Presence Of Self-incompatibility Research Articles

Palynological studies and their implication in the compatibility of tuberose cultivars

Determination of palynological characters of commercial cultivars is significant in determining thecompatibility and intraspecific relationship, an important criterion in tuberose breeding. The presence ofself-incompatibility and seed sterility in tuberose has greatly hindered the conventional breeding methods asconfirmed through various studies. However, regulation of the incompatibility system and the principal factorbehind it has not been thoroughly investigated. The understanding of both male and female gametophytes andtheir functioning is a prerequisite which is still a less explored area in tuberose. Seventeen tuberose genotypesstudied showed the same inclination towards viability and germination determining a positive correlation.Analysis of pollen morphology and ultra-structure using a scanning electron microscope (SEM) revealed markedvariations among the genotypes. The distinct pollen ultra-structures revealed would serve as important featuresfor classification and character identification in taxonomy. It also ascertains the pollen function as evidenced bythe shrunken pollen of genotypes previously reported as sterile. These findings are vital to fully comprehendingthe breeding systems and reproduction biology of tuberose cultivars.

Construction of a high-density genetic linkage map and QTL analysis for hazelnut breeding

Hazelnut breeding is a slow activity due to the long lifecycle of the plant, the long time between pollination and reliable phenotype observation in the progeny, the presence of self-incompatibility and the high level of heterozygosity. Improved knowledge on the hazelnut genome and the development of marker-assisted selection would greatly facilitate breeding programs. Objective of this study was the construction of high-density genetic maps and the detection of QTL (quantitative trait loci) related to phenological, vegetative and productive traits, by using an F1 progeny obtained by crossing ‘Tonda Gentile delle Langhe’ (female parent, hereafter TGdL) with ‘Merveille de Bollwiller’ (syn. ‘Hall’s Giant’ male parent, MB). Genotyping-by-sequencing (GBS), followed by SNP mining using a Samtools-based pipeline, yielded 7,980 SNP markers. Independent linkage maps were constructed for each parent on the basis of the double pseudo-testcross mapping strategy. The linkage map for TGdL consisted of 1,236 markers covering a total genetic length of 900.4 cM, with a mean inter-marker distance of 0.83 cM. A reciprocal translocation was detected in TGdL between two non-homologous chromosomes. The linkage map for MB was based on segregation at 1,211 markers covering a total genetic length of 899.1 cM, with a mean inter-marker distance of 0.82 cM. Plant and nut traits were recorded during five years and statistically analyzed with molecular data to identify marker/QTL associations for flowering and bud burst time, sucker habit and nut traits, such as nut and seed size, roundness index, percent kernel and ease of pellicle removal.

Gametophytic self-incompatibility causes seedlessness in ‘Kagzi Kalan’ lemon (Citrus limon)

ABSTRACTThe present study aimed to study the flower and pollen structure, pollen viability, in vitro pollen germination of ‘Kagzi Kalan’ lemon (Citrus limon (L.) Osbeck), and in vivo pollen tube growth in self- and cross pollination to understand the mechanism of seedlessness. The results revealed that Kagzi Kalan had tetra-colporate spherical shaped pollen of uniform size. The results of Acetocarmine and FDA test and in vitro germination indicated normal pollen viability and germinability in Kagzi Kalan. In vivo pollen tube growth showed > 50% pollen germination on stigma in all treatments though a greater number of pollen tubes at the mid style, base of the style, and near the ovule was found in cross pollination. Contrary to this, despite optimum pollen germination (53.51–70.37%) in self-pollination treatments, none of the pollen tubes reached the base of the style due to abnormal growth of pollen tubes, viz. curvatures, inhibition of pollen tube growth, and callose deposition. The inhibition of pollen tubes at the mid style under self-pollination treatments, and production of seeded fruits under cross pollination treatments, indicate the presence of self-incompatibility and the site of inhibition of pollen tubes. Thus, gametophytic self-incompatibility (SI) caused seedlessness in Kagzi Kalan by blocking fertilization in the ovary.

DECONSTRUCTING HETEROSTYLY: THE EVOLUTIONARY ROLE OF INCOMPATIBILITY SYSTEM, POLLINATORS, AND FLORAL ARCHITECTURE

Darwin's early work on heterostyly and related style polymorphisms (the presence of two or three style morphs within a population) generated much interest to understand how precise interactions between ecological and genetic mechanisms influence the evolution of floral diversity. Here we tested three key hypotheses proposed to explain the evolution of heterostyly: (i) the presence of self-incompatibility; (ii) the role of pollinators in promoting dissasortative mating; and (iii) floral architecture, which restricts pollinators' movements and ensures more exact pollen deposition on their bodies. We combined data from experiments, field observations, and published studies to test whether evolution of style polymorphism in Narcissus is driven by the incompatibility system, pollinator guilds, or floral architecture, within a phylogenetic framework. Neither differences in pollinator environment nor the presence of genetic self-incompatibility were correlated with presence of style polymorphism. However, our results indicate that the evolution of style polymorphism was driven by the presence of a narrow and long floral tube.

Breeding systems, hybridization and continuing evolution in Avon Gorge Sorbus.

Interspecific hybridization and polyploidy are key processes in plant evolution and are responsible for ongoing genetic diversification in the genus Sorbus (Rosaceae). The Avon Gorge, Bristol, UK, is a world 'hotspot' for Sorbus diversity and home to diploid sexual species and polyploid apomictic species. This research investigated how mating system variation, hybridization and polyploidy interact to generate this biological diversity. Mating systems of diploid, triploid and tetraploid Sorbus taxa were analysed using pollen tube growth and seed set assays from controlled pollinations, and parent-offspring genotyping of progeny from open and manual pollinations. Diploid Sorbus are outcrossing and self-incompatible (SI). Triploid taxa are pseudogamous apomicts and genetically invariable, but because they also display self-incompatibility, apomictic seed set requires pollen from other Sorbus taxa - a phenomenon which offers direct opportunities for hybridization. In contrast tetraploid taxa are pseudogamous but self-compatible, so do not have the same obligate requirement for intertaxon pollination. The mating inter-relationships among Avon Gorge Sorbus taxa are complex and are the driving force for hybridization and ongoing genetic diversification. In particular, the presence of self-incompatibility in triploid pseudogamous apomicts imposes a requirement for interspecific cross-pollination, thereby facilitating continuing diversification and evolution through rare sexual hybridization events. This is the first report of naturally occurring pseudogamous apomictic SI plant populations, and we suggest that interspecific pollination, in combination with a relaxed endosperm balance requirement, is the most likely route to the persistence of these populations. We propose that Avon Gorge Sorbus represents a model system for studying the establishment and persistence of SI apomicts in natural populations.

A TALE OF TWO CONTINENTS: BAKER'S RULE AND THE MAINTENANCE OF SELF-INCOMPATIBILITY IN LYCIUM (SOLANACEAE)

Over 50 years ago, Baker (1955, 1967) suggested that self-compatible species were more likely than self-incompatible species to establish new populations on oceanic islands. His logic was straightforward and rested on the assumption that colonization was infrequent; thus, mate limitation favored the establishment of self-fertilizing individuals. In support of Baker's rule, many authors have documented high frequencies of self-compatibility on islands, and recent work has solidified the generality of Baker's ideas. The genus Lycium (Solanaceae) has ca. 80 species distributed worldwide, and phylogenetic studies suggest that Lycium originated in South America and dispersed to the Old World a single time. Previous analyses of the S-RNase gene, which controls the stylar component of self-incompatibility, have shown that gametophytically controlled self-incompatibility is ancestral within the genus, making Lycium a good model for investigating Baker's assertions concerning reproductive assurance following oceanic dispersal. Lycium is also useful for investigations of reproductive evolution, given that species vary both in sexual expression and the presence of self-incompatibility. A model for the evolution of gender dimorphism suggests that polyploidy breaks down self-incompatibility, leading to the evolution of gender dimorphism, which arises as an alternative outcrossing mechanism. There is a perfect association of dimorphic gender expression, polyploidy, and self-compatibility (vs. cosexuality, diploidy, and self-incompatibility) among North American Lycium. Although the association between ploidy level and gender expression also holds for African Lycium, to date no studies of mating systems have been initiated in Old World species. Here, using controlled pollinations, we document strong self-incompatibility in two cosexual, diploid species of African Lycium. Further, we sequence the S-RNase gene in 15 individuals from five cosexual, diploid species of African Lycium and recover 24 putative alleles. Genealogical analyses indicate reduced trans-generic diversity of S-RNases in the Old World compared to the New World. We suggest that genetic diversity at this locus was reduced as a result of a founder event, but, despite the bottleneck, self-incompatibility was maintained in the Old World. Maximum-likelihood analyses of codon substitution patterns indicate that positive Darwinian selection has been relatively strong in the Old World, suggesting the rediversification of S-RNases following a bottleneck. The present data thus provide a dramatic exception to Baker's rule, in addition to supporting a key assumption of the Miller and Venable (2000) model, namely that self-incompatibility is associated with diploidy and cosexuality.

Self-Compatibility Inheritance in Tomatillo (Physalis Ixocarpa Brot.)

Self-Compatibility Inheritance in Tomatillo (Physalis Ixocarpa Brot.) One of the main limiting factors to improve tomatillo is the presence of self-incompatibility which has been reported to be gametophytic. In an early research, a self-compatible plant was found in the Rendidora landrace and this allowed us to investigate the inheritance of self-compatibility gene (s) in tomatillo. The following crosses were performed: self-compatible x self-incompatible, self-compatible x self-compatible and self-incompatible x self-incompatible and their respective reciprocal crosses. Segregation ratios on self-compatibility versus self-incompatibility in their offspring indicate that self-compatibility is not inherited via cytoplasm, so the responsible gene is located in chromosomes. The inheritance of self-compatibility is due to a single dominant gene (Sc) which is a mutation at the S locus. Self-compatible individuals are strictly heterozygous (Sc,4) and finally, the self-compatibility allele (Sc), in the male side (Sc,4), seems to be non functional when self-pollinating the Sc,4 stigma. A single gene controlling stem pubescence was also found.

Density-Dependent Pollinator Visitation and Self-Incompatibility in Upper Great Lakes Populations of Trillium grandiflorum

2003.-Trillium grandiflorum is a widely distributed, non-clonal, long-lived, white-flowered perennial herb. We examined the pollination biology and self-compatibility of Trillium grandiflorum in five populations distributed across northern Wisconsin and the western Upper Peninsula of Michigan. Self-pollination was almost entirely ineffective in producing seeds in all populations, suggesting strong self-incompatibility. Natural seed set varied slightly across populations, with an average of 71% of ovules fertilized per fruit. At the population level, seed set was not limited by receipt of pollen. At the plant level, seed set per flower first increased, then decreased in response to an increasing density of flowering plants within 2 m. This suggests that neighboring flowers facilitate pollinator visitation at low densities then compete for visits at higher densities. Observed pollinator visitation rates support this interpretation. The presence of self-incompatibility and the absence of clonal spread could make Trillium grandifiorum vulnerable to disruptions in pollinator service.

Genetic Control of Self-Incompatibility in Centromadia (Hemizonia) Pungens Subsp. Laevis (Madiinae, Asteraceae)

The presence of self-incompatibility was tested in Centromadia pun gens subsp. laevis and the genetic basis of the self-incompatibility response was explored using crossing studies. We performed full diallel crossing experiments among 10 individuals from one natural population and four F1 families. We observed a strong self-incompatibility response in all individuals tested, with a significant difference in seed set between selfed and outcrossed matings. Most pairwise matings among parental plants were compatible, with some nonreciprocally incompatible matings (i.e., the matings were successful in one direction, but not the other), and only one reciprocally incompatible mating. The full diallel crossing studies among sibs in the four F1 families showed two major compatibility classes. These results are consistent with a single-locus sporophytic self-incompatibility system in this species.

Quantitative analysis of pollination diallels of two Australian species of Pandorea (Bignoniaceae)

The genus Pandorea, family Bignoniaceae, occurs naturally in Australia. Pandorea pandorana and P. jasminoides were used in intraspecific diallel crosses in order to test for the presence of self-incompatibility and the effect of genotype. Both species were found to be highly self-incompatible. Only 2 out of 353 (0.6%) selfpollinations compared to 337 out of 485 (69.5%) of outcross-pollinations of P. pandorana set fruit. Similarly, for P. jasminoides, 4 out of 235 (1.7%) self-pollinations and 175 out of 296 (59.1%) of outcross pollinations set fruit. Both reciprocal and genotype effects were found in P. pandorana. Fruit-set differences occurred between two different genotypes of P. jasminoides, but reciprocal effects were not found. Data were analysed using generalized linear models with a logit-link function assuming a binomial error distribution. The relative merits of the various models are discussed.