Effect of Self-fertilization on Performance, Breeding and Germplasm Management of Four Local Faba Bean Cultivars

Faba bean is self- and cross-fertilized species. The consequences of self-fertilization are important factors determining the germplasm management in such species with levels of heterogeneity and heterozygsity. Effects of self-fertilization on floral, yield and yield components characters were evaluated by comparing two levels of selfing, produced in bee-proof cages, in open-pollination at two locations in Sudan. Selfing process results in no significant differences in yield and yield components within each cultivar. Autofertile lines with reduced partial dependence on insects for seed set could be produced. Spatial isolation should be used to maintain the genetic purity of such lines. An alternate strategy for entries multiplication should focus on increasing heterozygosity and the maintenance of cross-fertilization inside the entries to prevent contamination with foreign pollens. Our results follow the previous knowledge on faba bean genetic resources conservation and management.

Self-fertilization in a gonochoristic fish yellow catfish

Sex control techniques are in great demand for aquaculture because of the huge benefits of mono-sex production.In a previous study on yellow catfish(Tachysurus fulvidraco),intersex individuals were produced by administrating 17α-methyltestosterone(MT)or aromatase inhibitor letrozole(LZ).The ovarian and testicular portions of intersexual gonads developed well and were completely separated,arousing our interest in producing self-fertilizable fish and clone-like fish populations.In this study,yellow catfish fry were treated with a combination of MT and LZ at a low dose(5 mg kg^(-1)MT,300 mg kg^(-1)LZ)at a low water temperature(27.0℃,mixed sex-producing temperature,LL group)and a high temperature(33.5◦C,male-producing temperature,HL group),and with a high dose(10 mg kg^(-1) MT,600 mg kg^(-1) LZ)at a low water temperature(LH group),during 12-65 days post-hatching,the critical period of sex differentiation.Both XX and XY intersex were produced with different percentages at the same time through co-treatment with MT and LZ,with or without the help of male-producing temperature.The highest percentage of XY intersex(53%in XY,36%in XX and XY)and XX intersex(47%in XX,25%in XX and XY)was produced in LH and HL groups,respectively.Results of gonadal morphology,histology,and sperm dynamic analysis indicate that some XX and XY intersex individuals were capable of self-fertilization through artificial insemination.The reproductive performance of these intersex individuals was then investigated by injecting spawning agents,dissecting gonads,and artificially fertilizing eggs with their own sperm.The XX,XY,and YY genotypic individuals were produced by the self-fertilization of XY intersex individuals.The present study successfully produced high percentages of XX and XY intersex and conducted self-fertilization by mating the eggs and sperm of a single intersex individual.Self-fertilization in fish will show great potential in aquaculture genetics and breeding,for example,generating highly homozygous(or"clonal")genetic material,producing mono-sex populations,and identifying unknown sex determination modes.In particular,the cloning method of producing genetic materials will be greatly beneficial for maintaining advantageous traits through self-fertilization generation after generation.

Assortative mating and self-fertilization differ in their contributions to reinforcement, cascade speciation, and diversification

Cascade speciation and reinforcement can evolve rapidly when traits are pleiotropic and act as both signal/cue in nonrandom mating. Here, we examine the contribution of two key traits-assortative mating and self-fertilization--to reinforcement and （by extension） cascade speciation. First, using a population genetic model of reinforcement we find that both assortative mating and self-fertilization can make independent contributions to increased reproductive isolation, consistent with reinforcement. Self-fertilization primarily evolves due to its 2-fold transmission advantage when inbreeding depression （d） is lower （d〈 0.45） but evolves as a function of the cost of hybridization under higher inbreeding depression （0.45 〈 d〈 0.48）. When both traits can evolve simultaneously, increased self-fertilization often prohibits the evolution of assortative mating. We infer that, under specific conditions, mating system transitions are more likely to lead to increased reproductive isolation and initiate cascade speciation, than assortative mating. Based on the results of our simulations, we hypothesized that transitions to self-fertilization could contribute to clade-wide diversification if reinforcement or cascade speciation is common. We tested this hypothesis with comparative data from two different groups. Consistent with our hypothesis, there was a trend towards uniparental reproduction being associated with increased diversification rate in the Nematode phylum. For the plant genus Mimulus, however, self-fertilization was associated with reduced diversification. Reinforcement driving speciation via transitions to self-fertilization might be short lived or unsustainable across macroevolutionary scales in some systems （some plants）, but not others （such as nematodes）, potentially due to differences in susceptibility to inbreeding depression and/or the ability to transition between reproductive modes.

Differential Gene Expression Between Cross-Fertilized and Self-Fertilized Kernels During the Early Stages of Seed Development in Wheat

In order to understand molecular basis of cross-fertilized kernel advantage and heterosis, improved differential display of mRNA was used in this study to analyze alterations in gene expression between cross-fertilized and self-fertilized kernels at 2, 4, 6, 8, 10 and 12 days after pollination (DAP) by using 3 wheat hybrids with different level of heterosis. Four patterns of differential expression were observed: (i) bands observed in cross-fertilized kernels but not in self-fertilized kernels (BCnS); (ii) bands occurring in only self-fertilized kernels but not in cross-fertilized kernels (BSnC); (iii) cDNA over-expressed in cross-fertilized kernels compared to self-fertilized kernels (OEC); (iv) cDNA under-expressed in cross-fertilized kernels compared to self-fertilized kernels (UEC). Further analysis showed that BCnS is positively correlated with heterosis, but BSnC is negatively correlated with heterosis. Four differentially expressed cDNA fragments were verified by reverse-northern blot and sequence homology search in GenBank showed that one of them was new sequences; the other exhibited higher similarity to NBS-LRR type resistance protein, 1,6-bisphosphatase and photosystem Ⅱ chlorophyll a-binding protein psbB, respectively, which indicated diverse pathways may be involved in heterosis formation.

Preliminary Study of Low Self-fertile Rate of ‘Kuijin' Apricot

To research the self-sterility of apricot, the pollen germination of ‘Kuijin＇apricot was conducted in vitro, and pollen viability was determined by germination on solid medium. Meanwhile, the effects of different media on its pollen germination and the growth of pollen tubes were analyzed. The results showed that the optimum media for pollen germination and growth of pollen tubes were 10% sucrose ＋0.1% boric acid and 5% sucrose ＋ 0.01% boric acid respectively. The self-pollination setting rate of ‘Kuijin＇ apricot was 4.70%, indicating that ‘Kuijin＇ apricot was self-incompatible. The reasons for the self-incompatibility of ‘Kuijin＇ were explored according to its pollen weight and pollen quantity. The results showed that self-pollinate setting rate of ‘Kuijin＇ apricot was closely related to the length of pollen tubes,but it had no direct correlation with pollen quantity.

Comparison of growth and survival of larvae among different shell color stocks of bay scallop Argopecten irradians irradians(Lamarck 1819)

In order to improve production and breed new broods of bay scallop Argopecten irradians irradians, different-colored orange, purple and white lines were established by two mating methods of self-fertilization and mass spawning at a commercial scallop hatchery in spring, 2002. And then larval growth and survival of different lines was compared to test whether there is a relationship between shell color and growth and survival at early developmental stage. Both growth and survival have no significant differences among different experimental larvae of self-fertilization or mass spawning. Results are as following in the order of orange, purple and white shell stock. For the self-fertilization, growth rates of larvae were 6.174, 6.412, and 6.599 μm/d, respectively. Survival rates of larvae at Day 3 were 74.41%, 76.86%, and 82.05%; Day 6 were 49.14%, 65.63%, and 52.79%; and Day 9 were 25.06%, 20.80%, and 26.47%, respectively. For the mass spawning, the growth rates were 7.836, 7.941, and 7.878 μm/d, respectively. Survival rates at Day 3 were 93.05%, 91.95%, and 92.50%; Day 6 were 79.17%, 78.05%, and 82.50%; and Day 9 were 34.72%, 36.67%, and 38.33%, respectively. The absence of any relationship between shell color and growth and survival at the larval stage may be resulted from their common genetic basis.

Breeding system and its consequence on fruit set of a rare sand dune shrub Eremosparton songoricum(Fabaceae:Papilionoideae):implications for conservation

The breeding system and its consequence on fruit set of Eremosparton songoricum（Litv.） Vass.,a rare shrubby legume occurring in moving or semi-fixed sand dunes of Central Asian deserts,were examined by manipulative experiments and observational studies in natural populations during the period of 2007-2009.The results showed that E.songoricum exhibits a mixed mating system.It is self-compatible,but depends strictly on pollinators to set fruits.Only two effective pollinators were detected and they triggered the specialized pollination mechanism（a ＇brush type＇ and ＇tripping mechanism＇）.Geitonogamy becomes predominant in natural populations,because（74.5±1.3）% of visiting activity happened within or between inflorescences and（24.3±1.4）% occurred between ramets.As a result,inbreeding depression caused by geitonogamous selfing inevitably happened under natural conditions,showing 2.36 times less fruit set than was achieved by hand cross-pollination.The results explained the rarity of the species due to its breeding system,and will assist to develop suitable conservation strategies in severe desert environments.

Inbreeding and Inbreeding Depression in a Deciduous Shrub, Magnolia salicifolia, in the Understory of a Japanese Beech Forest

Authors conducted pollination experiments and genetic analyses using microsatellite loci for a natural population of a shrub species,Magnolia salicifolia,in a secondary Japanese beech forest in Hakkoda mountains,northern Japan,to analyze inbreeding and inbreeding depression that involve sexual reproduction and population genetic structure of the species.The pollination experiments revealed that self-fertilization through geitonogamy is possible and that the magnitude of inbreeding depression(δ)at the embryonic stage is substantial(δ=0.42),suggesting that the inbreeding depression due to self-fertilization decreases seed production of the natural population.The genetic analyses showed discrepancy in the level of inbreeding between life history stages:the inbreeding coefficient for the juvenile and adult stage was 0.17 and 0.01,respectively,implying that most of inbred progenies cannot grow to the adult stage in the population,since the cumulative inbreeding depression is severe.These results are consistent with the hypothesis that explains mechanisms causing stable maintenance of severe inbreeding depression in partially inbred populations by focusing on the selective interference among deleterious mutations.It is suggested that some reproductive traits facilitating outcrossing in the species would be attributed to the severe cumulative inbreeding depression.

Impact of Bee Pollination on Yield of Faba Bean (<i>Vicia faba</i>L.) Grown under Semi-Arid Conditions

The effect of honeybee (Apis mellifera carnica) on yield was investigated in open-pollinated faba bean cultivars and three inbred generations produced from them (once-selfed, twice-selfed, and thrice-selfed). All entries were grown in cages under two pollination conditions: presence of bees (cross-pollination) or absence of bees (self-pollination). The open-pollinated generations gave the highest performance in the presence and absence of bees. In the presence of bees, the open-pollinated and their inbred entries gave higher performance in all of the studied traits than in the absence of bees;the average improvement in yield and its components was 22%. The highest improvement percentage in yield performance was shown by more inbred entries (thrice-selfed > once-selfed), indicating that in faba bean populations, the performance of inbred generations was chiefly associated with the tripping of flowers, which is usually governed by successfully fertilized flowers, i.e., plants result from selfing in faba bean population needs to be visited by pollinating insects (bees) to set more seeds. It concluded that honeybee has an important role in increasing faba bean yield in semi-arid conditions;hence, it is important to provide a pollinator friendly environment for their foraging places and nesting sites to secure food supply.

Biological nitrogen fixation in cereal crops:Progress,strategies,and perspectives

Nitrogen is abundant in the atmosphere but is generally the most limiting nutrient for plants.The inability of many crop plants,such as cereals,to directly utilize freely available atmospheric nitrogen gas means that their growth and production often rely heavily on the application of chemical fertilizers,which leads to greenhouse gas emissions and the eutrophication of water.By contrast,legumes gain access to nitrogen through symbiotic association with rhizobia.These bacteria convert nitrogen gas into biologically available ammonia in nodules through a process termed symbiotic biological nitrogen fixation,which plays a decisive role in ecosystem functioning.Engineering cereal crops that can fix nitrogen like legumes or associate with nitrogen-fixing microbiomes could help to avoid the problems caused by the overuse of synthetic nitrogen fertilizer.With the development of synthetic biology,various efforts have been undertaken with the aim of creating so-called‘‘N-self-fertilizing’’crops capable of performing autonomous nitrogen fixation to avoid the need for chemical fertilizers.In this review,we briefly summarize the history and current status of engineering N-self-fertilizing crops.We also propose several potential biotechnological approaches for incorporating biological nitrogen fixation capacity into non-legume plants.

What ecological factors favor the shift from distyly to homostyly? A study from the perspective of reproductive assurance

Aims Distyly is one of the most widespread floral polymorphisms pro-moting cross-fertilization.Evolutionary transition from obligate cross-fertilized distyly to predominantly self-fertilized homostyly is frequently documented in various groups.However,empirical stud-ies concerning the ecological factors connected with this transition are still lacking.Primula chungensis,suggested to be evolving from distyly to homostyly,provides an ideal model for the study of the ecological factors concerned with this transition.We study P.chun-gensis to understand if autonomous self-fertilization would provide reproductive assurance for the self-fertilized homo-styled morph in the field.Methods the incompatibility features of P.chungensis were tested with hand-pollination experiments.We compared the capacity of autonomous self-fertilization between the distylous and homo-styled morph of P.chungensis in the field by excluding the pollinators with bags.In addition,the degrees of herkogamy of some P.chungensis plants were between the short-styled and homo-styled morphs.these plants were studied to understand whether they were able to obtain greater reproductive assurance when the herkogamy in the flowers was reduced.Important Findings All three morphs of P.chungensis were highly self-and intra-morph compatible.the degree of herkogamy positively correlated with the capacity for autonomous self-fertilization.A negative correlation between the degree of herkogamy and the magnitude of pollen limitation was found,but no significant correlation was found between the degree of herkogamy and the contribution of cross-fertilization to overall fertilization.this study suggests that reducing the degree of herkogamy can significantly increase the reproductive assurance for a self-compatible plant.Our results provided evidence that the homo-styled morph of P.chungensis had the highest capacity for autonomous self-fertilization and the highest seed production in the field,because autonomous self-fertilization provided reproduct-ive assurance for the homo-styled morph.this may cause selection towards the transition from distyly to homostyly.