Backcross Research Articles

Genetic analysis of bacterial wilt resistance in eggplant (Solanum melongena L.)

Bacterial wilt triggered by Ralstonia solanacearum is one of the major devastating diseases causing significant yield reduction in eggplant. F1 hybrids (18 CARI-1 based F1 hybrids and 12 publicly available hybrids/varieties) were evaluated for bacterial wilt resistance, yield, and yield attributing traits. CARI-1 based F1 hybrids showed superiority in yields, however showed a varied level of resistance to bacterial wilt. Further, inheritance and gene action involved in resistance to Ralstonia solanacearum was studied. CARI-1 was crossed with two susceptible parents, Arka Neelachal Shyama and Pusa Purple Long to develop six generations for both the combinations. The genetic control of resistance to bacterial wilt was found to be polygenic in the case of the Arka Neelachal Shyama x CARI-1 derived population. While di-genic with complementary gene action in the case of Pusa Purple Long x CARI-1 F2 population, however deviation in expected ratios was observed in back cross populations. Generation mean analysis revealed the presence of epistasis. For Arka Neelachal Shyama x CARI-1 derived population, owing to the prevalence of additive × additive non-allelic interaction with a negative sign, delaying of selection to later generations, otherwise inter mating between the selected segregates accompanied by selfing for one or more generation(s) is advised for the aggregation of favorable alleles for enhancement of resistance. Similarly, for Pusa Purple Long x CARI-1 population, the simple selection can be efficient due to the prevalence of additive gene action. The inheritance details accumulated in this study would facilitate the introgression of bacterial wilt resistance into elite commercial genotypes.

The Persian (English) walnut (Juglans regia L.) assortment of Hungary: Nut characteristics and origin

Persian walnut growing has a long-term tradition in Hungary. The walnut breeding started with the domestication of French varieties propagated by seeds in the 1910s, which was not successful. From the 1950s the Hungarian breeding research used selections from the local population, cross breeding and back crosses as breeding methods. The aim of this paper is to examine the origin and the nut characteristics of the Hungarian bred varieties registered on the National Variety List. The grafted trees for sample collection were planted in spring of 1990 at the Experimental Fields. Strong relationships between nut height and dried nut weight, dried nut weight and kernel weight, nut width and dried nut weight, nut diameter and nut width, dried nut weight and nut diameter, kernel weight and nut diameter as described in the literature was confirmed. Another relation (nut width and kernel weight) showed a strong relation too. All of the Hungarian bred varieties have a unique genetic background. The relation is not apparent between the introduced and the local varieties in all cases. It was concluded from the genetic pattern that the French seedling varieties might have not influenced the Hungarian varieties in the extent it was supposed formerly.

Variability and inheritance of fiber length and wilt resistance in a complex 4-5 specific and backcross hybridization of cotton

In this paper presents data of researches about fiber length in the 4-5 species. The largest number of plants with the indicated analyzed trait in hybrid combinations, obtained with the participation of the variety Omad, appeared with a number of variations in fiber length at 35,0-36,0 mm and above. Investigation of 4-species hybrids of F2 and back cross hybridization allowed some improvement in the average value of trait when compared with F1. Despite the emergence of transgressive plants with fiber length 36,1-37,0 mm and above, the average trait of composite 5 species hybrids F2 remained almost at the level of F1, i.e. 35.5-36.0 mm. The greatest number of positive recombinants occurred in 5 species back crossing developed with the participation of Termez-31.

Variability and inheritance of fiber length and wilt resistance in a complex 4-5 specific and backcross hybridization of cotton

In this paper presents data of researches about fiber length in the 4-5 species. The largest number of plants with the indicated analyzed trait in hybrid combinations, obtained with the participation of the variety Omad, appeared with a number of variations in fiber length at 35.0-36.0 mm and above. Investigation of 4-species hybrids of F2 and back cross hybridization allowed some improvement in the average value of trait when compared with F1. Despite the emergence of transgressive plants with fiber length 36.1-37.0 mm and above, the average trait of composite 5 species hybrids F2 remained almost at the level of F1, i.e. 35.5-36.0 mm. The greatest number of positive recombinants occurred in 5 species back crossing developed with the participation of Termez-31.

Doubled haploid production in advanced back cross generations and molecular cytogenetic characterization of rye chromatin in triticale �wheat derived doubled haploid lines

The rye genome has shown potential for improvement of bread wheat, where wheat-rye substitutions and translocations have been and are frequently used in resistance breeding. Crosses belongs to different generations viz., BC₁F₁, BC₁F₂, BC₁F₃, BC₁F₄ and BC₂F₃ of triticale × wheat derived were used for different haploid induction parameters using Gogon grass (<i>Imperata cylindrica)</i> as a pollen source. The percentage of pseudo seed formation ranged from 34.55% for BC₁F₂ to 63.77 for BC₁F₁ crosses, the haploid embryo formation ranges from 9.43% for BC₁F₁ to 30.2% for BC₁F₂, the haploid plant generation ranges from 19.36% for BC₁F₂ to 63.25% for BC₁F₁. Four doubled haploids were developed from ITSN 105/58 × VL 802 × VL 802 of BC₂F₃ underwent molecular cytogenetic analyses using the probes, viz., rye genomic rDNA, pSc 119 and pAs1. FISH and GISH analysis revealed an IBL.1RS translocation and substitution of 5R chromosome instead of the 5D chromosomes in these doubled haploids.

Evaluation of the 3rd Generation of Backcrosses and its Parents of Two Bread Wheat (Triticum aestivum L.) Cultivars for Salt Tolerance

A field experiment was conducted during the winter season of 2017-2018 at the Center of Plant Breeding and Genetics, AlTuwaitha Research Station (30km southeast of Baghdad) to evaluate the performance of two bread wheat genotypes at the 3rd back cross generation with their parents, cv. Furait , Baraka and Iraq under saline field condition (12 dSm-1). The objective of this study was to evaluate the beneficial effects of different back crosses and its parents in targeted field condition, on grain yield and its components of bread wheat. Results showed that the two generations of (Furait x Baraka) and (Furait x Iraq) were significantly exceeded their parents and gave the highest values of spikes m-2 (207.0 , 196.3), grain spike-1 ( 37.0, 39.0), 1000 seed weight (34.3, 33.3g ) and grain yield m-2 (244.4, 242.7g), respectively. Phenotypic variation and the percentage of broad sense heritability for plant height, tillers m-2, grains spike-1, 1000 seed weight and grain yield m-2 were highest compared with the value of environmental variation, and emphasized the important of genotypic variation and the ability to improve the desirable quantitative traits and reflects the high percentage of heritability.

Production of doubled-haploid(DH) selfed-progenies in ‘Banpeiyu’ pummelo [Citrus maxima (Burm.) Merr.] and its genetic analysis with simple sequence repeat markers

The genetic analysis of five haploid plants (BX1-BX5) of ‘Banpeiyu’ pummelo (BP), [Citrus maxima (Burm.) Merr.] using 32 simple sequence repeat (SSR) markers carried out for the purpose of confirming their gynogenetic origin and genetic differences. As the results, all the haploid plants possessed only either one of the BP alleles, confirming that they are gynogenetic origin. We also confirmed that BX1 and its doubled haploid (BX1-DH) have exactly the same SSR alleles. Interestingly, all the five haploids had common alleles on the linkage group (LG) 6 in the case of three markers. Then, we performed self-pollination of DH plants and reciprocal crosses between DH and BP, which has strong self-incompatibility. The seeds obtained by these crosses germinated in vitro or ex vitro normally and developed into diploid seedlings, except for one tetraploid seedling. Genetic analysis of these seedlings with 32 SSR markers revealed that segregation ratios of the 32 loci in the 30 BP inbred, 30 BP x DH and 30 DH x BP progenies mostly fitted to the expected ratios. However, significantly distorted segregation ratios were found in one, five and three SSR markers for BP inbred, BP x DH and DH x BP progenies, respectively. All of the 30 DH inbred progenies showed exactly the same SSR alleles as the original DH. This is the first example in which self and back cross progenies of DH in fruit crops were genetically analyzed using SSR markers.

Dominant early heading without yield drag in a sister-line BC breeding progeny DEH_229 is controlled by multiple genetic factors with main-effect loci

Dominant early heading (DEH) in rice (Oryza sativa L.) is of interest in both breeding and genetics. The genetic mechanisms underlying DEH have remained largely unclear. We have developed a near-isogenic DEH line without yield drag named DEH_229 by sister-line backcross (BC) breeding with MH63, a restorer, as the genetic background. We conducted a pilot genetic investigation under both short-day (SD) and long-day (LD) conditions. The DEH line harbored only 1.06% variation in the genome sequence relative to MH63. The variants were distributed throughout the genome. Using QTL mapping by sequencing (QTL-seq) on an F2 population derived from a cross of MH63 × DEH_229, 57 loci were detected under the SD condition. Joint mapping employing a genome-wide association study with accessions from the 3000 rice genome sequencing project (3K-RG), reduced the number of QTL by 43.9%. Using Rice Functional Genomics & Breeding (RFGB) database, the number of SNP cluster regions within the QTL regions reduced by 27.3%. Further comparison of the genome variation between DEH_229 and MH63 in addition to gene annotation information revealed a new DEH allele of DTH3 with multiple variable sites as a possible major factor underlying the early-heading phenotype of DEH_229. An InDel marker, ZMEH_1, was designed based on the variation between DEH_229 and MH63 within this region. It accounted for 86.0% of heading date variation under both SD and LD conditions in 109 randomly chosen progeny derived from extreme lines of the MH63 × DEH_229 population. This study reveals the genetic complexity of DEH in the near-isogenic line and may provide useful material and marker information for plant molecular breeding.

An integrated linkage map of interspecific backcross 2 (BC2) populations reveals QTLs associated with fatty acid composition and vegetative parameters influencing compactness in oil palm

BackgroundMolecular breeding has opened new avenues for crop improvement with the potential for faster progress. As oil palm is the major producer of vegetable oil in the world, its improvement, such as developing compact planting materials and altering its oils’ fatty acid composition for wider application, is important.ResultsThis study sought to identify the QTLs associated with fatty acid composition and vegetative traits for compactness in the crop. It integrated two interspecific backcross two (BC2) mapping populations to improve the genetic resolution and evaluate the consistency of the QTLs identified. A total 1963 markers (1814 SNPs and 149 SSRs) spanning a total map length of 1793 cM were integrated into a consensus map. For the first time, some QTLs associated with vegetative parameters and carotene content were identified in interspecific hybrids, apart from those associated with fatty acid composition. The analysis identified 8, 3 and 8 genomic loci significantly associated with fatty acids, carotene content and compactness, respectively.ConclusionsMajor genomic region influencing the traits for compactness and fatty acid composition was identified in the same chromosomal region in the two populations using two methods for QTL detection. Several significant loci influencing compactness, carotene content and FAC were common to both populations, while others were specific to particular genetic backgrounds. It is hoped that the QTLs identified will be useful tools for marker-assisted selection and accelerate the identification of desirable genotypes for breeding.

Screening of rice (Oryza sativa L.) for salinity tolerance at seedling stage under hydroponic condition

Rice is one among the foremost suitable crop for saline soils although it's usually considered moderately sensitive to salinity. The phenotypic response of twenty rice genotypes with salt stress at EC=12 dsm-1 was assessed under hydroponic condition at seedling stage. The rice genotypes FL-478, IR68144-2B-2-2-3-1-120, IR-68144-2B-2-2-3-1-127 were found tolerant, while IR-91167-99-1-1- 1-3, NUD-3, NUD-2, CSR-13, IR-92953-49-1-3 and NDRK-2008 showed moderately tolerant to salinity and genotypes NDR-359, MTU-1010, TARAMON, SAMBHA MANSURI, SWARNA IR-28 and AYYAR showed vulnerable to salinity. Tolerant varieties are suggested to use as donor parents for salinity tolerance in back cross breeding and for allele mining for salinity tolerance gene/QTLs.

QTL dissection of floral traits in Streptocarpus (Gesneriaceae)

Flower shape and colour are key plant traits which are often strongly correlated with pollinator choice and reproductive isolation. To understand the genetic changes underlying variation in these traits, we performed the first QTL analyses of these traits in Streptocarpus (Gesneriaceae) using a segregating backcross (BC) population of (S. rexii × S. grandis) × S. grandis. Composite traits of floral dimensions were dissected into smallest definable subtraits to examine the efficiency of QTL mapping and correlation between composite and subtrait-specific QTLs. Strong dominance effects were observed in the F1 for many S. rexii traits but for few S. grandis traits. In the BC plants new phenotypes appeared that may be the result of transgressive segregation. Many phenotypic correlations were found between floral dimension traits, which was probably due to the co-localisation of QTLs on the linkage groups. Two regions were associated with large numbers of size and shape traits (17 linked on LG1 and eight linked on LG12), to which the first principal component was also mapped. QTLs of composite traits were mostly overlapping with subtraits, although a few QTLs were newly discovered in subtrait mapping. Strong QTLs were detected for time to flowering and for floral pigmentation traits, ventral lobe pigmentation and the yellow spot. The absence of linkage of floral dimension traits and flower pigmentation suggests that genetic regulation of floral form in Streptocarpus allows versatility, perhaps allowing fast response to changing selective pressures from pollinators.

Characterization and Selection of Bruchid [Callosobruchus maculatus (F.)] Tolerant Greengram [Vigna radiata (L.) Wilczek] Genotypes

Bruchid, a cosmopolitan and most notorious field carryover storage grain pest in greengram causes severe damage in storage conditions. Hence, breeding efforts were made to develop bruchid tolerant genotypes involving two agronomically superior genotypes DGGV-2 and DGGV-7 and two bruchid tolerant genotypes V-02-709 and V-02-802. The F3 genotypes were screened through a ‘free choice test’ and further evaluated under the ‘force choice test’ for confirmation of resistance. The genotypes derived from the F3 family involving cross between V-02-802 × DGGV-7 and V-02-802 × DGGV-2 were found to be resistant with a longer mean developmental period (34.76 days and 33.53 days), low infestation (27.66 and 30.33 %) and low susceptibility index (0.039 and 0.043). The correlation amongst the various parameters, the mean developmental period has shown significantly negative correlation (r = -0.848) with susceptibility index; indicating that the resistance genotypes have shown a delay in a developmental period which can reduce the seed loss during storage condition. Hence, the superior genotypes can be further backcrossed with resistant source V-02-802 to recover bruchid resistant genes and can be used in breeding programmes aimed at the development of bruchid resistance lines.

Detecting CSSLs and yield QTLs with additive, epistatic and QTL\xd7environment interaction effects from Oryza sativa \xd7 O. nivara IRGC81832 cross

Chromosome segment substitution lines (CSSLs) are useful tools for precise mapping of quantitative trait loci (QTLs) and the evaluation of gene action and interaction in inter-specific crosses. In this study, a set of 90 back cross lines at BC2F8 generation derived from Swarna x Oryza nivara IRGC81832 was evaluated for yield traits under irrigated conditions in wet seasons of 3 consecutive years. We identified a set of 70 chromosome segment substitution lines, using genotyping data from 140 SSR markers covering 94.4% of O. nivara genome. Among these, 23 CSSLs were significantly different for 7 traits. 22 QTLs were detected for 11 traits with 6.51 to 46.77% phenotypic variation in 90 BILs. Three pleiotropic genomic regions associated with yield traits were mapped on chromosomes 1, 8 and 11. The marker interval RM206-RM144 at chromosome 11 was recurrently detected for various yield traits. Ten QTLs were identified consistently in the three consecutive years of testing. Seventeen pairs of significant epistatic QTLs (E-QTLs) were detected for days to flowering, days to maturity and plant height. Chromosome segments from O. nivara contributed trait enhancing alleles. The significantly improved lines and the stable QTLs identified in this study are valuable resource for gene discovery and yield improvement.

Agronomic traits and resistance of pepper lines selected by molecular assistance to Phytophthora Blight from different resistance sources

Belonging to the Oomycete genus, Phytophthora capsici has wide range host profile and is responsible of many devastating diseases in many countries. In addition to time consuming problem for transferring resistance to susceptible varieties, backcrossing method causes losing of genes providing resistance to susceptible varieties. In this study transferring P. capsici resistance genes to susceptible red pepper lines with molecular marker assistance was aimed during 12 years breeding period. Two different breeding populations from CM334 and PM217 were compared by stem inoculation test at receptivity, inducibility and stability stage. CM334 was found more effective for transferring all resistance components while PM217 was found suitable for keeping agronomic traits along with two important resistance component inducibility and stability. These two resistant components were found highly correlated length of stem necrosis. C-29 and C-18 have improved from CM334 as resistant as CM334; P-73 and P-77 have been improved satisfactorily resistant and yielded lines from PM217. Molecular marker assistance proved that resistance of lines differentiate phenotypically despite the genotypes have same genes.

Construction of wild soybean backcross introgression lines

Construction of wild soybean backcross introgression lines

Design and Analysis of a Wideband Low-Scattering Endfire Antenna Using a Moth Tail-Inspired Metamaterial Absorber and a Surface Waveguide

This article presents a wideband endfire antenna codesigned with broadband low-scattering characteristics. The wideband reflection and endfire radiation attribute the success to the supported dual-resonance surface waves, and the broadband low scattering owes to the combination of a metamaterial absorber (MA) absorption and an incident penetration of a frequency-selective surface (FSS). Based on the transmission line model, a surface waveguide (SWG) which can support dual-resonance surface waves is adopted and analyzed to realize the wideband reflection response (4.95–6.83 GHz) and endfire radiation. Also, the SWG can be seen as an FSS for the normal incidence. In addition, a wideband MA, which is inspired by the luna moth’s escape from bat attack, is designed and integrated with the SWG to realize low back radar cross section (RCS) in the frequency range from 0.5 to 12.5 GHz. The reflection, radiation, and scattering performance are validated by the full-wave simulation and experimental verification.

Genetic analysis of partial resistance to vine decline in watermelon [Citrullus lanatus (Thunb.) Matsum&amp;Nakai

Vine decline or sudden wilt caused by a complex of pathogens with unknown etiology is emerging as most destructive disease of watermelon in the southern part of India. In this direction ICAR-IIHR, has identified a prebred line derived from Citrullus amarus viz., BIL-53 to be field tolerant to this disease. This study was planned to understand the genetics of vine decline resistance in this accession. The BIL-53 used as resistant parent was crossed with icebox accession, IIHR‐140–152, a susceptible genotype to develop F1, F2, BC1 and BC2 generations and observe the segregation for disease reaction. The results in F2 and backcross progenies suggested that resistance is governed by a single recessive gene. BIL-53 is also known to possess resistance to WBNV and hence, this line can be used in resistance breeding programs to develop combined resistance to vine decline and watermelon bud necrosis orthotospovirus employing back cross breeding. Further, this line can be tested as a rootstock in overcoming vine decline as an immediate measure.

Introgression of QTLs determining sorghum downy mildew (SDM) resistance into elite maize line UMI 79 through marker-assisted backcross breeding (MABC)

Sorghum downy mildew (SDM), caused by Peronosclerospora sorghi is one of the important diseases in maize. Here, we illustrate the transfer of two QTLs for SDM on chromosome 3 and 6 from UMI 936 (w) into an elite maize inbred line UMI 79 through marker-assisted backcross breeding (MABC). For foreground selection, plants carrying heterozygote allele for the QTLs for SDM were selected from F1 and three back cross (BC1-BC3) generations using simple sequence repeat (SSR) markers linked to the targeted QTLs region of SDM. Consequently, foreground positive plants from BC3F1 generation selfed to produce BC3F2 and plants carrying the favorable alleles for the QTLs for SDM were selected followed by stringent phenotyping against SDM and advanced to BC3F3. As a result, two improved lines (79/936–1–7-7-7-46-46 and 79/936–1–7-7-10-80-80) possessing QTLs for SDM were obtained. Background selection using 146 SSR markers distributed evenly across the maize genome revealed 92.45% and 89.68% recovery of recurrent parent genome (RPG) in two improved lines. Phenotypic characterization of the improved lines showed more than 90% of recovery of the recurrent parents in morphological traits and a resistance to SDM. In conclusion, the newly developed SDM resistant inbred lines are a potential source for improving SDM resistance in maize breeding programs.

Conversion of partial restorer Swarna into restorer by transferring fertility restorer Rf gene(s) through marker assisted back cross breeding (MABB) in rice

The major constraints in hybrid rice breeding are availability of limited number of parental lines with specific desirable traits and lower frequency of restorers among elite breeding lines. The popular, high-yielding mega-rice variety Swarna, has been identified to be a partial restorer (as it has only one of major fertility restorer genes, Rf4) and hence cannot be utilized directly in the hybrid rice breeding. To convert the partial restorer to complete restorer, a cross was made between Swarna and a stable restorer KMR3R possessing Rf3 and Rf4 genes and developed BC1F5 and BC2F4 populations by marker-assisted back cross breeding (MABB). The SSR marker DRRM-RF3-10 linked to Rf3 gene located on chromosome 1, clearly distinguished restorers from partial restorers. All the improved lines of Swarna possessing Rf3 and Rf4 genes showed complete fertility restoration in test crosses with higher grain yield heterosis. Few rice hybrids developed by using converted restorers were evaluated in multi location testing under the All India Co-ordinated Rice Improvement Project (AICRIP). The results indicated that new rice hybrids expressed higher heterosis with matching grain quality attributes like Swarna. This study provides significantly novel and relevant restorers to enhance and economize future hybrid rice breeding programs.

Inheritance pattern of the flightless characteristic in Harmonia axyridis

The genetic basis of the flightless characteristic in Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) was studied using two crossbreeding experiments to verify the inheritance of the flightless character which may be relevant if mating with wild populations takes place. In the first experiment, the segregating population (F2) was obtained by random mating within each F1 line. The proportion of flightless individuals reached 24–29% in the F2 generation. In the second experiment, the F1 individuals were crossed with the flightless individuals to develop a backcross (BC) population, which showed that the proportion of flightless individuals reached 33–59% in the BC population. Although the quantitative variation of flight ability in H. axyridis could also be due to a large proportion of loci with small effects, our results suggest that the flightless mutation is largely controlled by a single locus and that only H. axyridis individuals homozygous for the recessive alleles show the flightless characteristic.