Level Of Heterosis Research Articles

The formation of nicotine heterosis is mainly achieved by enhancing the nicotine transport capacity in hybrids

Nicotine exhibits obvious heterosis, which can be used to create Nicotiana tabacum L. (tobacco) varieties with varying nicotine content. However, the reasons for the formation of nicotine heterosis and its relationship to nicotine transport and accumulation remain unknown. This study conducted a comprehensive analysis of six tobacco hybrids with varying heterosis levels and their parent materials from various aspects, such as phenotype, physiology, and transcriptomics. The results showed that the direct path coefficient of transport heterosis to nicotine heterosis was highest in hybrids, at 0.98, and a highly significant positive correlation between the two. The plant height, thick stalk circumference, large flow of tissue fluid in the stalk, and high nicotine concentration of tobacco were the underlying factors that led to the strong nicotine transport capacity of hybrids. The formation of nicotine transport heterosis in hybrids was mainly influenced by non-additive gene effects (accounting for 89.93%), with over-dominant effects playing a dominant role (accounting for 58.79%). Among non-additive expression DEGs, nicotine transporter related multi antimicrobial extrusion protein, drug/metabolite transporter, ABC family transporter, and glutathione S-transferase were significantly upregulated in hybrid strains. The RT-qPCR results indicated that these genes related nicotine transport also exhibited heterosis at the expression level. Our results revealed that the formation of nicotine heterosis is mainly achieved by enhancing the nicotine transport capacity in hybrids. The results are not only beneficial for promoting the theoretical study of nicotine heterosis in tobacco and the breeding and utilization of hybrids, but are also of great significance for guiding nicotine production and promoting its multipurpose utilization.

Heritability and Variability of Productivity Traits in Spring Soft Wheat Hybrids of the First to Fourth Generations

Abstract A higher varietal specificity in the manifestation of traits in parental varieties was noted compared to hybrids. Two component traits of ear productivity in a series of generations were analyzed against the background of various factors, shifts in their average values and their impact on yield were predicted and determined. The phenotypic dominance index (hp) in the first generation was determined by the number of grains per ear and the weight of 1000 grains, combinations with a high level of heterosis were identified. Under the conditions of the Apsheron region, the effects of interaction between genotype and environment were determined in nine varieties of spring soft wheat and seven hybrid populations F1…F4 formed with their participation. A reliable effect of environmental conditions on all the studied traits was established. The contribution of the “year” factor to the number of grains per ear in varieties and hybrids was 10.9 and 13.9%, respectively; to the weight of 1000 grains – 5.8 and 19.5%; to the yield – 47.3 and 41.1%. The genetic component made a significant contribution to the weight of 1000 grains in varieties and hybrids (81.5 and 58.8%), as well as to the number of grains in varieties (38.4%).

Relationship Between Heterosis and Genetic Distance Determined by SSR Markers in Oriental Tobacco

Hybrid cultivars could be beneficial to achieve high leaf yields while maintaining good quality properties in oriental tobacco. Identification of parents constitutes a major part of a hybrid breeding program. The aim of the present study was to determine the relationship between the genetic distance of parents determined by simple sequence repeats (SSR) markers and heterosis levels in hybrids produced from those parents for leaf yield and quality properties in oriental tobacco. Twenty-one hybrids produced by half diallel crossing among seven tobacco genotypes used in oriental tobacco production in Turkey were grown along with their parents in three locations in 2012 and 2013. Twenty-nine SSR markers were used to determine genetic distances among seven tobacco genotypes. A total of 80 alleles were produced by all twenty-nine markers. Average number of observed alleles per polymorphic marker was 2.96. Twenty-seven of 80 alleles were observed in only one of the seven parents. The polymorphic information content of markers varied from 0.215 to 0.810 (average 0.480). Mid-parent heterosis levels ranged from 18.03 to 42.00% for leaf number, between -19.75 and 38.06% for leaf width, between -17.51 and 36.25% for leaf length, between -34.38 and 76.12% for leaf yield, between -78.30 and 154.01% for sugar content and between -45.40 and 143.29% for nicotine content. Heterosis levels were correlated with genetic distances between parents for leaf number in Erbaa 2012 and Tokat 2012 locations, for leaf width in Erbaa 2013 location, for leaf length in Erbaa 2013 location, and for leaf yield in Tokat 2012 location only. SSR markers were very effective to determine genetic distance of oriental tobacco, and only two markers could distinguish all seven genotypes used in the study. The findings indicated that genetic distance determined by SSR markers used in the present study is not sufficient to predict hybrid performance in oriental tobacco.

Maize breeding effects on grain yield genetic progress and its contribution to global yield gain in Argentina

Context or problemMaize production in Argentina has increased in recent years, following the global gain (GG) in grain yield (GY). The GG in GY depends on genetic progress (GP), which requires frequent quantification to detect potential plateaus and variations in its contribution to the GG. In this sense, hybrid adoption in Argentina shifted from double- and three-way to single cross (F1) hybrids in the 1990s, thereby increasing the level of heterosis of released hybrids. Since heterosis increase may have had a greater impact on estimates of maize GG than those based on a single cross type, GP based exclusively on F1 hybrids and its contribution to GG could be lower than that including different types of crosses. Objective or research questionThe main objectives of this work were to (i) analyze grain yield GP, (ii) dissect grain yield GP into the corresponding trends in its physiological determinants and numerical components, and (iii) estimate the relative contribution of GP to GG in the main maize producing region of Argentina for the period marked by significant changes in heterosis level (i.e. from 1960s to 1990s) and the period of massive adoption of F1 hybrids (from 1990s onwards). MethodsWe used a dataset obtained at the core of the mentioned region (INTA Pergamino; 33°56’S, 60°34’W) from era-decade experiments (ERA) including 24 hybrids released between 1965 and 2016 and grown with no abiotic or biotic restrictions. We quantified GY, its numeric components (KN: kernel number m−2, KW: individual kernel weight) and its physiological determinants (BT: total shoot biomass at maturity, HI: harvest index). ResultsA GP of 0.84 % y−1 was computed for GY from 1965 to 1993, and of 0.51 % y−1 thereafter. We also detected genetic progress for KN (0.53 % y−1) and BT (0.26 % y−1) but not for KW. A GP of 0.66 % y−1 was computed for HI up to 1993, which plateaued thereafter. A 40 % contribution of GP to GG was estimated for the Pergamino site from 1965 to 1993, predominantly driven by changes in heterosis level. The contribution dropped to 32 % from 1993 onwards, when F1 hybrids were massively adopted by the farmers. This contribution was much smaller (e.g. 19 %) in areas less representative of the target population of environments of dominant breeding programs. ConclusionsOur findings underline that the relative contribution of GP to GY improvement at the regional level varies markedly depending upon the period included in the analysis and the environment used for evaluation. The decline observed at less representative locations of the main target population of environments may guide breeders in their decision for developing new programs.

Studies on Genetic Divergence Analysis in Black Gram (Vigna mungo L. Hepper) Genotypes

In order to select superior genotypes for the creation of genetic stock for hybridization program or the introduction of a crop variety, plant breeders can assist from genetic diversity both within and between plant species. Mahalanobis D2 Statistics was used to conduct the current study on Genetic Divergence and clustering pattern utilizing twenty eight different genotypes of Black gram. The experiment was conducted in Randomized Block Design with three replications at Plant Breeding Farm, Department of Genetics and Plant Breeding, Faculty of Agriculture, Annamalai University, Chidambaram, Tamil Nadu, India. Nine different biometrical characteristics were observed and documented viz., plant height at maturity (PH), pod length (LP), number of branches per plant (NBPP), number of clusters per plant (NCPP), number of pods per cluster (NPPC), number of pods per plant (NPPP), number of seeds per pod (NSPP), 100 seed weight (SW), and seed yield per plant (SY). All of these characters have a significant degree of variability, according to an analysis of variance. Mahalanobis (D2) static revealed considerable genetic diversity among the genotypes. Genotypes were grouped into 6 clusters. Cluster VI was the largest including 11 genotypes. The intra-cluster distance for cluster IV is the maximum and the lowest intra-cluster distance was reported for cluster II. The highest inter-cluster distance was revealed between cluster I and III and then between cluster II and III. This demonstrates unambiguously that the genotypes in this cluster exhibit a wide range of genetic variation and may be useful in a black gramme hybridization scheme to increase production. Between clusters I and II, the minimal inter-cluster distance was discovered. The percentage that each character contributed to the overall divergence was as follows: the number of pods per plant (50.997), the greater seed output (50.997), and the 100 seed weight (29.456). (8.121). It is proposed that crossings between parents from the most divergent clusters should show the highest level of heterosis as well as the greatest degree of genetic architectural variability.

Breeding chili pepper for simultaneous improvement in leaf curl virus and anthracnose disease tolerance and commercially important traits

ABSTRACT In a large portion of the tropics, there is a demand for the development of hybrid chilies (Capsicum annuum L.) with high pungency, antioxidant vitamins, and tolerance to chili leaf curl virus, and anthracnose. Six genetically diverse parents were crossed in half-diallel fashion to develop 15 F1 hybrids to assess the level of heterosis, combining ability and gene action for 17 quantitative traits. The inheritance of most traits was apparently controlled by non-additive gene action. “Bidhan Chili 4” recorded the maximum, significant, GCA effects in a desired direction for PDIs of leaf curl virus and anthracnose along with commercially important traits. The maximum extent of heterobeltiosis was for oleoresin content followed by ascorbic acid and capsaicin contents, PDIs of chili leaf curl virus and anthracnose, and fruit yield per plant. The hybrids “Bidhan Chili 4 × Chili 38-Ragi” and “Pant C 1 × Bidhan Chili 4” could be isolated on the basis of their average performance, heterosis manifested in them, and SCA effects. Such hybrids could make a difference by meeting the horticultural requirements, high yield, disease tolerance and pungency, of commercial chili growing zones in the tropics. Hybrid vigor is available for commercial production of chili hybrids. A different approach from hybrid vigor is to isolate pure lines from segregating generations of potential heterotic F1s to increase fruit yield, quality attributes, and resistance to the chili leaf curl virus and anthracnose disease.

Genetic control of plant height in corn lines in diallel crosses

The article presents the results of a study of corn hybrids cultivated in diallelic crosses (p(p+1)/2) according to the trait “plant height”. The experiment included 11 self-pollinated lines (method 2, model 1) and 55 hybrids. As a result of the research, the height of plants in parental lines and F1 hybrids was determined (a total of 3960 measurements were made), the effects of TCA and SCA dispersion, the level of heterosis were calculated, and the genetic components that control the manifestations of the studied trait were determined. The highest plant heights were in the lines SPK 13, SPK 14, SPK 17, SPK 21. Relatively high group average values of plant heights of hybrids were found with the lines SPK 14, SPK 18, SPK 17, SPK 16. A high effect of TCA and a high dispersion of SCA were determined in the line SPK 14. High effects of SCA were detected in combinations with the lines SPK 14, SPK 12, SPK 16. True heterosis of more than 20% was determined in 45 hybrids in 2017 and in 9 hybrids in 2018. Adequacy of the additive-dominant model in 2017. obtained by excluding the lines SPK 13, SPK 14, SPK 15, SPK 17 from the calculations. In 2018, the non-allelic effect of genes was not determined. The experiment established that control of plant height in the model population was carried out by at least 5 genes or groups of genes in 2017 and 9 genes in 2018.

Heterosis and combining ability in intraspecific (G. hirsutum L.) and interspecific (G. hirsutum L. × G. barbadense L.) cotton hybrids

The inheritance of most important economic characters, heterosis and combining ability were studied in six interspecific (G. hirsutum L. × G. barbadnese L.) and three intraspecific hybrid combinations. There were found different types of inheritance of productivity, boll weight and lint percentage and fiber length in the individual crosses. The genetic variance for productivity and fiber length was mainly non-additive, while for lint percentage it was additive. Although non-additive genetic variance prevailed for productivity and fiber length, only individual crosses showed positive heterosis, outperforming the better parent. Of the female forms, the cultivar Helius was identified as a very good general combiner for productivity. From the male forms the cultivar Ashkabat emerged as a very good general combiner for productivity, boll weight and lint percentage. The cultivars Mytra (female), Karshinski-2 and C-6037 (male) were determined as very good general combiners for fiber length. All these cultivars, with the exception of C-6037, had low SCA variances, their high GCA was mainly due to additive gene effects, and they were very suitable for synthetic selection. The cross Helius × Ashkabat was found to be most valuable for the selection of productivity because of the highest mean performance and the highest level of heterosis with high SCA effects. All intraspecific hybrids were found to be most promising for improving lint percentage. The interspecific cross combinations Mytra × C-6037, Helius × C-6037 and Mytra × Karshinski-2, having the longest fibers, the first two with high SCA effects were most valuable for fiber length improvement.

Interpretation of Mean Values and Extent of Heterosis Bottle Gourd [Lagenaria siceraria (Mol.) Standl.

Aims: To Study the mean values and heterosis for fruit yield with associated traits of bottle gourd.
 Study Design: Randomized block design.
 Place and Duration of Study: The seeds of F1 hybrids were produced during summer 2021 at Potato Research Station, S. D. Agricultural University, Deesa.
 Methodology: The experimental material consisted of twelve parents, their 35 Line × Tester crosses and one standard check (ABGH 1).
 Results: The study was undertaken to reveal mean and per cent heterosis level in bottle gourd [Lagenaria siceraria (Mol.) Standl.]. An examination of mean data of parents with (F1) hybrids for fruit yield and associated traits revealed that DBG 5 amongst females and ABGS 11-17 amongst males, while NDBG 132 × PUNJAB LONG, LOCAL × ABGS 14-25, and LOCAL × ABGS 11-17 amongst hybrids exhibited higher mean value for fruit yield per plant with some of its associated traits. The significant relative heterosis, heterobeltiosis and standard heterosis were perceived in many hybrids for different component traits. The F1 hybrids, NDBG 132 × PUNJAB LONG (75.30, 53.04 & 21.64 %), LOCAL × ABGS 14-25 (34.99, 27.77 and 20.71 %) and LOCAL × ABGS 11-17 (31.82, 23.49 and 19.27 %) manifested significant and positive heterosis over mid parent, better parent and the standard check ABGH 1 for fruit yield per plant. These crosses were also given best mean performance, hence hold promising for commercial exploitation.
 Conclusion: The analysis of variance revealed that significant differences among the parents for all traits. This indicated a sufficient variability in the parents (i.e., lines and testers) for studied trait. The best heterotic crosses NDBG 132 × PUNJAB LONG, LOCAL × ABGS 14-25, LOCAL × ABGS 11-17 and GPBG 108 × ABGS 11-24 for fruit yield per plant revealed significant positive heterosis over mid parent, better parent and standard check.

Heterosis and combining ability estimates for okra (<i>Abelmoschus esculentus</i> L. Moench) varieties for yield attributing characters in Sudan savanna of Nigeria

Two location trials were conducted at the Teaching and Research Farm of the University of Maiduguri and screen house of the Faculty of Agriculture during 2018/2019 dry season to estimate the combining ability variance, general combining ability (GCA) effects of parents and specific combining ability (SCA) effects of crosses with six okra genotypes. They include: three improved varieties NHAe 47-4, LD-88, Clemson spineless and three locals, Chalawa, Syria and Sola, crossed in a 3 x 3 line x tester mating design to generate nine F1 hybrids. All the F1s along with their parents were evaluated in a Randomized Complete Block Design (RCBD) and Completely Randomise Design (CRD), with 3 replications. Positive heterosis were observed for number of fruits per plant in the crosses Chalawa x NHAe47-4, Chalawa x Clemson Spineless, this directly indicated their important contributions toward total fruit yield in okra. The variance of GCA and SCA revealed that both additive and non-additive gene actions were important in the control of most agronomic.The ratio of GCA/ SCA indicates greater preponderance of non-additive gene action for the characters in all the traits except number of leaves per plant and days to 50% flowering which were controlled by additive gene actions. The parent Syria was the overall best general combiner among the lines for all characters in the field and Chalawa was the overall best general combiner for all characters measured among lines in the screen house. LD88 recorded the highest GCA effects for all of the characters among testers in both experiments. Similarly, in the field, the hybrid Sola x NHAe47-4 recorded the maximum SCA effect for all characters except days to 50% flowering; Syria x NHAe47-4 was the best SCA for most characters except plant height and also the cross between Syria x Clemson Spineless was the best SCA for most characters except number of fruits per plant. In the screen house, the cross between Chalawa x NHAe47-4, showed superior SCA for all characters measured. Appreciable level of heterosis was observed for most of the characters studied, the overall maximum positive significant heterosis for total fruit yield (kg/ha) was observed in crosses Syria x LD88 (52.80) and Chalawa x NHAe47-4(123.30) over better parents. The preponderance of non-additive genetic effect and the tremendous level of heterosis observed among the characters in the parents and their crosses studied would be great asset in choosing the okra varieties for intercrossing and development of hybrids varieties for commercial production of okra.

Studies on Promising Restorer Lines for Yield and Yield Components in Rice (Oryza sativa L.)

The present investigation was carried out at Regional Agricultural Research Station, Maruteru with a set of 30 experimental hybrids developed by crossing three male sterile lines with 10 testers in Line × Tester mating design during kharif, 2022. The resultant 30 hybrids were evaluated in Randomized Block Design with two replications along with the parents and hybrid check, HRI-174 during rabi, 2022-23. Analysis of variance for yield and yield components revealed significant differences among the genotypes, parents, hybrids and parents vs. crosses for most traits, indicating significant differences among parents and hybrids, in addition to significant levels of heterosis for the traits studied. In general, the hybrids had recorded higher grain yield per plant, compared to the lines and were observed to be early and relatively tall with a more number of productive tillers per plant and increased panicle length compared to the parents. The hybrids, APMS 15A×RGL 5613, APMS 15A×MTU 1213, APMS 17A×RGL 5613 and APMS 17A ×MTU 2055had recorded significant and positive relative heterosis, heterobeltiosis and standard heterosis of more than 25 per cent for grain yield per plant and were identified as promising heterotic combinations for further evaluation and commercial exploitation.

Scarce Evidence of Heterosis for Growth Traits in Peruvian Guinea Pigs.

This study aimed to estimate the heterosis for productive traits in a two-way crossbreeding scheme. Four guinea pig lines were originally selected for the following traits: line P1 for the growth rate, P2 for the partial feed conversion rate, M1 for the growth rate of the litter at 10 days of age, and M2 for the litter size at birth. The comparison included 176 purebreds (P1: 46, P2: 43, M1: 54 and M2: 33) and 150 crosses (P1P2: 42, P2P1: 38, M1M2: 11 and M2M1: 59); body weights at birth, 10 days, weaning and 60 days of age were analyzed. A linear fixed-effect model was used, and heterosis was estimated as the difference between the average performance of the crossbred and pure-line animals. The pure line comparisons showed that P2 was lower than P1 for weight at 10 days and weaning weight, while all other comparisons between the paternal and maternal pure lines were not significant. The results indicated significant positive heterosis effects for both types of crosses, but only for birth weight: 3.7% for paternal crosses and 12.7% for maternal crosses. The heterosis estimates were mostly positive but not significant for all other traits. A reason for the low levels of heterosis could be that the lines are not very genetically differentiated. These results suggest that applying a two-way crossbreeding scheme within paternal and maternal guinea pig lines for meat production is not recommended due to the absence of heterosis for growth traits.

Genetic and molecular regulation of increased photosynthetic cell number contributes to leaf size heterosis in Arabidopsis

Heterosis is an important genetic phenomenon that has been observed and widely utilized in agriculture. However, the genetic and molecular bases of heterosis are unclear. Through transcriptome-wide association studies (TWAS) and expression quantitative trait locus (eQTL) analysis to integrate genome, transcriptome, and heterotic phenotype of a half-sibling Arabidopsis hybrid population, we report that the genetic and molecular bases of variations in leaf growth heterosis can be explained by the varied expression levels of growth-regulating genes resulting from distinct sets of heterozygous eQTLs carried by the half-sibling hybrids. In F1 versus parent, the degree of up-regulated gene expression in the cell cycle pathway in the shoot apex and the photosynthesis pathway in true leaf positively correlates with true leaf area heterosis level, and this is affected by the accumulation of superior heterozygous eQTLs. This was further corroborated by the major contribution of increased photosynthetic cell number to leaf area heterosis.

Inheritance of fodder and seed productivity characteristics by F1 winter triticale hybrids

Purpose and Objectives. To characterize the inheritance of fodder and seed productivity characteristics by F1 winter triticale hybrids from reciprocal crossings. To select promising F1 combinations that show strong heterosis in three or more performance traits. Materials and Methods. The study was carried out at the Department of Fodder, Grain and Technical Crops Breeding of the Institute of Fodder and Agriculture of Podillia of NAAS in 2021 and 2022. The farming techniques were traditional for the forest-steppe. Parents and F1 were sown in a hybrid nursery using a manual marker; the interrow distance was was 30 cm; the interplant distance in the rows was 10 cm. Nine winter triticale varieties of different eco-geographical origins served as the starting material for direct and reverse crossings: Bozhych, Buzhanske, and Pavlodarskyi originating from Ukraine; Tornado, Khleborob, Soyuz, Sergiy, and Sibirskiy from Russia; and NTH 1933 from China. The heterosis degree was determined according to Matzinger et al. [15] and S. Fonseca, F. Patterson. Results and Discussion. Analysis of inheritance in F1 hybrids showed that the productive tillering capacity was inherited by different types, with negative overdominance (55%) and heterosis (20%) prevailing. Due to intra-allelic interactions of genes functioning in a heterozygous state only, selection of genotypes in early hybrid generations may be ineffective. However, there is a high probability of identification of transgressions of increased tillering in later hybrid generations. A combination with positive dominance, Khleborob / NTH 1933 (hp = 0.6; Ht = 3.3%; Hbt = -2.5%), is worth of special attention for selection of genotypes that would have increased tillering capacity. Combinations with negative overdominance (depression) are of little value in breeding for enhanced tillering. Our data on winter triticale demonstrated that the spike length inheritance by F1 hybrids had a wide spectrum: 10% of hybrid combinations showed positive overdominance (heterosis), 25% – positive dominance, 35% – intermediate inheritance, 15% – negative dominance, and 20% – negative overdominance (depression). This is attributed to different geographical and genetic origins of varieties selected for crossing. It should be noted that the Pavlodarskyi / Serhiy and Buzhanske / Pavlodarskyi hybrid combinations inherited spike length by depression. That is, it is possible to select winter triticale plants with relatively short spikes but with increased numbers of kernels among the distinguished hybrid combinations. Analysis in the Pavlodarskyi / Sergiy hybrid population proved that it was possible to select genotypes that would combine a relatively increased number of kernels per spike with an increased weight of kernels per spike. In the Sibirskiy / Pavlodarskyi, Tornado / Pavlodarskyi and Pavlodarskyi / Soyuz hybrid combinations with intermediate inheritance of the “kernel number per spike” trait, it was possible to select genotypes with small numbers of kernels, but kernels were heavier compared to those in the parental forms. The Bozhych / Pavlodarskyi and Sibirskiy / Pavlodarskyi hybrid combinations with positive dominance of the “kernel weight per plant” trait had intermediate inheritance of the “productive stem number” trait, the “spike length” trait and the “kernel number per spike” trait. Selection for increased weight of thousand kernels and, consequently, for increased weight of kernels per plant will be more effective in these combinations. It should be said that it is possible to generate genotypes with elongated spikes from these hybrid combinations. Negative dominance of the “productive stem number” trait, intermediate dominance of the “spike length” and “kernel number” traits, but little positive overdominance of the “kernel weight per spike” and the “kernel weight per plant” traits were intrinsic to the Pavlodarskyi / Soyuz hybrid combination. It is possible to identify genotypes with small numbers of productive stems and kernel numbers similar to those in a parent, but with an increased weight of thousand kernels. Conclusions. Analysis of the variability of the fodder and seed productivity traits in F1 winter triticale hybrids established that hybrid combinations differed significantly in terms of heterosis level and inheritance type. All possible variants of phenotypic dominance, from positive to negative overdominance, were identified. For such traits as the productive tillering, kernel weight per spike, kernel weight per plant, and dry matter weight per plant, depression was noted in most combinations (55–60%).

Alfalfa: directions and results of breeding

Purpose. Generalization of the results of breeding work with alfalfa (Medisago L.) based on many years of foreign and domestic research. Methods. Monitoring, system analysis, economic-mathematical approach, statistical and monographic. Results. The main areas of breeding alfalfa are presented, including increasing seed productivity, nitrogen fixation, and resistance to adverse abiotic (wintering conditions, drought, increased soil acidity) and biotic (pathogens, diseases and pests) factors, improving feed quality, and creating transgenic plants. The results of the multi-year selection work carried out by the Institute of Feed Research and Agriculture of Podillia of NAAS on the creation of alfalfa seed varieties tolerant to increased soil acidity, have been concretized. The research results on the population variability of self-incompatibility of alfalfa plants evaluation are given, which made it possible to develop a plan for creating synthetic varieties with increased and stable level of heterosis of feed and seed productivity traits. Conclusions. Alfalfa is a valuable feed crop that occupies a leading position among perennial legumes. There are a number of challenges for this culture that need to be solved through breeding. Laboratory and field methods of evaluating alfalfa resistance to aluminum and increased soil acidity were developed due to which the Sinyuha and Radoslav alfalfa varieties were created and introduced into production. This technique contributes to: achieving a relatively high level of feed and seed productivity in combination with plant tolerance to increased soil acidity and other negative environmental factors; the expansion of the zone of optimal cultivation of alfalfa seeds in Ukraine significantly north of the previously defined limits; minimization or complete exclusion of specific negative factors, taking into account the biological and morphological features of the available starting material when creating alfalfa varieties and hybrids.

A systematic dissection in oilseed rape provides insights into the genetic architecture and molecular mechanism of yield heterosis.

Heterosis refers to the better performance of cross progeny compared with inbred parents, and its utilization contributes greatly to agricultural production. Several hypotheses have been proposed to explain heterosis mainly including dominance, over-dominance (or pseudo-overdominance) and epistasis. However, systematic dissection and verification of these hypotheses are rarely documented. Here, comparison of heterosis level across different traits showed that the strong heterosis of composite traits (such as yield) could be attributed to the multiplicative effects of moderate heterosis of component traits, whether at the genome or locus level. Yield heterosis was regulated by a complex trait-QTL network that was characterized by obvious centre-periphery structure, hub QTL, complex up/downstream and positive/negative feedback relationships. More importantly, we showed that better-parent heterosis on yield could be produced in a cross of two near-isogenic lines by the pyramiding and complementation of two major heterotic QTL showing partial-dominance on yield components. The causal gene (BnaA9.CYP78A9) of QC14 was identified, and its heterotic effect results from the heterozygous status of a CACTA-like transposable element in its upstream regulatory region, which led to partial dominance at expression and auxin levels, thus resulting in non-additive expression of downstream responsive genes involved in cell cycle and proliferation, eventually leading to the heterosis of cell number. Taken together, the results at the phenotypic, genetic and molecular levels were highly consistent, which demonstrated that the pyramiding effect of heterotic QTL and the multiplicative effect of individual component traits could well explain substantial parts of yield heterosis in oilseed rape. These results provide in-depth insights into the genetic architecture and molecular mechanism of yield heterosis.

Introgression of Heterotic Genomic Segments from Brassica carinata into Brassica juncea for Enhancing Productivity.

Interspecific hybridization resulted in the creation of B. juncea introgression lines (ILs) generated from B. carinata with increased productivity and adaptability. Forty ILs were crossed with their respective B. juncea recipient parents to generate introgression line hybrids (ILHs) and the common tester (SEJ 8) was used to generate test hybrids (THs). Mid-parent heterosis in ILHs and standard heterosis in THs were calculated for eight yield and yield-related traits. Heterotic genomic regions were dissected using ten ILs with significant mid-parent heterosis in ILHs and standard heterosis in THs for seed yield. A high level of heterosis for seed yield was contributed by 1000 seed weight (13.48%) in D31_ILHs and by total siliquae/plant (14.01%) and siliqua length (10.56%) in PM30_ILHs. The heterotic ILs of DRMRIJ 31 and Pusa Mustard 30 were examined using polymorphic SNPs between the parents, and a total of 254 and 335 introgressed heterotic segments were identified, respectively. This investigation discovered potential genes, viz., PUB10, glutathione S transferase, TT4, SGT, FLA3, AP2/ERF, SANT4, MYB, and UDP-glucosyl transferase 73B3 that were previously reported to regulate yield-related traits. The heterozygosity of the FLA3 gene significantly improved siliqua length and seeds per siliqua in ILHs of Pusa Mustard 30. This research proved that interspecific hybridization is an effective means of increasing the diversity of cultivated species by introducing new genetic variants and improving the level of heterosis.

Transcriptomic and methylomic analyses provide insights into the molecular mechanism and prediction of heterosis in rice.

Heterosis has been widely used in multiple crops. However, the molecular mechanism and prediction of heterosis remains elusive. We generated five F1 hybrids [four showing better-parent heterosis (BPH) and one showing mid-parent heterosis], and performed the transcriptomic and methylomic analyses to identify the candidate genes for BPH and explore the molecular mechanism of heterosis and the potential predictors for heterosis. Transcriptomic results showed that most of the differentially expressed genes shared in the four better-parent hybrids were significantly enriched into the terms of molecular function, and the additive and dominant effects played crucial roles for BPH. DNA methylation level, especially in CG context, significantly and positively correlated with grain yield per plant. The ratios of differentially methylated regions in CG context in exons to transcription start sites between the parents exhibited significantly negative correlation with the heterosis levels of their hybrids, as was further confirmed in 24 pairwise comparisons of other rice lines, implying that this ratio could be a feasible predictor for heterosis level, and this ratio of less than 5 between parents in early growth stages might be a critical index for judging that their F1 hybrids would show BPH. Additionally, we identified some important genes showing differential expression and methylation, such as OsDCL2, Pi5, DTH2, DTH8, Hd1 and GLW7 in the four better-parent hybrids as the candidate genes for BPH. Our findings helped shed more light on the molecular mechanism and heterosis prediction.

Studies on the Molecular Basis of Heterosis in Arabidopsis thaliana and Vegetable Crops

Heterosis is an important phenomenon for high-yield crop breeding and is utilized for breeding F1 varieties in horticultural crops. However, its molecular mechanism has not been elucidated, and compared to cereals, heterosis is less explored at the molecular level in horticultural crops. In this review, we compiled the new genetic and epigenetic studies on heterosis in horticultural crops. Because of the difficulty of predicting the level of heterosis from the parental genetic distance, molecular approaches are being used to study its molecular basis in horticultural crops. Transcriptome analyses in vegetables have identified photosynthesis-related genes as important in heterosis. Analysis of noncoding RNAs has suggested their involvement in regulating the heterosis of vegetative and fruit tissues. Quantitative trait locus (QTL) analysis has revealed the association of heterozygosity of a specific locus or multiple loci with heterosis of vegetative and fruit tissues. A higher level of DNA methylation was noted in the heterotic F1 of Brassica rapa leafy vegetables, while the roles of other epigenetic modifications such as histone marks have not been explored.

Yuan Longping, a great world hunger fighter

Yuan Longping, a great world hunger fighter