Inbreeding Depression Values Research Articles

Seed quality and germination performance increase with cross-pollination in members of subtribe Orchidinae (Orchidaceae)

Abstract Over half of angiosperms have self-incompatibility systems to avoid self-pollination and inbreeding depression. Many members of Orchidaceae are self-compatible, but they may be prone to negative consequences of self-pollination. We investigated the effects of both within-flower (autogamy) and within-plant (geitonogamy) self-pollination, and cross-pollination on fruit set, seed quality, and germination rates in 11 related orchid taxa of subtribe Orchidinae. We hand-pollinated flowers and measured fruit set to estimate pre- and postzygotic barriers. We collected morphometric data on embryos and seeds and calculated the percentage of seeds with embryos and seed viability. We then calculated inbreeding depression values for each treatment for each taxon. Ten taxa produced fruits when self-pollinated, but germination rates and seed size increased with cross-pollination. Higher seed viability was correlated with larger embryos/seeds. However, geitonogamous pollination generally resulted in the lowest seed quality compared with autogamy and cross-pollination, with high values of inbreeding depression being detected. Only seven of the 11 taxa (Anacamptis papilionacea, Himantoglossum adriaticum, Ophrys apifera, Ophrys bertolonii, Orchis patens subsp. brevicornis, Orchis provincialis, and Serapias vomeracea) were confirmed as self-compatible. These results show that cross-pollination improves overall seed quality, and that the assessment of self-compatibility in orchids should be based on postfruiting stages.

Impact of inbreeding on growth and development of young open-pollinated progeny of Eucalyptus globulus

The use of open-pollinated seeds from seed orchards is a common strategy for the deployment of genetically improved eucalypts, including Eucalyptus globulus, an important pulpwood tree in many temperate climate areas. However, seed quality can be affected by the rate of selfing and to a lesser extent by contamination from pollen outside the orchard. Inbreeding between related parents and especially from self-crosses is known to cause diminished growth and developmental abnormalities in the resulting progeny. This study looks at the magnitude and variation in selfing and the impact in inbreeding depression across several E. globulus families collected over the years in a seed orchard. The effects on growth and development of outcrossed and selfed progeny were studied across five progeny trials, after pedigree reconstruction of the open pollinated progeny based on SSR genotyping. An additive genetic mixed linear model was fitted to the data to evaluate the impact of inbreeding on height growth. The results showed a significant inbreeding depression, with a height growth reduction of 15% in selfed progeny, when compared with crosses from unrelated parents. These inbreeding depression values varied among families, ranging between 7% and 24%, evidencing the importance of genetic background. Contamination rates were on average 10% suggesting long distance pollen dispersal was present. A small number of abnormal phenotypes (less than 10%) was observed in the field. This was associated with specific, unrelated, crosses and not to high inbreeding rates such as found among selfed progeny. The relevance of these results for orchard management and parent selection is discussed.

Pamukta (Gossypium hirsutum L.) Nep ve Lif Kalite Özellikleri Üzerine Modifiye Tekrarlamalı Seleksiyonun Etkisi

The aim of this research was to evaluate the efficiency of the recurrent selection method for increasing ginning out-turn, optimizing fiber characters and neppiness in cotton breeding. This study started with the creation of 24 F1 combinations at Nazilli Cotton Research Institute in 2013. According to recurrent selection method, plants of 45 populations were evaluated for the first cycle of the recurrent selection procedure such that the F1: C1S0 was evaluated in 2017, the F2: C1S1 in 2018 and the F3: C1S2 in 2019. The fiber nep number and size decreased with each filial generation (from F1 to F3). Generally, high heritability coupled with genetic advance was estimated for ginning out-turn, fiber characters and neppiness. The results of inbreeding depression values indicated that ginning out-turn and fiber length in the population increased while the fibers became coarser under stable fiber strength. In addition, inbreeding depression for nep and SCN (Seed Coat Neps) number were higher than that of nep and SCN size. Our results showed that the recurrent selection method can be successfully applied in a cotton breeding program.

Route Analysis Through Filial Generations of Modern Varieties of Tomato (Solanum lycopersicum L.)

Objective: To measure the efficiency of using advanced generations of some commercial tomato hybrids for small farmers and to identify the most important yield components associated with yield. Design/Methodology/Approach: Seven saladette-type hybrids of indeterminate growth were evaluated, as well as their respective generations F2s and F3s under greenhouse conditions. The evaluation of the three generations was carried out during the 2013 agricultural cycle. Three harvests were made at 82, 94 and 136 days after transplanting. The experiment was a randomized complete block design, with 4 replications and 10 plants per replication. Results: Results indicated that there were significant differences for a few traits in F2 and F3. Path analysis showed that the total number of fruits had the highest direct and indirect effects on yield through generations. Limitations of the study/implications: The usefulness of advanced generations of tomato commercial hybrids would depend on the genetic background of the parental lines that take part in such as hybrids, as some hybrids would present high inbreeding depression depending on the genetic composition of their progenitors. Findings/Conclusions: Advanced generations of ‘LORETO’, ‘CUAUHTÉMOC’ and ‘ESPARTACO’ could be used by the small growers since low values of inbreeding depression were observed in F2 and F3 families

Potential Adoption of the F2 Generation of Some TYLCV-Resistant Tomato Hybrids in Commercial Production under Natural Field Infection

The economic feasibility of using the tomato yellow leaf curl virus (TYLCV) resistant F1 tomato hybrids (Solanum lycopersicum L.) may be improved with the possibility of using their F2 generation in commercial production. Hence, this study was performed to evaluate the F1 and F2 generations of 15 TYLCV resistant/tolerant commercial tomato hybrids during the 2018 and 2019 fall season to identify the best hybrids and F2 populations for commercial production. Both F1 and F2 populations were evaluated separately for TYLCV resistance, yield, and fruit quality traits. Broad sense heritability (H2b) values of TYLCV-resistance were high, being > 60% in hybrids 186, Goldstone, Rabha, SV0922 and SV8320 in both seasons. F1 and F2 populations of ‘186’, ‘Dania’, ‘PS550’, ‘Rozalina’, ‘SV0922’, ‘SV8320’, and ‘Tyrmes’ had the highest total yield (TY)/plant, low TYLCV disease (TYLCVD) mean scores, acceptable fruit quality traits, and average fruit weight > 80 g. Desirable inbreeding depression (ID) values were observed for TYLCVD-mean score in F2 populations of most evaluated hybrids; for TY/plant in F2 populations of ‘SV3773’ in both seasons, and in populations of ‘186’, ‘448’, ‘Goldstone’, ‘Rabha’, ‘SV8320’ and ‘SV0922’ in the second season. Most hybrids had desirable significant ID values for fruit quality traits. Accordingly, it is concluded that the F2 populations of hybrids 186, SV0922 and SV8320 may be used in commercial tomato production under TYLCV-infection in fall season, as these populations recorded high h2b values for TYLCV-resistance trait and desirable ID for TYLCV-resistance, yield, and fruit quality traits.

Effects of crossing distance on fitness components in the carnivorous plant Pinguicula moranensis (Lentibulariaceae)

AbstractPlant species vary in the pollination distance at which negative fitness effects are expressed, and it has been proposed that optimal mating should occur at a distance large enough to diminish the risks of inbreeding, but short enough to prevent outbreeding depression. In a natural population of Pinguicula moranensis we assessed the fitness of plants (seeds per fruit) and their progeny (germination and seedling survival) as a function of pollination distance by hand‐pollinating with donors from five distances: 0 m (self‐fertilization), 1, 4 and 460 m (within‐population) and 9,900 m (between‐population) under in situ and ex situ conditions. We found that average values for fitness components were consistently lower in the in situ experiment than in the ex situ experiment. Under both conditions, the self‐fertilization treatment had the lowest values. Inbreeding depression values were high (0.94 to 0.98), corresponding with the values expected for an outcrossing species subjected to self‐fertilization. Overall, no evidence of outbreeding depression was detected. Considering that our experiment was restricted to one single donor population and one recipient population, our results indicate that despite the within‐population patchy distribution of individuals, biparental inbreeding could occur at low rates, due in part to short seed dispersal distance. However, pollen movement of at least 1 m is apparently sufficient to reverse negative effects.

Heterosis, inbreeding depression and combining ability studies in garden pea (Pisum sativum L.)

In the present investigation, fifteen hybrids were developed during 2014-15 by utilizing five lines (Line 12, Line 13, Line 14, Line 15 and Line 17) and three testers (Matar Ageta, Palam Triloki and Arkel) and, were evaluated along with their parents for heterosis and combining ability studies following randomized complete block design during 2015-16. Same material was evaluatedin F2 during 2016-17 to ascertain the inbreeding depression. A wide range of residual heterosis over better parent and standard checks was observed in F2 generation for pod yield and related traits. Significant values of inbreeding depression and inbreeding vigour were found for almost all the traits in different crosses. Cross L13 x T2 exhibited maximum significant and negative residual heterosis over better parent (22.59%) and SC1 (17.39%) for days to 50% flowering and for days to first picking (9.50%), also exhibited maximum significant and negative residual heterosis (12.83%) over better parent for days to first picking. Studies on GCA effects revealed that line 17 was best general combiner for number of pods per plant, pod yield per plant and amongst testers, Palam Triloki for days to 50% flowering and days to first picking.On the basis of per se performance, extent of heterosis and specific combining ability effects, hybrid 17 x Palam Triloki and L13 × Palam Triloki were identified as the best crosses for earliness in F1 and F2 respectively. L17 x Arkel and L17 x Palam Triloki were observed as best hybrid for high green pod yield per plant, pods per plant and number of pods per plant in F1 and F2 respectively.

Estimation of Gene Effect for yield, yield Components and Foliar Diseases of Two Faba Bean Hybrids at Nubaria Region

Two crosses of faba bean (Giza716xGiza40) and (Giza716xNubaria2), each represented by six population (P1, P2,F1, F2, BC1 and BC2) were tested for yield, yield components, growth attributes and two diseases (chocolate spot andrust). Heterosis in F1, which exhibited highly significant positive effects were detected for number of branches /plant,number of pod /plant, number of seed /plant, seed yield /plant and plant height in the two crosses over mid and betterparents. Significant negative Heterosis effects were obtained for chocolate spot and rust diseases in the two crosses overmid parents. Highly significant positive values of inbreeding depression were detected for number of branches/ plant,number of pods/plant, number of seed /plant, seed yield /plant, 100-seed weight and plant height in both crosses.However, highly significant negative values of inbreeding depression were found for chocolate spot and rust diseases inthe two crosses. Over dominance towards the higher parent were detected for number of branches/plant, number ofpods/plant, number of seeds/plant, seed yield /plant and plant height in both crosses. It was also found that overdominance controls spot and rust diseases in the second cross. Additive gene effects were significant for all characters,excepted number of seed/plant and seed yield/plant in both crosses. Dominance effects were highly significant for alltraits, excepted, seed yield/plant and plant height in both crosses and rust disease in second cross. Additive x additive,additive x dominance and dominance x dominance types of gene action were significant for most traits in both crosses,except, chocolate spot and rust disease. In both crosses, high heritability values in broad sense were detected for all traitswhich, ranged between 63.20 for rust disease and 85.32 % for reaction to chocolate spot and for cross (Giza 716 X Giza40). However, cross (Giza 716 X Nubaria2) had values ranged from 60.7% for reaction to rust to 70.93% for seedyield/plant in (Giza 716 x Nubaria2). The values of heritability in narrow sense were detected for all traits which, rangedbetween 60.19 to 80.36% for resistance to rust and chocolate spot disease in first cross, respectively and between 59.36and 68.42% for number of pods/plant and seed yield / plant in the cross (G.716 x Nubaria.2).The estimates of expectedgenetic advance from selection in F2 generation reflected low or moderate values for all studied traits in both crosses thatranged between 7.78 cm for plant height to 1.8 for rust disease in cross (Giza 716 X Giza 40) and between 8.13 cm forplant height to 1.84 for number of branches/plant in (Giza 716 X Nubaria2) cross.

GENETICAL ANALYSIS OF YIELD AND ITS COMPONENTS FOR THREE FABA BEAN CROSSES USING SIX PARAMETER MODELS

The objectives of this study were to estimates some genetic parameters of yield and its components as well as the extent of heterosis, inbreeding depression, heritability, genetic advance and behavior of gene action in three faba bean crosses. This investigation was carried out at Sakha Agricultural Research Station, ARC, Kafr El-Sheikh, Egypt during 2012 / 13, 2013 / 14 and 2014 / 15 seasons. Six populations; P1, P2, F1, F2 , BC1 and BC2 of the three crosses i., e, Giza 40 x D 2, Giza 40 x D5 and Giza 40 x D 8 were sown in randomized complete blocks design with three replications. The data were analyzed by generation mean analysis method proposed by Gamble (1962).Scaling test was significantly differed from zero for all traits in all crosses, indicating the presence of all types of non -allelic interactions. Positive and significant dominance gene effects was observed for most of the studied traits in the three crosses, whereas, the (additive x additive) gene effects were relatively more important than the additive (a) effects but less important than dominance effects. The dominance x dominance (dd) gene effects were more important and higher in magnitude than additive x additive (aa) epistatic effects in the inheritance of most studied traits in all crosses. Significant heterosis over mid-parent in desirable direction was found for yield and its components in the three crosses due to over-dominance in most cases. It could be concluded that selection for seed yield and its components should be delayed to later generations in breeding programs. Positive and highly significant heterosis over better - parent was obtained for number of pods and seeds / plant in the first and second crosses, seed yield / plant and 100-seed weight in the second and third crosses. Significant positive values of inbreeding depression were detected for number of branches / plant in the first and third crosses, number of seeds / plant in the first cross, number of pods / plant and seed yield / plant in the first and second crosses. Heritability estimates in broad-sense were higher than corresponding values of narrow-sense in all crosses. Heritability estimates in narrow-sense were low for plant height in the second cross (14.39 %) and seed yield / plant in the same cross (17.53 %), indicating that these traits were influenced by non-heritable effects. The high values of predicted genetic advance (Ga %) were associated with high values of narrow-sense heritability and vise-versa.

Uncertain pollination environment promotes the evolution of a stable mixed reproductive system in the self-incompatible Hypochaeris salzmanniana (Asteraceae).

The transition from outcrossing to selfing is a repeated pattern in angiosperm diversification and according to general theory this transition should occur quickly and mixed reproductive systems should be infrequent. However, a large proportion of flowering plants have mixed reproductive systems, even showing inbreeding depression. Recently, several theoretical studies have shown that mixed mating systems can be stable, but empirical studies supporting these assumptions are still scarce. Hypochaeris salzmanniana, an annual species with populations differing in their self-incompatibility expression, was used as a study case to assess the stability of its mixed reproductive system. Here a descriptive study of the pollination environment was combined with measurements of the stability of the self-incompatibility system, outcrossing rate, reproductive assurance and inbreeding depression in four populations for two consecutive years. The reproductive system of populations exhibited a geographical pattern: the proportion of plants decreased from west to east. Pollinator environment also varied geographically, being less favourable from west to east. The self-incompatibility expression of some populations changed markedly in only one year. After selfing, progeny was mainly self-compatible, while after outcrossing both self-incompatible and self-compatible plants were produced. In general, both reproductive assurance and high inbreeding depression were found in all populations and years. The lowest values of inbreeding depression were found in 2014 in the easternmost populations, which experienced a marked increase in self-compatibility in 2015. The mixed reproductive system of H. salzmanniana seems to be an evolutionarily stable strategy, with selfing conferring reproductive assurance when pollinator attendance is low, but strongly limited by inbreeding depression. The fact that the highest frequencies of self-compatible plants appeared in the environments most unfavourable to pollination suggests that these plants are selected in these sites, although high rates of inbreeding depression should impede the complete loss of self-incompatibility. In H. salzmanniana, year-to-year changes in the frequency of self-incompatible individuals are directly derived from the balance between reproductive assurance and inbreeding depression.

Inbreeding depression on growth and survival of full-sib family of Manila clam (Ruditapes philippinarum)

In present study, the inbreeding depression (ID) of growth and survival of Manila clam (Ruditapes philippinarum) was investigated at larval and juvenile stages. Nine inbred families (A2, B2, C2, D2, E2, F2, G2, H2 and I2) were established by mating within nine full-sib families with expected inbreeding coefficient of 0.25. Inbred families showed significant differences in shell length and hatching rate of D-larvae (straight-hinged larvae). The larvae of the nine inbred families grew slower than those of control group (CG), and their ID value ranged from 0.81% ± 6.09% to 16.10% ± 1.49%. The ID value of larval survival rate varied between 27.47% ± 9.36% and 70.50% ± 13.66%. The ID was also detected for juvenile growth in A2, B2, C2, and D2, which ranged from 4.60 ± 2.21 to 17.71 ± 7.73. The A2 family maintained the highest juvenile survival rate, whereas the other inbred families exhibited ID values varying between 62.79% ± 4.54% and 96.14% ± 0.87%. The linear relationship of estimated ID between growth and survival was negatively correlated (R = −0.434, P < 0.05). The results of this study suggested that the ID of growth was common at the larval stage but was less prevalent at juvenile stage. In contrast, the ID of survival increased from larval to juvenile stage. A better understanding of the effect of inbreeding may aid to selective breeding of Manila clam.

DETECTION AND ESTIMATION OF DIFFERENT COMPONENTS OF GENETIC VARIABILITY (ADDITIVE, DOMINANCE AND EPISTASIS) UNDER STRESS AND NON-STRESS CONDITIONS IN BREAD WHEAT 1- ESTIMATION OF GENETIC COMPONENTS UNDER TWO LEVELS OF NITROGEN FERTILIZATION IN TWO BREAD WHEAT CROSSES

This investigation aimed to study the potentiality of heterosis expression, heritability, expected genetic advance, nature of gene actions and potance ratio for some quantitative traits (grain yield and its contributory characters, heading date and plant height) in two bread wheat crosses Sids 1 x Gemmeiza 5 and Gemmeiza 9 x Sids 4 were chosen for the percent study on the base of wide variability. Six populations (P1, P2, F1, F2, BC1 and BC2) were used to estimate genetic parameters under two levels of nitrogen fertilization (35 kg N/fed and 70 kg n/fed). The results can be summarized as follows: The hybrid combination Sids 1 X Gemmeiza 5 was detected to be the highest cross showed significant useful heterosis for grain yield per plant (37.58% and 76.11%) under 35 kg.n. /f and 70 kg.N./f, respectively. Inbreeding depression values were found to be highly significant in most cases in the two crosses under investigation. 3. The F2-deviations (E1) were significant for plant height and number of spikelets / main culm spike for all crosses under the both of nitrogen fertilization levels. Also backcross-deviations (E2) were found to be significant for heading date, main culm spike length, number of spikelets / main culm spike and number of kernels per spikelet under the two levels of nitrogen fertilization. The additive gene effects (a) were found to be significant for heading date, plant height and 1000 grains weight for all crosses under investigation under the two levels of nitrogen fertilization. Dominance gene effects (d) were found to be significant in the two crosses for number of spikelets/main culm spike under 35kg.N./f only. The three epistatic types additive × additive, additive × dominance and dominance × dominance were found to be significant for most traits under investigation. High heritability estimates in broad sense were detected for nearly all traits studied. high estimates of narrow sense heritability were found for all crosses for heading date, plant height, number of spikes per plant, main culm spike length, number of kernels per spikelets, number of kernels per main culm spike and grain yield per plant under 35 kg.N./fed. High genetic advance under selection was found to be associated with high narrow sense heritability estimates for number of spikes per plant and grain yield per plant for all crosses under 35 kg.N./f. The breeder can use cross Sids 1 X Gemmeiza 5 in breeding programs that it has high heterosis for yield character and its components and high genetic advance under selection was found to be associated with high narrow sense heritability estimates for number of spikes per plant and grain yield per plant.

What happens after inbreeding avoidance? Inbreeding by rejected relatives and the inclusive fitness benefit of inbreeding avoidance.

Avoiding inbreeding, and therefore avoiding inbreeding depression in offspring fitness, is widely assumed to be adaptive in systems with biparental reproduction. However, inbreeding can also confer an inclusive fitness benefit stemming from increased relatedness between parents and inbred offspring. Whether or not inbreeding or avoiding inbreeding is adaptive therefore depends on a balance between inbreeding depression and increased parent-offspring relatedness. Existing models of biparental inbreeding predict threshold values of inbreeding depression above which males and females should avoid inbreeding, and predict sexual conflict over inbreeding because these thresholds diverge. However, these models implicitly assume that if a focal individual avoids inbreeding, then both it and its rejected relative will subsequently outbreed. We show that relaxing this assumption of reciprocal outbreeding, and the assumption that focal individuals are themselves outbred, can substantially alter the predicted thresholds for inbreeding avoidance for focal males. Specifically, the magnitude of inbreeding depression below which inbreeding increases a focal male’s inclusive fitness increases with increasing depression in the offspring of a focal female and her alternative mate, and it decreases with increasing relatedness between a focal male and a focal female’s alternative mate, thereby altering the predicted zone of sexual conflict. Furthermore, a focal male’s inclusive fitness gain from avoiding inbreeding is reduced by indirect opportunity costs if his rejected relative breeds with another relative of his. By demonstrating that variation in relatedness and inbreeding can affect intra- and inter-sexual conflict over inbreeding, our models lead to novel predictions for family dynamics. Specifically, parent-offspring conflict over inbreeding might depend on the alternative mates of rejected relatives, and male-male competition over inbreeding might lead to mixed inbreeding strategies. Making testable quantitative predictions regarding inbreeding strategies occurring in nature will therefore require new models that explicitly capture variation in relatedness and inbreeding among interacting population members.

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.

GENETIC STUDIES ON SOME TRAITS RELATED TO DROUGHT TOLERANCE IN RICE

This investigation aimed to evaluate some genotypes of rice (Oryza sativa L.) under different irrigation conditions in order to study their genetic behavior to assess their drought tolerance. The genetic materials used in this investigation were six parental varieties and their six populations (P1, P2, F1, F2, BC1 and BC2) for three crosses were obtained from crossing among them. These populations were evaluated during 2010 and 2011 seasons at the Rice Research and Training Center, Sakha, Kafr El-Sheikh, Egypt. The parental varieties were Giza 177, IRAT1444, Sakha 105, IRAT 170, IR 64 and Azucena. The irrigation applied were two levels of flash irrigation, the first level was irrigation every 8 days and the second was irrigation every 12 days as well as control (irrigation every 4 days). The obtained results revealed that genotypic mean squares were highly significant for all studied traits, indicating the presence of real differences among genotypes. Furthermore, the variation due to irrigation levels and genotype x levels interaction were also highly significant for all traits except for flag leaf area. The results indicated the presence of significant differences among crosses for all studied traits under the three levels of irrigation. However, the results also revealed the presence of a highly significant difference among populations within crosses as well as among populations within each cross for all studied traits under the three irrigation levels, indicating that these genotypes gave different performances under different irrigation conditions. The second cross (Sakha 105 x IRAT 170) was the best combination, which recorded the highest values for most of the studied traits except for leaf rolling score and drought susceptibility index (DSI). The second and third crosses exhibited highly significant (MP) heterotic values for most of the studied traits except for fertility percentage. Positive inbreeding depression values were associated with high significant positive heterosis, indicating the role of dominance genes in the genetic expression of these traits. This fact is emphasized by high values of heritability in broad sense with low values of heritability in narrow sense for most of the studied traits. Positive and highly significant genotypic and phenotypic correlations were found between yield and flag leaf area and all studied root traits under drought conditions. Therefore, the hybrid rice breeding programs should be taken these traits in consideration for improving yield and its components under drought stress.

ESTIMATION OF GENETIC PARAMETERS FOR GRAIN YIELD AND ITS COMPONENTS IN THREE BREAD WHEAT CROSSES UNDER LOW INPUT OF NITROGEN FERTILIZER

Six populations (P1, P2, F1, F2, BC1 and BC2) of three bread wheat(Triticum aestivum L.) crosses, mamely Gemmeiza 9 x MayonS//CrowS/VeeS (cross I), Attila/Sids 1 x Sakha 94 (cross II) and Mayon S//Crow S/VeeS x Attila /Sids 1 (cross III) were used to estimate genetic parameters for grain yield/plant and certain related characters under two nitrogen fertilizer levels; (40 Kg N/Fed [low level] and 75 Kg N/Fed (recommended level]). Results revealed that heterosis values were positive and significant relative to better-parent in the three crosses under the two nitrogen levels for most of the studied characters. Meanwhile, heterosis values were negative and significant for number of kernels/spike in the first and the third crosses under low level of nitrogen N1, and the third cross under recommended level N2 and for kernel weight in the second cross under N1. In the second and third crosses under N2, positive and significant inbreeding depression values were recorded for all studied characters in the first cross except for kernels/spike under both N1 and N2, for kernels/spike in the second cross under both N1 and N2, for spikes/plant and grain yield in the third cross under N1 and N2, whereas negative significant values were obtained for kernels/spike in the third cross and for kernel weight in the second and third ones under both levels of nitrogen. Over-dominance above the higher parent was detected for spikes/plant and grain yield in all crosses under the two levels of nitrogen, for kernels/spike in the first cross under N2 as well as in the second cross under N1 and N2 and for kernel weight in the first cross under two levels. The other types of dominance were also studied. Scaling tests (A, B, C and D) indicated the presence of non-allelic gene interactions for all studied characters in all crosses under both levels of nitrogen. Additive genetic variance was highly significant for all traits in the three crosses under N1 and N2. Dominance variance was significant for all characters in all crosses, except for kernels/spike and kernel weight in the second cross under N1 and for all characters except for kernels/spike in the first cross, for kernel weight in the second cross and for all characters except for kernel weight in the third one under N2. Epistasis effects were present for most studied traits in the three crosses under both levels of nitrogen. F2 deviations (E1) was significant for kernel weight in all crosses, spikes/plant in the second and third crosses and grain yield in the second cross under N1 as well as for spikes/plant and kernel weight in all crosses and grain yield in the first and second crosses under N2. Back-cross deviations (E2) were significant for kernel/spike and grain yield in the first cross, for kernel weight in the second cross and for all characters in the third cross under N1 as well as for spikes/plant and grain yield in the first cross, for kernels/spike and kernels weight in the second cross and for all characters except for spikes/plant in the third cross under N2. Broad sense heritability estimates were relatively high under both N1 and N2. Selection in segregating generation could be effective to produce lines that have high yielding ability under low level of nitrogen fertilizer (40 kg N/fed).

Fine‐scale response to landscape structure in Primula vulgaris Huds.: does hedgerow network connectedness ensure connectivity through gene flow?

AbstractVariation in pollen flow, mating performances, and seed dispersal were examined using direct and indirect approaches in contrasted hedgerow networks (i.e., dense vs. sparse) of the distylous Primula vulgaris. Seed dispersal reached negligible distances, and no difference was observed between the two hedgerow networks. On the contrary, pollen flow through Bombylius sp. activity was impeded in the dense hedgerow network. Furthermore, P. vulgaris was found to be partially self‐compatible in our study site. The lower pollen flow in the dense hedgerow network, and especially in small populations, is likely to have unusually favoured self‐compatibility and hence selfing in P. vulgaris short‐style morph. In addition, the inbreeding depression values recorded were higher in the dense hedgerow network. Our results suggested that a dense hedgerow network does not necessarily ensure connectivity in Primula vulgaris in terms of gene flow. This study provides evidence for considering landscape structure in the microevolutionary processes.

Kosteletzkya virginica displays mixed mating in response to the pollinator environment despite strong inbreeding depression

Mixed mating systems often evolve despite strong inbreeding depression, but there have been few experimental tests of this observation. Kosteletzkya virginica, a perennial dicot halophytic species of the Family Malvaceae, is native to brackish portions of coastal tidal marsh in the United States of America and was introduced into China in 1993. Pollination of K. virginica occurs through insect vectors and by delayed self-pollination via stylar movement. In the same two naturalized populations of K. virginica during 2005–2007, we measured (i) inbreeding depression across a range of life-cycle stages, (ii) pollination failure rate, and (iii) selfing rate estimated by AFLP markers. Results indicate that inbreeding depression values for the two naturalized populations during 2005–2007 ranged from 0.620 ± 0.036 to 0.656 ± 0.032, and mean inbreeding depression was 0.640 ± 0.006. Pollinator failure rates at the two naturalized K. virginica populations during 2005–2007 ranged from 0.091 ± 0.039 to 0.174 ± 0.061, and selfing rate ranged from 0.247 ± 0.018 to 0.468 ± 0.031. Population selfing rates are significantly and positively correlated with field estimates of pollinator failure (P = 0.008 < 0.01, R 2 = 0.857). Our data provide an empirical demonstration of a mixed mating system response to the pollinator environment in the presence of strong inbreeding depression.

Selection through Male Function Favors Smaller Floral Display Size in the Common Morning GloryIpomoea purpurea(Convolvulaceae)

In self-compatible, hermaphroditic plants, display size-the number of flowers open on a plant at one time-is believed to be influenced by trade-offs between increasing geitonogamous selfing and decreasing per-flower pollen export as display size increases. Experimental results presented here indicate that selection through male function favors smaller display sizes in Ipomoea purpurea. In small arrays, plant display size was manipulated experimentally, and female selfing rate, male outcross success, and total male fitness were estimated using genetic markers and likelihood and regression analyses. As would be expected if larger displays experience greater geitonogamy, selfing rate increased with display size. However, the per-flower amount of pollen exported to other plants decreased with display size. The magnitude of this effect is more than sufficient to offset the increase in selfing rate, resulting in reduced per-flower total male fitness with increasing display size. The low values of inbreeding depression previously reported for this species would enhance this effect.

Componentes genéticos de médias e depressão por endogamia em populações de milho-pipoca

Dez populações de milho-pipoca (PR 038, PR 079, RR 046, SC 016, PR 017, BRS Angela, SC 002, PR 009, PR 023 e SE 013) foram avaliadas com os objetivos de obter estimativas de depressão por endogamia e componentes genéticos de média. O delineamento experimental utilizado foi o de blocos ao acaso em esquema de parcelas subdivididas, nos quais os tratamentos primários foram os níveis de endogamia (S1 e S0) e os tratamentos secundários as populações, com três repetições. O ensaio foi conduzido nas cidades de Maringá e Iguatemi-PR, no ano agrícola de 2001/2002. Foram avaliadas as características altura de plantas, altura de espigas, rendimento de grãos e capacidade de expansão. Foram observados menores valores de depressão por endogamia e predominância de efeitos gênicos aditivos para capacidade de expansão em relação ao rendimento de grãos. As populações BRS ANGELA e SC 002 apresentaram maior probabilidade de sucesso na obtenção de linhagens com boa capacidade de expansão.