Inheritance Of Male Sterility Research Articles

Seed germination of gynodioecious species: theoretical considerations and a comparison of females and hermaphrodites.

Better seed germination of females than of hermaphrodites is not a major contributor to the greater geometric lifetime fitness that females require to be maintained in a gynodioecious population. Gynodioecy is a sexually dimorphic breeding system in which females (F, male sterile) and hermaphrodites (H) coexist in the same population. For plants with nuclear (biparental) inheritance of male sterility, theory predicts that except when the product of selfing rate (s) and inbreeding depression (δ) in H is high (sδ > 0.50), F must compensate (female advantage) for the loss of gene transmission via pollen production by producing more or higher-quality offspring than H to be maintained in the population. For species with cytoplasmic (maternal) inheritance of male sterility, the female requires only a small compensation in seed production or some other offspring fitness trait to persist. Reallocation to seeds of resources saved by loss of pollen production is expected to increase the quantity (number) and/or quality (mass, germinability) of seeds produced by F, thus compensating for the lack of pollen production. The primary aim of our study was to compare seed germination of F and H via a literature review. Based on theoretical considerations, we hypothesized that seeds of F should germinate better or equally as well as those of H. We found that of 235 case studies for 47 species Fgerm > Hgerm in 48.1%, Fgerm = Hgerm in 38.3% and Fgerm < Hgerm in 13.6%. Our results are very similar to those of a previously published meta-analysis that included germination of F and H for 12 species. For 162 cases on seed size, F > H in 29.0%, F = H in 63.6% and F < H in 7.4%. Since [(Fgerm > Hgerm) < (Fgerm ≤ Hgerm)] and [(Fseedsize > Hseedsize) < (Fseedsize ≤ Hseedsize)], these results suggest that seed quality is not a major fitness component of female advantage.

Maternal sex effects and inbreeding depression under varied environmental conditions in gynodioecious Fragaria vesca subsp. bracteata

Gynodioecy (coexistence of females and hermaphrodites) is a sexual system that occurs in numerous flowering plant lineages. Thus, understanding the features that affect its maintenance has wide importance. Models predict that females must have a seed fitness advantage over hermaphrodites, and this may be achieved via seed quality or quantity. Females in a population of Fragaria vesca subsp. bracteata, a long-lived gynodioecious perennial, do not demonstrate a seed quantity advantage, so this study explored whether females produced better quality seed via maternal sex effects or avoidance of inbreeding depression (IBD). Families of selfed and outcrossed seed were created using hermaphrodite mothers and families of outcrossed seed were created using female mothers. The effects of these pollination treatments were assessed under benign conditions early in life and under varied conditions later in life. To test for an effect of maternal sex, fitness components and traits associated with acclimation to variable environments of progeny of outbred hermaphrodites and females were compared. To test for expression of IBD, fitness parameters between inbred and outbred progeny of hermaphrodites were compared. Offspring of females were more likely to germinate in benign conditions and survive in harsh resource environments than outbred progeny of hermaphrodites. IBD was low across most life stages, and both the effect of maternal sex on progeny quality and the expression of IBD depended on both maternal family and resource condition of the progeny. The effect of maternal sex and IBD on progeny quality depended on resource conditions, maternal lineage and progeny life stage. In conjunction with known lack of differences in seed quantity, the quality advantages and IBD observed here are still unlikely to be sufficient for maintenance of gynodioecy under nuclear inheritance of male sterility.

Inheritance of A1system of cytoplasmic-nuclear male sterility in pearl millet [Pennisetum glaucum(L). R. Br.

Inheritance of male sterility and fertility restoration of the A1 system of cytoplasmic-nuclear male sterility in pearl millet was investigated using 12 crosses among three diverse male sterile lines (A-lines) and four diverse restorers (R-lines). Individual plants from R- lines were used to make crosses on A-lines. The segregation pattern of male sterile (S) and male fertile (F) plants observed in F2 and BC1 in two seasons at ICRISAT, Patancheru was suggestive more likely of a single-gene control of male sterility and fertility restoration. However, a 3-gene model of male sterility/fertility restoration where dominant alleles at any two of the three duplicate complimentary loci will lead to male fertility could not be ruled out, nor could be ruled out a 2-gene control with duplicate interaction. There was indication of variability even within a highly inbred R-line for fertility restoration gene(s). Depending on the genetic constitution of the R-lines at these loci, even the 3-gene model can lead to single-gene segregation ratios as observed in most of the F2s and backcrosses, and 2-gene ratios as observed in a few F2s and backcrosses. The deviations from these expected ratios in some of the crosses influenced by modifiers and environmental conditions generally resulted from the excess of fertile plants in the rainy season or excess of sterile plants in the dry season, the more so in crosses involving an A-line which has been reported to be relatively more unstable for male sterility.

Inbreeding effect on male and female fertility and inheritance of male sterility in Nemophila menziesii (Hydrophyllaceae)

Models of the evolution of gynodioecy assume that inbreeding affects male and female fertility equally and ignore quantitative variation in sex expression. The objectives of this study were to assess inbreeding effects, genetic background, and plant maturity on male and female fertility and the mechanism of male sterility inheritance for Nemophila menziesii (Hydrophyllaceae). Frequency of male-sterile flowers, number of anthers and ovules, and percentage of viable pollen were measured on plants from different pedigrees and five inbreeding levels (F = 0, 0.0625, 0.25, 0.5, and 0.75). Quantitative variation in male sterility was evident. As inbreeding increased, anther and ovule number decreased; the effect on anther number was greater than on ovule number. Pedigrees varied in number of male-sterile flowers and inbreeding effects. Frequency of male-sterile flowers was greatest among first flowers. No trade-off between male and female fertility was detected. A model attributing male sterility to a cytoplasmic locus and restoration to male fertility to a nuclear locus accounted for the distribution of complete sterility and hermaphroditism over the pedigrees. This study suggests that models of the evolution and maintenance of gynodioecy should allow for quantitative variation in male and female fertility components due to inbreeding, pedigree, and plant maturity.

Characterisation of an environmentally induced genic male sterile line of indica rice (Oryza sativa spp. Indica)

Environmentally induced genic male sterility has been successfully used in a 2-line system to produce hybrid rice, with the potential to further increase yield. Elite sterile lines need to be developed for a target production environment to successfully use this novel male sterility system. In this study, a new male sterile line, B06S, identified by Jiangxi Agricultural University, China, was characterised for its flowering characteristics, male fertility behaviour, and the inheritance of male sterility. Flowering characteristics were observed in a sterility-inducing season in Nanchang, China. Compared with the typical fertile cultivars Gui99 and Zhongfu906, B06S started flowering at about the same time, had a slightly longer plant flowering duration (18 days) and a similar panicle flowering duration (6 days), and took longer (6 days) to reach 90% flowering spikelets. Also, at the day of peak flowering, B06S started flowering about 2 h earlier and had an earlier peak flowering time (10.00 am), and the percentage of spikelets flowering before noon was slightly lower (83.8%). Spikelet flowering of B06S lasted 5 h, which was more than 2 h longer than the existing sterile lines. Although B06S showed similar openness to other typical sterile lines (PA64S and 595S), it had a higher stigma exsertion rate (82.5%), larger stigma area (0.92 mm2), and longer stigma viability (4 days). Both pollen and spikelet were completely sterile for more than 75 consecutive days when the environmental temperature was above 24°C, otherwise they would have been fertile. Fertility was slightly influenced by photoperiod. Increased fertility was induced when photoperiod was shorter than 11 h per day. Genetic analysis using the F2 and BC1 populations of 6 crosses indicated that male sterility of B06S was predominantly controlled by a recessive major gene. B065S can be grown in large quantity in the winter nursery in Hainan Island, China. A number of crosses combinations between B065S and indica cultivars had significantly higher yield than the best widely grown hybrids in Jiangxi and other parts of China with similar climates. The best early maturing (B06S × 458) and late maturing (B06S × Gui99) hybrids had 8.9 and 10.3% higher yield than the best currently used hybrids (Jinyou402 and Jinyiugui99, respectively), and will be released in 2007.

Effects of seed size, inbreeding and maternal sex on offspring fitness in gynodioecious Plantago coronopus

Summary Male steriles (MS) must have a fitness advantage relative to hermaphrodites (H) if they are to be maintained in gynodioecious species. We report experiments in which we disentangle the relative contributions of seed size, inbreeding and maternal sex to the fitness advantage of male steriles in Plantago coronopus L. Seed size effects were observed throughout growth experiments in the glasshouse and were reflected in all biomass measurements. In the field, seed size effects resulted in a fourfold increase in standardized seed production per initial buried seed after 2 years between small (mean weight = 0.13 mg) and large (0.20 mg) seeds. Inbreeding depression, calculated from seed to seed was δ = 0.37 after one generation of selfing and δ = 0.93 after the second generation of selfing. Regression of log(1 − δ) on inbreeding level suggested synergistic epistasis in fitness. Even after taking into account the effects of seed size and inbreeding level, the offspring of a male sterile mother had a 16% advantage over a hermaphrodite, but this disappeared when the progeny sex ratio (the ratio of MS : H individuals among the offspring) was taken into account. In the field, offspring of large seeds had both a higher overall incidence of flowering, and a higher probability of flowering in their first year, thus generating an extra cohort of individuals. The high inbreeding depression in fitness after two generations of selfing was also due to a very low incidence of flowering among the S2 individuals. Flowering probability therefore appears to be a critical trait in this system. In the field, the contributions of seed size variation (15%) and inbreeding (9%) combine with 48% higher seed production to give a total fitness advantage of 70% of male steriles relative to hermaphrodites. This is probably sufficient for maintenance of gynodioecy under nuclear‐cytoplasmic inheritance of male sterility. Both inbreeding effects (as a consequence of the sexual system) and pleiotropic effects (of the genes coding for male sterility) play a role in the maintenance of gynodioecy in this species, with an apparently greater role for the latter.

Inheritance of Male Sterility in Japanese Apricot (Prunus mume)

Pollen fertility and inheritance patterns of male sterility were analyzed in various cultivars and selections of Japanese apricot (Prunus mume Sieb. et Zucc.). Male sterility segregated differently in two types of crosses. In pairings of male-sterile and male-fertile parents, progenies were either all male-fertile, all male-sterile, or mixed. Crossing two male-fertile plants resulted in offspring that were either all male-fertile or mixed. Male sterility in Japanese apricot appears to be of the gene-cytoplasmic type. The genotypes of 10 cultivars and three selections are determined.

Inheritance of male-sterility in soybean

Genetic studies on a spontaneous male-sterile/female-fertile soybean mutant identified at the Embrapa Soybean breeding program were carried out in Londrina County, State of Parana, South Brazil. The mutant showing segregation for male-sterility (BR97-17958) was selected within F 5 progeny lines derived from the BR5(6) x Paranaiba cross performed in 1995. The F 1 , F 2 and F 3 generations from test-crossings among heterozygous plants of the BR97-17958 line and recessive homozygous plants (male-sterile) of the T 266H (ms 1 ms 1 ), T 259H (ms 2 ms 2 ), T 273H (ms 3 ms 3 ), T 274H (ms 4 ms 4 ), T 277H (ms 5 ms 5 ) and T 295H (ms 6 ms 6 ) lines were studied to identify whether this mutant defines a new locus or represents an independent mutation in one of the six loci already described. The F 1 , F 2 , and F 3 plants from the crosses were visually classified as presenting normal phenotype of male fertility or male-sterility. Results from inheritance and allele test study among the mutant genotypes and the recessive homozygous male-sterile lines (ms 1 , ms 2 , ms 3 , ms 4 , ms 5 and ms 6 ) provided evidence that the male-sterile characteristic of the line BR97-17958 have a simple recessive Mendelian inheritance and represents a mutation in a locus different from the ms-loci already described.

Transgene insertion induced dominant male sterility and rescue of male fertility using round spermatid injection.

Transgene insertions in the mouse often cause mutations at chromosomal loci. Analysis of insertion mutations that cause male sterility may lead to the identification of novel molecular mechanisms implicated in male fertility. Here we show a line of transgenic mice with dominant inheritance of male sterility (DMS) that was found amid several lines that were normally fertile. Transgene-positive males from this line invariably were sterile, whereas transgenic females and transgene-negative male littermates were fertile. Histologic analysis and TUNEL staining for apoptotic cells in DMS testis showed spermatogenesis arrest at metaphase of meiosis I (M-I), accompanied by massive apoptosis of spermatocytes. Meiosis I arrest was incomplete, however, as small numbers of spermatids and spermatozoa were found. Both round spermatids and spermatozoa were evaluated for their permissiveness in the assisted reproductive technologies intracytoplasmic sperm injection (ICSI) and round spermatid injection (ROSI). Surprisingly, ROSI but not ICSI gave live offspring, suggesting that mature sperm had deteriorated by the time of recovery from the epididymis. Mapping the transgene insertion by fluorescence in situ hybridization revealed a site on chromosome 14 D3-E1. Two candidate genes, GFR alpha 2 and GnRH, that were previously mapped to that region and the functions of which in spermatogenesis are well established were not altered in DMS. As a consequence, positional cloning of the DMS locus will be essential to identify new molecules potentially involved in arrest at M-I. Furthermore, mice carrying this genetic trait might be useful for studies of assisted reproductive technologies and male contraceptives.

Inheritance of male sterility in apricot

Progenies (total of 1,114 seedlings) from crosses representing all possible genotypic combinations between 4 male-fertile and 1 male-sterile apricot parents were scored for the male sterility trait. Crosses between putative heterozygous normal cultivars yielded 25% of male-sterile seedlings, which supports a previous hypothesis that male sterility is controlled by a recessive allele of one nuclear locus. Crosses between those parents and putative homozygous normal cultivars did not produce any male-sterile tree. Finally, the proportion of male-sterile progeny in crosses between a male-sterile and two male-fertile cultivars depended on the genotype of the male parent. When it was heterozygous approximately 50% of the progeny was sterile, whereas when a homozygous fertile parent was used, no male-sterile progeny was obtained. These results confirm a previously proposed model, in which the male sterility trait in apricot is controlled by a single recessive gene.

Inheritance of male hybrid sterility in the house musk shrew (Suncus murinus, Insectivora, Soricidae).

Two geographic races of the house musk shrew (Suncus murinus) were crossed and intercrossed in the laboratory. Many cases of male sterility were detected among the hybrids. Segregation analysis of the pedigree data showed that the inheritance of male sterility in interracial hybrids of S. murinus can be described within the framework of monogene polyallele model with sterility of a single allele combination. This model is similar if not identical to that proposed by Dobzhansky and Muller.

Inheritance of male-sterility and dwarfism in watermelon [ Citrullus lanatus (Thunb.) Matsum. and Nakai

Preliminary studies of a dwarf, male-sterile watermelon showed that male-sterility was controlled by a pair of recessive nuclear genes; it appeared simultaneously with dwarfism and its dwarf gene was different from the three known dwarf genes. Pollen aborted completely in male-sterile plants. Potential uses for the dwarf, male-sterile watermelon are also discussed.

EVOLUTION OF UNISEXUALITY IN THE HAWAIIAN FLORA: A TEST OF MICROEVOLUTIONARY THEORY.

The evolution of separate sexes as a means of avoiding self-fertilization requires the controversial coexistence of large inbreeding depression and high selfing rate in the ancestral hermaphrodite population. Fitness components of adult females and hermaphrodites in nature, of their open-pollinated progeny, and of experimental selfs and outcrosses onto hermaphrodites were compared in endemic Hawaiian Bidens sandvicensis, all of whose known populations are gynodioecious, consisting of a mixture of females and hermaphrodites. Multilocus selfing rates of hermaphrodites were also estimated, and sex morph ratio monitored over four seasons in three populations of B. sandvicensis and one population of gynodioecious B. cervicata. Total mean inbreeding depression in seed set (in the glasshouse), germination rate (in an open-air nursery on Kauai), and first year survivorship and fecundity in the field were estimated as 0.94 (SE 0.04), and occurred primarily in drought months. Lower survivorship and fecundity of selfs were partially explained by their consistently smaller size. Open-pollinated seed of females had significantly lower germination rate, proportion flowering, and fecundity than outcrossed progeny of hermaphrodites, suggesting moderate biparental inbreeding in females and a lack of any non-outcrossing advantage to progeny of females. In all fitness components, open-pollinated progeny of hermaphrodites were inferior to those of females and to outcrosses, and in most components were superior to selfs. Total performance of open-pollinated progeny of females relative to those of hermaphrodites was calculated as 2.3 (SE = 0.4), but since inflorescences of females also set 20% to 50% more seed than those of hermaphrodites, their total relative ovule success was estimated as 3.2 (SE = 0.5). If inheritance of male sterility is nuclear, this superiority is sufficient to maintain females in frequencies over 20% in populations, whose actual frequencies ranged from 14% to 33%. In four populations, selfing rates of hermaphrodites, assayed in seedlings, were 0.50, 0.45, 0.25, and 0.30, but since substantial inbreeding depression occurred prior to germination, the mean selfing rate of hermaphrodite ovules exceeded 0.57. Female frequencies were significantly higher in the two populations with higher hermaphrodite selfing rate. These results suggest that inbreeding depression can exert a profound influence on the mating system of self-compatible plants on Hawaii and perhaps other oceanic islands, and can be sufficiently strong to electively favor the elimination of the male function.

Identification and inheritance of male sterility in groundnut (Arachis hypogaea L.)

Some plants without pods but with gynophores were observed in two F4 progenies of two crosses of goundnut (Arachis hypogaea L.). The flowers on these plants had translucent white anthers with no or a few sterile pollen grains. Three such plants in the succeeding generation were hand pollinated with pollen from a short-duration Indian cv. JL 24. The resulting F1 hybrid plants (male sterile x ‘JL 24’) were normal. Chi-square tests for segregation for male fertile and male sterile plants in F2 and F3 generations indicated that the male sterility in these crosses of groundnut is governed by two recessive genes. We designate these genes as ms1 and ms2 with ms1ms1ms2ms2 being a male sterile genotype.

Inheritance and Linkage Studies in Peach

Inheritance of male sterility in peach [Prunus persica (L.) Batsch] Plant Introduction (PI) 240928 was investigated. Crosses of PI 240928 with five wild-type clones yielded all male-sterile offspring, indicating dominant gene action. Inheritance of the sweet kernel trait in peach was studied in F1 and F2 progeny of `Summer Beaut' nectarine (sweet kernel) × `Biscoe' peach (bitter kernel). All four F1 progeny were bitter. Segregation in an F2 of 80 progeny fit a ratio of 3 bitter: 1 sweet. We propose that the gene controlling the sweet kernel trait be designated sk. Sweet kernel (sk) was linked to nectarine (g) at a map distance of 17 cM. Evaluation of the peach PI collection showed that PI 129678 (`Stanwick' nectarine) and PI 34685 (`Quetta' nectarine) were the only clones with a sweet kernel. Crosses between `Davie II' and `Honeyglo' nectarine (dwdw) confirmed that the gene conferring the dwarf phenotype in progeny of `Davie II' is non-allelic to dw.

SELFING ABILITY AND MALE STERILITY IN SENECIO VERNALIS WALDST. ET KIT. (ASTERACEAE) FROM ISRAEL

Two major findings relating to the breeding system of Senecio vernalis from Israel are reported. First, isolation experiments failed to confirm the existence of a widespread, truly self-compatible and predominantly self-pollinating breeding system in Israeli populations of S. vernalis. However, a single S. vernalis plant derived from a natural stand at Jerusalem was found to be self- compatible and strongly self-pollinating. In its progeny, there were signs of inbreeding depression commonly associated with selfed offspring of outbreeding species. Selfing ability ratios in this progeny indicate a single dominant gene for selfing ability in S. vernalis. The implications of these observations for the origin of S. vulgaris are briefly discussed. Second, the occurrence of gynodioecy in S. vernalis populations from Israel is reported. Although male sterile plants are recognizable by the complete absence of pollen on their exposed stigmas, there probably exists a large amount of variation within and between plants for pollen production. Infertile pollen grains of male steriles differ in size, shape, and sculpturing from those of hermaphrodites. At the Mt. of Olives, in Jerusalem, the frequency of male steriles was found to be 9.1%. There is some preliminary evidence for differences in floret (= ovule) number between the two gender types. Although the inheritance of male sterility appears to be predominantly cytoplasmically controlled, additional mechanisms restoring male fertility have to be postulated to account for the data observed in one of the crosses. The male sterility system in S. vernalis should therefore be referred to as “nuclear-cytoplasmic.”

Observations on Inheritance of Male Sterility in Apricot

Male sterility is defined as the deviant condition in normally bisexual plants when no viable pollen is formed (Frankel and Galun, 1977). Male sterility has been exploited as an effective tool to aid hybrid seed production in many crops. Using this trait, seed producers can transform one inbred from a planned hybridization into a “female” line, thereby ensuring seed of hybrid origin on the male-sterile parent (Janick, 1972). However, male sterility is an undesirable characteristic in scion cultivars of Prunus to be used for fruit production because this trait would restrict yield in large monocultural production blocks. From the viewpoint of an apricot breeding program, male sterility is a characteristic to be avoided (Scott and Weinberger, 1944). A review of apricot (Prunus armeniaca L.) pollen fertility (Burgos, 1991) indicated that only two cases of male-sterile apricot cultivars (‘Arrogance’ and ‘Colorao’) have been described (Garcia et al., 1988). In this paper we show where several male-sterile trees were observed in progenies from controlled hybridizations in P. armeniaca, and we propose a preliminary inheritance model of the trait. Nine different crosses with a total of 378 trees were scored for the male sterility trait. Male-sterile anthers can be distinguished visually from normal fertile anthers during the bloom period. Shrunken, discolored anthers are indicative of male-sterile pollen and provide a sharp contrast to the swollen, yellow appearance of normal pollen-fertile anthers (Connors, 1927). Several samples of shrunken, discolored anthers were chosen randomly to

Inheritance of male sterility in Trifolium hirtum All

The inheritance of male sterility was studied using a set of intra and interpopulation crosses from Californian populations of rose clover (Trifolium hirtum All.). The F2 gave higher frequencies of male steriles in interpopulation crosses than in intrapopulation crosses. Several F2 families gave ratios that were compatible with models of two and three complementary genes. However, the frequency distribution of male sterility among F3 families rejected such models. Given that single and two gene models were rejected, we interpret the results using a cytoplasmic-nuclear model with more than two restorer loci which is at least consistent with the observed results.

The origin ofMentha X gracilis (Lamiaceae). I. Chromosome numbers, Fertility, and three morphological characters

Employing nine clones ofMentha arvensis and four clones ofM. spicata, 932 F, hybrids were synthesized and compared to 20 clones ofM. x gracilis. Two clones ofM. x gracilis with 60 somatic chromosomes were matched to a selected F1 hybrid. The other 18 clones ofM. x gracilis had somatic chromosome numbers of 60, 72, 84, and 96, and while these chromosome numbers appeared in the F1 progeny, morphological matches correlated with their correct chromosome numbers were not synthesized. The range of pollen and seed fertility, as well as the inheritance of male-sterility, leaf pubescence, and crispness, indicates that no one character can be used to identifyM. x gracilis, but all characters can be explained fromM. arvensis x M. spicata.

Genetics of gynodioecy in Hawaiian Bidens (Asteraceae)

Inheritance of male sterility in all gynodioecious species of Hawaiian Bidens was investigated by experimental crosses conducted in greenhouses. Both male-sterile individuals and hermaphrodites were segregated in the progenies of open-pollinated female and hermaphroditic plants growing in nature. The ratios (H:MS) of 1:0, 1:1, 3:1 were observed in the F1 generations; 3:1 and 15:1 in the F2 generations; and 1:1 and 3:1 in the backcrosses. Thirteen interspecific triple crosses and all quadruple crosses gave MS progenies, indicating a directly allelic relationship among male sterility genes in all gynodioecious species. Based on these results, A digenic-cytoplasmic model was proposed, and the evolution of gynodioecy in Hawaiian Bidens was discussed.