural University, Ludhiana, during summer 2013. Large variations were observed for all the characters studied. Based on mean performance BDRC1, EDC and PIB-258-T were identified as early flowering and best grain yielding lines. PIB-258-T and PIB-1268 were identified as dual purpose i.e. excellent in grain yield, chlorophyll content and stover yield as well. Maximum phenotypic and genotypic coefficient of variation was observed for grain yield (45.83; 43.57), spike sterility (42.93; 35.31) and stover yield (39.57; 33.86). The highest heritability and expected genetic advance (% of the mean) were observed in grain yield (92.8%; 85.35%) and downy mildew (90.13%; 59.29%), respectively. Thus the data have the direct relevance in identifying best desired plant model of pearl millet as summer crop.

Partial conversion of elite maintainer genotype mas99 into new male sterile line suitable for aerobic and drought conditions through backcross breeding in rice

Two populations were developed and advanced to BC3 generation using IR70369A and KCMS31A CMS lines as donors and MAS 99 as recurrent parent. In BC3F1 generation, the populations were evaluated with parents for morpho-floral traits under aerobic field condition. In both crosses, the mean values of number of tillers/plant (22 & 27), plant height at maturity (74 & 73cm), days to 50% flowering (95 & 97 days) were found comparable to the recurrent parent with superior floral traits such as pollen sterility (100%), stigma exertion (30% & 25%) and spikelet sterility (100%). IR70369A × MAS99 cross derived plants, A04, A35, A47, A65, A84 and KCMS31A × MAS99 cross derived plants, B06, B27, B30, B34 and B44 were identified as superior MAS99 converted CMS plants as indicated by morpho-floral traits and advanced to BC4F1. Between two crosses, IR70369A × MAS99 cross derived population was superior for days to 50% flowering and stigma exertion rate.

Effect of cytoplasmic male sterility type on chlorophyll content in leaves of grain sorghum hybrids

New types of CMS-inducing cytoplasms cannot be applied to hybrid sorghum breeding without knowledge of their effects on major biological and commercial plant traits. In our studies of F1 hybrids obtained by crossing of two sets of isonuclear CMS lines (with nuclear genomes of cv. Pishchevoye 614 (P614) and Zhelyozyornoye 10 (Zh10)) to two pollen parents (cv. Pishchevoye 35 (P35) and Mercury), we focused our attention on the effects of A3, A4, 9E, and M35-1A cytoplasms on chlorophyll content at different developmental stages of sorghum plants. It was found that hybrids with different types of male-sterile cytoplasm differed in chlorophyll content, and the genotypes of the CMS line and the pollen parent influenced the manifestation of cytoplasmic differences. In the F1 hybrids obtained with CMS lines possessing the P614 genome, sterile M35-1A cytoplasm increased chlorophyll a content, in comparison to 9E cytoplasm. In the F1 hybrids obtained with CMS lines with the Zh10 genome and the P35 pollen parent, sterile A4 cytoplasm increased the sum of chlorophyll a and b, in comparison to A3 and 9E cytoplasms, whereas no differences were recorded in the F1 hybrids obtained with Mercury. The F1 hybrids obtained with CMS lines with the P614 genome showed heterosis for total chlorophyll content at the tillering stage. Overdominance of this trait was observed in hybrids with M35-1A cytoplasm; true heterosis exceeded analogous indices in 9E cytoplasm by 19.0 %, and the hypothetical heterosis, by 20.6 %. These data demonstrate that the application of new types of CMS-inducing cytoplasms allows raise of F1 hybrids with heterosis for chlorophyll content. Thus, such types can be used to increase hybrid productivity.

COMBINING ABILITY AND HETEROSIS IN QUASI AROMATIC RICE (Oryza sativa L.)

The experiment was conducted to study general and specific combining ability (GCA and SCA) and to estimate heterosis estimation at experimental farm of Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur during T. Aman, 2006 and 2007 seasons. Eleven rice parental lines consisting of two quasi CMS lines in BC3 generation as lines and nine restorer lines as testers along with their eighteen F1s and a check variety (BRRI dhan37) were used for combining ability study in a line x tester mating design for eight characters. Ratio of general combining ability (GCA) to specific combining ability (SCA) variances above unity were observed for 1000-grain weight(g) indicating predominance of additive gene action for controlling the character. Among mother parents, CMS-1 appeared as good general combiner for panicle length, 1000-grain weight(g), and grain length–breadth ratio. Among male parents, Benaful, Oval Tapi and Sorukamini-1 were observed to be good general combiners for most of the characters studied. The cross combinations, CMS-1 × Kataribhog, CMS-2 × Maloti-1 and CMS-2 × Keora were found as good specific combiners for most of the characters under study. Good specific combiners were evolved from all kinds of combinations of general combiners indicating additive and non-additive types of gene effect for inheritance. Maximum hybrids showed desired significant standard heterosis for panicle length and 1000-grain weight. None of the hybrids showed desired and significant standard heterosis simultaneously for any three or more characters.

Mitochondrial SSRs and their utility in distinguishing wild species, CMS lines and maintainer lines in pigeonpea (Cajanus cajan L.)

AbstractAnalysis of the pigeonpea mitochondrial genome sequence identified 25 SSRs. Mononucleotide SSR motifs were the most abundant repeats followed by dinucleotide and trinucleotide repeats. Primer pairs could be designed for 24 SSRs, 23 of which were polymorphic amongst the 22 genotypes consisting of cytoplasmic male sterile (CMS or A) line, maintainer or B line and wild Cajanus species representing six different CMS systems viz., A1, A2, A4, A5, A6 and A8. These markers amplified a total of 107 alleles ranging from 2 to 10 with an average of 4.65 alleles per locus. The polymorphic information content for these markers ranged from 0.09 to 0.84 with an average of 0.52 per marker. Hence, the present study adds a novel set of 24 mitochondrial SSR markers to the markers repository in pigeonpea, which would be useful to distinguish the genotypes based on mitochondrial genome types in evolutionary and phylogenetic studies.

ESTIMATION OF STANDARD HETEROSIS FOR REPRODUCTIVE TRAITS IN NEWLY SYNTHESIZED TEST RICE (Oryza sativa L.) HYBRIDS

An experiment was carried to estimate heterotic performances of newly developed test hybrids utilizing CMS system during Rabi 2011 using RCBD design. Five known CMS lines and sixteen developed R-lines were crossed through line × tester analysis. Eighty test hybrids were developed. It is very difficult to find a hybrid earlier to BRRI dhan28 as life cycle of 140 days. Heterosis for days to first flowering varied from -6.23% to 16.35% with a SD of 4.47 meanwhile heterosis for days to 80% flowering varied from -9.24% to 11.04% with a SD of 4.03. Among eighty crosses seventy two were found positive heterosis for days to first flowering but sixty four crosses were found for days to 80% flowering. RG-BU08-016R crosses with IR58025A (-2.68*) and IR62820A (-3.42**) showed significant negative standard heterosis for days to first flowering. Five crosses of IR58025A showed significant negative heterosis with RG-BU 08-005R (-3.42*), RG-BU 08-006R (-5.28**), RG-BU 08-013R (-4.129**), RG-BU 08-016R (-5.78**), RG-BU 08-018R (-4.06*) for days to 80% flowering. Besides these 4 crosses of IR62820A showed significant negative heterosis with RG-BU 08-007R (-2.32*), RG-BU 08-016R (-6.03*), RG-BU 08-018R (-4.58**) followed by GAN 46A/RG-BU 08-006R (-4.58*), BRRI 1A/RG-BU 08-001R (-2.55**) and BRRI 1A/RG-BU 08-006R (-9.24**) resulted significant negative heterosis for days to 80% flowering. Positive heterosis were recorded for IR58025A with RG-BU 08-007R (26.97**), RG-BU 08-0046R (8.77**) and RG-BU 08-105R (14.44**) for PER and RG-BU 08-018R (42.46**), RG-BU 08-046R (112.30**), RG-BU 08-057R (27.46*) for SER. While two R-lines, RG-­BU 08-013R (25.41**) and RG-­BU 08-057R (7.21*) were found having significant positive heterosis for panicle exertion rate crosses with IR62820A but RG-BU 08-025R (52.82**), RG-BU 08-057R (122.66**) and RG-BU 08-063R (37.38**) were found having significant positive heterosis for SER. IR62820A/RG-BU08-057R showed significant positive heterosis for both panicle and stigma exertion rate. GAN46A/RG­-BU 08-063R (5.65* & 133.02**) was recorded showing significant positive heterosis for both panicle and stigma exertion rate where. But the crosses of IR68888A was not shown exhibiting a great contribution for panicle and stigma exertion rate except RG-BU08-018R (25.94**). Meanwhile the crosses of BRRI1A was recorded having significant positive heterosis for PER with RG-­BU08-005R (13.41**), RG-­BU08-007R (5.65*) and RG-BU08-097R (25.94**) as well as RG-BU08-007R (133.02**), RG-BU08-013R (48.19**) and RG-BU08-038R (29.21*) were recorded having significant positive heterosis for SER.

GENETIC DIVERSITY AMONG MAINTAINER LINES OF RICE (Oryza sativa L.) BASED ON CLUSTER ANALYSIS

An experiment was conducted at the experimental field of Bangladesh Rice Research Institute (BRRI), Gazipur during T. Aman season 2007. Ten maintainer lines were evaluated to identify most diverse maintainer lines in respect of morphological traits for developing heterotic rice hybrids based on clustering and days to maturity. Based on mean values of different morphological traits and maturity, 10 maintainer lines were classified into four distinct clusters. Maximum Euclidean distance from centroids was observed in cluster 2 whereas cluster 3 and 4 found in the centroids. Most of the maintainer lines were grouped into early and medium maturing clusters while the remaining two lines were clustered into very early and late maturing clusters. Very early maturing group contained maintainer line (D.ShanB) with dissi cyto source and fell into cluster 3. It had short plant stature with short flag leaf but had high spikelet fertility and thousand grain weight. Early maturing group contained maintainer lines having 4 different cyto sources revealed early maturing group featured with cyto source variation with high panicle number/m2 and very good yield potentiality. Grouping the maintainer lines on the basis of maturity period yield per plot was proportionally higher in late maturing line. Only a single line Gan46B fell into late maturing group and had highest yield. This fact suggests possibility of corresponding CMS line of Gan46B could be used as female if restorer lines are selected from early maturing group. Medium maturing group had some added advantage like medium duration with diverse cyto sources and good yielding ability. If restorer lines are selected from late maturing group with high yield potentiality proper hybrid rice combination become available for Boro season and it would be better because rice hybrid perform better under irrigated Boro eco system. One hundrade and nineteen days growth duration also very good for T. Aman season.

COMBINING ABILITY EFFECTS AND PER-SE PERFORMANCES OF MORPHO REPRODUCTIVE TRAITS IN RICE (Oryza sativa L.)

To study combining ability effects of developed CMS and restorer lines an experiment was carried out at the experimental farm, Department of Genetics and Plant Breeding, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Salna, Gazipur during Aman 2011 and Boro 2011-12 following RCBD design through line × tester analysis in three replications. Five known CMS lines and sixteen developed Restorer lines were considered for through line × tester analysis. Among sixteen restorer lines, only four showed significant negative GCA effects for all these three traits for earliness. The estimated of gca effects of parents indicated that seven parents and sixteen crosses contributed highly significant negative effects for plant height which were responsible for dwarfing character. Fifteen crosses and eight parents showed significant negative sca estimates for days to first flowering and twenty crosses for maturity. Considering both SCA effects and per se performances for days to 1st flowering and maturity; the crosses of IR 58025A with RG-BU08-005R, RG-BU08-006R, RG-BU08-016R, RG-BU08-018R and RG-BU08-025R were found as the best specific combiner. Among 80 crosses fifty two crosses showed significant positive SCA effects along with above average perse performances for grain yield. Ten crosses of IR 58025A, seven crosses of GAN46A, fourteen crosses of IR 62829A, nine crosses of IR 68888A and ten crosses of BRRI 1A showed significant positive SCA effects along with mean values resulting significant positive SCA effects and above average perse performances with all five CMS lines for grain yield.

Molecular characterization and application of a novel cytoplasmic male sterility-associated mitochondrial sequence in rice.

BackgroundCytoplasmic male sterility (CMS) is a maternally inherited inability to produce functional pollen found in numerous flowering plant species. CMS is associated with mitochondrial DNA mutation, novel chimeric open reading frames (ORFs), and rearrangement of coding and noncoding regions of the mitochondrial genome.ResultsBLAST (Basic Local Alignment Search Tool) analysis indicated that L-sp1, a new sequence-characterized amplified region, is non-homologous to atp6-orfH79 (or atp6-orf79) and WA352 cloned CMS-associated genes. L-sp1 was found in 11 of 102 wild rice accessions belonging to four AA genome species: Oryza rufipogon, Oryza nivara, Oryza glumaepatula, and Oryza meridionalis. Using L-sp1, two new CMS lines were developed, from either low natural fertility plants or sterile plants, by backcrossing BC1F1 with Yuetai B. Northern blot and RT-PCR revealed that L-sp1 was only expressed in the anthers of w1/YTB, w2/YTB, w1/YTB//YTB, and w2/YTB//YTB when in the same cytoplasm background.ConclusionsL-sp1 is a single-copy chimeric CMS-associated gene found in the mitochondrial genome. It can be expressed in anthers with the same specific cytoplasm background, and will be a useful molecular marker for the development and marker-assisted selection of new CMS lines.Electronic supplementary materialThe online version of this article (doi:10.1186/s12863-015-0205-0) contains supplementary material, which is available to authorized users.

Inheritance of reversions to male fertility in male-sterile sorghum hybrids with 9E male-sterile cytoplasm induced by environmental conditions

Heritable phenotypic alterations occurring during plant ontogenesis under the influence of environmental factors are among the most intriguing genetic phenomena. It was found that male-sterile sorghum hybrids in the 9E cytoplasm from the F1 and F2 generations, which were obtained by crossing CMS lines with different fertile lines grown in field conditions, when they have been transferred to greenhouse produce fertile tillers. Lines created by the self-pollination of revertant tillers exhibit complete male fertility upon cultivation under various environments (in the field, “dry plot,” “irrigated plot”). In a number of test-crosses of revertants to CMS lines in the 9E cytoplasm, restoration of male fertility in F1 hybrids was found, indicating that revertants possess functional fertility-restoring genes. A high positive correlation was found between the fertility level of the test-cross hybrids and the hydrothermal coefficient (the ratio of the sum of precipitation to the sum of temperatures) during the booting stage and pollen maturation (r = 0.75…0.91; P < 0.01), suggesting that a high level of plant water availability is needed for the expression of fertility-restoring genes of revertants. These data show that the fertility-restoring genes for the 9E cytoplasm are dominant in conditions of high water availability and recessive in drought conditions; reversions to male fertility are due to up-regulation of fertility-restoring genes by a high level of water availability. Comparative MSAP-analysis of DNA of malesterile and male-fertile test-cross hybrids using HpaII/MspI restrictases and primers to polygalacturonase gene ADPG2, which is required for cell separation during reproductive development, and gene MYB46, the transcription factor regulating secondary wall biosynthesis, revealed differences in the number and the length of amplified fragments. Changes in the methylation of these genes in conditions of drought stress are apparently the reason for male sterility of sorghum hybrids in the 9E cytoplasm. These data demonstrate that methylation of nuclear genes in sterility-inducing cytoplasm may be one of mechanisms causing the CMS phenomenon.

In vitro maintenance of CMS lines of Indian cauliflower: an alternative for conventional CMS-based hybrid seed production

SummaryThree Ogura cytoplasmic male-sterile (CMS lines) of Indian cauliflower (Brassica oleracea var. botrytis L.; Ogu1A, Ogu2A and Ogu3A) were compared for their in vitro regeneration ability using two types of explant, hypocotyls and curds (i.e., pre-floral fleshy apical meristems). The highest rate of in vitro establishment and the highest multiplication index were recorded in Ogu3A. Ogu2A showed poor in vitro establishment. The choice of explant had a significant impact on the morphogenetic potential of all three lines. Among the two types of explant, curds proved to be more efficient for the initial establishment of cultures.The highest rate of in vitro establishment and multiplication index were recorded for Ogu3A on Murashige and Skoog (MS) medium supplemented with 2.5 mg l-1 kinetin, 0.2 mg l-1 _- naphthaleneacetic acid and 0.2 mg l-1 gibberellic acid. The three CMS lines also showed significant variations in the numbers of roots induced per shoot.The maximum number of primary roots per shoot was recorded in Ogu3A on 0.5_ MS medium supplemented with 1.0 mg l-1 indole-3-butyric acid. In vitro-raised plants were hardened and used successfully for F1 hybrid development.When the F1 hybrids developed using in vitro-maintained or conventionally maintained CMS lines were compared, it was observed that variations in plant height, days to 50% curd maturity (DCM), and net curd fresh weight (FW) were lower in those F1 hybrids developed through in vitro-maintained CMS lines. In F1 hybrids developed from in vitro-raised CMS lines, the range of standard deviation (SD) values as percentages of the mean value for DCM and net curd FW were 2.5 - 3.7% and 6.6 - 10.7%, respectively. In contrast, the corresponding SD values ranged from 5.8 - 7.9% and from 13.6 - 19.9% for F1 hybrids developed from conventionally maintained CMS lines.This in vitro protocol, using curd explants, will be useful for the rapid multiplication of breeding lines of cauliflower without inbreeding depression, and for high-quality hybrid seed production.