Heterosis Effects Research Articles

Hybrids and the Flora of Thailand revisited: Hybridization in the South-East Asian genus Cryptocoryne (Araceae)

ABSTRACT. The South-East Asian genus Cryptocoryne has been shown to hybridize more frequently than expected. Data are presented on the known naturally occurring hybrids including information on their discovery, naming, and recognition as hybrids. Many artificial hybrids produced over the years indicate that there are only relatively few barriers to crossing. A heterosis effect is prevalent in many encountered Cryptocoryne hybrids. Vegetative propagation is clearly an advantage in the establishment of hybrid populations and also in detecting the hybrids, since inferior hybrids have disappeared naturally. Our results on Cryptocoryne also suggest that when the South-East Asian floras become as well-known as temperate ones, the number of natural hybrids will be similar to those presently known from temperate regions.

Evidence of Economic Heterosis and Genetic Control of Fruit Yield and Yellow Vein Mosaic Virus Disease Severity Traits of Okra

Evidence of Economic Heterosis and Genetic Control of Fruit Yield and Yellow Vein Mosaic Virus Disease Severity Traits of Okra) Ten diverse genotypes of cultivated and wild species were crossed in half diallel fashion to produce 45 F1 hybrids to determine mode of gene action, extent of economic heterosis and dominance effect, and to estimate combining ability for eight quantitative traits. Predictability ratio revealed overwhelming response of non-additive gene action for controlling fruit length, number of fruits per plant, and fruit yield per plant; additive gene effects for days to 50% flowering, while both additive and non-additive genetic control for node number at first flowering, fruit weight, fruit girth, and PDI of YVMV disease. Appropriate breeding strategies for improvement of studied traits are highlighted here. Significant standard heterosis over two commercial hybrids, Shakti and Abantika was comparatively lower in magnitude for fruit yield per plant (4.62 % and 17.59 %, respectively) and higher in magnitude for PDI of YVMV disease (-71.28 % and -72.28 %, respectively). Partial- to overdominance effects were involved in the inheritance of the studied traits. BCO-1 and 11/RES-6 were identified as potential donors for future use. The study could able to identify an outstanding hybrid (BCO-1 × Arka Anamika) having high tolerance both under field and artificial conditions. This hybrid would definitely make a room in okra growing zones of the tropics after critical testing..

Heterosis and direct effects for Charolais-sired calf weight and growth, cow weight and weight change, and ratios of cow and calf weights and weight changes across warm season lactation in Romosinuano, Angus, and F cows in Arkansas.

The use of Brahman in cow-calf production offers some adaptation to the harsh characteristics of endophyte-infected tall fescue. Criollo breeds, such as the Romosinuano, may have similar adaptation. The objectives were to estimate genetic effects in Romosinuano, Angus, and crossbred cows for their weights, weights of their calves, and ratios (calf weight:cow weight and cow weight change:calf weight gain) across lactation and to assess the influence of forage on traits and estimates. Cows ( = 91) were bred to Charolais bulls after their second parity. Calves ( = 214) were born from 2006 to 2009. Cows and calves were weighed in early (April and June), mid- (July), and late lactation (August and October). Animal was a random effect in analyses of calf data; sire was random in analyses of cow records and ratios. Fixed effects investigated included calf age, calf sex, cow age-year combinations, sire breed of cow, dam breed of cow, and interactions. Subsequent analyses evaluated the effect of forage grazed: endophyte-free or endophyte-infected tall fescue. Estimates of maternal heterosis for calf weight ranged from 9.3 ± 4.3 to 15.4 ± 5.7 kg from mid-lactation through weaning ( < 0.05). Romosinuano direct effects (of the cow) were -6.8 ± 3.0 and -8.9 ± 4.2 kg for weights recorded in April and June. Calf weights and weight gains from birth were greater ( < 0.05) for calves of cows grazing endophyte-free tall fescue except in mid-summer. Cow weight change from April to each time was negative for Angus cows and lower ( < 0.05) than other groups. Cows grazing endophyte-free tall fescue were heavier ( < 0.05) at all times but had more weight loss in late lactation. Angus cows had the lowest ( < 0.05) ratios (negative) of cow weight change:calf weight gain, indicating an energy-deficit condition. Cows grazing endophyte-free tall fescue had more negative ( < 0.05) values for this trait but not in early lactation ( < 0.05). Estimates of heterosis ranged from 12.8 ± 9.5 to 28.6 ± 9.4 kg for cow weight, 7.9 ± 3.0 to 15.8 ± 5.0 kg for cow weight change, and 0.07 ± 0.03 to 0.27 ± 0.1 for cow weight change:calf weight gain. Direct Romosinuano effects ranged from 14.8 ± 4.2 to 49.8 ± 7.7 kg for cow weight change and 0.2 ± 0.04 to 0.51 ± 0.14 for cow weight change:calf weight gain. The adaptive ability of Romosinuano in temperate fescue regions may be favorable with respect to relative cow and calf weight but may be a consequence of lower milk-producing ability.

Genetics of resistance to downy mildew in muskmelon (Cucumis melo L.)

To identify parents and specific combination of parents for resistance to downy mildew, thirty Ft hybrids were developed by crossing six female parents with five male parents in a line x tester mating design. Adult muskmelon plants of parents and hybrids were evaluated in greenhouse and field conditions. Significant variances for general combining ability (GC A) and specific combining ability (SC A) indicated the importance of both additive and non-additive gene actions for the expression of resistance. Inbred lines IIHR 352 (Cucumis melo var. reticulatus), IIHR 190 (Cucumis melo var. reticulatus) and IIHR 122 demonstrated consistently high and negative GCA effects in both screening conditions. Arka Jeet x IIHR 121, Arka Jeet x IIHR 122, Punjab Sunehri x IIHR 190, Punjab Sunehri x IIHR 718, IIHR 681 x IIHR 121, IIHR 681 x IIHR 122 and IIHR 352 x IIHR 616 were the hybrids expressed high per se performance, high midparent heterosis and high SCA effects. The study highlights the importance of harnessing useful genes from diverse parental lines to improve resistance to Pseudoperonospora cubensis in adapted muskmelon varieties/cultivars.

Heterosis and Combining ability studies in intra-specific derivatives of Wal (Lablab purpureus (L.) Sweet)

Eight genotypes of Wal viz., DPLW-46, DPLW-61, DPLW-10, DPLW-31, DPLW-15, DPLW-48, DPLW-51, DPLW-29 and their crosses made in half diallel fashion were evaluated to estimate the combining ability and heterosis effects for yield and yield component characters. The proportion of δ 2 g/δ 2 s revealed preponderance of non additive gene action for inheritance of all the characters. All the parents exhibit significant estimates for combining ability for one or more characters. The parents viz., DPLW-29, DPLW-15 and DPLW-51 were good combiner for most of the characters. Among the crosses DPLW -46 X DPLW-29, DPLW-51 X DPLW-29, DPLW-46 X DPLW-61, DPLW-15 X DPLW-51 and DPLW-46 X DPLW-10 were identified as promising cross combinations and recorded highest significant positive heterosis over mid and better-parents for seed yield per plant. These heterotic cross combinations could be exploited to get superior segregants.

ИЗМЕНЧИВОСТЬ И НАСЛЕДОВАНИЕ ХОЗЯЙСТВЕННО ЦЕННЫХ ПРИЗНАКОВ И СВОЙСТВ У ГИБРИДОВ F1 ТОМАТА ДЛЯ МЕХАНИЗИРОВАННОЙ УБОРКИ

In the system of full diallel crossing 11 x 11, 110 F1 tomato hybrids for mechanical harvesting were obtained. The results of study of the degree of variability and the character of dominance and heterosis effect of F1 hybrids based on economically valuable traits at one-time harvesting. The degree of variability and the nature of the inheritance of economically valuable features and properties of F1 tomato hybrids depends on the initial forms for hybridization, the direction of crossing and the conditions of its growing.

Theory and practice of using heterosis effect in winter rye

Introduction. The article describes the efficiency of creation of new starting material for breeding of cultivars, hybrids and their parental components in connection with the necessity for intensification of rye grain production for the society’s needs and food security of Ukraine.The aim and tasks of the study. The survey proved that the modern trends in winter rye breeding enabled obtaining new starting material for breeding cultivars and hybrids with a set of economically valuable traits.Implementation of winter rye hybrids in production will stabilize the rye grain market in Ukraine and provide science-based norms of rye bread consumption.Material and methods. The source material for creating hybrids of winter rye were varieties and vintage designs. Method of creating hybrids – breeding of the heterosis.Results and Discussion. Winter rye hybrids are plants of a new type, which were created on the basis of sterile and fertile lines with a high combination capacity. The grain yield of hybrids is attributable to the heterosis effect for all its elements and achieved mainly due to productive tillering, redistribution of biological yield capacity and a positive response to farming practices, which can significantly reduce the seeding rate. Hybrids were noticed to have an increased ratio of grain to straw in favor of grain; they responded well to intensive technologies of cultivation. The economical effect from growing hybrids was 25-50% higher than that from growing populations-cultivars.Currently the State Register of Plant Varieties of Ukraine includes 4 domestic rye hybrids and 7 hybrids of foreign breeding.All domestic rye hybrids were created by the Plant Production Institute nd. a V. Ya. Yuriev of NAAS.Conclusions. Studies that will encourage further development of heterosis breeding of winter rye include genetic and economic optimization of the selection of lines both in fertile and in sterile cytoplasm; methods for producing hybrid seeds and cultivation technologies of hybrids under regulating environmental factors. Progress on these issues will contribute to practical breeding and creation of winter rye hybrids.

Heterosis studies for yield and fiber quality traits in intra hirsutum hybrids of cotton (&lt;italic&gt;Gossypium hirsutum&lt;/italic&gt; L.)

The present study was performed to evaluate the heterosis effects for seed cotton yield and fiber quality traits of 56 hybrids and their parents involving seven lines and eight testers along with a check at Acharya N.G. Ranga Agricultural University, Hyderabad. The results showed that, range of relative heterosis varied from -3.40 to 13.29 in ginning percentage, -5.28 to 14.10 in 2.5% span length, -8.72 to 8.25 in uniformity ratio, -16.39 to 14.88 in micronaire value, -5.97 to 10.02 in bundle strength and -32.57 to 113.40 in seed cotton yield per plant, where, highest number of crosses (24) with significant mid parental heterosis in desirable direction was observed for seed cotton yield per plant followed by 2.5 % span length (16) and ginning percentage (12). Desirable and significant heterosis over better parent was observed in the crosses for all the studied characters except for uniformity ratio. A good number of crosses recorded significant standard heterosis over check for all the studied parameters except for uniformity ration and micronaire value. Apart from showing considerable level of heterosis for seed cotton yield, the crosses AKH 9331 x HAG 1055 exhibited good level of heterosis for ginning percentage, Galama x L 604 and Galama x JK 344 for uniformity ratio, Galama x HAG 1055, AKH 9331 x HAG 1055 and CPD 420 x IC 356932 for 2.5% span length and CPD 420 x JK 344 and BC 68-2 x LK 861 for bundle strength. So these crosses could be exploited to improve the yield along with one or more fiber quality traits through heterosis breeding.

Heterosis, Combining Ability, and Character Association in Bottle Gourd for Yield Attributes

ABSTRACTThough Bottle gourd [Lagenaria siceraria (Molina) Stand] has a wide range of genetic variability, very little attention has been paid to its genetic improvement and commercial cultivation. Investigations were carried out to assess the breeding value of parental lines by combining ability analysis with the Line × Tester method to understand the usefulness of heterosis breeding to develop F1 hybrids for commercial cultivation. Nine lines and four testers were crossed to produce 36 hybrid combinations. The parents and hybrids were evaluated for growth and yield characters. There were differences among hybrids and parents for all characters. Variance associated with lines indicated significant differences for all characters except days to first male flower anthesis, number of seed per fruit, and 100 seed weight. For testers, variances exhibited significant differences among genotypes except for vine length, days to first male flower anthesis, days to first female flower anthesis, sex ratio, fruit width, fruit flesh thickness, number of seed per fruit, 100 seed weight, and yield per plant. The variance due to the interaction between lines and testers was significant for all characters except node at first female flower anthesis. The specific combining ability (sca) variances were greater than general combining ability (gca) variances and the ratio of gca/sca variances did not exceed unity, indicating the predominance of nonadditive gene action for all traits. Mean performance and gca effects of parents indicated the superiority of the lines Punjab Long, Kalyanpur Long Green, and Pusa Naveen and testers NDBG-164 and Samrat for most yield attributing characters. Based on mean performance, heterosis and sca effects, hybrids from the crosses ‘Pusa Naveen × NDBG-164’, ‘Pusa Naveen × Punjab Komal’, and ‘NDBG-121 × Samrat’ could be promising for commercial exploitation of fruit yield in F1 hybrids. Number of fruit per vine and fruit flesh thickness were significantly and positively correlated with yield. From path analysis, number of fruit per vine, days to first male flower anthesis, fruit cavity size, fruit weight, days to first fruit harvest, and total soluble solids (TSS) were identified as reliable components of yield and exerted positive, direct effects on yield. When selecting the best hybrids for yield in bottle gourd, more emphasis should be given to number of fruit per vine, fruit flesh thickness, days to first male flower anthesis, fruit cavity size, fruit weight, days to first fruit harvest, and TSS.

Hybrid breeding boosted molecular genetics in rye

History of rye (Secale cereale L.) breeding began from the first targeted selections made in Germany by the Probsteier Seed Cooperative around 1850, and over 150 years breeding yielded a tremendous amount of results. Rye has also long been used as cytological subject due to its low number of chromosomes and their size. However, genetic findings in rye up to the early 1980s were rather scant. About 120 genes could be assigned to seven linkage groups. Only through the development of new methods such as C-banding, in situ DNA hybridization, enzymology and molecular marker techniques achieved an enormous progress. Particularly, the latter was driven by agronomic success of hybrid breeding in rye. The basic genetic knowledge resulted from intra- and interspecies genetic diversity assay and phylogenetic studies in the genus Secale using nuclear and cytoplasmic molecular markers facilitated successful selection of parents for hybrid breeding and hence contributed to improvement of heterosis effects. Main achievements in rye hybrid breeding and genetic mechanisms exploited for different hybrid breeding strategies are discussed. The utilsation of landraces and wild relatives via advanced backcross procedures, combined by QTL analysis and introgression libraries, contributed to increase of heterotic effects. Those marker-assisted approaches became the basis of recent hybrid breeding of rye. Prediction of hybrid performance can also be improved significantly by marker-assisted selection and genomic selection based on genomewide marker data. The findings in rye genetics (including phylogenetic, mapping and population studies) are reviewed in their relation with the hybrid breeding purposes and demands. Overall, about 450 morphological and biochemical traits are mapped throughout the genome plus about 5,000 DNA markers. They are not only associated with individual chromosome or segments but also efficiently used for comparative mapping (evolutionary studies) introgression monitoring, QTL tagging, and marker-assisted selection.

Genetic and environmental factors affecting reproductive traits in sows in an outdoor production system

The aim of this study was to characterize the genetic (crossbreeding and additive genetic) and environmental factors affecting reproduction of sows on an outdoor production system. Data from the Experimental Swine Unit of Facultad de Agronomía, Progreso, Uruguay, were used. The breeding herd included purebred Pampa Rocha (P) and Duroc (D), as well as hybrid (H: P×D and D×P) sows. Pampa Rocha is considered the only local swine breed of Uruguay. The dataset contained 1309 litter records from 197 sows (136 P, 22 D and 39 H) collected from 1997 to 2011. Feeding was based on grazing, restricting the use of concentrate to the breeding herd. The variables analysed were: number of piglets born alive (PBA), average piglet weight of the litter at birth (ABW), number of piglets weaned (PW), average piglet weight of the litter at weaning (AWW), survival from birth to weaning (S) and weaning-to-conception interval (WCI). The following fixed factors were included in the final model: year of farrowing, time of the year (month or season, depending on the variable analysed), inbreeding of the sow, parity number, weaning age, direct breed effects, individual heterosis, repeated measures on the sow (used to estimate the permanent environment effect), and the animal random effect. Duroc sows produced 1.1 more PBA (p=0.03) than P sows. Significant heterosis effects were found for PBA (0.88 piglets, p=0.009) and for PW (0.72 piglets, p=0.03). Hybrid sows produced 1.43 and 1.15 piglets more than P sows, and 0.33 and 0.29 piglets more than D sows, born alive and weaned, respectively. No differences in other variables between genotypes were found. Heritability values (SE) were 0.13 (0.06) for PBA, 0.31 (0.08) for ABW, 0.14 (0.06) for PW, 0.17 (0.02) for AWW, 0.10 (0.01) for S and 0.08 (0.03) for WCI. Winter and spring farrowings resulted in heavier piglets at birth (p<0.001) and at weaning (p<0.01), but no effect on PBA, P and S was observed. Weaning-to-conception interval was greater in summer months (p<0.001). The results suggest seasonal reproductive behaviour. The local breed (P) compared well with a conventional one (D). Furthermore, the crossbred dam appeared attractive due to heterosis in litter traits.

Growth Properties and Biomass Production in the Hybrid C4 Crop Sorghum bicolor.

Hybrid vigor (heterosis) has been used as a breeding technique for crop improvement to achieve enhanced biomass production, but the physiological mechanisms underlying heterosis remain poorly understood. In this study, to find a clue to the enhancement of biomass production by heterosis, we systemically evaluated the effect of heterosis on the growth rate and photosynthetic efficiency in sorghum hybrid [Sorghum bicolor (L.) Moench cv. Tentaka] and its parental lines (restorer line and maintainer line). The final biomass of Tentaka was 10-14 times greater than that of the parental lines grown in an experimental field, but the relative growth rate during the vegetative growth stage did not differ. Tentaka exhibited a relatively enlarged leaf area with lower leaf nitrogen content per leaf area (Narea). When the plants were grown hydroponically at different N levels, daily CO2 assimilation per leaf area (A) increased with Narea, and the ratio of A to Narea (N-use efficiency) was higher in the plants grown at low N levels but not different between Tentaka and the parental lines. The relationships between the CO2 assimilation rate, the amounts of photosynthetic enzymes, including ribulose-1,5-bisphosphate carboxylase/oxygenase, phosphoenolpyruvate carboxylase and pyruvate phosphate dikinase, Chl and Narea did not differ between Tentaka and the parental lines. Thus, Tentaka tended to exhibit enlargement of leaf area with lower N content, leading to a higher N-use efficiency for CO2 assimilation, but the photosynthetic properties did not differ. The greater biomass in Tentaka was mainly due to the prolonged vegetative growth period.

ESTIMATION OF HETEROSIS AND GENETIC PARAMETERS FOR SOME FLOWERING AND VEGETATIVE TRAITS IN MAIZE USING THE DIALLEL CROSS METHOD

A diallel cross among inbred lines of maize (Zea mays L.) with medium maturity and an evaluation to estimate the genetic parameters for days to 50 % tasseling, days to 50% silking, plant and ear heights, resistance to late wilt disease, ear position were carried out. Mean squares were significant for all of the studied traits. Hybrids mean squares were highly significant for the all studied traits under both planting dates and combined analysis, except days to 50% silking. Indicating that the hybrids performance differed from planting date to another. The highest negative heterosis effect was exhibited by cross P5XP2, P6 x P2, P2 x P6, P3 x P5and P3 x P6 over better parent, crosses P5 x P2 , P6 x P2 and P2 x P6 over mid- parents and crosses P5 x P1, P3 x P2 , P4 x P2 ,P5 x P2 , P6 x P2 , P2 x P6 , P3 x P5 and P3 x P6 over check varieties for tasseling date. For days to 50% silking showed that highest significant and negative heterotic effect was exhibited by crosses P6 x P1, P6 x P2, P2 x P6, P4 x P3 and P3 x P6 over mid- parents and all crosses had highly significant and negative heterosis over check varieties, the highest significant and negative heterotic effects were reported by P6 x P1, P6 x P2, P2 x P6, P4x P3 and P3 x P6 over mid- parents and, P3 x P2, P4 x P2 reciprocal, P5 x P2, P6 x P2 and P3 x P6 over check varieties, The highest significant and positive heterotic effect was exhibited by P3 x P5 and P4 x P3 (40.35 and 37.46%) over better-parent and mid-parents respectively, P4 x P2 (13.93%) highest negative significant heterotic effect over check varieties for plant height. For ear height cross P4—P3 showed maximum negative heterosis over check varieties. For resistance to late wilt disease results regarding significant for crosses P1 x P3,P3 x P1,P1 x P4 ,P4 x P1,P1—P5 and P5 x P1 (1.522%) over mid-parents , indicating that these crosses are the best combinations for resistance to late wilt disease. For ear position , 25 crosses show highly significant and negative heterosis over better-parent value for ear position ,P4 x P3 showed maximum negative heterosis over better-parent and over mid-parents . Seven crosses show highly significant and negative heterosis over check varieties value for ear position, P6 x P4 (-8.92%) showed maximum negative heterosis over check varieties. Heritability estimates in broad sense were generally higher at combined data. In the combined data percentage of heritability in the narrow sense for studied traits ranged from 20% for plant height to 46% for days to 50% tasseling or silking. Heritability estimates were low for plant and ear heights in narrow sense (20% and 28%) and the same in broad sense (29% and 38%), respectively. Heritability estimates in broad sense were medium (29% -64%) of all studied traits. Hence it could be concluded that these crosses may be useful for improving maize grain yield program.

Interspecific hybridization in Cucumis leads to the divergence of phenotypes in response to low light and extended photoperiods.

With the aim of improving shade tolerance of cucumber, Cucumis × hytivus, a newly synthesized allotetraploid, was obtained by crossing a shade tolerant wild relative, Cucumis hystrix, with a cultivated cucumber, Cucumis sativus L. ‘BejingJietou.’ The results show that the new C. × hytivus only partly is an intermediate hybrid and it has not only chlorophyll deficiency, which recovers during leaf development, but also lower carotenoid content. Three light conditions with the combination of different light intensities and photoperiods were employed to investigate the photosynthetic response of these three Cucumis species to low light and long photoperiod. The consistent order of Pmax and DWS being lowest in C. hystrix, medium in C. × hytivus and highest in ‘BejingJietou’ suggests the three species to have genetically different photosynthetic efficiency, which relates well with the natural habitats of the parent species and the hybrid as intermediate. C. × hytivus appears to be inhibited by the low light levels to the same extent as the cultivated ‘BeijingJietou,’ which indicates neither improvement of shade tolerance nor hypothetical heterosis effect in C. × hytivus. However, unexpectedly, the PSII of C. hystrix was affected by the long photoperiod in the long term, suggested by the decrease of Fv/Fm. This sensitivity toward day length has not been passed on to C. × hytivus.

Identification of QTL markers contributing to plant growth, oil yield and fatty acid composition in the oilseed crop Jatropha curcas L.

BackgroundEconomical cultivation of the oilseed crop Jatropha curcas is currently hampered in part due to the non-availability of purpose-bred cultivars. Although genetic maps and genome sequence data exist for this crop, marker-assisted breeding has not yet been implemented due to a lack of available marker–trait association studies. To identify the location of beneficial alleles for use in plant breeding, we performed quantitative trait loci (QTL) analysis for a number of agronomic traits in two biparental mapping populations.ResultsThe mapping populations segregated for a range of traits contributing to oil yield, including plant height, stem diameter, number of branches, total seeds per plant, 100-seed weight, seed oil content and fatty acid composition. QTL were detected for each of these traits and often over multiple years, with some variation in the phenotypic variance explained between different years. In one of the mapping populations where we recorded vegetative traits, we also observed co-localization of QTL for stem diameter and plant height, which were both overdominant, suggesting a possible locus conferring a pleotropic heterosis effect. By using a candidate gene approach and integrating physical mapping data from a recent high-quality release of the Jatropha genome, we were also able to position a large number of genes involved in the biosynthesis of storage lipids onto the genetic map. By comparing the position of these genes with QTL, we were able to detect a number of genes potentially underlying seed traits, including phosphatidate phosphatase genes.ConclusionsThe QTL we have identified will serve as a useful starting point in the creation of new varieties of J. curcas with improved agronomic performance for seed and oil productivity. Our ability to physically map a significant proportion of the Jatropha genome sequence onto our genetic map could also prove useful in identifying the genes underlying particular traits, allowing more controlled and precise introgression of desirable alleles and permitting the pyramiding or stacking of multiple QTL.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0326-8) contains supplementary material, which is available to authorized users.

Белковые маркеры в анализе генетического разнообразия, селекции и семенном контроле кукурузы

Во Всероссийском институте генетических ресурсов растений им. Н. И. Вавилова (ВИР) биоразнообразие местных стародавних сортов, популяций и линий кукурузы, а также дикорастущих родичей изучают с целью выявления генотипов, ценных для селекции. На этом этапе, как и при реализации селекционных программ, для решения многих вопросов используют молекулярные маркеры. Методы молекулярного анализа, основанные на белковых и ДНК-маркерах, позволяют с большей полнотой и надежностью выявлять полиморфизм популяций, идентифицировать и регистрировать генотипы (биотипы), определять их соотношение в популяциях, линиях и т. п. В статье приведены результаты проводимой в течение многих лет в ВИР под руководством В. Г. Конарева работы по внедрению белковых маркеров в анализ исходного материала и селекцию кукурузы. Материалом для исследований послужили образцы теосинте и его естественного гибрида с кукурузой, собранного в Мексике экспедицией С. М. Букасова в 1926 г. и сохраненных в коллекции ВИР им. Н. И. Вавилова, а также образцы других диких родичей трипсакум и коикс. Разработанные В. Г. Конаревым и его учениками методы успешно используют в семенном контроле кукурузы: идентификации и контроле однородности линий, анализе гибридности и сопровождении гибридной селекции, включая предсказание эффекта гетерозиса и контроль за включением в селекционный материал ряда хозяйственно-ценных признаков. Принятые в качестве отечественных и международных стандартных лабораторных методов семенного контроля методы электрофореза запасного белка семян кукурузы — зеина — успешно внедрены в работу государственных контролирующих органов систем Россельхознадзора и Россельхозцентра.

Disaggregating polyploidy, parental genome dosage and hybridity contributions to heterosis in Arabidopsis thaliana.

Heterosis is the phenomenon whereby hybrid offspring of genetically divergent parents display superior characteristics compared with their parents. Although hybridity and polyploidy can influence heterosis in hybrid plants, the differential contributions of hybridity vs polyploidy to heterosis effects remain unknown. To address this question, we investigated heterosis effects on rosette size and growth rate of 88 distinct F1 lines of Arabidopsis thaliana consisting of diploids, reciprocal triploids and tetraploids in isogenic and hybrid genetic contexts. 'Heterosis without hybridity' effects on plant size can be generated in genetically isogenic F1 triploid plants. Paternal genome excess F1 triploids display positive heterosis, whereas maternal genome excess F1 s display negative heterosis effects. Paternal genome dosage increases plant size in F1 hybrid triploid plants by, on average, 57% (in contrast with 35% increase displayed by F1 diploid hybrids). Such effects probably derive from differential seed size, as the growth rate of triploids was similar to diploids. Tetraploid plants display a lower growth rate compared with other ploidies, whereas hybrids display increased early stage growth rate. By disaggregating heterosis effects caused by hybridity vs genome dosage, we advance our understanding of heterosis in plants and facilitate novel paternal genome dosage-based strategies to enhance heterosis effects in crop plants.

A long-term genetic study reveals complex population dynamics of multiple-source plant reintroductions

A major challenge of using multiple-source populations in reintroductions for restoration and species conservation is to adequately assess the trade-off between the benefits of counteracting inbreeding depression via heterosis, and the risks of maladaptation and reduced fitness through outbreeding depression. In the 1990s, populations of the perennial plant Arenaria grandiflora rapidly declined and were nearing extinction in the Fontainebleau forest, France. This was likely due to inbreeding depression and/or fixation of deleterious alleles. To restore A. grandiflora in the Fontainebleau forest, a reintroduction experiment was conducted in 1999 using transplants from both local and non-local populations. Eight and twelve years later, we carried out a genetic study using microsatellite markers to assess the temporal dynamics of the genetic composition of reintroduced populations. We show that genetic diversity increased significantly in the reintroduced populations compared to the local-source population and that this increased diversity has been maintained for over ten years, highlighting the benefits of mixing individuals of multiple-source populations for restoration of small and inbred populations. Our results also suggest that the level of individual admixture between local and non-local genetic sources might affect individual fitness, which is influenced by the opposing effects of heterosis, inbreeding and outbreeding depressions and local adaptation.

Evaluation of the growth and carcass quality of diallel crosses of four strains of Nile tilapia (Oerochromis niloticus)

This study examined four commercial lines of Nile tilapia (Oerochromis niloticus) ultimately to implement a breeding program to produce clean fillets from an all-male fish population that is grown to 1kg. Contemporary progenies were produced to perform a complete 4×4 diallel cross. Two experimental populations were studied: (1) a set of hormonal sex-reversed (SR) progeny populations that were processed at 1kg to obtain carcass quality data and (2) a set of populations that did not receive hormone treatment (no hormone, NH) that were used to assess growth between 100g to 400g. The growth traits of 3997 NH fish from 124 families were recorded at 400g, and the processing plant traits were obtained from 2721 SR fish from 99 families. In general, all sources of variation were highly significant for most traits with the effect of linebreeding explaining the largest (from 35 to 50%) fraction of the explained variance (FEV) for all traits, except for the dressing percentage, for which the effect of the general combining ability (gca) was the most important source of variation (51%). The gca exerted the second most important effect on the body weight, fillet weight, and abdominal fat percentage, and reciprocal effects constituted the second most important influence on the head, dressing and fillet percentages, with an FEV of 20% to 35% being observed. The maternal effect was relatively important only for the specific growth rate (SGR), explaining 26% of the total variance. The effect of heterosis was highly significant for all traits but corresponded to only 5% or less of the explained variance for almost all traits, except for the fillet percentage and for days to 1000g with FEVs of 16% and 9%, respectively. In the NH population, the heterosis for all traits indicates a favorable effect of crossbreeding, particularly the heterosis for body weight (6.7%) and average daily gain (6.8%). In the SR population, the levels of heterosis demonstrated the favorable moderate effects of crossbreeding on the body wt. at 400g (4.0%), days to 1kg (−6.3%), average abdominal fat % (−7.4%), and fillet yield (1.6%). These results suggest that crossbreeding does not further improve the exploitation of genetic variation for single traits in this particular farmed tilapia population; however, the observed composite trait fillet productivity, i.e., the total biomass of fillet produced per number of farmed fish,yielded promising levels of heterosis with levels that reached 38% and 43% in specific crosses. Furthermore, four of six cases exhibited a cross that was better than the best pure line, demonstrating that profit heterosis is a relevant parameter to consider for assessing breeding strategies. Statement of relevanceTotal biomass of fillet produced, yielded promising levels of heterosis.

Crossability among modern roses and heterosis of quantitative and qualitative traits in hybrids

Nine divergent popular hybrid rose cultivars and 22 of their F1 hybrids were studied to determine the extent of crossability and heterosis effects for several quantitative and qualitative traits in the climatic conditions of Faisalabad, Pakistan. The percentage of pollen germination differed across cultivars. Gruss-an-Teplitz exhibited the maximum value for pollen germination (46.5%), followed by Autumn Sunset (38.9%). Iceberg, being triploid, presented the lowest percentage of germination. All cultivars exhibited a strong correlation between pollen germination percentages in the lab and crossing success under field conditions. The cultivar Handel showed remarkable fruit-set and crossing success. In contrast, the cultivar Iceberg exhibited very poor crossing success rates. The setting of hips after crossing was maximal in the crosses Handel × Louise Odier and Autumn Sunset × Casino (83% each). The number of seeds in a single hip varied among cultivars. The potential for heterotic and heterobeltiotic was also variable and showed contrasting performance between F1 progenies for various qualitative and quantitative traits. The parent cultivars and progenies were sorted into five major groups by cluster analysis based on phenotypic variation. Phenotypic and genotypic coefficients of variability and heritability percentages varied among all parent cultivars for all morphological traits.