Pollen Fertility Of Hybrids Research Articles

​Comparative Study of Crossability Behavior in Intra-specific and Inter-specific Crosses of Vigna radiata and Vigna mungo

Background: The basic plant material consisted of 9 mungbean and 5 urdbean genotypes. 42 different crosses were made comprising 13 Vigna radiata x V. radiata, 4 V. radiata x V. mungo and 25 V. radiata x V. mungo crosses. Varying degree of success has been achieved in obtaining intraspecific and interspecific crosses having desired variability for yield and yield contributing traits along with MYMV resistance. Methods: The present investigation was done at Agricultural Research Farm, Banaras Hindu University, Varanasi, during Kharif, 2019 and Summer, 2020. 42 intra-specific and inter-specific cross combinations were initially examined for their crossability. Out of these, six promising crosses with higher crossability percent were further analyzed for hybrid pollen fertility, hybrid lethality and, evaluation of F1 and parents for different yield traits. Result: Crossability per cent found highest in intraspecific cross HUM 2 x IPM 02-3 (41.86%) in mungbean while, in urdbean cross NDU 1 x R3/12 (41.38%). In interspecific crosses, the maximum crossability per cent was found in SKAU M 365 x R3/28 (34.92%). Two mungbean genotypes (HUM 2 and HUM 26) and two urdbean genotypes (R3/12 and R3/28) can be further utilized for genetic improvement through inter-specific hybridization as there cross combinations are better performing on the basis of yield attributes along with MYMV resistance.

Анализ фертильности пыльцы у анеуплоидных гибридов с замещениями отдельных хромосом или их плеч у хлопчатника вида G.hirsutum L.

Analysis of pollen fertility in interspecific aneuploid F1 hybrids with substitutions of specific chromosomes (2, 4, 6, 7, 18) and chromosome arms (telo 6, telo11) of the cotton genome G. hirsutum L. revealed a decrease in fertility in all hybrid plants. It was shown that hybrid monosomics for chromosome 2 were characterized by a slight decrease in pollen fertility; hybrid monosomics of different families with substitution on chromosome 4 and on chromosome 6 - a significant decrease; hybrid monosomics with substitution on chromosome 7 and 18, as well as monotelodisome hybrid plants with substitution of an individual arm of chromosome 6 or 11 - a strong decrease, which indicated the existence of specific differences in pollen fertility in hybrid monosomic plants with substitution of specific chromosomes of the cotton genome due to the formation of partially unbalanced haplo-deficient gametes.

Studies on cross compatibility in interspecific crosses of Vigna radiata × Vigna umbellata species

The present study was undertaken to study the crossability barriers in interspecific crosses of Vigna radiata × Vigna umbellata. The basic materials of this experiment comprising of five mungbean MYMV Susceptible genotypes and five rice bean MYMV resistant genotypes. Interspecific crosses were attempted by utilizing rice bean genotypes as male parents and mungbean genotypes as female parents. The successful pod set was observed on 12 crosses out of 25 interspecific crosses of Vigna radiata and Vigna umbellata. The results revealed that highest crossability per cent was recorded in the crosses Yellowmung × KBR-1 (17.30 %), DGGV-2× RBL-35 (16.0%), Selection-4×KBR-1 (11.80%), Chinamung × KBR-1 (11.0%) and BGS-9× RBL-35 (10.20%) which were considered as successful crosses. This suggests that the parents of these four interspecific cross combinations may be ideal for transfer of useful genes across the two divergent species and to broaden the genetic base of interspecific hybrid and further, the existence of moderate hybrid pollen fertility (78.24%) coupled with moderate seed germination percentage (36.84%), lower hybrid lethality (21.43%) and lower hybrid breakdown (7.14%) was observed in Chinamung × KBR-1 followed by cross Selection-4 ×KBR-1. In the present investigation prominent observation noticed are strong pre-fertilization as well as post fertilization barriers were present in the cross between V. radiata and V. umbellata, while, growth and lethality of interspecific hybrid seedlings were influenced by the genotypes of both the parental species.

Effect of cytoplasms and genetic backgrounds of parental lines on fertility restoration in Brassica juncea hybrids

Cytoplasm diversification was recognized as one of the most important objective in sustainable exploitation of heterosis. Isonuclear alloplasmic cytoplasmic male sterile (CMS) lines with Moricandia arvensis (mori), Diplotaxis erucoides (eru), Diplotaxis berthautii (ber) cytoplasms were developed in the six diverse Brassica juncea genetic backgrounds (NPJ 112, NPJ 139, LES 1-27, SEJ 8, EC 308575 and Pusa Agarni). Each of these 18 CMS lines were crossed with six locally developed restorers possessing fertility restorer gene from Moricandia arvensis to assess the effect of sterile cytoplasms and nuclear backgrounds of parental lines (A and R) on fertility restoration. Comparison of 108 single cross hybrids, 36 hybrids in each cytoplasm, revealed that the hybrids based on mori cytoplasm was significantly different from the ones possessing ber and eru cytoplasms for mean percent pollen fertility. Further, paired comparisons of the mean per cent pollen fertility of hybrids revealed that the per cent pollen fertility in hybrids was influenced by the genetic backgrounds of parents. However, this effect was not consistent for any cytoplasm or nuclear background of parents. Regression analyses involving percent pollen fertility and seed set in the hybrids, both under open and self pollinated conditions, did not observe any significant association. For diversification of mori based CMS-FR systems eru and ber cytoplasms can be used for sustainable exploitation of heterosis in Indian mustard.

Abyssinian pea (Lathyrus schaeferi Kosterin nom. nov. pro Pisum abyssinicum A. Br.) is a problematic taxon

The Abyssinian pea (Pisum abyssinicum A. Br.), concerned in this review, is known from Ethiopia and Yemen, where it is cultivated along with the common pea (Pisum sativum L. subsp. sativum). The continuously reproduced notion of its possible spontaneous occurrence in the wild ascends to suppositions made in the XIX century and is not based on any actual data. P. abyssinicum is of practical interest owing to its extra early ripening and resistance to bacterial blight. Morphologically it is very similar to P. sativum but its crossability with it is bad as either seed or pollen parent. Traditionally this reproductive barrier was associated with karyological differences. The Abyssinian pea karyotype is variable as 1–2 reciprocal translocations were reported. At the same time there are accessions not differing from the standard karyotype of P. sativum with respect to reciprocal translocations, yet their crossability with the latter is very low and the pollen fertility of F1 and F2 hybrids is lowered. Data were reported on influence of the region of Linkage Group III, containing a gene known to participate in the conflict of nucleus and plastids in remote crosses of peas, on the pollen fertility of hybrids with abyssinian pea. With their karyological variability, the known accessions of the Abyssinian pea are very close to each other genetically, as they diverged just about 4000 years ago. The presence of alleles of molecular markers common with Pisum fulvum Sibth. et Smith on the one hand and P. sativum L. subsp. elatius (Bieb.) Schmalh. on the other hand evidences in favour of an old hypotheses by L.I. Govorov that the Abyssinian pea originated from their spontaneous hybrid. This spontaneous cross may have taken place under cultivation, in Yemen or Afar Depression. A representative of P. sativum subsp. elatius was revealed, the F1 hybrids of which with the Abyssinian pea as a seed parent had fully fertile pollen. P. abyssinicum× P. fulvum crosses provide the best hybrid seed outcome among remote crosses conducted, so that P. abyssinicum can be used as a ‘bridge’ for gene introgression from P. fulvum to P. sativum. Rather a high evel of reproductive isolation of the Abyssinian pea from other representatives of the genus conforms the biological species concept, however the disposition of P. abyssinicum accessions as a small cluster among accessions of P. sativum subsp. elatius on molecular phylogeny reconstructions violates the phylogenetic species concept. Most authors assume the Abyssinian pea as a species, Pisum abyssinicum, some as a subspecies, P. sativum subsp. abyssinicum (A. Br.) Berger. Perhaps it would be most correct to consider it as a hybridogenic species. Because of the recent subsuming of the genus Pisum L. into the genus Lathyrus and with respect to the existing name Lathyrus abyssinicus A. Br. (a synonym of L. sativus L.), the Abyssinian pea is given a new name Lathyrus schaeferi (A. Braun) Kosterin nomen novum pro Pisum abyssinicum A. Braun), in honour of Hanno Schaefer, who substantiated the revision of tribe Fabeae by molecular reconstruction of its phylogeny. New combinations of Lathyrus sectio Pisum (L.) Kosterin combinatio nova and Lathurus fulvus (Sibthrop et Smith) Kosterin combinatio nova are proposed.

Breeding Relationships in Macaronesian Tolpis (Asteraceae-Cichorieae): F1 Hybrid Pollen Fertility Within and Among Populations from the Azores, Canary Islands, and Madeira

Abstract The pollen fertility of F1 hybrids, ranging from progeny within natural populations to synthetic hybrids between species of Tolpis from three archipelagos in Macaronesia, was determined. Pollen fertility of F1 hybrids of inter-archipelago crosses from the Azores, Canaries, and Madeira were generally lower than crosses between populations or species in the same archipelagos. Lower pollen fertility was pronounced in hybrids between plants from the Canaries and the other archipelagos, which is concordant with a more distant phylogenetic relationship between the Canaries, and the Azores and Madeira. Lower average pollen fertility was seen between plants from different as compared to the same clades in the Canary Islands. However, low pollen fertilities were also detected between plants from some populations/species in the same archipelagos, and even among progeny of individual maternal plants. Some hybrids with reduced fertility had meiotic irregularities, suggesting chromosomal rearrangements; in ot...

Double‐Neutral Genes, Sa‐n and Sb‐n, for Pollen Fertility in Rice to Overcome Indica × Japonica Hybrid Sterility

A major obstacle in the development of superior intersubspecific hybrids between subspecies (indica and japonica) of Asian cultivated rice (Oryza sativa L.) is partial sterility of the F1 generation. Neutral genes, Sa‐n, Sb‐n, and Sc‐n, for pollen fertility have the potential to overcome F1 pollen sterility. The present study was planned to find double‐neutral genes for pollen fertility and to evaluate their effect on pollen fertility of intersubspecific hybrids. Five genotypes were crossed with eight isogenic lines to mine neutral genes for pollen fertility. Pollen fertility of hybrids was observed in F1 and F2, and segregation ratios were recorded in F2 to confirm the neutral genes. The results showed that DN18 and DN75 had double‐neutral genes (Sa‐n and Sb‐n) whereas DN22 had three neutral genes Sa‐n, Sb‐n, and Sc‐n at Sa, Sb, and Sc pollen sterility loci, respectively. Furthermore, we found a single neutral gene (Sc‐n) for pollen fertility at the Sc locus and neutral gene for embryo sac fertility at the S5 locus in DN13. DN18 and DN75 were crossed with numerous typical japonica and indica cultivars. Results showed that double‐neutral genes could overcome most of the intersubspecific hybrid pollen sterility. These lines could be used for the development of high yielding indica × japonica hybrids and neutral genes could be introgressed into elite cultivars of Asian cultivated rice for fertility restoration.

Natural hybridization between Elymus repens and E. hispidus assessed by AFLP analysis

Hybrid speciation within the genus <em>Elymus</em> is analyzed and discussed. The supposed hybrid origin of <em>Elymus</em> x <em>mucronatus</em> between <em>Elymus repens</em> and <em>Elymus hispidus</em> was tested. In this aim, pollen viability and AFLP variation of putative progenitors and progenies from two natural populations were studied. Pollen fertility of hybrids ranging from 0 to 91.95% (average 59.50%) indicates the occurrence of F1 hybrids and backcross hybrids. Seven EcoRI/MseI AFLP primer combinations generated a total of 477 AFLP fragments (300 polymorphic) for 48 parental and hybrid individuals. UPGMA and principal coordinates analysis of the AFLP data set show that hybrids are closer to <em>E. hispidus</em> than to <em>E. repens</em> and suggest unidirectional introgression towards <em>E. hispidus</em>. AFLP fragments of the hybrid taxon were additively inherited from the parental species and no hybrid-specific bands were identified. AFLP analysis validates the hybrid status of <em>E.</em> ×<em>mucronatus</em>. Populations in which <em>E. repens</em>, <em>E. hispidus</em> and their hybrids co-occur still progress from early hybridization stages of F1 hybrids to an advanced hybridization stage of a well-established hybrid swarm. <em>E.</em> ×<em>mucronatus</em> is potentially self-sustaining by predominant vegetative reproduction by rhizomes and partial fertility leading to the development of mature seeds. We propose to consider <em>Elymus</em> ×<em>mucronatus</em> as a new species of hybrid origin in the Polish flora.

Geographical variation in postzygotic isolation and its genetic basis within and between twoMimulusspecies

The aim of this study is to investigate the evolution of intrinsic postzygotic isolation within and between populations of Mimulus guttatus and Mimulus nasutus. We made 17 intraspecific and interspecific crosses, across a wide geographical scale. We examined the seed germination success and pollen fertility of reciprocal F(1) and F(2) hybrids and their pure-species parents, and used biometrical genetic tests to distinguish among alternative models of inheritance. Hybrid seed inviability was sporadic in both interspecific and intraspecific crosses. For several crosses, Dobzhansky-Muller incompatibilities involving nuclear genes were implicated, while two interspecific crosses revealed evidence of cytonuclear interactions. Reduced hybrid pollen fertility was found to be greatly influenced by Dobzhansky-Muller incompatibilities in five out of six intraspecific crosses and nine out of 11 interspecific crosses. Cytonuclear incompatibilities reduced hybrid fitness in only one intraspecific and one interspecific cross. This study suggests that intrinsic postzygotic isolation is common in hybrids between these Mimulus species, yet the particular hybrid incompatibilities responsible for effecting this isolation differ among the populations tested. Hence, we conclude that they evolve and spread only at the local scale.

Unveiling cryptic species diversity of flowering plants: successful biological species identification of Asian Mitella using nuclear ribosomal DNA sequences

BackgroundAlthough DNA sequence analysis is becoming a powerful tool for identifying species, it is not easy to assess whether the observed genetic disparity corresponds to reproductive isolation. Here, we compared the efficiency of biological species identification between nuclear ribosomal and chloroplast DNA sequences, focusing on an Asian endemic perennial lineage of Mitella (Asimitellaria; Saxifragaceae). We performed artificial cross experiments for 43 pairs of ten taxonomic species, and examined their F1 hybrid pollen fertility in vitro as a quantitative measure of postzygotic reproductive isolation.ResultsA nonlinear, multiple regression analysis indicated that the nuclear ribosomal DNA distances are sufficient to explain the observed pattern of F1 hybrid pollen fertility, and supplementation with chloroplast DNA distance data does not improve the explanatory power. Overall, with the exception of a recently diverged species complex with more than three biological species, nuclear ribosomal DNA sequences successfully circumscribed ten distinct biological species, of which two have not been described (and an additional one has not been regarded as a distinct taxonomic species) to date.ConclusionWe propose that nuclear ribosomal DNA sequences contribute to reliable identification of reproductively isolated and cryptic species of Mitella. More comparable studies for other plant groups are needed to generalize our findings to flowering plants.

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.

Weed evolution after crop gene introgression: greater survival and fecundity of hybrids in a new environment

Crop-wild hybridization may produce offspring with lower fitness than their wild parents due to deleterious crop traits and outbreeding depression. Over time, however, selection for improved fitness could lead to greater invasiveness of hybrid taxa. To examine evolutionary change in crop-wild hybrids, we established four wild (Raphanus raphanistrum) and four hybrid radish populations (R. raphanistrum x Raphanus sativus) in Michigan (MI), USA. Hybrid and wild populations had similar growth rates over four generations, and pollen fertility of hybrids improved. We then measured hybrid and wild fitness components in two common garden sites within the geographical range of wild radish [MI and California (CA)]. Advanced generation hybrids had slightly lower lifetime fecundity than wild plants in MI but exhibited c. 270% greater lifetime fecundity and c. 22% greater survival than wild plants in CA. Our results support the hypothesis that crop-wild hybridization may create genotypes with the potential to displace parental taxa in new environments.

Molecular diversity of CMS sources and fertility restoration in the genus: Helianthus

Molecular characterization of 28 CMS sources and the fertile cytoplasm of H. annuus in sunflower demonstrated that cytoplasms different by their origin show a considerable similarity that cannot be expected from their pedigree. Cluster analysis using the UPGMA method allowed differentiating 10 mitochondrial (mt) types based on RFLP data. Characteristic proteins specific for one or more CMS sources could be identified which correspond to the mt types. In addition, the data obtained on fertility restoration for a subset of nine new CMS sources support the classification of the cytoplasms made on mtDNA level as demonstrated in the UPGMA dendrogram. A map-based cloning approach is followed for the isolation of the restorer gene Rf1, which restores pollen fertility in hybrids based on PET1. Markers closely linked to the restorer gene could be identified using AFLP and RAPD technologies. A bacterial artificial chromosome (BAC) library was constructed using the sunflower restorer line RHA325 and pBeloBAC11 as vector. The first sunflower BAC library corresponds to 1.7 haploid genome equivalents (104,736 clones average insert size approx. 50 kb). Use of STS markers, which had been developed from RAPD markers, allowed to identify three BAC clones by colony hybridization against high density filters. DNA fingerprinting using HindIII allowed to build a contig for the restorer locus Rf1.

Transfer of PLRV resistance fromSolanum verrucosum Schlechdt to potato (S. tuberosum L.) by protoplast electrofusion

Somatic fusions between an accession of the diploid wild speciesSolanum verrucosum and a dihaploid S.tuberosum genotype were produced in order to incorporate resistance to potato leafroll virus (PLRV). In total 15 somatic hybrids out of 16 regenerants were obtained. Identification of hybrids was based on additive RAPD patterns, general morphological characteristics, chromosome numbers and chloroplast counts in stomata guard cells. A field trial was performed with the hybrids, their two parents and the control cultivar Kennebec to assess field performance and phenotypic variability. Yield parameters varied considerably among somatic hybrids. Some of the hybrids gave significantly higher yields, tuber numbers and tuber weights than both parents. Pollen fertility of hybrids ranged from 19 to 77%. Twelve hybrids were found to be resistant to PLRV.

Mating systems and interfertility of swamp milkweed (Asclepias incarnata ssp. incarnata and ssp. pulchra)

We investigated the breeding system and interfertility of both subspecies of Asclepias incarnata. We performed hand-pollinations in the glasshouse to compare fruit-set from self- vs. cross-pollinations and to assess interfertility in crosses between the subspecies. We also used horizontal starch-gel electrophoresis to infer mating-system parameters from open-pollinated progeny arrays in three natural populations over two consecutive years. Plants of ssp. incarnata were about 1/6 as likely to mature hand self-pollinated fruits as were ssp. pulchra plants. Furthermore, plants varied significantly in both self- and cross-fertility. Fertile offspring resulted from intersubspecific crosses, but hybrid plants showed reduced pollen fertility relative to parental plants, which is similar to what has been reported for wider hybrid crosses among milkweeds. Reduced pollen fertility in hybrids, along with geographical barriers, may contribute to maintaining subspecific differentiation. Based on allozyme markers, naturally pollinated populations were largely outcrossed (tm ranged from 0.881 to 0.986). Plants varied significantly with respect to outcrossed male fertility (rp ranged from 0.186 to 0.396) but not self-fertility (rt was not significantly different from 0). Outcrossing rate did not differ significantly among populations or between years. We found swamp milkweed to be neither fully self-compatible nor self-incompatible, which adds to growing evidence of the complexity of milkweed breeding systems. Variation in frequencies of alleles modifying the expression of the self-incompatibility system could explain some of this complexity.

Characterization of Foxtail Millet, Setaria italica (L.) P. Beauv., in Pakistan Based on Intraspecific Hybrid Pollen Semi-sterility.

Sixteen strains of foxtail millet, Setaria italica (L.) P. Beauv., originally collected from Pakistan were crossed with three strains which had previously been used as testers for classifying six landrace groups based on hybrid pollen sterility. Wide variation was observed in pollen fertility of the F1 hybrids, ranging from 14.2% to 94.7%, while pollen fertility of all the selfed Pakistani strains and testers was normal. Pakistani strains were classified into type C (8 strains), type BC (2) and type X (6) on the basis pollen fertility of more than 75% is normal fertility. No A, B or AC type strains were detected. Type C was found in land-races collected from Punjab Province, the southern part of the North-West Frontier Province (N. W. F. P.) and Baltistan. Type X was distributed in the northern part of N. W. F. P. and an adjacent area of the western part of Gilgit Agency, in the northeastern part of Gilgit Agency and in Baltistan. Different landrace groups were suggested among the strains of type X by the variation in hybrid sterility observed with each tester. This observation was strongly supported by an almost sterile hybrid between type X strains from N. W. F. P. and the northeastern part of Gilgit Agency. Type BC was found in Gilgit Agency and Baluchistan. Landrace groups classified by hybrid pollen fertility did not show any clear relationship with morphological groups which had a different geographical distribution. The present results imply that S. italica, with various phylogenetic backgrounds, might have been introduced into this region several times, and subsequently evolved into three distinct morphological groups.

Chromosome evolution within theOrnithogalum tenuifolium complex (Hyacinthaceae), with special emphasis on the evolution of bimodal karyotypes

Hypotheses on the evolution of the karyotypes of 8 chromosome races (2n = 4, 6, 8, 10, 12, 16-two forms, 26) within theOrnithogalum tenuifolium complex are discussed. Four of the karyotypes are strictly bimodal: 2n = 8 (6 long and two short chromosomes), 2n = 10 (6 long and 4 short chromosomes), 2n = 12 (6 long and 6 short chromosomes) and 2n = 16 (12 long and 4 short chromosomes). The hypotheses are tested by means of measurements of nuclear DNA content, studies of meiosis and pollen fertility of hybrids, and comparisons of karyotype morphology. The results indicate that the E. African 2n = 12 chromosome race is the most primitive and has given rise to the other chromosome races. The 2n = 6 race is found to have a significantly higher fitness than the 2n = 12 race.

An analysis of interspecific hybrids and phylogenetic implications inCucumis (Cucurbitaceae)

Investigations on interspecific crossability in 8Cucumis species (2n = 24) and chromosome pairing and pollen fertility of their hybrids from 15 combinations have been utilized for tracing the phylogenetic relationships among these taxa and factors responsible for their differentiation. A collective evaluation of data suggests that there are three broad groups of species, one of the spiny fruited interfertile species, whose hybrids show varying degree of chromosome associations and low to high pollen fertility; the second of species with non-spiny fruits, which are completely incompatible with the former but weakly compatible with the cultivated species,C. melo L. to produce partly developed seeds, and the third group ofC. metuliferus E. Mey. exSchrad. andC. melo and its different botanical varieties. The species with spiny fruits can be further divided based on karyomorphological similarities and/or on relative genomic affinity, indicated by chromosome pairing and hybrid pollen fertility.

Interspecific Hybridization and Its Evolutionary Significance in the Genus Aquilegia

Various hybrid combinations of 18 species and varieties ofAquilegia were produced, and several cross-pollinations were made which failed to produce hybrids. Pollen fertility of hybrids was generally high, with a total mean of approximately 50%, but highly variable among hybrid combinations and consistently lower than that of parental species. With the exception of frequent occurrence of giant pollen grains and rare synaptic failure of one or two homologous pairs, meiotic behavior in hybrid pollen mother cells appeared to be completely regular.