Eggplant Breeding Research Articles

Genetic parameters of drought tolerance for agromorphological traits in eggplant, wild relatives, and interspecific hybrids

AbstractCrop wild relatives (CWRs) have barely been used in eggplant (Solanum melongena) breeding. However, introgression breeding may help in coping with the challenges posed by climate change. During the rainy and dry seasons, we evaluated nine accessions of eggplant, nine accessions of seven related species (of which six are CWRs and one is a cultivated relative), and 12 interspecific hybrids. Drought tolerance scores, calculated as ratios of growing rates and ratios of mean values during the rainy and dry seasons, were obtained for vegetative growth and yield‐related traits. Considering the vegetative growth and yield‐related traits evaluated, the F1 hybrid progenies of eggplant with S. insanum MEL1 × INS2 and MEL4 × INS3, S. anguivi MEL6 × ANG1, and S. dasyphyllum MEL6 × DAS1, plus the S. sysimbriifolium accession SIS1, displayed drought tolerance. Small to large gaps were observed between phenotypic and genotypic CVs of drought tolerance scores, reflecting variable influence of environmental factors on drought tolerance of the traits evaluated. In addition, the narrow‐sense heritability was generally moderate, indicating that genes with dominance and/or epistasis effects may be involved in the expression of drought tolerance. High genotypic correlations for drought tolerance scores between pairs of traits such as branching index and leaf length, leaf petiole diameter and plant height, number of stamens per flower, and fruit pedicel length suggest that drought tolerance of these traits is controlled by genes that are in linkage disequilibrium and/or have pleiotropic effects. The results are relevant for the development of drought‐tolerant cultivars of eggplant.

Association of Heterotic Groups with Morphological Relationships and General Combining Ability in Eggplant

The identification of heterotic groups may provide an important advantage for hybrid eggplant (Solanum melongena) breeding. In this study, we evaluated the combining ability and heterotic patterns of eggplant lines in order to develop improved eggplant cultivars resistant to Fusarium oxysporum f. sp. melongenae (FOM). A set of 62 inbred lines was evaluated with 32 morphological descriptors and their relationships were analyzed through a multivariate cluster analysis. A subset of 39 inbred lines was selected and, together with 15 sister lines, they were crossed with two testers to investigate their general combining ability (GCA) and to establish heterotic groups. Twenty selected inbred lines with high GCA were intercrossed using a half-diallel mating design. Eighty-two hybrids were obtained and evaluated for yield and yield components. We found no association between morphological distance and membership to specific heterotic groups. However, heterosis for yield was found in hybrids among parents from different heterotic groups or that were included in all heterotic groups. Among the hybrids evaluated, some were found to be highly productive and resistant to FOM, being candidates for the registration of new cultivars with dramatically improved characteristics.

Transcriptomics analysis unravels the response to low temperature in sensitive and tolerant eggplants

Low temperature is one of the stresses which threaten eggplant during its whole growth period, resulting in the inhibition of growth and development and the loss of yield. It is essential to realize the key genes and pathways in response to low temperature for eggplant breeding. To compare the transcriptomics profiling of two eggplant varieties with differential low temperature tolerance, we conducted the present experiment. Gene ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were used for comparing the transcriptomics profile. Here, a total of 2854 and 2697 differentially expressed genes were identified in A153 which was selected from the local variety and locally named ‘Chengdumiqie’ and A80 (CGN22911) following the low temperature treatment. Through GO analysis, we found that sequence-specific DNA binding was the representative of GO term in the unique differentially expressed genes (DEGs) of both varieties. The KEGG analysis of unique DEGs showed that in both varieties plant hormone signal transduction was the most dominant group. Further analysis revealed that several significant differences existed in the plant hormone signal transduction between two varieties. Finally, the analysis of transcription factor families revealed the complex transcriptional regulation in both cultivars. These findings provided a new insight into the molecular mechanisms responsible for response to low temperature and genetic improvement in eggplant.

Performance of a Set of Eggplant (Solanum melongena) Lines With Introgressions From Its Wild Relative S. incanum Under Open Field and Screenhouse Conditions and Detection of QTLs

Introgression lines (ILs) of eggplant (Solanum melongena) represent a resource of high value for breeding and the genetic analysis of important traits. We have conducted a phenotypic evaluation in two environments (open field and screenhouse) of 16 ILs from the first set of eggplant ILs developed so far. Each of the ILs carries a single marker-defined chromosomal segment from the wild eggplant relative S. incanum (accession MM577) in the genetic background of S. melongena (accession AN-S-26). Seventeen agronomic traits were scored to test the performance of ILs compared to the recurrent parent and of identifying QTLs for the investigated traits. Significant morphological differences were found between parents, and the hybrid was heterotic for vigour-related traits. Despite the presence of large introgressed fragments from a wild exotic parent, individual ILs did not display differences with respect to the recipient parent for most traits, although significant genotype × environment interaction (G × E ) was detected for most traits. Heritability values for the agronomic traits were generally low to moderate. A total of ten stable QTLs scattered across seven chromosomes was detected. For five QTLs, the S. incanum introgression was associated with higher mean values for plant- and flower-related traits, including vigour prickliness and stigma length. For one flower- and four fruit-related-trait QTLs, including flower peduncle and fruit pedicel lengths and fruit weight, the S. incanum introgression was associated with lower mean values for fruit-related traits. Evidence of synteny to other previously reported in eggplant populations was found for three of the fruit-related QTLs. The other seven stable QTLs are new, demonstrating that eggplant ILs are of great interest for eggplant breeding under different environments.

Construction of a SNP-Based Genetic Map Using SLAF-Seq and QTL Analysis of Morphological Traits in Eggplant.

Eggplant (Solanum melongena; 2n = 24) is an economically important fruit crop of the family Solanaceae that was domesticated in India and Southeast Asia. Construction of a high-resolution genetic map and map-based gene mining in eggplant have lagged behind other crops within the family such as tomato and potato. In this study, we conducted high-throughput single nucleotide polymorphism (SNP) discovery in the eggplant genome using specific length amplified fragment (SLAF) sequencing and constructed a high-density genetic map for the quantitative trait locus (QTL) analysis of multiple traits. An interspecific F2 population of 121 individuals was developed from the cross between cultivated eggplant “1836” and the wild relative S. linnaeanum “1809.” Genomic DNA extracted from parental lines and the F2 population was subjected to high-throughput SLAF sequencing. A total of 111.74 Gb of data and 487.53 million pair-end reads were generated. A high-resolution genetic map containing 2,122 SNP markers and 12 linkage groups was developed for eggplant, which spanned 1530.75 cM, with an average distance of 0.72 cM between adjacent markers. A total of 19 QTLs were detected for stem height and fruit and leaf morphology traits of eggplant, explaining 4.08–55.23% of the phenotypic variance. These QTLs were distributed on nine linkage groups (LGs), but not on LG2, 4, and 9. The number of SNPs ranged from 2 to 11 within each QTL, and the genetic interval varied from 0.15 to 10.53 cM. Overall, the results establish a foundation for the fine mapping of complex QTLs, candidate gene identification, and marker-assisted selection of favorable alleles in eggplant breeding.

Single Marker Analysis and Mapping of QTLs Governing Fruit Weight in Eggplant (Solanum melongena L.)

Eggplant is one of the most popular solanaceous vegetable crops in India and across the world. Development of high-yielding varieties and hybrids is the major focus of breeders. Yield is a very complex trait affected by various genetic and external factors. The lack of knowledge of the inheritance of fruit traits in eggplant has limited the use of molecular markers to fasten breeding programme. The authors conducted the present investigation at the research field of Vegetable Science Division, ICAR-IARI, New Delhi, India. A total of 168 F2 plants derived from Pusa Safed Baingan 1 × Pusa Uttam were phenotyped for fruit weight. Wide variations were observed for this trait ranging from 15.2 to 248.3 g, and the skewness was less than 1, suggesting that the trait followed a normal distribution in F2 and suitable for QTL analysis. Polymorphism survey using 241 SSR markers showed 18 polymorphic markers, which were subjected to bulked segregant analysis. Single-marker analysis using genotypic data revealed the positions of 3 QTLs influencing fruit weight. One QTL (qsfwpu1) was detected in linkage group 1, and two QTLs (qsfwpu3 and qsfwpu2) were identified in linkage group 4. These QTLs explained 14.06–19.44% to total phenotypic variation and were classified as major QTLs, suggesting that these QTLs play an important role in controlling yield. These QTLs may be very useful in the future molecular marker-assisted breeding of eggplant to develop a variety and cloning of target genes of interest.

Draft genome sequence of Solanum aethiopicum provides insights into disease resistance, drought tolerance, and the evolution of the genome.

BackgroundThe African eggplant (Solanum aethiopicum) is a nutritious traditional vegetable used in many African countries, including Uganda and Nigeria. It is thought to have been domesticated in Africa from its wild relative, Solanum anguivi. S. aethiopicum has been routinely used as a source of disease resistance genes for several Solanaceae crops, including Solanum melongena. A lack of genomic resources has meant that breeding of S. aethiopicum has lagged behind other vegetable crops.ResultsWe assembled a 1.02-Gb draft genome of S. aethiopicum, which contained predominantly repetitive sequences (78.9%). We annotated 37,681 gene models, including 34,906 protein-coding genes. Expansion of disease resistance genes was observed via 2 rounds of amplification of long terminal repeat retrotransposons, which may have occurred ∼1.25 and 3.5 million years ago, respectively. By resequencing 65 S. aethiopicum and S. anguivi genotypes, 18,614,838 single-nucleotide polymorphisms were identified, of which 34,171 were located within disease resistance genes. Analysis of domestication and demographic history revealed active selection for genes involved in drought tolerance in both “Gilo” and “Shum” groups. A pan-genome of S. aethiopicum was assembled, containing 51,351 protein-coding genes; 7,069 of these genes were missing from the reference genome.ConclusionsThe genome sequence of S. aethiopicum enhances our understanding of its biotic and abiotic resistance. The single-nucleotide polymorphisms identified are immediately available for use by breeders. The information provided here will accelerate selection and breeding of the African eggplant, as well as other crops within the Solanaceae family.

Molecular markers linked to bacterial wilt (Ralstonia solanacearum) resistance gene loci in eggplant (Solanum melongena L.)

Bacterial wilt (BW) (Caused by Ralstonia solanacearum) is the most devastative soil-borne disease in eggplant, causing sudden wilting of the plants before flowering, followed by yellowing of leaves and stunted growth. The molecular marker linked to BW resistance loci will help in the selection and development of elite eggplant resistant cultivars. Bulked segregant analysis (BSA) was performed in two segregating F2 populations with BW resistance. These populations were derived from the cross between resistant cultivars CARI–1 and IIHR–7 and susceptible cultivars Rampur Local and Arka Kushmakar (IIHR–108). The present inheritance studies indicated that the eggplant BW resistance is governed by single dominant gene. A total of 390 single sequence repeat (SSR) markers were used in the survey of parental polymorphism, and 42 SSRs were found to be polymorphic. The SSR markers, emb01D10, emh11I06, emh02E08, and SSR–46 co–segregate with resistant and susceptible genotypes of the two F2 populations and linked to BW resistance loci. These four SSR markers are followed mendelian genetics for subsequent generations. In addition, they are useful in marker-assisted selection and eggplant breeding effectively. This is the first report describing the association of SSR markers with BW resistance loci in eggplant.

Genetic divergence among eggplant genotypes under high temperatures

ABSTRACT The aim of this study was to estimate the genetic divergence among eggplant genotypes for agronomic traits in order to gather information for the selection of genotypes in eggplant breeding programs for tolerance to high temperatures. Ten traits recommended by the International Board for Plant Genetic Resources were analyzed in 24 genotypes, arranged in a randomized complete block design with four replicates. Data were submitted to analysis of variance (P<0.01) and later to the UPGMA and Tocher grouping methods, using the generalized Mahalanobis distance (D2) as dissimilarity measure. Three and six groups of similarity were obtained, respectively, for the multivariate techniques used, UPGMA and Tocher, with concordance in the grouping of 87.50% of the genotypes. The characters fruit length (34.71%), fruit width (35.96%) and fruit length/width ratio (14.08%) were the main contributors to genetic divergence, explaining 90.72% of total genetic dissimilarity. The genotypes presented considerable genetic variability for all agronomic traits analyzed and can be used in eggplant genetic breeding programs for high temperatures.

Molecular characterisation of eggplant and related species: stability analysis for yield and reaction to bacterial wilt under the humid subtropics of North Eastern India

ABSTRACTEggplant (Solanum melongena L.) is an important solanaceous vegetable crop grown worldwide over tropics and subtropics. Bacterial wilt (caused by Ralstonia solanacearum) is one of the most serious diseases of the crop, especially in the humid tropics. The present investigation was carried out using 26 accessions of eggplant including wild relatives aiming to identify stable genotypes of eggplant with tolerant to bacterial wilt. The accessions were characterised using 40 simple sequence repeat (SSR) markers. Thirty-four markers were found polymorphic and produced 136 alleles with an average of four alleles per marker. All the markers have shown amplification across accessions of eggplant-related species. Markers EES-050, EES-065, and EES-066 were highly informative. Among the species, scarlet eggplant (Solanum aethiopicum var.gilo) was found to be the closest to S.melongena. Markers, EES-031 and EES-051, were specific to the accessions with tolerance to bacterial wilt. Based on the three-year evaluations, the disease incidence (DI) ranged from 1.27% (S.torvum) to 72.85% (S.melongena var. Kasi Taru). The AMMI and GGE biplot analyses have shown the significant contribution of genotype variation over the environment and interaction. The local eggplant accessions (Bhola Nath, RCMB-10, Singh Nath and RCMBL-1) were found highly stable for yield with lowest wilt incidences when compared to other Indian accessions. The results suggested the incorporation of local accessions/landraces into the eggplant breeding programmes aiming to develop stable cultivars with improved yield and resistant to bacterial wilt.Abbreviation: AMMI, Additive Main-Effects and Multiplicative Interaction; GGE, Genotype Main Effect plus Genotype-by-Environment Interaction; SSRs, Simple Sequence Repeats; QTLs,Quantitative Trait Loci; AMOVA, Analysis of Molecular Variance;

Correlation and path coefficient analyses of yield and yield components of eggplant (Solanum melongena) in a coarse-textured Ultisol

Assessment of variability and understanding of traits relationship in eggplant species are vital pre-requisite for formulating an effective breeding programme. We studied 23 genotypes of eggplants in a coarse-textured Ultisol using a randomized complete block design experiment with three replications. Data were collected on number of branches, number of leaves, number of nodes and internodes, stem diameter, plant height, floral and yield traits. Results revealed significant (p = 0.05) variation in the flowering and fruiting pattern of the genotypes. ‘Yalo x K3BC2P1′ gave the highest individual fruit weight of 80.8 g. Individual fruit weight contributed the highest direct positive effect on the fruit yield. It acted majorly through plant height, number of branches, number of leaves and number of days to first fruit set as revealed in the path coefficient result. Individual fruit weight, number of fruits per plant, plant height, number of days to 50% flowering, number of branches, numbers of days to first flowering and 50% fruit set had positive direct effect on yield. These traits should be considered in developing high yielding eggplant breeding programme.

First successful backcrossing towards eggplant (Solanum melongena) of a New World species, the silverleaf nightshade (S. elaeagnifolium), and characterization of interspecific hybrids and backcrosses

Silverleaf nightshade (Solanum elaeagnifolium Cav.) is a drought tolerant invasive weed native to the New World. Despite its interest for common eggplant (S. melongena L.) breeding, up to now no success has been obtained in introgression breeding of eggplant with American Solanum species. Using an interspecific hybrid between common eggplant and S. elaeagnifolium as maternal parent we were able to obtain several fruits with viable seed after pollination with S. melongena pollen. Twenty individuals of the first backcross (BC1) generation were crossed again to the S. melongena parent and second backcross (BC2) seed was obtained for 17 of them, suggesting that most of the genome of S. elaeagnifolium is likely to be represented in the set of BC2 families. Five plants of each of the two parents, interspecific hybrid and BC1 generation were characterized with morphological descriptors and for pollen viability. The interspecific hybrid was intermediate among parents, although in overall morphological characteristics more similar to the S. elaeagnifolium parent. However, pollen viability of the hybrid was very low (2.6%). The BC1 generation was intermediate in characteristics between the hybrid and the S. melongena parent, with pollen viability increasing to an average of 19.4%. The root system of the interspecific hybrid indicated that it is able to explore larger areas of the soil than the S. melongena parent. The phenolics profile of the fruit of the two parents and hybrid revealed a higher diversity in phenolic constituents in S. elaeagnifolium compared to S. melongena, where the major phenolic compound was chlorogenic acid, while the interspecific hybrid was intermediate. By using flow cytometry it was found that S. elaeagnifolium, S. melongena, and their interspecific hybrid were diploid, although the genome size of S. elaeagnifolium was slightly smaller than that of S. melongena. Our results represent the first report of successful development of backcross generations of common eggplant with a New World Solanum species. This makes available a relatively unexplored, phylogenetically distant genepool for eggplant breeding. The backcross materials obtained can make a relevant contribution to developing new eggplant cultivars with new nutritional and environmental properties.

Untargeted Metabolomics Analysis of Eggplant (Solanum melongena L.) Fruit and Its Correlation to Fruit Morphologies.

Eggplant is one of the most widely cultivated vegetables in the world and has high biodiversity in terms of fruit shape, size, and color. Therefore, fruit morphology and nutrient content become important considerations for both consumers and breeders who develop new eggplant-based products. To gain insight on the diversity of eggplant metabolites, twenty-one eggplant accessions were analyzed by untargeted metabolomics using GC-MS and LC-MS. The dataset of eggplant fruit morphologies, and metabolites specific to different eggplant fruit accessions were used for correlation analysis. Untargeted metabolomics analysis using LC-MS and GC-MS was able to detect 136 and 207 peaks, respectively. Fifty-one (51) metabolites from the LC-MS analysis and 207 metabolites from the GC-MS analysis were putatively identified, which included alkaloids, terpenes, terpenoids, fatty acids, and flavonoids. Spearman correlation analysis revealed that 14 fruit morphologies were correlated with several metabolites. This information will be very useful for the development of strategies for eggplant breeding.

Estimation of Heterosis of Yield and Yield-Related Traits in the African Eggplant (Solanum Aethiopicum) Hybrids

African eggplant is an important fruit and leafy vegetable in Africa. Heterosis over mid and better parents was estimated in eight crosses of eggplant involving eight pure lines in a field experiment in 2012 and 2013 cropping seasons. The experiment was laid out using a randomized complete block design with three replications. Collected data was subjected to analysis of variance and significant differences were further subjected to Duncan Multiple Range Test. The aim of this study was to identify superior hybrids that can be advanced in the eggplant breeding program for improved yield and related traits. Significant variation was observed among all traits measured for the parents and hybrids. The highest fruit number was observed in NHS10-40 and in NHS 10-71 x NHS 10-40 among the parents and hybrids respectively. The highest heterosis was recorded in the cross between NHS10-71 x NHS10-40.

Diallel genetic analysis for multiple traits in eggplant and assessment of genetic distances for predicting hybrids performance.

Evaluation and prediction of the performance of hybrids is important in eggplant (Solanum melongena) breeding. A set of 10 morphologically highly diverse eggplant parents, including nine inbred S. melongena and one weedy S. insanum accessions, were intercrossed according to a half-diallel mating design without reciprocals to obtain 45 hybrids. Parents and hybrids were evaluated for 14 morphological and agronomic conventional descriptors and 14 fruit morphometric traits using Tomato Analyzer. Genetic distances among parents were estimated with 7,335 polymorphic SNP markers. Wide ranges of variation and significant differences were observed in the set of 55 genotypes for all traits, although the hybrids group had significantly higher vigour and yield than parents. General and specific combining abilities (GCA and SCA) were significant for most (GCA) or all (SCA) traits, although a wide variation was obtained for GCA/SCA ratios. Many relevant traits associated to vigour and yield had low GCA/SCA ratios and narrow-sense heritability (h2) values, while the reverse occurred for most fruit shape descriptors. Broad-sense heritability (H2) values were generally high, irrespective of GCA/SCA ratios. Significant correlations were found between traits related to size of leaf, flower and fruit, as well as among many fruit morphometric traits. Genetic distances (GD) among parents were coherent with their phylogenetic relationships, but few significant and generally low correlations were found between GD and hybrid means, heterosis or SCA. The results provide relevant information for developing appropriate strategies for parent selection and hybrid development in eggplant and suggest that GD among parents have limited value to predict hybrid performance in this crop.

Genetic diversity and population structure of worldwide eggplant (Solanum melongena L.) germplasm using SSR markers

Two hundred and eighty-seven worldwide eggplant accessions were examined for genetic diversity and population structure analysis with 45 SSR markers. The results resolved 242 alleles across all the accessions. Gene diversity ranged from 0.104 to 0.832 with an average of 0.558. Polymorphic information content ranged from 0.102 to 0.815 with an average of 0.507. The genetic diversity analysis classified all accessions into four groups, and the data showed that gene exchanges occurred in two groups during germplasm introduction, domestication, and improvement; however, the frequency was low. Population structure analysis classified 269 accessions into two subgroups, and the remaining 18 accessions were defined as admixed. The accessions from the same geographic origin tend to be clustered into same group. These results provide new insights into the exploitation of genetic diversity of germplasm for eggplant breeding program.

English

Wild relatives of eggplants represent a good source of variation for breeding programmes, in particular for traits related to biotic and abiotic stresses and also fruit quality traits. However, wild species remain largely unexploited for eggplant breeding compared to other crops like tomato. Seven cultivated eggplant accessions (SM001-02, SM001-04, SM001-06, SM001-07, SA002-02, SA002-03 and SMA003-03) were crossed with three wild accessions (ST004-03 (Solanum tovum), San005-01 (Solanum anguivi) and SA002-08 (Solanum aethiopicum)) in an open field using completely randomized design. The success of fruit and seed set as well as seed germination depended on the cross combination and the direction of the cross. In this regard, no fruit set was recorded when the wild accessions were used as female parents. The highest fruit set and mean number of seeds/fruit was obtained from the crosses Sm001-07 × ST004-03 (6%; 264 seeds) and Sm001-07 × San005-01 (5.7%, 114 seeds), respectively. The germination of hybrid seeds was recorded in only three crosses, SM001-07 × ST004-03, SM001-07 × San005-01 and SA002-02 × San005-01 with germination range from 3.3 to 16.6%. However, plantlets from these seeds did not survive after two weeks of germination. The hybridity of the putative interspecific F1 hybrids (through tissue culture) was confirmed with a morphological marker. These hybrids obtained will contribute to broadening the genetic background of cultivated eggplant species used in this study and to the genetic enhancement of this crop. Key words: Crossability, eggplant, fruit set, germination, introgression, seed set, wild relatives.

Genomic Tools for the Enhancement of Vegetable Crops: A Case in Eggplant

Dramatic advances in genomics during the last decades have led to a revolution in the field of vegetable crops breeding. Some vegetables, like tomato, have served as model crops in the application of genomic tools to plant breeding but other important crops, like eggplant (Solanum melongena), lagged behind. The advent of next generation sequencing (NGS) technologies and the continuous decrease of the sequencing costs have allowed to develop genomic tools with a greatly benefit for no-model plants such as eggplant. In this review we present the currently available genomic resources in eggplant and discuss their interest for breeding. The first draft of eggplant genome sequence and the new upcoming improved assembly, as well as, the transcriptomes and RNA-based studies represent important genomic tools. The transcriptomes of cultivated eggplant and several wild relatives of eggplant are also available and have provided relevant information for the development of markers and understanding biological processes in eggplant. In addition, a historical overview of the eggplant genetic mapping studies, performed with different types of markers and experimental populations, provides a picture of the increase over time of the precision and resolution in the identification of candidate genes and QTLs for a wide range of stresses, and morpho-agronomic and domestication traits. Finally, we discuss how the development of new genetic and genomic tools in eggplant can pave the way for increasing the efficiency of eggplant breeding for developing improved varieties able to cope with the old and new challenges in horticultural production.

Production and characterization of an amphidiploid derived from interspecific hybridization between Solanum melongena L. and Solanum aculeatissimum Jacq.

Abstract Interspecific hybridization was carried out between cultivated eggplant (Solanum melongena L.) and its wild relative Solanum aculeatissimum, which has root-knot nematode and verticillium wilt resistance for eggplant improvement. The amphidiploid was obtained by embryo rescue and chromosome doubling. Comparisons of morphology, combined with flow cytometric, cytology, and SSR analyses confirmed the hybrid nature of the amphidiploid. The amphidiploid differed in morphology from both parent plants. The amphidiploid is shrub type, with thorns on leaves and stems, which is the typical character of S. aculeatissimum. Cytological analysis showed normal pairing between the two genomes occurred, although multivalents were observed, however, the pollen viability of the amphidiploid was lower compared to both parent plants. SSR analysis showed that the amphidiploid contained genomic fragments from both parents, further indicating the hybrid nature. The results from our study suggest that novel traits may be incorporated in eggplant breeding through the production of amphidiploid and the backcrossing of these plants with elite cultivars.

High Efficiency Callus Induction and Regeneration of Solanum torvum Plants

Callus induction and plant regeneration play a key role in transgenic technology. Although much progress has been made with respect to eggplant, this type of research is insufficiently developed in Solanum torvum (a wild relative of eggplant), which contains a large number of resistance genes. Here, a high-efficiency regeneration system of S. torvum was established. Stem segments and leaves were cultured on Murashige and Skoog (MS) medium supplemented with 0.5–3.0 mg·L−1 6-benzyladenine (6-BA) and 0.1–0.6 mg·L−1 α-naphthaleneacetic acid (NAA). The highest callus induction ratio (100%) was produced on MS + 1.0 mg·L−1 6-BA + 0.5 mg·L−1 NAA. The combination of 0.5 mg·L−1 BA and 1.0 mg·L−1 2,4-dichlorophenoxyacetic acid in MS medium (double microelement) was the best for plant regeneration. Well-developed shoots rooted on half-strength MS medium supplemented with 0.1 mg·L−1 indole-3-acetic acid (IAA). These results will be helpful for functional verification of resistance genes from S. torvum and may be useful to those working in the field of eggplant breeding.