Low Inbreeding Depression Research Articles

Inbreeding Depression for Dry Pod Yield and its Components in Chilli (Capsicum annuum L.)

A study was conducted on “Inbreeding depression for dry pod yield and its components in chilli (Capsicum annuum L.)” at the Department of Vegetable Crops, Horticultural College and Research Institute, TNAU, Periyakulam, India during 2013-14. The investigation was carried out with six selected genotypes of chilli namely Arka Lohit, K 1, LCA 334, LCA 625, PKM 1 and Pusa Jwala. All the crosses also revealed inbreeding depression for most of the characters. These traits can be improved effectively through pedigree method of selection. In general, the crosses K 1 x PKM 1 and K 1 x Pusa Jwala were identified as promising hybrids since they depicted significant negative inbreeding depression for green and dry fruit yield and its important yield contributing characters. Low inbreeding depression for yield and yield related traits were exhibited by Pusa Jwala x PKM 1, LCA 625 x K 1 and K 1 x Arka Lohit. The segregating materials generated during this study may be utilized for the identification and selection of desirable recombinants in advanced generations in order to develop high yielding varieties with specific attributes.

High Rates of Self-Fertilization in a Marine Ribbon Worm (Nemertea).

Organisms capable of self-fertilization ("selfing") typically exhibit two evolutionary syndromes: uniting high inbreeding depression with low levels of selfing, or low inbreeding depression with high levels of selfing. We examined the effect of inbreeding on fecundity and time to first reproduction in an apparently self-compatible, simultaneously hermaphroditic marine nemertean worm Prosorhochmus americanus. Adult and juvenile worms were raised in isolation or in pairs. Isolated worms produced significantly more offspring than paired worms (in the adult experiment), and did not exhibit inbreeding avoidance (in the juvenile experiment). The selfing rate of six natural populations was evaluated using 17 species-specific, microsatellite markers, and was consistent with preferential selfing (mean: 0.843, SD: 0.027). Our results showed that P. americanus exhibited an interesting suite of life-history traits, uniting high colonization potential through self-fertilization and high fecundity, with no dispersive larval stage, and with moderate levels of gene flow. We believe that P. americanus is an ideal model system for studies of mating system evolution, inbreeding, and sex allocation.

Molecular marker associated with a deleterious recessive anomaly in Eucalyptus grandis seedlings

The identification of an anomaly with deleterious effect and Mendelian segregation (3 normal: 1 abnormal) allowed the detection of a marker linked to a locus for the anomalous phenotype. This marker could be useful in marker-assisted breeding programs and for understanding this anomaly. Due to the mixed mating systems in Eucalyptus genera, outcrossing populations exhibit low inbreeding depression (abnormalities). In this study, we identified a developmental anomaly in a controlled cross of Eucalyptus grandis, with Mendelian segregation. The anomaly was characterized by branching, reduced height, smaller individual leaf area, and asymmetrical leaf shape. To investigate and evaluate the anomaly detected, we performed morphological and molecular analysis. The genitors and bulks of normal and abnormal individuals were screened with random primers. The polymorphic markers that co-segregated with the anomalous phenotype were selected, validated, converted into SCAR markers and analyzed in silico. Morphological analysis showed significant differences between normal and abnormal phenotypes. The co-segregating marker was present in one genitor, in all abnormal individuals, and in 31 % of normal individuals (recombinants). In silico analyses revealed a mutation of two base pairs between the contrasting phenotypes and identified the marker in an intergenic region presenting partial identity with an expressed sequence tag (EST) of Bet v1-like genes. A marker was developed to identify the recessive allele for the anomaly in E. grandis. This will be important for management of crosses in eucalypt breeding programs and in anomaly studies.

Self-Incompatibility inUlex europaeus: Variations in Native and Invaded Regions

Premise of research. The mating systems of introduced plant species are important components of their invasive success because they can favor reproductive assurance during the colonization process. The hypothesis known as Baker’s rule implies that colonizing species should evolve toward a lower dependence on pollinators, a higher self-fertility, and a lower inbreeding depression. Here, we test these predictions by comparing the mating system of the perennial shrub Ulex europaeus (Fabaceae) in regions from its native and invaded ranges.Methodology. We performed controlled pollinations on plants from two regions of origin (Brittany and Scotland) and two invaded regions (New Zealand and Reunion) grown in a common garden. We tested the possibility of autonomous pollination; estimated the relative seed set of selfing versus outcrossing; and recorded the viability, mass, and germination capacity of the seeds produced.Pivotal results. Ulex europaeus cannot set seeds in the absence of active pollination. Seed set...

Heterotic Effects in Fls and Inbreeding Depression in F2 Hybrids of Sunflower

Genetically diverse female lines of sunflower were crossed with male testers to get heterotic hybrids. Studies were carried-out during 2008-2010 at Experiment filed of Agriculture Research Institute, Tandojam, Sindh, Pakistan. Six female lines like T-4-0319, PAC-0505, HO-I, Hysun-33, Peshawar-93 and CMS-03 and three testers i.e., PAC-0306, PAC-64-A and SF-187 were crossed in a line ´ tester mating design, thus 18 F1 and F2 hybrids were developed for evaluation of heterosis and inbreeding depression for days to initial flowering, days to maturity, leaves/plant, plant height (cm), head diameter (cm), 1000-achene weight (g), seed yield kg/ha and oil yield kg/ha. The experiment was conducted in a randomised complete block design with four replications. The analysis of variance revealed significant differences among parents, F1s and F2 hybrids for all the traits studied. The existence of significant genetic variability among the plant traits is particularly useful because variations in these traits would allow further improvement in sunflowerseed yield and oil traits. The F1 hybrids HO-I ´ PAC-0306 and HO-I PA ´ C-64-A exhibited desirable negative mid and better parent heterosis for days to initial flowering, days to maturity and plant height. These hybrids also manifested desirable positive heterotic effects for leaves/plant, head diameter, 1000-achene’s weight, seed yield and oil yield. Inbreeding depression for phenological, seed yield and oil traits showed that desirable high inbreeding depression was observed in hybrids HO-I ´ P´AC-64-A, HO-I ´ PAC-0306 and HO-I ´ SF-187 for days to initial flowering, similarly T-4-0319 ´ PAC-0306, PAC-0505 ´ SF-187 and HO-I ´ PAC-64-A explicated maximum but rewarding inbreeding depression for days to maturity. The F2 hybrids Hysun-33 ´ SF-187 and Peshawer-93 ´ PAC-64-A may be the most desirable ones in the sense that they recorded comparatively moderate inbreeding depression with enough number of leaves to be productive if F2 hybrids are to be exploited for hybrid vigour. Low inbreeding depression for various traitsindicated that such hybrids some how favour the usefulness of F2 hybrids in sunflower.

Pollen limitation and the contribution of autonomous selfing to fruit and seed set in a rewarding orchid

• Although rewarding orchids are believed to have a high pollination efficiency, pollination success is often low, suggesting that rewarding orchids may be prone to pollen limitation. Assuming that selfing contributes significantly to fruit and seed set (i.e., reproductive assurance) and that the quality of selfed seeds is high (i.e., low inbreeding depression), it can be hypothesized that under these circumstances populations evolve to facultative or even complete self-pollination.• In this study, we performed emasculation and pollen supplementation experiments in the field to assess the extent of outcross pollen limitation and the contribution of autonomous self-pollination to fruit and seed set in the rewarding orchid Epipactis palustris. Hand-pollinations using cross and self-pollen were performed in the greenhouse to investigate the impact of selfing on seed set and seed quality and to assess the magnitude of inbreeding depression.• Fruit set under natural conditions was high: ca. 70% of all flowers set fruit. Percentage fruit set of emasculated plants was 56%, implying that fruit set in about 14% of all flowers was the result of autonomous self-pollination. Pollen supplementation significantly increased fruit and seed set, indicating strong outcross pollen limitation. Hand-pollination with cross pollen resulted in significantly higher seed set and seed quality compared with manual self-pollination, indicating high levels of early inbreeding depression (δ = 0.46 ± 0.08).• Overall, these results indicate that, despite the high pollination efficiency, populations of this rewarding orchid species were strongly pollen limited. Costs of early inbreeding depression, on the other hand, were high, which may prevent rapid evolution of complete selfing.

Development of a forensic identity SNP panel for Indonesia.

Genetic markers included in forensic identity panels must exhibit Hardy-Weinberg and linkage equilibrium (HWE and LE). "Universal" panels designed for global use can fail these tests in regional jurisdictions exhibiting high levels of genetic differentiation such as the Indonesian archipelago. This is especially the case where a single DNA database is required for allele frequency estimates to calculate random match probabilities (RMPs) and associated likelihood ratios (LRs). A panel of 65 single nucleotide polymorphisms (SNPs) and a reduced set of 52 SNPs have been selected from 15 Indonesian subpopulations in the HUGO Pan Asian SNP database using a SNP selection strategy that could be applied to any panel of forensic identity markers. The strategy consists of four screening steps: (1) application of a G test for HWE; (2) ranking for high heterozygosity; (3) selection for LE; and (4) selection for low inbreeding depression. SNPs in our Indonesian panel perform well in comparison to some other universal SNP and short tandem repeat (STR) panels as measured by Fisher's exact test for HWE and LE and Wright's F statistics.

INHERITANCE OF SOME RICE ROOT CHARACTERS AND PRODUCTIVITY UNDER WATER STRESS CONDETIONS

This study was implemented during three successive seasons; 2011, 2012 and 2013 at the experimental farm of Rice Research and Training Center, Sakha, Kafr El-Sheikh, Egypt. Six rice genotypes with different water stress tolerance were crossed Three crosses viz; cross I {Tsuyuake (tolerant) X Sakha 103 (sensitive)} were produced, cross II {Zenith (tolerant) X Sakha 104 (moderate)} and cross III {BL1 (moderate) X Sakha 106 (sensitive)}. Six populations of P1, P2, F1, BC1, BC2, and F2 for each cross were used in the present study. Results indicated that high differences between the six parents for all root characters, as well as, grain yield and its related traits under water stress conditions. Parent Tsuyuake gave the highest mean values for most of the studied traits, while, the lowest mean values were recorded for Sakha 106 rice cultivar. Highly significant positive heterosis and heterobeltiosis was estimated for some root characters and grain yield and its component especially in crosses I and II. Negative over dominance were recorded for root fresh weight, days to 50% heading, plant height and grain yield/plant in cross III, as well as, 100 grain weight in the three crosses and sterility percentage in crosses I and III. Low and positive inbreeding depression values were estimated for 100 grain weight in crosses I and III. Epistatic gene effect had a significant contribution in inheritance of all studied characters. Additive genetic variance was greater than the dominance genetic variance for root volume and grain yield/plant in cross II, root fresh weight and days to 50% heading in crosses II and III, root / shoot ratio in crosses I and III ,as well as, plant height and panicle length in the three crosses. Heritability in broad sense ranged from low to intermediate and high in the three crosses but was low in narrow sense. Low predicted genetic advance (3.99) for root number / plant to high value (30.15) for root length in the cross III were found. Tsuyuake and Zenith may be useful genotypes in breeding program for water stress condition. This conclusion might be useful for rice breeders in planning a selection program for improving root characters and productivity of rice under stress conditions.

LIFETIME INBREEDING DEPRESSION, PURGING, AND MATING SYSTEM EVOLUTION IN A SIMULTANEOUS HERMAPHRODITE TAPEWORM

Classical theory on mating system evolution suggests that simultaneous hermaphrodites should either outcross if they have high inbreeding depression (ID) or self-fertilize if they have low ID. However, a mixture of selfing and outcrossing persists in many species. Previous studies with the tapeworm Schistocephalus solidus have found worms to self-fertilize some of their eggs despite ID. The probability for selfing to spread depends on the relative fitness of selfers, as well as the genetic basis for ID and whether it can be effectively purged. We bred S. solidus through two consecutive generations of selfing and recorded several fitness correlates over the whole life cycle. After one round of selfing, ID was pronounced, particularly in early-life traits, and the conservatively estimated lifetime fitness of selfed progeny was only 9% that of the outcrossed controls. After a second generation of selfing, ID remained high but was significantly reduced in several traits, which is consistent with the purging of deleterious recessive alleles (the estimated load of lethal equivalents dropped by 48%). Severe ID, even if it can be rapidly purged, likely prevents transitions toward pure selfing in this parasite, although we also cannot exclude the possibility that low-level selfing has undetected benefits.

Inbreeding depression in castor bean (Ricinus communis L.) progenies

The purpose of this study was to investigate inbreeding depression (DE) in castor bean. From a population derived from the Guarani cultivar, 60 mother plants were sampled. Three types of progenies were obtained from each one: from self-pollination (AU), from crosses (CR) and from open pollination (PL). Grain yield of the progenies was evaluated in two locations. There was a strong interaction of progenies x locations, which led to obtaining estimates within each location. Broad variation was observed in inbreeding depression, with mean values of 6.7% and 13.4%, comparing AU progenies with PL progenies. It was observed that the population has high potential for selecting promising inbred lines. The frequency of mother plants generating progenies with simultaneous high general combination capacity and low inbreeding depression was low. Recurrent selection will increase the occurrence of parent plants associating these two properties, which is necessary for obtaining superior synthetic varieties.

MUTATIONAL MELTDOWN IN SELFINGARABIDOPSIS LYRATA

The majority of plant species and many animals are hermaphrodites, with individuals expressing both female and male function. Although hermaphrodites can potentially reproduce by self-fertilization, they have a high prevalence of outcrossing. The genetic advantages of outcrossing are described by two hypotheses: avoidance of inbreeding depression because selfing leads to immediate expression of recessive deleterious mutations, and release from drift load because self-fertilization leads to long-term accumulation of deleterious mutations due to genetic drift and, eventually, to extinction. I tested both hypotheses by experimentally crossing Arabidopsis lyrata plants (self-pollinated, cross-pollinated within the population, or cross-pollinated between populations) and measuring offspring performance over 3 years. There were 18 source populations, each of which was either predominantly outcrossing, mixed mating, or predominantly selfing. Contrary to predictions, outcrossing populations had low inbreeding depression, which equaled that of selfing populations, challenging the central role of inbreeding depression in mating system shifts. However, plants from selfing populations showed the greatest increase in fitness when crossed with plants from other populations, reflecting higher drift load. The results support the hypothesis that extinction by mutational meltdown is why selfing hermaphroditic taxa are rare, despite their frequent appearance over evolutionary time.

Purging of inbreeding depression within a population of Oxalis alpina (Oxalidaceae)

Variation among individuals in levels of inbreeding depression associated with selfing levels could influence mating system evolution by purging deleterious alleles, but empirical evidence for this association is limited. We investigated the association of family-level inbreeding depression and presumed inbreeding history in a tristylous population of Oxalis alpina (Oxalidaceae). Mid-styled individuals possessed the greatest degree of self-compatibility (SC) and produced more autogamous capsules than short- or long-styled individuals. Offspring of highly self-compatible mid-styled individuals showed reduced inbreeding depression. Mid-styled plants that produced capsules autogamously exhibited reduced stigma-anther separation compared to mid-styled plants that produced no capsules autogamously. Reduced inbreeding depression was not correlated with stigma-anther separation, suggesting that self-compatibility and autogamy evolve before morphological changes in stigma-anther separation. Purging of inbreeding depression occurred in SC mid-styled maternal families. Low inbreeding depression in SC mid-styled plants may lead to retention of the mid-styled morph in populations, despite the occurrence of higher selfing rates in mid-styled relative to short- or long-styled morphs. Variation among individuals in levels of self-fertilization within populations may lead to associations between inbreeding lineages and lower levels of inbreeding depression, influencing the evolution of mating systems.

ANALYSIS OF INBREEDING DEPRESSION IN MIXED-MATING PLANTS PROVIDES EVIDENCE FOR SELECTIVE INTERFERENCE AND STABLE MIXED MATING

Hermaphroditic individuals can produce both selfed and outcrossed progeny, termed mixed mating. General theory predicts that mixed-mating populations should evolve quickly toward high rates of selfing, driven by rapid purging of genetic load and loss of inbreeding depression (ID), but the substantial number of mixed-mating species observed in nature calls this prediction into question. Lower average ID reported for selfing than for outcrossing populations is consistent with purging and suggests that mixed-mating taxa in evolutionary transition will have intermediate ID. We compared the magnitude of ID from published estimates for highly selfing (r > 0.8), mixed-mating (0.2 ≤ r ≥ 0.8), and highly outcrossing (r < 0.2) plant populations across 58 species. We found that mixed-mating and outcrossing taxa have equally high average lifetime ID (δ= 0.58 and 0.54, respectively) and similar ID at each of four life-cycle stages. These results are not consistent with evolution toward selfing in most mixed-mating taxa. We suggest that prevention of purging by selective interference could explain stable mixed mating in many natural populations. We identify critical gaps in the empirical data on ID and outline key approaches to filling them.

Comparative Reproductive Biology in Co-Occurring Invasive and NativeImpatiensSpecies

Two alien Impatiens species are spreading in Europe and share habitats with the native Impatiens noli-tangere. We studied their reproductive biology to estimate which traits facilitate invasiveness. Flower morphology was examined, insect observations were made, and hand pollination treatments were performed. Floral biology differed among species. Impatiens glandulifera and I. noli-tangere presented large quantities of sucrose-dominant nectar, contrary to Impatiens parviflora. The latter had high autonomous selfing ability (81.4% fruit set) linked to complete self-compatibility. No inbreeding depression was detected for this species. The second alien, I. glandulifera, showed lower autonomous selfing (9.3% fruit set), with high self-compatibility and low inbreeding depression (). No evidence of autonomous selfing was found for the native, which presented the lowest self-compatibility and the highest inbreeding depression (). However, all species can be considered self-compatible. Impatiens glandulifera flow...

Genetic Restoration of the Florida Panther

The rediscovery of remnant Florida panthers (Puma concolor coryi) in southern Florida swamplands prompted a program to protect and stabilize the population. In 1995, conservation managers translocated eight female pumas (P. c. stanleyana) from Texas to increase depleted genetic diversity, improve population numbers, and reverse indications of inbreeding depression. We have assessed the demographic, population-genetic, and biomedical consequences of this restoration experiment and show that panther numbers increased threefold, genetic heterozygosity doubled, survival and fitness measures improved, and inbreeding correlates declined significantly. Although these results are encouraging, continued habitat loss, persistent inbreeding, infectious agents, and possible habitat saturation pose new dilemmas. This intensive management program illustrates the challenges of maintaining populations of large predators worldwide.

Pollination of an invasive orchid, Cyrtopodium polyphyllum (Orchidaceae), by an invasive oil-collecting bee, Centris nitida, in southern Florida

The lack of appropriate pollinators is believed to be an impediment to naturalization of orchids. We studied the self-compatibility and pollination of an invasive, showy, rewardless, terrestrial orchid ( Cyrtopodium polyphyllum (Vell.) Pabst ex F. Barrios) in southern Florida. Pollination treatments indicated that the orchid is self-compatible but not autogamous. Visitor observations indicated that the orchid is pollinated by an invasive specialist oil-collecting bee ( Centris nitida Smith). The presence of the invasive Centris nitida has probably contributed to the naturalization of this probable oil reward mimicking orchid in Florida. We contrasted our results in the orchid’s invasive range with those reported in two studies in the orchid’s native range. In the invasive range in Florida, the orchid experiences a lower inbreeding depression. In both areas, the orchid is pollinated by Centris species and the pollination of the orchid is apparently enhanced by the presence of oil-rewarding species of the Malpighiaceae.

Low inbreeding depression in a sexual trait in the stalk-eyed fly Teleopsis dalmanni

The genic capture hypothesis implies that the expression of sexual ornaments largely depends on genes affecting resource acquisition and use. The ornaments should thus show high degree of directional dominance typical of life-history traits, and conse- quently, they should be severely affected by inbreeding. Here we investigated the effect of inbreeding on a sexual ornament (male eyespan) in stalk-eyed fly, Teleopsis dalmanni. For comparison, we also measured inbreeding depression in non-sexual morphological traits: female eyespan as well as wing and thorax lengths in both sexes. Both eyespan, and other morphological traits we measured, showed significant inbreeding depression. In accord with predictions of genic capture hypothesis, male eyespan did decrease under inbreeding significantly more than female eyespan. However, the decline in male eyespan was fully explained by overall decline in body length. Moreover, the magnitude of inbreeding depression in male eyespan was considerably lower than that typically observed for life- histories; in fact, it fitted within the range typically characterizing morphological traits. We therefore conclude that our results provide weak support for genic capture hypothesis.

Reduced inbreeding depression after species range expansion.

Many species expanded their geographic ranges from core "refugium" populations when the global climate warmed after the Pleistocene. The bottlenecks that occur during such range expansions diminish genetic variation in marginal populations, rendering them less responsive to selection. Here, we show that range expansion also strongly depletes inbreeding depression. We compared inbreeding depression among 20 populations across the expanded range of a common European plant, and found that marginal populations had greatly reduced inbreeding depression. Similar patterns were also revealed by multilocus computer simulations. Low inbreeding depression is predicted to ease conditions for the evolution of self-fertilization, and selfing is known to be particularly frequent in marginal populations. Therefore, our findings expose a remarkable aspect of evolution at range margins, where a history of expansion can reverse the direction of selection on the mating system, providing a parsimonious explanation for the high incidence of selfing in marginal populations.

Reproductive biology of the andromonoecious Cucumis melo subsp. agrestis (Cucurbitaceae).

Cucumis melo subsp. agrestis (Cucurbitaceae) is cultivated in many African regions for its edible kernels used as a soup thickener. The plant, an annual, andromonoecious, trailing-vine species, is of high social, cultural and economic value for local communities. In order to improve the yield of this crop, the first step and our aim were to elucidate its breeding system. Eight experimental pollination treatments were performed during three growing seasons to assess spontaneous selfing, self-compatibility and effects of pollen source (hermaphroditic vs. male flowers). Pollination success was determined by pollen tube growth and reproductive success was assessed by fruit, seed and seedling numbers and characteristics. The pollinator guild was surveyed and the pollination distance determined both by direct observations and by indirect fluorescent dye dispersal. The species is probably pollinated by several Hymenoptera, principally by Hypotrigona para. Pollinator flight distances varied from 25 to 69 cm. No evidence for apomixis or spontaneous self-pollination in the absence of insect visitors was found. The self-fertility index (SFI = 0) indicated a total dependence on pollinators for reproductive success. The effects of hand pollination on fruit set, seed number and seedling fitness differed among years. Pollen tube growth and reproductive success did not differ between self- and cross-pollinations. Accordingly, a high self-compatibility index for the fruit set (SCI = 1.00) and the seed number (SCI = 0.98) and a low inbreeding depression at all developmental stages (cumulative delta = 0.126) suggest a high selfing ability. Finally, pollen origin had no effect on fruit and seed sets. This andromonoecious species has the potential for a mixed mating system with high dependence on insect-mediated pollination. The selfing rate through geitonogamy should be important.

CORRELATED EVOLUTION OF MATING STRATEGY AND INBREEDING DEPRESSION WITHIN AND AMONG POPULATIONS OF THE HERMAPHRODITIC SNAILPHYSA ACUTA

Inbreeding depression is one of the main forces opposing the evolution of self-fertilization. Of central importance is the hypothesis that inbreeding depression and selfing coevolve antagonistically, generating either low selfing rate and high inbreeding depression or vice versa. However, there is limited evidence for this coevolution within species. We investigated this topic in the hermaphroditic snail Physa acuta. In this species, isolated individuals delay the onset of egg laying compared to individuals having access to mates. Longer delays ("waiting times") indicate more intense selfing avoidance. We measured inbreeding depression and waiting time in a large quantitative-genetic experiment (281 outbred families derived from 26 natural populations). We observed large genetic variance for both traits and a strong positive genetic covariance between them, most of which resided within rather than among populations. It means that, within populations, individuals with higher mutation load avoided selfing more strongly on average. This genetic covariance may result from pleiotropy and/or linkage disequilibrium. Whatever its genetic architecture, the fact it emerges specifically when individuals are deprived of mates suggests it is not fortuitous and rather reflects the action of natural selection. We conclude that a diversity of mating strategies can arise within populations subjected to variation in inbreeding depression.