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A special issue of Plants (ISSN 2223-7747).

Deadline for manuscript submissions: closed (29 February 2020) | Viewed by 60332

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Dr. Ornella Calderini

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Institute of Biosciences and Bioresources (IBBR), CNR,via Madonna Alta 130, 06128 Perugia, Italy
Interests: plant cell cycle and meiosis; plant development and reproduction; signal transduction via MAPK genes related to development and stress responses; plant functional genomics in model (Arabidopsis and Medicago truncatula) and crop species; bioenergy crops; biodiversity; heterosis
Special Issues, Collections and Topics in MDPI journals

Dr. Carla Scotti

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Council for Agricultural Research and Economics (CREA), Rome, Italy
Interests: methods in alfalfa variety constitution (synthetics and free-hybrids) and breeding for forage production and quality in alfalfa; secondary metabolite synthesis in Medicago spp.: symbiotic nitrogen fixation in Medicago spp. – Sinorhizobium meliloti; functional genomics in Medicago spp.

Special Issue Information

Dear Colleagues,

The phenomenon of heterosis was first described by Darwin as having a positive effect on plant traits, as displayed by cross-fertilized over self-fertilized progenies in the vegetable kingdom. Shull and East’s rediscovery of heterosis in 1906 paved the way for the introduction of the first maize hybrid varieties in the US market in early 1930. Since then the occurrence of hybrid vigor has been proven for many plant species (allogamous and autogamous) and for several characteristics (biomass and resistance to biotic and abiotic stress).

Genetic control studies on hybrid vigor support the different hypotheses that have been suggested and debated (dominance, over-dominance, epistasis) and, in general, it is accepted that the three mechanisms are not mutually exclusive.

The advances in dissecting the molecular mechanisms underlying heterosis seem to indicate that new patterns of whole-genome coordinated activities differently modulated in the various sets of genes (e.g. syntenic/non-syntenic, dosage-dependent genes), plant tissues, developmental stages, and in timing (e.g., altered circadian-mediated gene expression) are involved in the higher performances of heterotic hybrids vs the parental lines. These new patterns of genome activity in hybrids can be the result of multiple molecular mechanisms documented in several recent studies: gene expression variation (differential/non-differential variation relative to the parental lines; additive/non-additive variation; cis- and trans-acting regulatory variation of parental alleles), gene complementation (from presence/absence variation and active/non-active variation between parents), epigenetic regulation (e.g., DNA methylation).

The effort to tackle heterosis from the genetic, epigenetic, and molecular point of view, seems to have led to a more and more complex depiction of heterosis itself, hampering a generalized scientific theory to thoroughly cover the phenomenon. On the other hand, plant breeders keep on working successfully with breeding schemes in many crops and vegetables estimating parental genotype ‘combining abilities’ to catch the best ‘well combining’ parental lines and consequently the most heterotic hybrids. It is then clear that the genetic, epigenetic, and molecular dissection of the ‘well combining’ genotypes is also of great interest in the view of establishing a consistent heterotic pattern (i.e., groups of parental lines consistently displaying heterosis in hybrids) in different plant species.

For these purposes, the current Special Issue welcomes experimental work, reviews, commentaires on phenotypic, genetic, and molecular analysis of hybrid vigor in plants, with a particular focus on non-model species, as a means to offer a wide frame for discussing the recent progress in the field.

Dr. Ornella Calderini
Dr. Carla Scotti
Guest Editors

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12 pages, 1827 KiB

Open AccessArticle

Comparison of the Ability to Control Water Loss in the Detached Leaves of Wedelia trilobata, Wedelia chinensis, and Their Hybrid

by Qilei Zhang, Guangxin Chen, Jundong Huang and Changlian Peng

Plants 2020, 9(9), 1227; https://doi.org/10.3390/plants9091227 - 18 Sep 2020

Cited by 8 | Viewed by 2257

Abstract

In the process of biological invasion, hybridization between invasive species and native species is very common, which may lead to the formation of hybrids with a stronger adaptability. The hybrid of Wedelia trilobata (an alien invasive species) and Wedelia chinensis (an indigenous congener) has been found in South China. In our previous study, we found that the hybrid showed heterosis under cadmium stress. However, the results of this experiment demonstrated that the leaves of the hybrid had no heterosis in controlling water loss. The results showed that the water loss rate of W. trilobata was the slowest, that of W. chinensis was the fastest, and that of the hybrid was in the middle. Compared with W. chinensis and the hybrid, W. trilobata accumulated more abscisic acid (ABA) in leaves to control water loss. After the leaves were detached, W. chinensis leaves suffered the most serious damage, the lowest maximum photochemical efficiency, the most serious membrane lipid peroxidation, and the largest accumulation of malondialdehyde and reactive oxygen species. Compared with W. chinensis and its hybrid, the leaves of W. trilobata could accumulate more antioxidant enzymes and antioxidants, and the total antioxidant capacity was the strongest. The results demonstrate that the ability of the hybrid to reduce water loss was lower than that of W. trilobata, but higher than that of W. chinensis. They showed that the drought resistance of the hybrid may be higher than that of W. chinensis, and it might threaten the survival of W. chinensis. Full article

(This article belongs to the Special Issue Plants Heterosis)

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15 pages, 2434 KiB

Open AccessArticle

Hybrid Breeding for MLN Resistance: Heterosis, Combining Ability, and Hybrid Prediction

by Christine Nyaga, Manje Gowda, Yoseph Beyene, Wilson T. Murithi, Juan Burgueno, Fernando Toledo, Dan Makumbi, Michael S. Olsen, Biswanath Das, Suresh L. M., Jumbo M. Bright and Boddupalli M. Prasanna

Plants 2020, 9(4), 468; https://doi.org/10.3390/plants9040468 - 08 Apr 2020

Cited by 10 | Viewed by 4128

Abstract

Prior knowledge on heterosis and quantitative genetic parameters on maize lethal necrosis (MLN) can help the breeders to develop numerous resistant or tolerant hybrids with optimum resources. Our objectives were to (1) estimate the quantitative genetic parameters for MLN disease severity, (2) investigate the efficiency of the prediction of hybrid performance based on parental per se and general combining ability (GCA) effects, and (3) examine the potential of hybrid prediction for MLN resistance or tolerance based on markers. Fifty elite maize inbred lines were selected based on their response to MLN under artificial inoculation. Crosses were made in a half diallel mating design to produce 307 F1 hybrids. All hybrids were evaluated in MLN quarantine facility in Naivasha, Kenya for two seasons under artificial inoculation. All 50 inbreds were genotyped with genotyping-by-sequencing (GBS) SNPs. The phenotypic variation was significant for all traits and the heritability was moderate to high. We observed that hybrids were superior to the mean performance of the parents for disease severity (−14.57%) and area under disease progress curve (AUDPC) (14.9%). Correlations were significant and moderate between line per se and GCA; and mean of parental value with hybrid performance for both disease severity and AUDPC value. Very low and negative correlation was observed between parental lines marker based genetic distance and heterosis. Nevertheless, the correlation of GCA effects was very high with hybrid performance which can suggests as a good predictor of MLN resistance. Genomic prediction of hybrid performance for MLN is high for both traits. We therefore conclude that there is potential for prediction of hybrid performance for MLN. Overall, the estimated quantitative genetic parameters suggest that through targeted approach, it is possible to develop outstanding lines and hybrids for MLN resistance. Full article

(This article belongs to the Special Issue Plants Heterosis)

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16 pages, 273 KiB

Open AccessCommunication

Heterotic Effect of Different Cytoplasmic Combinations in Sunflower Hybrids Cultivated Under Diverse Irrigation Regimes

by Vikrant Tyagi, Satwinder Kaur Dhillon, Gurpreet Kaur and Prashant Kaushik

Plants 2020, 9(4), 465; https://doi.org/10.3390/plants9040465 - 07 Apr 2020

Cited by 9 | Viewed by 2475

Abstract

The sunflower hybrids hold a narrow cytoplasmic diversity. Besides, the heterotic effect of wild cytoplasmic combinations of sunflower on important traits under water stress has not been explored in detail. Here, we evaluated the different sunflower cytoplasmic combinations in sunflower hybrids using cytoplasmic male sterile (CMS) sources as female parents. We used a total of sixteen sunflower genotypes representing twelve CMS lines from wild and conventional sources along with four restorer lines. Twelve CMS lines were crossed with four restorer lines to develop a total of 48 F₁ hybrid combinations. The hybrids were evaluated under two different environments (i.e., regular irrigation and water stress) for morphophysiological, yield, and biochemical traits over two years. Heterotic effect for various CMS sources was evaluated on all of the three possible scales, namely, better-parent heterosis (BPH), mid-parent heterosis (MPH), and heterosis as percent of check (PSH-996). For better-parent and mid-parent heterosis, the CMS sources Helianthus annuus, Helianthus argophyllus, and Helianthus debilis demonstrated positive better-parent heterosis for seed yield, oil content, and oleic acid irrespective of the environment. However, the hybrid combinations of different sources when using the genotype RCR8297 as the restorer parent recorded maximum average returns. Furthermore, chlorophyll meter (SPAD) reading positively correlated with days to 50% flowering, days to maturity, plant height, and number of leaves per plant in both the environments. Overall, this study identified and compared the heterotic effect of the different cytoplasmic combinations in sunflower under water stress as well as under normal irrigation environments. Full article

(This article belongs to the Special Issue Plants Heterosis)

16 pages, 4008 KiB

Open AccessArticle

In Arabidopsis thaliana Heterosis Level Varies among Individuals in an F₁ Hybrid Population

by Hasan Mehraj, Takahiro Kawanabe, Motoki Shimizu, Naomi Miyaji, Ayasha Akter, Elizabeth S. Dennis and Ryo Fujimoto

Plants 2020, 9(4), 414; https://doi.org/10.3390/plants9040414 - 27 Mar 2020

Cited by 2 | Viewed by 3826

Abstract

Heterosis or hybrid vigour is a phenomenon in which hybrid progeny exhibit superior yield and biomass to parental lines and has been used to breed F₁ hybrid cultivars in many crops. A similar level of heterosis in all F₁ individuals is expected as they are genetically identical. However, we found variation in rosette size in individual F₁ plants from a cross between C24 and Columbia-0 accessions of Arabidopsis thaliana. Big-sized F₁ plants had 26.1% larger leaf area in the first and second leaves than medium-sized F₁ plants at 14 days after sowing in spite of the identical genetic background. We identified differentially expressed genes between big- and medium-sized F₁ plants by microarray; genes involved in the category of stress response were overrepresented. We made transgenic plants overexpressing 21 genes, which were differentially expressed between the two size classes, and some lines had increased plant size at 14 or 21 days after sowing but not at all time points during development. Change of expression levels in stress-responsive genes among individual F₁ plants could generate the variation in plant size of individual F₁ plants in A. thaliana. Full article

(This article belongs to the Special Issue Plants Heterosis)

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20 pages, 84012 KiB

Open AccessArticle

Cytoplasm Types Affect DNA Methylation among Different Cytoplasmic Male Sterility Lines and Their Maintainer Line in Soybean (Glycine max L.)

by Chunjing Lin, Bao Peng, Yongkuan Li, Pengnian Wang, Guolong Zhao, Xiaoyang Ding, Rong Li, Limei Zhao and Chunbao Zhang

Plants 2020, 9(3), 385; https://doi.org/10.3390/plants9030385 - 20 Mar 2020

Cited by 3 | Viewed by 2542

Abstract

Cytoplasmic male sterility (CMS) lines and their maintainer line have the same nucleus but different cytoplasm types. We used three soybean (Glycine max L.) CMS lines, JLCMS9A, JLCMSZ9A, and JLCMSPI9A, and their maintainer line, JLCMS9B, to explore whether methylation levels differed in their nuclei. Whole-genome bisulfite sequencing of these four lines was performed. The results show that the cytosine methylation level in the maintainer line was lower than in the CMS lines. Compared with JLCMS9B, the Gene Ontology (GO) enrichment analysis of DMR (differentially methylated region, DMR)-related genes of JLCMS9A revealed that their different 5-methylcytosine backgrounds were enriched in molecular function, whereas JLCMSZ9A and JLCMSPI9A were enriched in biological process and cellular component. The Kyoto Encyclopedia of Genes and Genome (KEGG) analysis of DMR-related genes and different methylated promoter regions in different cytosine contexts, hypomethylation or hypermethylation, showed that the numbers of DMR-related genes and promoter regions were clearly different. According to the DNA methylation and genetic distances separately, JLCMS9A clustered with JLCMS9B, and JLCMSPI9A with JLCMSZ9A. Thus, the effects of different cytoplasm types on DNA methylation were significantly different. This may be related to their genetic distances revealed by re-sequencing these lines. The detected DMR-related genes and pathways that are probably associated with CMS are also discussed. Full article

(This article belongs to the Special Issue Plants Heterosis)

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19 pages, 1156 KiB

Open AccessArticle

Exploring Heterosis in Melon (Cucumis melo L.)

by Marco Napolitano, Niccolò Terzaroli, Subash Kashyap, Luigi Russi, Elen Jones-Evans and Emidio Albertini

Plants 2020, 9(2), 282; https://doi.org/10.3390/plants9020282 - 21 Feb 2020

Cited by 15 | Viewed by 4429

Abstract

Heterosis is the superiority of an F₁ hybrid over its parents. Since this phenomenon is still unclear in melon, a half diallel experiment based on eight genetically distant breeding lines was conducted in six environments of Central Italy, assessing commercially important traits: yield, total soluble solids (TSS), and days to ripening (DTR). To estimate the additive (general combining ability; GCA) and the non-additive gene effects (specific combining ability; SCA), yield was analyzed by Griffing’s methods two and four, and the results were compared to the GGE (Genotype plus Genotype by Environment interaction) biplot methodology; TSS and earliness were evaluated only by Griffing’s method four. Overall, GCAs were significantly more relevant than SCAs for all examined traits. Least square means (LsM), mid-parent heterosis (MPH), best-parent heterosis (BPH), as well as Euclidean and Mahalanobis’ distances were calculated and compared with the genetic distance (GD). As a few correlations were found statistically significant (only for TSS), it was difficult to predict the value of a hybrid combination only by knowing the genetic distance of its parents. Despite this, heterosis was observed, indicating either the presence of epistatic effects (additive × additive interactions) and/or an underestimate of SCAs embedded within Griffing’s method. The significant Env × Entries source of variation suggests development of hybrids in specific environments. The results are discussed with a breeding perspective. Full article

(This article belongs to the Special Issue Plants Heterosis)

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13 pages, 907 KiB

Open AccessArticle

Gibberellins and Heterosis in Crops and Trees: An Integrative Review and Preliminary Study with Brassica

by Karen P. Zanewich and Stewart B. Rood

Plants 2020, 9(2), 139; https://doi.org/10.3390/plants9020139 - 22 Jan 2020

Cited by 1 | Viewed by 2501

Abstract

Heterosis, or hybrid vigor, has contributed substantially to genetic improvements in crops and trees and its physiological basis involves multiple processes. Four associations with the phytohormone gibberellin (GA) indicate its involvement in the regulation of heterosis for shoot growth in maize, sorghum, wheat, rice, tomato and poplar. (1) Inbreds somewhat resemble GA-deficient dwarfs and are often highly responsive to exogenous GA₃. (2) Levels of endogenous GAs, including the bioeffector GA₁, its precursors GA₁₉ and GA₂₀, and/or its metabolite GA₈, are higher in some fast-growing hybrids than parental genotypes. (3) Oxidative metabolism of applied [³H]GAs is more rapid in vigorous hybrids than inbreds, and (4) heterotic hybrids have displayed increased expression of GA biosynthetic genes including GA 20-oxidase and GA 3-oxidase. We further investigated Brassica rapa, an oilseed rape, by comparing two inbreds (AO533 and AO539) and their F₁ hybrid. Seedling emergence was faster in the hybrid and potence ratios indicated dominance for increased leaf number, area and mass, and stem mass. Overdominance (heterosis) was displayed for root mass, leading to slight heterosis for total plant mass. Stem contents of GA_19,20,1 were similar across the Brassica genotypes and increased prior to bolting; elongation was correlated with endogenous GA but heterosis for shoot growth was modest. The collective studies support a physiological role for GAs in the regulation of heterosis for shoot growth in crops and trees, and the Brassica study encourages further investigation of heterosis for root growth. Full article

(This article belongs to the Special Issue Plants Heterosis)

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15 pages, 891 KiB

Open AccessCommunication

Diallel Analysis of Chilli Pepper (Capsicum annuum L.) Genotypes for Morphological and Fruit Biochemical Traits

by Aiswarya C. S., Vijeth S, Sreelathakumary I and Prashant Kaushik

Plants 2020, 9(1), 1; https://doi.org/10.3390/plants9010001 - 18 Dec 2019

Cited by 11 | Viewed by 5426

Abstract

Chilli pepper is commercially cultivated as a spice and is also used for the extraction of a colouring agent. Here, we performed a diallel genetic study involving five chilli pepper varieties. Parents and their hybrid were evaluated for fifteen morphological and five biochemical traits over two crop seasons under open field conditions. Variation was recorded for all of the studied traits. Similarly, significant values for general combining ability (GCA) and specific combining ability (SCA) variance were obtained for all of the traits. The ratio of σ² SCA/σ² GCA indicates that non-additive gene effects were predominant for all the studied traits except for fruits plant⁻¹. Based on SCA effects, cross combinations P2 × P5, and P4 × P5 were determined excellent for flesh thickness, yield components and vitamin C. These hybrids are recommended for multilocation testing to assess their suitability for commercial cultivation. Overall, this work presents useful information regarding the genetics of important morphological and biochemical traits in chilli pepper. Full article

(This article belongs to the Special Issue Plants Heterosis)

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16 pages, 3047 KiB

Open AccessArticle

Transgressivity in Key Functional Traits Rather Than Phenotypic Plasticity Promotes Stress Tolerance in A Hybrid Cordgrass

by Blanca Gallego-Tévar, Brenda J. Grewell, Rebecca E. Drenovsky and Jesús M. Castillo

Plants 2019, 8(12), 594; https://doi.org/10.3390/plants8120594 - 12 Dec 2019

Cited by 1 | Viewed by 2730

Abstract

Hybridization might promote offspring fitness via a greater tolerance to environmental stressors due to heterosis and higher levels of phenotypic plasticity. Thus, analyzing the phenotypic expression of hybrids provides an opportunity to elucidate further plant responses to environmental stress. In the case of coastal salt marshes, sea level rise subjects hybrids, and their parents, to longer tidal submergence and higher salinity. We analyzed the phenotypic expression patterns in the hybrid Spartina densiflora x foliosa relative to its parental species, native S. foliosa, and invasive S. densiflora, from the San Francisco Estuary when exposed to contrasting salinities and inundations in a mesocosm experiment. 37% of the recorded traits displayed no variability among parents and hybrids, 3% showed an additive inheritance, 37% showed mid-parent heterosis, 18% showed best-parent heterosis, and 5% presented worst-parent heterosis. Transgressivity, rather than phenotypic plasticity, in key functional traits of the hybrid, such as tiller height, conveyed greater stress tolerance to the hybrid when compared to the tolerance of its parents. As parental trait variability increased, phenotypic transgressivity of the hybrid increased and it was more important in response to inundation than salinity. Increases in salinity and inundation associated with sea level rise will amplify the superiority of the hybrid over its parental species. These results provide evidence of transgressive traits as an underlying source of adaptive variation that can facilitate plant invasions. The adaptive evolutionary process of hybridization is thought to support an increased invasiveness of plant species and their rapid evolution. Full article

(This article belongs to the Special Issue Plants Heterosis)

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15 pages, 1122 KiB

Open AccessArticle

Selection of Parental Material to Maximize Heterosis Using SNP and SilicoDarT Markers in Maize

by Agnieszka Tomkowiak, Jan Bocianowski, Dominika Radzikowska and Przemysław Łukasz Kowalczewski

Plants 2019, 8(9), 349; https://doi.org/10.3390/plants8090349 - 14 Sep 2019

Cited by 14 | Viewed by 3889

Abstract

The chief aim of plant breeding is to improve varieties so as to increase their yield and breeding traits. One of the first stages of breeding is the selection of parental forms from the available gene pool of existing varieties. To date, costly and laborious methods based on multiple crossbreeding and phenotypic selection have been necessary to properly assess genetic resources in terms of productivity, quality parameters, and susceptibility to biotic and abiotic stressors. The often long and complicated breeding cycle can be significantly shortened through selection using DNA markers. To this end, use is made of close couplings between the marker and the locus responsible for the inheritance of the functional trait. The aim of this study was to identify single nucleotide polymorphism (SNP) and SilicoDArT markers associated with yield traits and to predict the heterosis effect for yield traits in maize (Zea mays L.). The plant material used in the research consisted of 19 inbred maize lines derived from different starting materials, and 13 hybrids resulting from crossing them. A two-year field experiment with inbred lines and hybrids was established at two Polish breeding stations on 10 m² plots in a randomized block design with three replicates. The biometric measurements included cob length, cob diameter, core length, core diameter, number of rows of grain, number of grains in a row, mass of grain from the cob, weight of one thousand grains, and yield. The isolated DNA was subjected to DArTseq genotyping. Association mapping was performed in this study using a method based on the mixed linear model with the population structure estimated by eigenanalysis (principal component analysis of all markers) and modeled by random effects. Narew, Popis, Kozak, M Glejt, and Grom were the hybrids used in the study that showed the highest significant heterosis effect in 2013 and 2014. The similarity between parental components determined on the basis of SNP and SilicoDArT marker analysis did not exceed 33%. It was found that the genetic similarity between parental components, determined on the basis of SNP and SilicoDArT markers, reflected their degree of relationship, and correlated significantly with the effect of heterosis. As the results indicate, the parental components for heterosis crosses can be selected based on genetic similarity between parental components evaluated using SNP and SilicoDArT markers, supported with information on the origin of parental forms. Of the markers we analyzed, 76 were selected as being significantly associated with at least six traits observed in 2013 and 2014 at both the Łagiewniki and Smolice stations. Full article

(This article belongs to the Special Issue Plants Heterosis)

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Review

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25 pages, 1188 KiB

Open AccessReview

Exploitation of Heterosis in Pearl Millet: A Review

by Rakesh K. Srivastava, Srikanth Bollam, Vijayalakshmi Pujarula, Madhu Pusuluri, Ram B. Singh, Gopi Potupureddi and Rajeev Gupta

Plants 2020, 9(7), 807; https://doi.org/10.3390/plants9070807 - 27 Jun 2020

Cited by 11 | Viewed by 10613

Abstract

The phenomenon of heterosis has fascinated plant breeders ever since it was first described by Charles Darwin in 1876 in the vegetable kingdom and later elaborated by George H Shull and Edward M East in maize during 1908. Heterosis is the phenotypic and functional superiority manifested in the F₁ crosses over the parents. Various classical complementation mechanisms gave way to the study of the underlying potential cellular and molecular mechanisms responsible for heterosis. In cereals, such as maize, heterosis has been exploited very well, with the development of many single-cross hybrids that revolutionized the yield and productivity enhancements. Pearl millet (Pennisetum glaucum (L.) R. Br.) is one of the important cereal crops with nutritious grains and lower water and energy footprints in addition to the capability of growing in some of the harshest and most marginal environments of the world. In this highly cross-pollinating crop, heterosis was exploited by the development of a commercially viable cytoplasmic male-sterility (CMS) system involving a three-lines breeding system (A-, B- and R-lines). The first set of male-sterile lines, i.e., Tift 23A and Tift18A, were developed in the early 1960s in Tifton, Georgia, USA. These provided a breakthrough in the development of hybrids worldwide, e.g., Tift 23A was extensively used by Punjab Agricultural University (PAU), Ludhiana, India, for the development of the first single-cross pearl millet hybrid, named Hybrid Bajra 1 (HB 1), in 1965. Over the past five decades, the pearl millet community has shown tremendous improvement in terms of cytoplasmic and nuclear diversification of the hybrid parental lines, which led to a progressive increase in the yield and adaptability of the hybrids that were developed, resulting in significant genetic gains. Lately, the whole genome sequencing of Tift 23D₂B₁ and re-sequencing of circa 1000 genomes by a consortium led by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) has been a significant milestone in the development of cutting-edge genetic and genomic resources in pearl millet. Recently, the application of genomics and molecular technologies has provided better insights into genetic architecture and patterns of heterotic gene pools. Development of whole-genome prediction models incorporating heterotic gene pool models, mapped traits and markers have the potential to take heterosis breeding to a new level in pearl millet. This review discusses advances and prospects in various fronts of heterosis for pearl millet. Full article

(This article belongs to the Special Issue Plants Heterosis)

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16 pages, 948 KiB

Open AccessReview

Heterosis Breeding in Eggplant (Solanum melongena L.): Gains and Provocations

by Ashish Kumar, Vinay Sharma, Bharat Taindu Jain and Prashant Kaushik

Plants 2020, 9(3), 403; https://doi.org/10.3390/plants9030403 - 24 Mar 2020

Cited by 36 | Viewed by 11051

Abstract

Heterosis (or hybrid vigor) results in a hybrid’s phenotypic superiority over its founder parents for quantitative and qualitative traits. Hybrid vigor is defined by mechanisms such as dominant complementation, over-dominance, and epistasis. Eggplant (Solanum melongena L.) is an essential vegetable crop and a good source of dietary minerals, vitamins, and anthocyanins, with a high oxygen radical absorbance capacity and low caloric value. Given the economic and nutritional significance of eggplants, breeding efforts focus on developing high-yielding varieties—mostly F₁ hybrids—with important traits. Studies indicate the successful exploitation of heterosis in the eggplant for a considerable improvement with respect to quantitative traits. In this direction, estimating heterosis for yield-related traits could well be useful for examining the most beneficial hybrid mix with the exploitation of top-quality hybrid. This review examines the current perception of the breeding and molecular aspects of heterosis in eggplants and cites several studies describing the mechanisms. Rendering and combining recent genomics, epigenetic, proteomic, and metabolomics studies present new prospects towards the understanding of the regulatory events of heterosis involved in the evolution and the domestication of the eggplant ideotype. Full article

(This article belongs to the Special Issue Plants Heterosis)

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9 pages, 378 KiB

Open AccessCommentary

The Pitfalls of Heterosis Coefficients

by Dominique de Vienne and Julie B. Fiévet

Plants 2020, 9(7), 875; https://doi.org/10.3390/plants9070875 - 09 Jul 2020

Cited by 3 | Viewed by 2573

Abstract

Heterosis (hybrid vigour) is a universal phenomenon of crucial agro-economic and evolutionary importance. We show that the most common heterosis coefficients do not properly measure deviation from additivity because they include both a component accounting for “real” heterosis and a term that is not related to heterosis, since it is derived solely from parental values. Therefore, these coefficients are inadequate whenever the aim of the study is to compare heterosis levels between different traits, environments, genetic backgrounds, or developmental stages, as these factors may affect not only the level of non-additivity, but also parental values. The only relevant coefficient for such comparisons is the so-called “potence ratio”. Because most heterosis studies consider several traits/stages/environmental conditions, our observations support the use of the potence ratio, at least in non-agronomic contexts, because it is the only non-ambiguous heterosis coefficient. Full article

(This article belongs to the Special Issue Plants Heterosis)

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