Comparison of two fertility restoration systems against photoperiod-sensitive cytoplasmic male sterility in wheat

A ‘two‐line system’ using photoperiod‐sensitive cytoplasmic male sterility (PCMS) caused by Aegilops crassa cytoplasm under a long‐day photoperiod ( 15 h) has been proposed as a new means of producing hybrid varieties in common wheat. The PCMS line is maintained by self‐pollination under short‐day conditions, and hybrid seeds can be produced through outcrossing of the PCMS line with a pollinator under long‐day conditions. Two kinds of fertility restoration systems against the PCMS are known. One is involved with a set of multiple fertility‐restoring (Rf) genes in the wheat cultivar ‘Norin 61’ located on (at least) chromosomes 4A, 1D, 3D and 5D. The other is controlled by a single dominant major Rf gene, Rfd1, located on the long arm of chromosome 7B in the wheat cultivar ‘Chinese Spring’. To examine the degree of fertility restoration by these two systems, nine PCMS lines were crossed with ‘Norin 61’ and ‘Chinese Spring’ as the restorer lines, and the F₁ hybrids were investigated. The degree of fertility restoration was estimated by comparing the seed set rates in the F₁ hybrids having the Ae. crassa cytoplasm and those with normal cytoplasm. The results revealed that the fertility restoration ability of a set of multiple Rf genes in ‘Norin 61’ was higher than that of the Rfd1 gene in ‘Chinese Spring’.     

Inheritance of root traits and phosphorus uptake in common bean (Phaseolus vulgaris L.) under limited soil phosphorus supply

Heterosis is an important way to improve yield and quality for many crops. Hybrid rice and hybrid maize contributed to enhanced productivity which is essential to supply enough food for the increasing world population. The success of hybrid rice in China has led to a continuous interest in hybrid wheat, even when most research on hybrid wheat has been discontinued in other countries for various reasons including low heterosis and high seed production costs. The Timopheevii cytoplasmic male sterile system is ideal for producing hybrid wheat seeds when fertility restoration lines with strong fertility restoration ability are available. To develop PCR-based molecular markers for use in marker-assisted selection of fertility restorer lines, two F₂ populations derived from crosses R18/ND36 and R9034/ND36 were used to map fertility restoration genes in the two elite fertility restorer lines (R-lines) R18 and R9034. Over 678 SSR markers were analyzed, and markers closely linked to fertility restoration genes were identified. Using SSR markers, a major fertility restoration gene, Rf3, was located on the 1B chromosome in both populations. This gene was partially dominant in conferring fertility restoration in the two restorer lines. SSR markers Xbarc207, Xgwm131, and Xbarc61 are close to this gene. These markers may be useful in marker-assisted selection of new restorer lines with T. timopheevii cytoplasm. Two minor QTL conferring fertility restoration were also identified on chromosomes 5A (in R18) and 7D (in R9034) in two R-lines.     

A YA-type cytoplasmic male-sterile source in common wheat

A new cytoplasmic male‐sterile (CMS) system for hybrid wheat breeding, YA‐type CMS line with the cytoplasmic mutant from the common wheat variety ‘CA8057’, was developed by the Institute of Genetics and Developmental Biology, Chinese Academy of Sciences. The pollen sterility of YA‐type CMS line was easily maintained but difficult to restore. Some sterile lines with desirable agronomic performance, such as msYA‐‘CA8057’ (BC₁₇), msYA‐‘Yuandong 6’ (BC₉), msYA‐‘Jin 411’ (BC₉), msYA‐‘WL1’ (BC₁₀), msYA‐‘Yanshi 9’ (BC₁₀), msYA‐‘BPm16’ (BC₉), msYA‐‘Jindong 8’ (BC₉) and msYA‐‘Jinmai 33’ (BC₉), were bred and a restorer line GR1 was screened with 26 new restorer lines being developed by transferring restorer genes from GR1. It was found that abnormal phenomena occurred at the uninucleate‐pollen stage and the abortive pollen was poor in starch content and other components. The variance analysis of agronomic traits in eight sterile lines indicated that there was no general negative effect of cytoplasm. The genetic analysis for fertility restoration showed that two pairs of independent major genes (designated YARf₁YARf₁YArf₂YArf₂) and some minor genes could be involved in the fertility restoration in restorer line GR1, and YARf₁ was epistatic over YARf₂ for the genetic effect of fertility restoration. As a new CMS system, the YA‐type CMS line was of potential value for hybrid wheat breeding and should be further studied.     

Inheritance and allelic relationships of fertility restoration genes for seven new sources of male-sterile cytoplasm in sunflower

The inheritance of fertility restoration of six mitomycin C and streptomycin‐induced cytoplasmic male‐sterile (cms) mutants and one cms line derived from Native American cultivar PI 432513 in sunflower was evaluated. These seven new cms sources were also compared with the commercially used cms PET1 (Helianthus petiolaris Nutt.) cytoplasm, using USDA inbred lines with restoration genes (Rf₁) specific for cms PET1 and new restoration lines identified for cms PI 432513. Restoration genes for cms PI 432513 were found in ‘Armavir’, VNIIMK, P21 and male‐fertile (MF) plants of PI 432513. F₂ and F₃ segregation ratios of crosses between cms PI 432513 and these restoration sources indicated a single dominant gene controlled fertility restoration. Progenies of cms PI 432513 testcrossed with F₁’s of half‐diallel crosses among the respective four homozygous restoration lines and RHA 274 suggested that the restoration genes of RHA 274, VNIIMK, P21 and PI 432513 were at the same locus. Restoration genes from VNIIMK, P21 and PI 432513 satisfactorily restored pollen stainability in the heterozygous condition. A very weak expression of the Rf gene in ‘Armavir’ was observed in the heterozygous condition. Fertility restoration capability of these genes for the six mutant cms HA 89 and cms HA 89 (in PET1 cytoplasm) was observed. The mutant cms HA 89 lines were also restored completely by RHA 266, RHA 274, RHA 280 and RHA 296, and F₂’s segregation ratios indicated single dominant gene control, implying a common cytoplasmic male sterility in all lines. F₁’s of half‐diallel crosses among RHA 266, RHA 273, RHA 274, RHA 280 and RHA 296 were testcrossed onto the cms lines, and their all MF progenies among lines, except RHA 280, confirmed that fertility restoration was controlled by a single Rf₁ gene locus. The restoration gene in confection line RHA 280, namely Rf₃, was at a different locus than Rf₁ and was equally capable of restoring all the cms lines. Cms HA 89 mutants and cms PI 432513 are in H. annuus cytoplasm, and are agronomically equal in hybrid performance to the cms PET1 used in commercial sunflower hybrids. These new cms lines will provide immediate alternative cms sources for reducing the genetic vulnerability resulting from the exclusive use of the single cms source PET1 in sunflower hybrid production.     

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.     

Localization of Genes in Rye that Restore Male Fertility to Hexaploid Wheat with timopheevi Cytoplasm

Four sets of wheat-rye addition lines were screened to localize genes in rye that restore male fertility to hexaploid wheat with timopheevi cytoplasm. One gene, designated Rfc3, was physically located in the distal 40 % of the long arm of chromosome 6R. No allelic variation at Rfc3 was found; normal male fertility was consistently observed in all F₁ hybrid combinations tested. A second gene, designated Rfc4, was located on the long arm of chromosome 4R. Variation between chromosomes 4R in the level of restoration was observed; fertility in hybrids ranged from 0 % to about 50 % of normal. Attempts to genetically map Rfc4 were inconclusive but suggested it was located 16.1 cM from the telomere of the long arm and at least 8.0 cM from the centromere. These restorers, particularly Rfc3, may have potential in hybrid wheat breeding programs and can be manipulated for production of male sterile triticale lines.     

小麦K型不育系育性恢复基因的遗传分析

选用K型不育系豫麦3号、S43及其相应的保持系,与恢复系豫麦2号和豫麦49组配了不育系//保持系/恢复系、不育系//不育系/恢复系和不育系/恢复系//保持系三种回交群体,对小麦K型不育系育性恢复基因进行了遗传分析。结果表明,不同恢复力的恢复系携带的恢复基因对数不同,恢复力较强的豫麦2号携带2对主效基因,恢复力较低的豫麦49仅携带1对主效基因。此外,还有微效基因对育性恢复起作用,这种基因不仅存在于恢复系中,也存在于不育系（保持系）中。在K型细胞质背景下,不携带恢复基因的雄配子的传递率很低,而雌配子传递正常。     

Comparative genetic analysis and molecular mapping of fertility restoration genes for WA,Dissi, and Gambiaca cytoplasmic male sterility systems in rice

The genetic relationship among three cytoplasmic male sterility (CMS) systems, consisting of WA, Dissi, and Gambiaca, was studied. The results showed that the maintainers of one CMS system can also maintain sterility in other cytoplasmic backgrounds. The F₁ plants derived from crosses involving A and R lines of the respective cytoplasm and their cross-combination with other CMS systems showed similar pollen and spikelet fertility values, indicating that similar biological processes govern fertility restoration in these three CMS systems. The results from an inheritance study showed that the pollen fertility restoration in all three CMS systems was governed by two independent and dominant genes with classical duplicate gene action. Three F₂ populations, generated from the crosses between the parents of good-performing rice hybrids, that possess WA, Dissi, and Gambiaca CMS cytoplasm, were used to map the Rf genes. For the WA-CMS system, Rf3 was located at a distance of 2.8 cM from RM490 on chromosome 1 and Rf4 was located at 1.6 cM from RM1108 on chromosome 10. For the Dissi-CMS system, Rf3 was located on chromosome 1 at 1.9 cM from RM7466 and Rf4 on chromosome 10 was located at 2.3 cM from RM6100. The effect of Rf3 on pollen fertility appeared to be stronger than the effect of Rf4. In the Gambiaca-CMS system, only one major locus was mapped on chromosome 1 at 2.1 cM from RM576. These studies have led to the development of marker-assisted selection (MAS) for selecting putative restorer lines, new approaches to alloplasmic line breeding, and the transfer of Rf genes into adapted cultivars through a backcrossing program in an active hybrid rice breeding program.     

Development of a cytoplasmic male‐sterile line NJCMS4A for hybrid soybean production

Cytoplasmic male‐sterile (CMS) lines are being used to produce hybrid seeds. Thus far, four CMS sources in soybean [Glycine max (L.) Merr.] have been reported in China. However, they are not sufficient or efficient in meeting the requirements of commercial soybean hybrid seed production. In this study, 33 varieties were tested for CMS using 45 crosses among 37 landraces and 17 annual wild soybean accessions (Glycine soja Sieb. et Zucc.). The cross of N23661 × N23658 showed partial to complete male sterility in backcross generations, while the corresponding reciprocal cross showed normal male fertility. Thus, the cytoplasm of N23661 is male‐sterile, the continuously backcrossed line is a male‐sterile line (designated NJCMS4A), and N23658 is its maintainer (designated NJCM4B). The male fertility of NJCMS4A was restored by another accession, Nansheng9403. Accordingly, NJCMS4A along with its maintainer and restorer composes a complete set of three lines for producing hybrid soybean. Using mitochondrial markers and sequence analyses, NJCMS4A is a CMS line with its cytoplasm not identical to the four previously reported CMS sources in soybean.     

Fertility restoration and nor suppression caused by Aegilops mutica chromosomes in alloplasmic hybrids and lines

By crossing Aegilops mutica with Triticum dicoccum as a bridge species and backcrossing with common wheat as a recurrent pollen parent, male sterile alloplasmic line(s) were produced. In progeny of the crosses, a self fertile plant with 42 chromosomes was selected and named R 20. From this plant several lines that possessed Rf (fertility restoring) genes and/or powdery mildew resistant genes were obtained. Apparently, the system of sterility-fertility of pollen can be applied for hybrid wheat production. In addition, the disease resistance may be used in breeding. The male fertile lines possessed one or more Ae. mutica sat-chromosome(s), which show the ability to suppress the nucleolar organizing regions of chromosomes 1B and 6B of common wheat. The relation between the sat-chromosomes and male fertility restoration is not yet clear. This revised version was published online in July 2006 with corrections to the Cover Date.     

Inheritance and mapping of a restorer gene for the rapeseed cytoplasmic male sterile line 681A

A novel cytoplasmic male sterility‐fertility restoration system has been developed in rapeseed (Brassica napus). The cytoplasmic male sterile line 681A was derived from a spontaneous male sterile mutant in a newly released double‐low rapeseed cultivar ‘Xiangyou 13′. The restorer line 714R was identified in the interspecific progeny from a B. napus×B. juncea‐cross. Genetic analysis showed that fertility restoration for 681A cytoplasmic male sterility was controlled by a single dominant nuclear gene which might originate from B. juncea. The RAPD marker S1039_‐520 was found to be linked to the restorer gene in F₂ progeny of 681A × 714R with a recombination frequency of 5.45%.     

Conversion of the genic male sterility (GMS) system of bell pepper (Capsicum annuum L.) to cytoplasmic male sterility (CMS)

Non‐pungent bell pepper (Capsicum annuum L.) lacks the cytoplasmic male sterility (CMS) nuclear restorer allele, Rf, and CMS cannot be employed in its F₁ hybrid seed production. To demonstrate that the genic male sterility (GMS) system in non‐pungent bell pepper can be converted to the CMS male sterility system, the conversion of GMS to CMS for non‐pungent bell pepper line GC3 was conducted by introgression of S‐type cytoplasm and the Rf allele from tropical pungent donors. After morphological traits were evaluated, two lines from BC₁F₁ containing S‐type cytoplasm and four lines from BC₂F₂ containing Rf allele, phenotypically similar to GC3, were obtained and could be employed as CMS male sterile lines and restorer lines for non‐pungent bell pepper. Four molecular markers potentially linked to traits of interest were also evaluated in BC₁F₁ and BC₁F₂ populations. This is the first time that GMS has been successfully converted to CMS in bell pepper, a significant contribution for bell pepper hybrid seed production.     

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.     

Development of dominant nuclear male-sterile lines with a blue seed marker in durum and common wheat

In order to develop genie male‐sterile lines with a blue seed marker, male‐sterile plants, controlled by a dominant nuclear gene Ms2, were used as female parents against a 4E disomic addition line ‘Xiaoyan Lanli’(2n= 44, AABBDD+4EII) as the male parent to produce monosomic addition lines with blue seed. Male‐sterile plants from the monosomic addition lines were pollinated with durum wheat for several generations and in 1989 a male‐sterile line with the blue grain gene and the male‐sterile gene Ms2 on the same additional chromosome was detected and named line 89‐2343. Using this line, the blue seed marker was successfully added to a short male‐sterile line containing Ms2 and Rht10. The segregation ratios of male sterility and seed colour as well as the chromosome figurations of different plants indicated that the blue grain genes, Ms2 and Rht10 were located on the same additional chromosome. Cytological analysis showed that the blue marker male‐sterile lines in durum wheat and common wheat were monosomic with an additional chromosome 4E. The inheritance ratio for blue seed male‐sterile plants and white seed male‐fertile plants was 19.7% and 80.3%, respectively, in common wheat. The potential for using blue marker sterile lines in population improvement and hybrid production is discussed.     

Development and use of a two-gene marker-aided selection system for fertility restorer genes in rice

We have established marker-aided selection strategies for the two major Rf genes (Rf3 and Rf4) governing fertility restoration of␣cytoplasmic-genetic male sterility (CMS) in rice. Polymorphisms between restorer and non-restorer␣lines were observed using RG140/PvuII for Rf3 located on chromosome 1 and S10019/BstUI for Rf4 located on chromosome 10. DNA polymorphisms associated with these two loci in restorer lines of wild abortive (WA), Dissi, and Gambiaca cytoplasm are conserved, suggesting that similar biological processes control pollen fertility in this diverse cytoplasm. Because of their close linkage to Rf genes and distinct banding patterns, STS markers RG140/PvuII and S10019/BstUI are well suited for marker-aided selection, enhanced backcross procedures, and pyramiding of Rf genes in agronomically superior non-restorer lines. The combined use of markers associated with these two loci improved the efficiency of screening for putative restorer lines from a set of elite lines. Positional analyses of Rf4 and the inheritance pattern of the polymorphism in S10019/BstUI suggest that Rf4, governing fertility restoration in WA-CMS in rice, is likely to be the same gene governing fertility restoration in BT- and HL-CMS that has a gametophytic effect, which explains why 100% pollen fertility in hybrids is impossible to attain.     

K型杂交小麦恢复基因的遗传研究

用Ｋ型小麦雄性不育系Ｋ１４９Ａ,保持系１４９（Ｂ）和３个恢复材料Ｌ７８３、太１０６和ＰＨ８５－４（Ｒ）及其杂交后代群体Ｆ１（Ａ／Ｒ）,Ｆ２,Ｂ２（Ａ／Ｆ）,Ｂ２′（Ａ∥ＢＲ）作为试验材料,对育性指标进行了比较,以恢复性遗传研究的最佳指标－套代自交结实率为育性指标,对Ｋ型小麦雄性不育系的育性恢复的遗传特点进行了初步分析,结果表明Ｋ型小麦雄性不育系是配子体不系,三个恢复材料的育性恢复受一对显性基因控制     

Investigation of possible associations between partial fertility restoration and agronomic traits in Triticum aestivum L.

Summary Many conventional hard red spring wheat (Triticum aestivum L. em Thell) lines, including several North Dakota cultivars, carry a gene (or genes) which restore partial male fertility to male sterile plants with Triticum timopheevi Zhuk. cytoplasm. Since this gene has no fertility restoration function in T. aestivum cytoplasm, the postulation can be made that it is being retained in conventional lines because of pleiotropic effects, favorable linkages or chance. The research reported in this paper examined these possibilities. Forty F₆ lines, derived from a single F₂ plant which was heterozygous for a gene (or genes) for partial fertility restoration, were evaluated for two years in a yield trial planted at Fargo, North Dakota. The 40 lines were testcrossed to a male sterile line having T. timopheevi cytoplasm, and the mean seed set of testcrosses was used as a measure of a line's fertility restoration potential. Twenty-seven lines had the gene for partial fertility, and 13 lines apparently lacked this gene. The 40 lines differed for heading date, anther extrusion, plant height, grain yield, 200-kernel weight, test weight, and grain protein percentage. However, comparisons of lines having the restorer gene with those lacking the gene did not provide any obvious explanation for the retention of the partial fertility restorer gene in the breeding stocks of the North Dakota conventional hard red spring wheat breeding program. The possibility that the restorer gene was linked with genes for resistance to stem rust or leaf rust also was evaluated by testing lines for their reaction to several races of rust. No conclusive association was found.Contribution from the Agric. Exp. Sta., North Dakota State University, Fargo, ND 58105, Journal Article no.     

莫迦小麦(Triticum macha L.) T型恢复基因Rf3和K型不育基因rfv1的连锁关系

为进一步明确莫迦小麦(Triticum macha) T型恢复基因Rf3与K型不育基因rfv1的连锁关系, 利用T型细胞质背景(T504A/Tm3314 F₂代和T504A//KTm3314A/90(13)21杂交分离群体)的可育株在K型细胞质下的育性测交分析, 明确了来自莫迦小麦的这2个基因连锁并不紧密, 交换值约为16.54%。可利用T型主效恢复基因Rf3提高含有T型主效恢复基因和K型主效不育基因的基础材料的选择效率。     

粳稻恢复系宁恢3-2育性恢复

两套粳稻雄性不育系(A)及其保持系(B)分别与宁恢3-2(R)杂交、回交、自交、获得两个组合的 F_1(A/R)、B_2(A//A/R)、B_2′(A//B/R)、F_2和 F_3,以花粉育性和种子育性作为恢复度指标,研究宁恢3-2育性恢复力的遗传。 结果表明,BT 六千辛 A 和 L 平壤3号 A的花粉以染败为主,在光学显微镜下不易区分分离世代植株中可育和不育花粉,故不宜用花粉育性作为恢复度指标进行遗传分析。以种子育性为指标,发现两个不育系是配子体不育类型,宁恢3-2对它们的育性恢复力是由一对显性恢复基因控制的。     

SSR and SCAR markers linked to the fertility-restoring gene for a D2-type cytoplasmic male-sterile line in wheat

‘Yi 4060’ is an elite restorer line of a non‐photoperiod‐sensitive D²‐type cytoplasmic male‐sterile (CMS) line of wheat. Random amplified polymorphic DNA (RAPD) and simple sequence repeat (SSR) markers were employed to map one major fertility‐restoring gene (D²Rf₁) in ‘Yi 4060′. The sterile and fertile DNA pools were established from individuals in BC₆, based on bulked segregant analysis. One RAPD marker E09, linked to D²Rf₁, was converted to a SCAR marker and designated as E09‐SCAR₈₆₅. The genetic distance between E09‐SCAR₈₆₅ and D²Rf₁ is 9.5 cM. Two SSR markers, Xgwm11 and Xgwm18, were also linked to a D²Rf₁ and co‐segregated with E09‐SCAR₈₆₅. The three molecular markers are useful in marker‐assisted breeding of the elite restorer lines for D² ‐type CMS lines in wheat.