Pollen Characteristics and Genetics of Induced and Spontaneous Genetic Male-Sterile Mutants in Rice

Pollen characteristics, inheritance and allelism of 23 genetic male-sterile (ms) mutants of rice (Oryza sativa L.) were investigated. Ten of the mutants were induced by ethyl methane sulfonate, one induced by ethyleneimine, seven induced by gamma rays, one induced by streptomycin, one derived from tissue culture and three were spontaneous mutants found in the field. Four pollen abortion types were observed among these ms mutants: 3 no-pollen (NP) type, 6 complete pollen abortion (CPA) type, 13 partial pollen abortion (PPA) type, and 1 stainable pollen abortion (SPA) type. Progeny tests over two years indicated that each of the mutants was inherited as a monogenic recessive. A partial diallel cross among the 23 ms mutants indicated that mutant E2 was allelic to G4, E5 was allelic to E9, N2 was allelic to N3, and that three other mutants, E3, G6 and T1, shared the same ms locus. Gene symbols ms-46 (t) through ms-63 (t) were assigned to these mutants.     

Male-sterility in the grain amaranth (Amaranthus hypochondriacus ex-Nepal) variety Jumla

Summary Twenty naturally occurring male-sterile plants were recovered from a normal population of the grain amaranth, variety Jumla. The identification of the male-sterile plants is possible during anthesis and after flowering. The male-sterility in this variety is conditioned by a single recessive nuclear gene ms.This research was supported by Grant No. AMA-KE-4-83-22 (CRG GRANT) from the National Academy of Science, USA. Reprint requests to V.K. Gupta.     

Characterization of cytoplasmic male sterility in Petunia hybrida. I. Localization,composition and activity of esterases

Summary Anthers of male fertile, cytosterile and restored male fertile clones of Petunia hybrida were compared for esterase activity and composition in subsequent stages of microsporogenesis. Three methods were applied (i) ultra-thin layer isoelectric focussing on polyacryl amide gels, (ii) quantitative spectrophotometrical assay, (iii) histochemical determination of total esterase activity associated to the azo-coupling method (Pearse, 1972).In male fertile and restorer idiotypes the isozyme patterns were quite similar. Both the number and intensity of bands increased gradually till the tetrad stage. In contrast, esterase activity in cytosterile anthers remained at a low level and hardy any new bands showed up in later stages. This unvariable, low activity level in cytosterile anthers was also found in the spectrophotometric assay. Histochemical determinations revealed that in male fertile anthers esterase activity is concentrated in the outer tapetal layer at late prophase and that it accumulates there till the early microspore stage. In male sterile anthers esterase accumulation in the tapetal cells stops at the moment that tapetal breakdown becomes visible. This suggests that differences in esterase activity and composition are an effect rather than a cause of the failing pollen formation.     

An ms2 male-sterile, female-fertile soybean sharing phenotypic expression with other ms mutants

Genetic and cytological studies of microsporogenesis and microgametogenesis were conducted with a natural male‐sterile, female‐fertile soybean mutant (BR97‐17971) found in an F₄ breeding line of the Brazilian soybean breeding programme. Allele tests with ms Type Collection from USDA/ARS showed that the gene was allelic to ms2. Conventional analysis of microsporogenesis revealed a differential meiotic behaviour from the normal one reported in ms2 male‐sterile plants. Sterile plants have different levels of meiotic abnormalities related to chromosome segregation. Despite segregational abnormalities in the first and second divisions leading to micronuclei formation, the main meiotic cause of pollen sterility was absent or the defective cytokinesis following telophase II. Absent or defective cytokinesis has never been reported in ms2 mutants, but it was reported in the ms1 and ms4 mutants. After telophase II, one to four nucleate microspores underwent degeneration. Cross‐sections of sterile plant anthers showed that, at telophase II, the tapetal cells with large vacuoles degenerated. Despite callose deposition around meiocytes, sterile plants did not form tetrads. They degenerated and collapsed after callose dissolution, forming an amorphous mass. Anthers from male‐sterile plants were shrivelled.     

Pollen mother cell and anther wall development in a photoperiod-insensitive male-sterile mutant of pigeon pea (Cajanus cajan (L.) Millsp.)

Summary The development of the pollen mother cells (PMC's) and anther wall of a male-sterile mutant was microscopically compared with that of fertile sib plants in pigeon pea (Cajanus cajan). Male-sterility was complete and caused by breakdown of microsporogenesis at prophase I. Delayed and incomplete development of the anther wall appeared to be responsible for PMC degeneration. The sterile mutant also differed from the fertile plants in the size and number of the PMC's.On leave from International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Hyderabad, India.     

Fertility improvement in autotetraploid sorghum. 3. Yields of cultivated tetraploids

Summary The development of tetraploid grain sorghum as a crop plant continues to show promise. Yields from bulk populations and lines withdrawn from such populations are now approaching levels realised by good diploid varieties. It seems that tetraploid grain sorghum populations in which high levels of recombination are attained by the use of the genetic male-sterile ms ₃, should respond profitably to the application of recurrent selection.Seconded from the Plant Breeding Institute, Trumpington, Cambridge.     

Microsporogenesis and anther wall development in male-sterile and fertile lines of pigeon pea (Cajanus cajan (L.) Millsp.)

Summary Microsporogenesis and anther wall development of male-sterile and fertile lines in pigeon pea (Cajanus cajan (L.) Millsp.) was examined microscopically. Male-sterility was complete and was caused by breakdown at the young tetrad stage. Degeneration of the tapetum by vacuolation occurred during the first division of meiosis and appeared responsible for pollen mother cell breakdown. Sterile plants also differed from the fertile plants in the enlargement of the inner middle layer of the anther wall, and in the lack of development of the endothecium.     

Frequencies of genetical factors determining male sterility in onion (Allium cepa L.) and their significance for the breeding of hybrids

Summary In selections of some more or less commonly grown onion varieties in the Netherlands the frequencies of genetical factors governing male sterility were determined. In the leading Dutch variety Rijnsburger the chromosomal factor ms was found to occur in a frequency of over 0.95 and the cytoplasmic factor S in a frequency of less than 0.01.As a consequence, a programme of breeding hybrid onions with the aid of this variety can be started in a simple way by selfing selected plants to produce B lines. Simultaneously seed is harvested from male-sterile plants in the same variety. Subsequently in the third, fifth or seventh year, backcrossing can be started to obtain corresponding A lines. For backcrossing the progenies of the initially selected male-sterile plants are used.The choice of the year in which backcrossing will be started depends mainly on circumstances and on one's personal views.     

Interaction between the eui gene and thermo-sensitive genic male sterility in rice

Panicle enclosure is a typical phenotype of almost all male-sterile rice lines. An elongated uppermost internode (eui) mutant exhibited notably rapid elongation of the uppermost internode at the heading stage; this is considered as a potential mechanism to eliminate panicle enclosure. We developed thermo-sensitive genic male-sterile (TGMS) eui mutants that were characterized by notably elongated uppermost internodes. The elongation of the uppermost internode in the TGMS eui mutant Changxuan 3S (CX) is mainly attributed to an increase in cell number and cell elongation, the latter being the more significant process. Temperature treatments revealed that the effects of temperature on panicle exsertion were similar to those on fertility and that the most temperature-sensitive stage coincides with the period from the formation of the pollen mother cell to meiosis during panicle initiation. These results indicate that elongation increases as temperature decreases and that the expression of the eui gene is more efficient at low temperatures than at high temperatures. In hybrid rice seed production using the TGMS eui mutant, the temperature range should be optimized at 24–28°C in order to preserve the development of completely male-sterile pollen and to eliminate panicle enclosure. Consequently, by using TGMS eui rice lines, gibberellin application can be avoided, thereby reducing the cost of hybrid seed production. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Development of SCAR and CAPS markers linked to a recessive male sterility gene in lettuce (<Emphasis Type="Italic">Lactuca sativa</Emphasis> L.)

Genetic male sterility (GMS) has been a useful system for the production of hybrid varieties in self-pollinated plants. We obtained a GMS line developed from a spontaneous mutation in lettuce (Lactuca sativa L.). Genetic analysis in our previous study revealed that the sterility was controlled by a recessive gene which was named ms-S. For simple and quick screening of individuals showing male sterility, we attempted molecular mapping of the ms-S locus using an amplified fragment length polymorphism (AFLP) technique. From the examination of 4,096 AFLP primer combinations, 63 AFLP markers were found to be linked to the gene and nine of them were successfully converted into sequence characterized amplified region (SCAR) markers and cleaved amplified polymorphic sequence (CAPS) markers. Linkage analysis indicated that these nine markers were closely linked to the ms-S gene and all were located on the same side of the gene. The minimum genetic distance between the ms-S gene and a marker was 3.1 cM. These results provide additional information for map-based cloning of the ms-S gene and will be of great help for lettuce breeding using GMS to produce F₁ hybrids.     

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.     

Disintegration of microsporocytes in a male sterile mutant of <Emphasis Type="Italic">Brassica napus</Emphasis> L. is possibly associated with endoplasmic reticulum-dependent autophagic programmed cell death

The mechanism of anther abortion in a male sterile (ms) line (Longyou 9S) of Brassica napus L. was evaluated by a combination of light and electron microscopies. Light microscopy showed that the tapetal cells of the ms line appeared smaller than those of its fertile line, sporogenous cells were rich in vacuoles, and pollen mother cells dismantled before the tetrad stage. Electron microscopy demonstrated that sporogenous cells were also rich in very long, plate-shaped endoplasmic reticulum cisternae that actively encircled portions of cytoplasm with organelles. In later stages, many large membrane-bound inclusions were observed in the sporogenous cells. These membrane-bound inclusions were lined by single or multiple layer(s) of the endoplasmic reticulum membranes and contained vacuoles, ribosome, plastid, mitochondria, small membrane-bound inclusion, and/or intact nuclei. In meiotic interphase and early meiosis prophase I, many vesicle aggregations and multivesicular bodies containing numerous vesicles appeared in pollen mother cells. More interestingly, some of the multivesicular bodies lay in deep cytoplasm or near cell wall, and some appeared fused with plasmalemma and released the inner vesicles out of plasmalemma. Such released vesicles gradually dispersed and later disappeared. The observations suggest that active endoplasmic reticulum-dependent autophagic programmed cell death and multivesicular body-dependent polar vesicle trafficking are probably present in the studied male sterile line.     

Pleiotropic effects of male sterility genes in hybrid tomatoes (Lycopersicon esculentum Mill.)

Summary The influence of seven recessive male-sterile alleles on early marketable yield, total marketable yield and average fruit weight in heterozygous F1 hybrid tomatoes was studied. Differences were found between nearisogenic F1 hybrid pairs, in the mutants ms-14, ms-17 and ms-18 for percentage of early marketable yield; in the mutants ms-17, ms-31 and ms-47 for average fruit weight; and in the mutants ms-14, ms-17 and ms-33 for total marketable yield. These differences may be attributed to pleiotropic effects of male-sterility alleles or genes highly linked to these alleles. The direction and the magnitude of the pleiotropic effect on a specific characteristic were found to be dependent on the general genetic background of the parental lines and the specific combining ability of the F1 hybrid. Interactions found in crosses between male-sterile and male-fertile female lines and parental lines suggest that male-sterility alleles affect the general combining ability of female lines. Such differences were demonstrated to be statistically significant for percentage of early marketable yield with mutant ms-18, for average fruit weight with mutants ms-47, and for total marketable yield with mutant ms-17 and ms-33. The absence of uniformity with respect to the pleiotropic effects and occasional deviations in the general combining ability are discussed.     

光周期敏感核不育水稻农垦58S不育花药的显微结构变化

本文观察了光敏感核不育水稻农垦58S 在小孢子发生和发育过程中不育和可育花药的显微结构差异。结果表明,不育花药在小孢子母细胞时期和减数分裂期,药隔维管束无导管和筛管,在单核晚期,有分化较差的导管和筛管,其薄壁细胞发育不良或退化,鞘细胞皱缩,由绒毡层的细胞质构成的原生质团不解体。药隔维管束发育异常和绒毡层延迟解     

Improvement of resistance to Fusarium head blight by recurrent selection in an intermating breeding spring wheat population using the dominant male-sterile gene ms 2

Four cycles of recurrent selection for FHB resistance were conducted in an intermating wheat breeding population using the dominant male-sterile gene ms ₂ during 1987–1991.Five cycles of phenotypic mass selection for male-sterile plants were evaluated using the soil-surface inoculation method in Experiment I. Experiment II evaluated changes in FHB scores during five cycles of progeny selection for fertile plants using the single-floret inoculation method. In Experiment I, the average level of FHB response increased to MR level in C₄, compared to MS level in C₀. The numbers of infected spikelets and diseased kernels decreased 0.32 and 2.68 per cycle, respectively. In Experiment II, the average level of FHB response increased to R level in C₄F₁. The numbers of infected spikelets and diseased kernels decreased 0.93 and 4.58 per cycle, respectively. In both experiments, the largest selection gains were realized in the first cycle. The frequencies of R and MR individuals were increased significantly. The frequencies of individuals with FHB response equal and/or superior to Sumai 3 were increased to 5–8% in C₄ and 25% in C₄F₁after the fourth cycle. Agronomic traits tended to be slightly improved in selected populations. Compared to 2% in C₀, about 34% of lines superior in both FHB resistance and agronomic traits in C₄F₁ were selected to enter the conventional breeding program for further evaluation. Sixty three semidwarf lines superior in both FHB resistance and yield potential were selected from the F₅ generations derived from C₁F₁ to C₄F₁. From them, two resistant cultivars with high-yielding potential were developed and commercialized in the Lower Yangtze Valley. Recurrent selection appears to be highly effective and feasible in shifting the average FHB response of the intermating population in the desirable direction, thereby enhancing the frequency of resistant individuals. This revised version was published online in July 2006 with corrections to the Cover Date.     

Pollen production in soybeans with respect to genotype,environment, and stamen position

Summary Our objective was to determine the average numbers of pollen grains from fertile plants (Ms ₁) and the average numbers of coenocytic microspores from genetic male sterile plants (ms ₁ ms ₁) in soybeans, Glycine max L. Merr. Comparisons were made between the average numbers of pollen grains and the average numbers of coenocytic microspores with respect to environment where plants were grown and to stamen position in the flower. Five male sterile lines were used. They included the North Carolina ms ₁ mutant, the cultivar Hark with the ms ₁ gene, and mutants identified as the Urbana, Tonica, and Ames male steriles. Three environments used were the Agronomy Farm, University of Georgia, Athens, Georgia; the Agronomy and Agricultural Engineering Research Center, Iowa State University, Ames, Iowa; and the Agronomy Greenhouse, Iowa State University, Ames, Iowa.Pollen production from fertile plants varied from 374 to 760 pollen grains per anther among genetic lines and environments. This variation may be an important consideration in selecting a male parent to use as a pollinator for hybrid seed production.Among fertile plants, the average numbers of pollen grains per anther of the separate stamen and and of the lower whorl of stamens were significantly different only in greenhouse-grown plants. Among male sterile plants, the average numbers of coenocytic microspores per anther of the separate stamen and of the lower whorl of stamens were significantly different in three genotype x environment combinations. These three exceptions did not conform to any genetic or environmental pattern. Deviations from the expected ratio of 4 pollen grains from fertile plants: 1 coenocytic microspore from sterile plants were attributed to initial differences in the average number of microspore mother cells between the two genotypes.Joint contribution: Agricultural Research Service, USDA, North Central Region, and Journal Paper No. J-8910 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa 50011; Project 2107.     

Genes for pollen fertility restoration in sunflowers

Summary Research on 16 sources of pollen fertility restoration revealed that this character was controlled in eight cases by one single dominant gene, in three cases by two complementary genes, in four cases by three complementary genes and in one case by the cumulative action of two nonallelic dominant genes.The presence of minor genes for restoration in the genotype of the fertile analogue B could effect partial fertility restoration in the cytoplasmic male-sterile line A, especially in late backcrosses, when its genotype becomes saturated with such polygenes.A second major gene Rf ₂ was identified among the investigated monogenic restorer sources.     

A stable cytoplasmic male-sterile line of Brassica juncea carrying restructured organelle genomes from the somatic hybrid Trachystoma ballii+B. juncea

A cytoplasmic male-sterile (CMS) line of Brassica juncea has been developed by combining the cytoplasm originating from the somatic hybrid Trachystoma ballii+B. juncea, and the nucleus of B. juncea cv. Pusa Bold by repeated backcrossing. Male-sterile plants closely resembled the normal fertile B. juncea in general morphology, but had delayed flowering (5–7 days) when compared with fertile ‘Pusa Bold’ which flowered in 45 days. Stamens of the male-sterile line were transformed into petaloid structures. Pollen abortion occurred after tetrad formation. Female fertility of the male-sterile line was normal. Molecular analysis of organelle genomes indicated extensive mitochondrial DNA recombinations in the CMS line. Preliminary analysis of the chloroplast genome of the CMS line also indicated chloroplast DNA recombination.     

Identification of a sequence-tagged site (STS) marker linked to a restorer gene for Ogura cytoplasmic male sterility in radish (Raphanus sativus L.) by non-radioactive AFLP analysis

To identify DNA markers linked to a fertility restorer (Rf) genefor Ogura cytoplasmic male sterility in radish (Raphanus sativus L.),a non-radioactive, amplified fragment length polymorphism (AFLP) analysiswas performed on bulked DNA samples from male-sterile and male-fertileradishes. Ten male-fertile and 10 male-sterile plants selected arbitrarilyfrom an F₂ population made by selfing of F₁ plant from a crossbetween a male-sterile (`MS-Gensuke') plant and a restorer (`Comet') plantwere used as material. Using 32 AFLP primer pairs, one AFLP fragment(AFLP190) which is specific to the bulked DNA samples from male-fertileF₂ plants was identified. AFLP190 was characterized by molecularcloning and nucleotide sequencing, and was converted to a sequence-taggedsite (STS) marker, STS190. A linkage analysis performed in 126individuals of two independent F₂ populations showed tight linkageof STS190 to the Rf gene. The rate of recombination between themarker and Rf was estimated to be less than 1%, making STS1901.2 cM from the gene.     

Digenic nature of male sterility in pepper (Capsicum annuum L.)

Summary A cross was made between two nearly isogenic lines differing for male sterility genes, viz. ms₁ms₁Ms₂Ms₂ s Ms₁Ms₁Ms₂ms₂. F₁ plants yielded F₂ populations which segregated either in 3:1 or 9:7 ratios of fertile vs male sterile individuals. Test crosses between male sterile and male fertile sibs in the 9:7 segregating populations provided a few lines in which most of the progenies were male sterile. A 3:1 ratio model of male steriles vs fertiles is suggested and the value of the system is discussed.Contribution A.R.O. Agricultural Research Organization, The Volcani Center, Bet Dagan 50 250, Israel No. 3703-E, 1992 series.