Development of CGMS system in ridge gourd [<Emphasis Type="Italic">Luffa acutangula</Emphasis> (Roxb.) L.] for production of F<Subscript>1</Subscript> hybrids

Cytoplasmic male sterile system in ridge gourd has been converted to cytoplasmic genetic male sterile (CGMS) system through the development of analogues of male sterile (MS) line, maintainer line and fertility restorer line. These lines were developed by crossing the MS mutant, regenerated through in vitro culture, with monoecious pollen parents Deepthi, Haritham, LA 101, CO 2, IC 92761 and IC 92685. All hybrids and the BC₁ generation developed by crossing with the recurring pollen parents Deepthi, Haritham and LA 101 were male sterile. Male sterile BC₁ plants have been advanced to BC₆ generation and the parental line LA 101 was proved to be a successful maintainer line, producing male sterile progeny in successive back cross generations. Analogue of cytoplasmic male sterile line, MS LA 101, was developed through back crossing and on crossing with fertility restorer lines Arka Sumeet and LA 102, this line excelled as female parent, resulting heterotic combinations. Mitochondrial marker rpS14 and SCAR Tm-53 were identified to yield male sterility specific markers whereas SSR marker 18956 has generated the male fertility specific marker. These primers are recommended for marker assisted selection of ridge gourd, for utilizing male sterility for hybrid seed production and for developing A, B and C lines in CGMS system.     

Investigations into the causes of segregation of Ogura male sterility in Bangladeshi cultivars of radish

In a series of three experiments during 1998‐99 and 1999‐2000 at Gazipur, Bangladesh, the causes of segregation of Ogura cytoplasmic genetic male sterility in local cultivars of radish were studied. Male‐sterile populations at the BC₅ and BC₆ generations were grown under a range of field temperatures for 2 years and the results on pollen fertility tests revealed that the expression of male sterility was not affected by temperature. Neither was a genotype‐year interaction found. The unexpected segregation observed in the male‐sterile backcross generations might be due to the presence of restorer alleles in the maintainer parents.     

Detection and characterization of two new CMS systems in faba bean (Vicia faba) *

Wide crosses were made to identify new cytoplasmic male sterility (CMS) systems in faba beans, based on the interaction of cytoplasm with restorer and maintainer alleles. A total of 330 F₁ hybrids were produced in both reciprocal forms. Male sterile segregates were observed in one reciprocal version in the F₂ generation of six crosses. Two of these crosses with female parents originating from Afghanistan and Egypt expressed stable male sterility in subsequent backcross generations. Based on the female parents of the two crosses, these two CMS systems were designated CMS 199 and CMS 297. CMS 199 was more stable than CMS 297 during backcross generations and across different environments. Maintainer and restorer lines for both CMS systems were identified. Lower expression of male sterility occurred in CMS 297 in the greenhouse during the winter generations than in isolation cages during the summer generations, which may be utilized to maintain male sterile lines by selfing. Regarding practical applications, the CMS 199 shows great promise for hybrid breeding in faba beans.     

Performance of pearl millet isonuclear hybrids involving different cytoplasmic male-sterility systems

The performance of pearl millet hybrids involving four sources of cytoplasmic male sterility (CMS), including the most-exploited A₁ source, was compared to evaluate the effects of cytoplasm on grain yield. The mean grain yield of hybrids possessing A₂, A₃ and A₄ cytoplasms was either similar to or significantly higher than that of their counterpart hybrids with A₁ cytoplasm. Hybrids based on A₃ and A₄ cytoplasms produced, on average, 8% more grain compared with those based on A₁ cytoplasm. This suggested that these CMS sources could be used as alternatives to A₁ cytoplasm to widen the cytoplasmic base of hybrids. The results indicated that most of the variation in hybrids was accounted for by pollinator and cytoplasm × pollinator interactions, suggesting the use of genetically diverse pollinators in pearl millet hybrid breeding.     

Maternal inheritance of male sterility in the progeny of a natural hybrid between Cajanus lineatus and C. cajan

Adoption of pigeonpea hybrids in central and southern India is showing high impact with on‐farm yield advantages of >30%. The hybrid pigeonpea technology, the first in any legume crop, is based on a cytoplasmic‐nuclear male‐sterility (CMS) system. For a long‐term sustainability of hybrid programme, it is imperative that both nuclear diversity and cytoplasmic diversity are maintained among hybrid parents. In this context, a continuous search for new CMS‐inducing cytoplasms is necessary. This paper reports detection of maternal inheritance of male sterility in the progeny derived from a natural hybrid between a wild relative [Cajanus lineatus (W. & A.) Maesen comb. nov.] of pigeonpea and an unknown pigeonpea [Cajanus cajan (L.) Millsp.] genotype. In the present study, the male sterility was maintained up to BC₇F₁ generation by an advanced breeding pigeonpea line ICPL 99044. This male sterility inducing cytoplasm of C. lineatus was tagged as A₆. In future, this CMS genetic stock can be used to develop a range of new pigeonpea hybrids with high yield and adaptation.     

Are ordinal rating scales better than percent ratings? a statistical and “psychological” view

Cytoplasmic male sterility (CMS) is considered an efficient genetic tool in pearl millet hybrid breeding. Of the several CMS sources available in pearl millet, A₁ is the only CMS widely exploited to produce commercial hybrids in India. To explore the possibility of using alternate CMS sources, we studied the cytoplasmic effects of different CMS sources on agronomic characters in pearl millet. Five CMS (A) lines representing A₁, A₂, A₃, A₄ and A₅ cytoplasms, their respective maintainer (B) lines and eight restorer (R) lines were used to generate 40 A × R and B × R experimental crosses. The experimental material was evaluated at two different locations in India. Analysis of combining ability and heterosis revealed that A₄ and A₅ cytoplasms had desirable effects for earliness. The A₅ CMS was found to be particularly promising, as compared to other CMS sources for improving grain yield. The study also indicated that the cytoplasmic effects on general combining ability (GCA) for various agronomic characters were largely non-significant. However, cytoplasmic effects on specific combining ability and heterosis were found to be modulated by cytoplasmic-nuclear interactions and influenced by the environmental conditions. The study also demonstrated the advantage of utilizing diverse male-sterile and restorer combinations in maximizing the productivity as well as for genetic and cytoplasmic diversification of hybrids in pearl millet.     

Genetic and cytological analysis of a new spontaneous male sterility in radish (<Emphasis Type="Italic">Raphanus sativus</Emphasis> L.)

A male sterile plant appeared in the radish breeding program at the Hubei Academy of Agricultural Sciences, Hubei, China. In its progeny, a two-type (half of plants male sterile, the other half male fertile) line 01GAB was established. An F₂ population of 260 plants from a cross of male-sterile 01GAB and a male fertile line 9802H segregated for male fertility in a 3:1 ratio indicating that fertility was restored by a single dominant gene, here designated RsMs. A PCR-based DNA marker specific to the male fertility Rfob gene in 9802H was absent in 01GAB. Linkage analysis placed the RsMs locus 10.7 cM away from the Rfo locus. In an F₂ population of hybrids between 01GAB and male fertile 9802B, a co-dominant DNA marker for the RSultr3.2A (a radish sulfate transporter gene) locus was linked to the RsMs locus at 1.5 cM suggesting that fertility restoration in 01GAB was located in the region with known male sterility restorers in radish. However, no maintainer for the 01GAB source of male sterility has been identified so far. Cytological observations have shown that the abnormalities in male sterile anthers first appeared in tapetum at the tetrad stage, followed by a hypertrophy of the tapetal cells at the vacuolate microspore period. These results suggest that male sterility in 01GAB is likely to be genetic in nature, or it may represent a new type of the cytoplasmic male sterility.     

Ethyloxanilates as specific male gametocides for wheat (Triticum aestivum L.)

Induction of male sterility by deployment of male gametocides holds immense potential in heterosis breeding of wheat. The efficacy of a new class of male gametocide for wheat (Triticum aestivum L.) is described: ethyloxanilates, the most active example of this class being ethyl 4‐fluorooxanilate (E4FO). E4FO induces male sterility, specifically, without detectable effects on various agronomic features and female fertility. The plants sprayed once with 0.15% E4FO exhibited 100% pollen and floret sterility without causing a significant reduction in total yield. E4FO was screened on 29 genotypes of wheat at 0.15% test concentration and was observed to induce 99.76 ± 0.37% male sterility. Thirteen F₁‐hybrids of wheat were produced using the gametocide in Winter 2000–2001 and were evaluated for their agronomic performance in Winter 2001–2002. The cross combinations viz., lines WR 544 × HW 2046 and HW 2044 × WR 956 have outperformed their respective better parents by 48.17% and 23.42% in grain yield/plant and thus have potential as hybrids.     

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.     

抗丝黑穗病、抗败育高粱A2细胞质雄性不育系A2Sx3197的选育

A₁Tx3197曾经是我国广泛应用的高粱细胞质雄性不育系,20世纪70年代末,由于高粱丝黑穗病病菌生理小种分化,该不育系以及用其配制的杂交种逐渐失去了对高粱丝黑穗病菌的抗性。同时该不育系小花败育日渐严重,制种产量极低,甚至造成绝收。为了改良A₁Tx3197的抗病性及抗败育性,本研究利用A₂保持系在A₁位点含有A₁育性恢复基因MS₁MS₁和在A₁细胞质背景下表现恢复的特点,以不育系A₁Tx3197为轮回亲本,以含有抗丝黑穗病、抗败育基因的BV₄为供体,通过杂交和多代回交,得到含有双抗基因的A₂类型细胞质雄性不育的保持系BSx3197(MS₁ms₁ms₂ms₂),在该材料自交的同时,用其对A₂细胞质雄性不育系进行细胞核代换,经过多代回交和自交,最终育成了抗丝黑穗病、抗败育的A₂细胞质雄性不育系A₂Sx3197和保持系BSx3197(MS₁MS₁ms₂ms₂)。结果表明,新选育的不育系A₂Sx3197在A₁和A₅细胞质背景下表现恢复,在A₂、A₃、A₄、A₆和9E细胞质背景下表现不育,丝黑穗平均发病率为0~0.8%,败育率为0~8.4%,抗丝黑穗病性、抗败育性明显优于被改良不育系,接近或达到抗原供体BV₄水平;而在抽穗期、株高、穗长、穗宽、千粒重、穗粒重、粒色、壳色、穗形、穗型等主要性状方面与A₁Tx3197差异不显著。     

Expression of resistance to Atherigona soccata in F1 hybrids involving shoot fly-resistant and susceptible cytoplasmic male-sterile and restorer lines of sorghum

In recent years, cytoplasmic male‐sterility (CMS) has been recognized as a potential danger to the stability of crop production and resistance to insect pests in sorghum. Therefore, the influence of CMS on the expression of resistance to sorghum shoot fly was studied at the ICRISAT, Patancheru, India using the interlard fishmeal technique. The experimental material consisted of 12 restorer, 12 CMS and the maintainer lines, and their 144 F₁ hybrids. Shoot fly‐resistant CMS lines were preferred for oviposition and had more damage because of deadhearts than the corresponding maintainer lines. The hybrids based on shoot fly‐resistant CMS × resistant restorer lines were significantly less preferred for oviposition than the hybrids based on other cross combinations and exhibited the highest frequency (69.1%) of shoot fly‐resistant hybrids. The hybrids based on glossy and trichomed parents had the highest frequency (>90%) of hybrids with glossy and trichome traits, emphasizing the need to transfer these traits into both parents for better expression in the F₁ hybrids. The expression pattern of trichome density, leaf glossiness and leaf sheath pigmentation in the F₁ hybrids and their parents suggested that the interactions between cytoplasmic and nuclear genes possibly control the expression of traits associated with resistance to sorghum shoot fly in the F₁ hybrids.     

野生稻（O.rufipogon）新胞质改良不育系稻米品质的研究

通过核置换回交，获得一种普通野生稻（O. rufipogon）雄性不育细胞质，称为FA细胞质，育成新质源不育系金农1A。研究表明，FA细胞质不育系与WA和HL不育系的恢保关系不同，野败型的保持系和恢复系、红莲型的保持系和恢复系都可以作为FA细胞质的保持系，而不能成为FA细胞质的恢复系。这是一种新发掘的水稻雄性不育细胞质源。FA细胞质突破了WA和HL细胞质恢保关系的遗传局限，扩大了保持系育种范围，可以用品质优良的栽培品种培育成优质稻米不育系。新质源不育系金农1A不育度高，不育性稳定，农艺性状优良，抗稻瘟病和白叶枯病，开花时间早，稻米12项品质指标全部达到农业部颁发的优质米一级或二级标准，实质性地提高了不育系的稻米品质和综合水平，为培育优质米杂交稻奠定良好的遗传基础。     

Stability of male-sterile sources and fertility restoration of their hybrids in pearl millet

Genetic background has a significant effect on the expression of cytoplasmic-nuclear male sterility (CMS) in pearl millet (Pennisetum glaucum (L.) R. Br.). Therefore, a reliable characterization of CMS sources requires the use of near-isonuclear lines and their hybrids. We used this approach to characterize five CMS sources (A₁, A₂, A₃, A_v, and A₄). Male sterility of 81A₄ was the most stable, followed by 81A₁ and 81A_v, indicating the relative merits of these CMS sources in breeding stable male-sterile lines. Male-sterile lines 81A₂ and 81A₃ were highly unstable, indicating their minimal value. Differential male fertility restoration patterns of hybrids made on 81A_V and 81A₄ suggest that the A_v and A₄ cytoplasms represent CMS systems that are different from each other and from A₁, A₂ and A₃. An evaluation of topcross hybrids of 15 diverse populations made on 81A₁ and 81A₄ showed that each population had restorers and maintainers of both cytoplasms and that the frequency of maintainers of A₄ was as high as, or higher than, that of the A₁ cytoplasm. Thus, use of the A₄ cytoplasm can substantially increase the probability of breeding stable male-sterile lines based on inbreds developed from diverse genetic backgrounds, and also provide the opportunity for breeding restorers from each of these diverse genetic sources.     

Haplotype analysis of CMS-associated DNA markers in sweet peppers

Cytoplasmic male sterility (CMS)/restorer-of-fertility (Rf) is an economical and efficient system to produce F₁ hybrid seeds. Although the CMS/Rf system has been used to produce hybrid seeds of hot peppers, this system has never been used for sweet pepper seed production, presumably due to the inability to select stable restorer lines during the breeding process. To test the feasibility of the CMS/Rf system in sweet pepper breeding, we investigated the distribution of haplotypes of previously developed, CMS-associated markers (orf456, ψ atp6-2, CRF-SCAR, OPP13-CAPS, PR-CAPS, and PR-SNP) in 27 commercial sweet pepper F₁ hybrids and 12 breeding lines. When CMS-associated cytoplasmic markers orf456 and ψ atp6-2 were applied, male sterile cytoplasm was not detected in commercial sweet pepper cultivars. When nuclear haplotype markers linked to Rf were applied, all sweet pepper cultivars showed haplotype 3, haplotype 1, and the rf genotype for OPP13-CAPS, PR-CAPS, and CRF-SCAR, respectively. In contrast, we were able to detect male sterile cytoplasm in some breeding lines, and we were also able to detect polymorphisms for PR-CAPS between stable and unstable maintainer lines. The 17T7-SNP also showed polymorphisms between unstable and stable maintainer (or restorer) lines. In conclusion, we expect that it will be possible to develop stable A, B, and C sweet pepper lines using CMS-associated markers and that this will eventually lead to successful implementation of the CMS/Rf system to produce F₁ hybrid sweet pepper seeds.     

Commercial viability of alternative cytoplasmic-nuclear male-sterility systems in pearl millet

Commercial viability of three cytoplasmic-nuclear male sterility (CMS) systems (A₄, A₅ and A_v) as potential alternatives to the most widely used A₁ system in pearl millet (Pennisetum glaucum (L.) R.Br.) was evaluated in terms of stability of complete male sterility of four isonuclear A-lines (81A₁, 81A₄, 81A₅ and 81A_v) and the level and stability of male fertility restoration of their 44 single-cross hybrids. Lines 81A₄ and 81A₅ had no pollen shedders (PS), and there were very low frequency of non-PS plants of these A-lines that had a maximum of 1–5% selfed seedset (SSS). In 81A₁ and 81A_v,there were, albeit low frequency (<1%) of PS plants, and relatively higher frequency of the non-PS plants in these two lines, the more so in 81A_v,had 1–5% and even greater SSS. Some hybrids made on each of the three A-lines (81A₁, 81A₄ and 81A_v) had high and stable male fertility, while others made on the same three A-lines displayed large variation in SSS across the environments, the more so in case of hybrids made on 81A_v. These results indicate that the A₄ CMS system provides a better alternative to the A₁ CMS system, while the A_v system does not. On the basis of highly stable male sterility and the highest frequency of pollinators behaving as maintainers, the A₅ CMS system appeared to be the best for A-line breeding. The commercial viability of this CMS system in breeding R-lines of grain hybrids, however, still remains to be ascertained as no hybrid on it was fully male fertile in any environment. This revised version was published online in August 2006 with corrections to the Cover Date.     

Inheritance of photoperiod sensitive genic male sterility and breeding of photoperiod sensitive genic male-sterile lines in rice (Oryza sativa L.) through anther culture

The fertility segregations of F₁, F₂, BCF₁ descended from crosses between PSGMR and japonica varieties, and F₁'s anther cultured homozygous diploid pollen plant populations (H₂) were studied to reveal the genetic mechanism of photoperiod sensitive genic male sterility in PSGMR under natural daylight length at Shanghai. Rate of bagged seed-setting was used as an indicator of fertility. Fifteen F₁ showed complete fertility similar to their parents. The ratio of completely sterile plants to fertile plants in fifteen F₂ and four BCF₁ was 1:15 and 1:3, respectively. The ratio of completely sterile to fertile diploid pollen plants in nine diploid populations (H₂) was 1:3. These results demonstrated that the photoperiod sensitive genic male sterility in PSGMR was governed by two pairs of independent major recessive genes. There were no significant fertility segregations in hybrids F₁ and selfed F₂ between Nongken 58S and its derivatives 7001S, 5088S, 5047S and M105-9S, indicating that the photoperiod sensitive genic male-sterile genes in Nongken 58S were allelic to those in its derivatives. Several photoperiod sensitive genic male-sterile diploid pollen lines were bred from anther cultured homozygous diploid populations (H₂) in about a three-year period. Most of these diploid lines showed significant fertility transformation and stable complete sterility from 5 August to 5 September, excellent agronomic traits and high resistance to blast and bacterial leaf blight. This revised version was published online in July 2006 with corrections to the Cover Date.     

Cytoplasmic differentiation using near-isonuclear polycytoplasmic male sterile lines in pearl millet

Summary Five near-isonuclear polycytoplasmic versions of 81A₁ and two of Pb 402A₃ male sterile lines of pearl millet (Pennisetum typhoides), along with their corresponding maintainer lines (81B and Pb 402B) were studied for 14 agronomic and two disease traits, and for isozymes of peroxidase in anthers and leaves for assessing cytoplasmic differences. Significant differences among isonuclear polycytoplasmic lines of both 81A₁ and Pb 402A₃, having the same genome and variable cytoplasms, were observed for several agronomic traits. Banding pattern of peroxidase isozymes revealed clear cut differences among cytoplasms. The results provide evidence for the influence of cytoplasmic factors on the phenotypic expression of nuclear genes.     

Determination of the frequencies of restorer- and maintainer-alleles involved in CMS1 and CMS2 in German chive varieties

There are two cytoplasmic male sterility (CMS)‐systems in chives (Allium schoenoprasum L.), which can be employed in hybrid breeding. However, the probability for selection of maintainer genotypes from German open pollinated varieties is not known. Therefore, the allelic frequencies of the restorer genes X and T involved in CMS¹ were determined in 12 German commercial chive varieties by test crossing single plants to male sterile, temperature‐insensitive genotypes [(S₁)xxT] for segregation analyses of offspring. Temperature sensitive genotypes [(S₁)xxT_] are able to produce pollen at higher temperatures, and should therefore be excluded from hybrid breeding to avoid self‐pollination of the maternal parent. The mean value of the frequency of the non‐restoring allele x in the populations examined was 0.62. The mean value of the allele t, which is responsible for the temperature insensitivity, was 0.9. As a consequence of these allelic frequencies about one‐third of all plants of the chive varieties examined were designated CMS₁ maintainer genotypes, leading to the production of temperature insensitive male sterile lines. The incidence of CMS₂ maintainers in the German varieties examined was nearly four times lower than CMS₁ maintainers. The mean value of the frequency of the non‐restoring allele _st2 involved in the CMS₂‐system was 0.29.     

水稻新质源(CMS-FA)雄性不育恢复基因的遗传研究

发掘水稻新型雄性不育细胞质源CMS-FA,育成系列优质米不育系和系列新质源恢复系,组配成强优势杂交稻组合的基础上研究新质源雄性不育恢复系的恢复基因遗传。采用新质源(CMS-FA)不育系金农1A与恢复系金恢3号杂交获得杂交F₁代种子,种植F₁代,收获自交F₂代种子。用F₁分别与不育系或保持系回交,获得(不育系//不育系/恢复系和不育系/恢复系//保持系)2个测交群体。同时种植P₁、P₂、F₁、F₂、B₁F₁和B₂F₁等群体,考察花粉染色率、套袋结实率和自然结实率,卡平方测验遗传分离适合度。结果表明,不育系与恢复系杂交F₁代正常可育,育性恢复(可育)基因为显性遗传。F₂代分离出可育︰不育适合3︰1,育性恢复(可育)基因为1对显性基因控制。B₁F₁和B₂F₁代2个测交群体的可育︰不育都适合1︰1分离规律,验证了F₂代育性恢复(可育)单基因的遗传模式。暂时确定新质源(CMS-FA)核质互作三系的基因型为不育系S(SS)、保持系F(SS)和恢复系S(FF)。     

Seed parent breeding efficiency of three diverse cytoplasmic-nuclear male-sterility systems in pearl millet

Pearl millet (Pennisetum glaucum (L.) R. Br.) hybrids, grown widely in India and to some extent in the US, are all based on an A₁ CMS source, leaving the pearl millet hybrids vulnerable to potential disease or insect pest epidemics. A comparison of this CMS system with two additional CMS systems (A₄ and A₅) in the present study based on isonuclear A-lines (seed parents) and their isonuclear hybrids showed that A-lines with the A₄ cytoplasm had much fewer pollen shedders and much reduced selfed seed set in visually assessed non-shedding plants as compared to those with the A₁ cytoplasm. A-lines with the A₅ cytoplasm had neither any pollen shedders nor did they set any seed when selfed. This showed that the A₅ CMS system imparts complete and most stable male sterility, followed by the A₄ and A₁ CMS systems. The frequency of maintainers, averaged across a diverse range of 26 populations, was highest for the A₅ CMS system (98%), followed by the A₄ (59%) and the A₁ (34%) system indicating the greatest prospects for genetic diversification of A-lines lies with the A₅ cytoplasm, and the least with the A₁ cytoplasm. Mean grain yield of hybrids with the A₁ cytoplasm was 5% more than the A₄-system hybrids, while there was no difference between the mean grain yield of hybrids based on A₁ and A₅ CMS systems. Based on these results, it is suggested that seed parents breeding efficiency will be the greatest with the A₅ CMS system, followed by the A₄ CMS system, and least with the currently commercial A₁ CMS system.