Characterization of the A4 cytoplasmic male-sterile lines of sorghum using RFLP of mtDNA

Three sorghum cytoplasmic male sterile lines CSV4 A(V), CSV4 A(G₁) and CSV4 A(M), grouped as A₄, were compared with a milo (A₁) and two other non-milo (A₂ and A₃) cytoplasms for their RFLP patterns of mitochondrial DNA (mtDNA). A 9.7 kb clone from pearl millet mtDNA discriminated each of the three A₄ entries whereas other maize and pearl millet mtDNA clones used could not distinguish this group completely. The molecular differences within the A₄ cytoplasmic group offer some explanation for the inconsistency in the fertility restoration behaviour of these A₄ lines obtained with a definite set of testers in the field. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genetics of fertility restoration in A2-based cytoplasmic genetic male sterility system in pigeonpea (Cajanus cajan)

The three short duration cytoplasmic genetic male sterility (CGMS) hybrids developed using A₂ (Cajanus scarabeoides) cytoplasm-based male sterile lines (CORG 990047A, CORG 990052A and CORG 7A) and the restorer inbred AK 261322 and their segregating populations (F₂ and BC₁F₁) were subjected to the study of inheritance of fertility restoration in pigeonpea. The fertility restoration was studied based on three different criteria, namely, anther colour, pollen grain fertility and pollen grain morphology and staining. The F₂ and BC₁F₁ populations of the three crosses, namely, CORG 990047A × AK 261322, CORG 990052A × AK 261322 and CORG 7A × AK 261322, segregated in the ratio of 3:1 and 1:1, for anther colour (yellow:pale yellow), pollen grain fertility (fertile:sterile) and for pollen grain morphology and staining. The above study confirmed that the trait fertility restoration was controlled by single dominant gene. This finding can be utilized for the identification of potential restorers, which can be further used in the development of CGMS-based hybrids in pigeonpea.     

Fertility restoration of new CMS sources in sunflower (Helianthus annum L.)

The development of commercial sunflower hybrids based on new CMS sources is of special interest for reducing the potential risk of vulnerability to pathogens and for increasing genetic diversity. From 263 test crosses involving nine new CMS sources, i.e. ANL1, ANL2, MAX1, PEF1, PET2, ANN1, ANN2, ANNS and ANN4, five lines were selected as potential restorers for PEF1, PET2 and ANN4. In test crosses between all nine CMS sources and these five restorer lines evaluated in 2 years, seven fully restored hybrids could be identified. These hybrids, based on ANL1, ANL2, MAX1, PEF1, PET2, and ANN4, showed good agronomic performance for plant height, days to flowering, maturity and oil content. Segregation analyses of the F2 populations indicate that a single dominant restorer gene was sufficient to restore pollen production of hybrids based on ANL2, PEF1 and PET2. For restoration of ANN4, two dominant complementary genes are required. In restoration of fertility in the crosses of ANL1 and MAX1 investigated, two dominant genes are involved each of which on its own allows the production of fertile plants.     

Frequency and fertility restoration efficiency of Rf3 and Rf4 genes in Indian rice

Identification of new parental lines is crucial for developing ecology‐specific hybrids with ideal agronomic performance. We screened a total of 570 different ecology‐specific Indian rice varieties for the presence of fertility restorer genes, Rf3 and Rf4 using tightly linked markers DRRM Rf3‐10 and RM6100, respectively. Among these varieties, 13% carried Rf3Rf3/Rf4Rf4, 31% carried rf3rf3/rf4rf4, 6% carried Rf3Rf3/rf4rf4 and remaining 50% carried Rf4Rf4/rf3rf3 allelic combinations. A mini set of 40 varieties with variable allelic combinations of fertility restorer genes were testcrossed with WA and Kalinga‐based CMS lines. All the 80 F₁s were evaluated for spikelet fertility and fertility restoration ability. Rf3Rf3/rf4rf4 genotypes mostly behaved as partial maintainers or partial restorers. In contrast, rf3rf3/Rf4Rf4 genotypes were partial or effective restorers. However, double dominant genotypes showed better fertility restoration than the genotypes containing Rf3 or Rf4 individually. Some of the genotypes showed unexpected restoration pattern implying occurrence of other fertility restorer(s) apart from Rf3 and Rf4. The perfect restorers and maintainers identified in this study can be directly used in hybrid rice breeding.     

A unique introgression from Moricandia arvensis confers male fertility upon two different cytoplasmic male-sterile lines of Brassica juncea

A Brassica juncea line carrying an introgression from Moricandia arvensis restored male fertility to two cytoplasmic male‐sterile (CMS) B. juncea lines carrying either M. arvensis or Diplotaxis catholica cytoplasm. Genetics of fertility restoration was studied in the F₁, F₂, F₃ and backcross generations of the cross between CMS and fertility‐restorer lines. No male‐sterile plants were found in F1‐F₃ generations of the cross between CMS [M. arvensis] B. juncea and the restorer. However, a 1: 1 segregation for male sterility and fertility was observed when the F1 was pollinated with non‐restorer pollen from a euplasmic line. These results clearly show that restoration is mono‐genic and gametophytic. In CMS lines carrying D. catholica cytoplasm, the restorer conferred male fertility to the F1 and showed 3: 1 and 1: 1 segregations for male fertility and sterility in F₂ and BC1 generations, respectively, indicating a monogenic, sporophytic mode of fertility restoration. The results were also supported by pollen stainability in the F1 which was about 65% in M. arvensis‐based CMS and >90% in D. catholica‐based CMS. The above results are discussed in the light of previous molecular studies which showed association between CMS and atpA in both systems.     

Tournefortii male sterility system in Brassica napus. Identification, expression and genetic characterization of male fertility restorers

A germplasm collection of 152 diverse rapeseed accessions from Canada, China, France, India, Poland and South Korea was assayed for identifying new fertility restorers and sterility maintainers for a Tournefortii (tour) cytoplasmic male sterility (CMS) system in rape‐seed. Only 16 (10.5%) genotypes showed complete fertility restoration following hybridization with tour CMS line NE 409A. Notable among these were GSL 8851, GSL 8953, Mokpo # 9, Mali, Buk‐wuk‐13, Kuju‐27 and Mokpo # 84. As many as 78 (51.3%) genotypes were perfect maintainers of sterility, the remaining 58 (38.2%) genotypes were classified as partial maintainers. To study the inheritance of fertility restoration, 20 CMS (tour) rapeseed lines were crossed with the four best fertility restorers, namely GSL 8851, GSL 8953, Kuju‐27 and Mokpo # 9, to obtain F₂ and test cross populations. Segregation data indicated that fertility restoration for tour CMS was governed by two genes, of which, one is stronger than the other (χ²_12:3:1). Differences in gene interactions were also observed (χ²_9:3:4) which could be explained on the basis of influence of female parent genotypes/or modified expression of the restorer gene(s) in different genetic backgrounds. Tests of allelism indicated that the restorer genes present in the four restorers evaluated were allelic.     

Combining ability of non‐adapted sources for male‐fertility restoration in Pampa CMS of hybrid rye*

Hybrid rye breeding and seed production relies on the cytoplasmic male sterility‐inducing Pampa (P)‐Cytoplasm. High levels of restoration were recently found in non‐adapted rye accessions from Argentina (Pico Gentario, Pastoreo Massaux) and Iran (IRAN IX). To analyse their relative superiority, five seed‐parent lines in P cytoplasm were crossed with five inbred lines of these sources and four adapted restorer lines. The 45 F1 hybrids were tested for male‐fertility restoration in three locations. Significant (P = 0.01) general and specific combining ability (GCA and SCA respectively) for male‐fertility restoration were found. The non‐adapted restorer lines were able to restore all seed‐parent lines similarly, resulting in hybrids with 55‐90% pollen shedding (mean 78%) compared with 2‐74% pollen shedding (mean 44%) when adapted restorer lines were used. Significant (P = 0.05) SCA effects were detected in 11 of 45 combinations, nine of them were crosses with adapted pollinator lines. Non‐adapted restorer lines showed a high phenotypic stability of male‐fertility restoration across locations. Introgression of these exotic sources into the adapted restorer gene pool by repeated backcrossing should result in environmentally stable male fertility in Pampa‐based rye hybrids.     

Genetic analysis of fertility restoration against photoperiod-sensitive cytoplasmic male sterility in Triticum aestivum cv. Norin 61

Triticum aestivum cv. Norin 26 with the Aegilops crassa cytoplasm becomes almost completely male sterile when grown under a long-day condition (15 h of light or longer), but is highly male fertile under a short-day condition (14.5h or less). This type of male sterility is called photoperiod-sensitive cytoplasmic male sterility (PCMS). Genetic analyses were made of the fertility-restoring (Rf) genes effective against PCMS that are present in T. aestivum cv. Norin 61. Conventional and monosomic studies indicated that restoration of fertility is controlled by multiple Rf genes located on at least four chromosomes: 4 A, 1D, 3D and 5D. The genetic mechanism of fertility restoration by the genes of‘Norin 61’differs from the mechanisms reported for‘Chinese Spring’and a‘Norin 26’mutant line.     

Inheritance and gene tagging of male fertility restoration of cytoplasmic-nuclear male-sterile line NJCMS1A in soybean

The F₁, F₂ and F_2:3 of the NJCMS1A × 'Zhongdou 5' cross were used to analyse the inheritance of the male fertility restoration of the cytoplasmic-nuclear male-sterile line NJCMS1A in soybean. The results of genetic analysis showed two pairs of dominant genes conferring the male fertility restoration of NJCMS1A, which further confirmed previous results. The F₂ population from the NJCMS1A × 'Zhongdou 5' cross was used for tagging the restorer genes for NJCMS1A with 664 pairs of simple sequence repeat primers selected randomly from the genetic linkage map of soybean published by Cregan et al. (1999) . Satt626 on linkage group M and Satt300 on linkage group A1 of the integrated linkage map by Song et al. (2004) were found to link to the two restorer genes of NJCMS1A. The maximum-likelihood estimates of the genetic distance between the two markers, Satt626 and Satt300, and the two restorer genes of 'Zhongdou 5' were 9.75 and 11.18 cM, respectively.     

Cytoplasmic male sterility in barley. III. Maintenance of sterility and restoration of fertility in the msml cytoplasm

Summary 58 varieties, strains or mutants of barley were tested in the msml cytoplasm in Finland, location ca. 61 N. Three (5%) were found to be partial restorers, the rest being maintainers of sterility. 31 Israeli strains of wild barley (ssp. spontaneum) were tested. About one third were maintainers of sterility, the majority partial restorers, and two strains were full restorers. There is probably polymorphism of the restorer gene in Israeli wild barley. Partial restoration displays an environmental response. The physiology of partial restoration is discussed.     

Mapping of minor quantitative trait loci (QTLs) conferring fertility restoration of wild abortive cytoplasmic male sterility and QTLs conferring stigma exsertion in rice

Cytoplasmic male sterility (CMS) hybrid rice has made a great contribution to the increase of rice yield globally. To facilitate the development of high‐quality pairs of the wild abortive (WA) male sterile and maintainer lines, the genetic basis of fertility restoration of WA‐CMS and stigma exsertion was investigated in this study using a testcross population with the WA‐CMS background. Seed‐setting rate and stigma exsertion rate were used as the indicators of the two traits, respectively. Results showed that four minor QTL regions from 9311 were responsible for the variation of seed‐setting rate, while a few minor QTLs and epistatic QTL pairs influenced stigma exsertion rate. These results would be of great use in the development of high‐quality pairs of WA male sterile and maintainer lines in rice.     

两份玉米CMS-C恢复系的育性恢复力测定及恢复基因的分子标记定位

为了发掘更多玉米C型不育胞质的强恢复系资源,本研究对2份自交系Z16和7250-14-1进行了恢复能力的测定、恢复基因的遗传分析及恢复基因的分子标记定位。结果表明, Z16和7250-14-1对C黄早四、C478、C698-3和CMo17均表现为育性恢复,而对C48-2则均表现为育性部分恢复。通过对玉米CMS-C不同亚组胞质测交鉴定发现, Z16对G48-2、EC48-2、ES48-2、RB48-2及类48-2均表现为不育性保持,而7250-14-1对G48-2、EC48-2、ES48-2表现为育性部分恢复,对RB48-2和类48-2则表现为不育性保持。Z16和7250-14-1对CMS-T不育系均表现为不育性保持,而对CMS-S不育系则均表现为育性部分恢复。遗传分析显示, Z16对C478和C黄早四的育性恢复均受1对基因控制;而7250-14-1对C黄早四及C478的育性恢复分别受1对基因及2对基因控制。利用(C黄早四×Z16)F2、(C黄早四×7250-14-1)F2群体分别对恢复基因进行分子标记定位,其中Z16的恢复基因被定位于标记B-1至第8染色体短臂末端区域,物理距离为494 kb; 7250-14-1的恢复基因被定位于第8染色体短臂的标记B-1和Chr8-86080之间,物理距离为249kb。该研究不仅为玉米CMS-C三系配套的生产利用提供了恢复基因资源,也为玉米CMS-C恢复基因的克隆及恢复机制的研究奠定了一定基础。     

Inheritance of male sterility mutations induced in haploid sorghum tissue culture

Summary A high frequency of male sterile mutants regeneration was shown in callus cultures derived from leaves and panicles of haploid sorghum (Ms_c1, A1 cytoplasm) and a spontaneous autodiploid obtained from this haploid. The cultures derived from the embryos of this autodiploid yielded significantly fewer mutants. Absolutely or partially male sterile mutants appeared among the regenerants or in the progeny of fertile regenerants. In the self-fertilized progenies of partially male sterile mutants and in the hybrids of sterile mutants with autodiploid line (i.e. under one and the same nuclear genome) male sterility mutations were inherited as cytoplasmic. Non-Mendelian segregation of sterile, partially male sterile and fertile plants was observed in these progenies. Partially male sterile plants were characterized by somatic segregation of male sterility genetic factors. In test-crosses with some CMS A1 fertility restorers, mutations were manifested as nuclear recessive while with others as nuclear dominant. These differences are supposed to be the result of interaction of fertility restorer genes of these testers with the novel cytoplasm. Male sterility mutations accompanied with female sterility were inherited as nuclear recessives.Abbreviations f fertile - ps partially male sterile - s male sterile plants     

Inheritance of fertility restoration in sunflower (helianthus annuus L.)

Summary Fertility restoration in the cross between a cytoplasmic male sterile line, 2 cm 183, and the restorer line, BCZ 111, (both obtained from France) was dominant in F₁ and segregated in a 9:7 ratio in the F₂ generation and thus suggested the action of two independent, complementary dominant genes controlling restoration. The behaviour of F₃ families broadly confirmed the F₂ ratio. The reasons underlying this pattern of inheritance has been discussed and the genetic symbols rf ₁ rf ₁ rf₂ rf₂and Rf ₁ Rf ₁ Rf ₂ Rf ₂ have been suggested for the male sterile and the restorer parents respectively.     

Inheritance of male fertility restoration of the cytoplasmic-nuclear male-sterile line NJCMS1A of soybean [Glycine max (L) Merr.]

At present, no report on inheritance of male fertility restoration has been released, yet more than 10 cytoplasmic-nuclear male-sterile soybean lines as well as their maintainers and restorers have been developed. Based on our previous work, 25 restorers for the male-sterile line NJCMS1A were identified and the inheritance of male fertility restoration for these restorers was studied. The results showed that F₁s between NJCMS1A and its restorers were completely male-fertile. The numbers of fertile and sterile plants in the F₂ population of Cross I (NJCMS1A × N23601) and Cross II (NJCMS1A × N23683) corresponded to a segregation ratio of 15:1, and the numbers of non-segregation lines, 3:1 segregation lines and 15:1 segregation lines in F_2:3 of the same two crosses fitted a 7:4:4 genotypic segregation ratio. The testcross BC₁F₁s between the F₁s of the above two crosses and NJCMS1A, NJCMS1B showed a 3:1 segregation ratio. Accordingly, it was inferred that two pairs of duplicate dominant genes controlled the male fertility restoration of NJCMS1A in both crosses. Meanwhile, F₂ of other 23 crosses between NJCMS1A and its 23 restorers showed a fertility segregation ratio of 3:1 or 15:1. The F₁s of the five testcrosses between NJCMS1A and the F₁s of five crosses selected from the above 23 crosses showed that fertility segregation was 3:1 in BC₁F₁s between NJCMS1A and F₁s of the crosses of which fertility segregation fitted 15:1 in F₂ population, while fertility segregation in BC₁F₁s was 1:1 for those fertility segregation fitted 3:1 in F₂ population. Allelism tests showed that restore genes of all restorers in the experiment were allelic to two pairs of dominant genes. All results showed that some restorers bore one pair of dominant restore gene and the others bore two pairs of duplicate dominant gene. The mechanism of F₁ male sterility of the cross N8855 × N2899 was discussed.     

Interspecific amphiploid‐derived alloplasmic male sterility with defective anthers,narrow disc florets and small ray flowers in sunflower

The cytoplasmic male‐sterility (CMS)/fertility‐restoration system is important for hybrid sunflower (Helianthus annuus L.) seed production. The objective of this study was to characterize two novel alloplasmic CMSs, designated CMS GRO1 and CMS MAX3, with defective anthers, narrow disc florets with no swollen corolla, and short, narrow ray flowers derived from two tetraploid amphiploids (AMPs). Among 26 tested lines, only AMP Helianthus cusickii/P 21 and HA 410 failed to restore male‐fertility. Segregation of CMS, male‐fertile plants and plants with reduced male‐fertility was observed both in the testcross progeny of a six line half‐diallel cross of F₁s with CMS MAX3 and in an F₂ population of CMS GRO1 × RHA 274. Male‐fertility restoration was controlled by at least two dominant genes. Detailed analysis of the mitochondrial genes may provide insight into the differences between these CMSs and other CMS lines. The new CMSs will facilitate the studies of the incompatibility between cytoplasmic and nuclear genes, especially for the alloplasmic CMS involving perennial species, and also provide unique ornamental flower types and CMS sources for hybrid sunflower breeding.     

Expression of male sterility in alloplasmic Brassica juncea with Erucastrum canariense cytoplasm and the development of a fertility restoration system

An alloplasmic mustard, Brassica juncea, has been synthesized by placing its nucleus into the cytoplasm of the related wild species Erucastrum canariense to express cytoplasmic male sterility. To achieve this, the sexual hybrid E. canariense (2n=18, E^cE^c) ×Brassica campestris (2n= 20, AA) was repeatedly backcrossed to B. juncea (2n= 36, AABB). Cytoplasmic male‐sterile (CMS) plants were recovered in the BC₄ generation. These plants are a normal green and the flowers have slender, non‐dehiscing anthers that contain sterile pollen. Nectaries are well developed and female fertility is > 90%. The fertility restoration gene was introgressed to CMS B. juncea from the cytoplasmic donor E. canariense through pairing between chromosomes belonging to B. juncea with those of the E. canariense genome. The restorer plants have normal flowers, with well‐developed anthers containing fertile pollen. Meiosis proceeds normally. Pollen and seed fertility averaged 90% and 82%, respectively. F₁ hybrids between CMS and the restorer are fully pollen fertile and show normal seed set. Preliminary results indicate that restoration is achieved by a single dominant gene. The constitution of the organelle genomes of the CMS, restorer and fertility restored plants is identical, as revealed by Southern analysis using mitochondrial and chloroplast probes atp A and psb D, respectively.     

Identification of the Rf gene conferring fertility restoration of the CMS Dian-type 1 in rice by using simple sequence repeat markers and advanced inbred lines of restorer and maintainer

Cytoplasmic male sterility of Dian‐type 1 (CMS‐D1) was developed 30 years ago in Yunnan. A major gene conferring fertility restoration for the CMS‐D1 system was detected by microsatellite markers in advanced inbred lines consisting of 196 maintainers and 62 restorers developed in breeding programmes of hybrid rice involving the CMS‐D1 system. The gene was mapped between two simple sequence repeat markers, OSR33 and RM228, on chromosome 10, and was temporarily designated as Rf‐D1(t). The genetic distances of the gene to the two microsatellite markers were 3.4 and 5.0 cM, respectively. This linkage was confirmed by using an F2 population derived from a cross between a CMS‐D1 line and a restorer. This study also demonstrated that using OSR33 was reliable and efficient for identification of restoring lines in hybrid rice breeding with the CMS‐D1 system.     

Molecular detection of WA‐CMS restorers from tropical japonica‐derived lines,their evaluation for fertility restoration and adaptation

Hybrid rice based on wild‐abortive cytoplasmic male sterility (WA‐CMS) is important in boosting rice production, which requires diverse parents to harness heterosis. For this, exploiting the diversity of japonica through tropical japonica (TRJ) lines is an excellent route. In this study, 310 TRJ‐based new plant type (NPT) lines were developed and evaluated for Rf3 and Rf4 genes. Gene‐based (DRRM‐Rf3‐5 and DRRM‐Rf3‐10) and functional marker (RMS‐SF21‐5) targeted Rf3 locus, while gene‐linked (RM6100) and functional marker (RMS‐PPR9‐1) targeted the Rf4 locus. The frequency of the restorer allele of Rf3 gene was lower when compared to that of Rf4. Combined phenotypic and molecular screening using gene‐based and functional markers identified 42 lines that carried Rf3 and/or Rf4 genes. All the selected lines produced fertile F₁s when crossed to a WA‐CMS line, “Pusa 6A”, but with varying levels of spikelet fertility. This is the first report of a marker‐cum‐phenotype‐based restorer selection using TRJ‐derived lines. Multilocation evaluation of these lines at three locations indicated better adaptation for grain yield in some of the lines.