Quantitative Trait Locus Mapping of Resistance to Turnip Yellows Virus in Brassica rapa and Brassica oleracea and Introgression of These Resistances by Resynthesis Into Allotetraploid Plants for Deployment in Brassica napus

Turnip yellows virus (TuYV) is aphid-transmitted and causes considerable yield losses in oilseed rape (OSR, Brassica napus, genome: AACC) and vegetable brassicas. Insecticide control of the aphid vector is limited due to insecticide resistance and the banning of the most effective active ingredients in the EU. There is only one source of TuYV resistance in current commercial OSR varieties, which has been mapped to a single dominant quantitative trait locus (QTL) on chromosome A04. We report the identification, characterisation, and mapping of TuYV resistance in the diploid progenitor species of OSR, Brassica rapa (genome: AA), and Brassica oleracea (genome: CC). Phenotyping of F1 populations, produced from within-species crosses between resistant and susceptible individuals, revealed the resistances were quantitative and partially dominant. QTL mapping of segregating backcross populations showed that the B. rapa resistance was controlled by at least two additive QTLs, one on chromosome A02 and the other on chromosome A06. Together, they explained 40.3% of the phenotypic variation. In B. oleracea, a single QTL on chromosome C05 explained 22.1% of the phenotypic variation. The TuYV resistance QTLs detected in this study are different from those in the extant commercial resistant varieties. To exploit these resistances, an allotetraploid (genome: AACC) plant line was resynthesised from the interspecific cross between the TuYV-resistant B. rapa and B. oleracea lines. Flow cytometry confirmed that plantlets regenerated from the interspecific cross had both A and C genomes and were mixoploid. To stabilise ploidy, a fertile plantlet was self-pollinated to produce seed that had the desired resynthesised, allotetraploid genome AACC. Phenotyping of the resynthesised plants confirmed their resistance to TuYV. Genotyping with resistance-linked markers identified during the mapping in the progenitors confirmed the presence of all TuYV resistance QTLs from B. rapa and B. oleracea. This is the first report of TuYV resistance mapped in the Brassica C genome and of an allotetraploid AACC line possessing dual resistance to TuYV originating from both of its progenitors. The introgression into OSR can now be accelerated, utilising marker-assisted selection, and this may reduce selection pressure for TuYV isolates that are able to overcome existing sources of resistance to TuYV.

Quantitative Trait Locus Analysis and Identification of Candidate Genes for Micronaire in an Interspecific Backcross Inbred Line Population of Gossypium hirsutum × Gossypium barbadense

Cotton is the most important fiber crop and provides indispensable natural fibers for the textile industry. Micronaire (MIC) is determined by fiber fineness and maturity and is an important component of fiber quality. Gossypium barbadense L. possesses long, strong and fine fibers, while upland cotton (Gossypium hirsutum L.) is high yielding with high MIC and widely cultivated worldwide. To identify quantitative trait loci (QTLs) and candidate genes for MIC in G. barbadense, a population of 250 backcross inbred lines (BILs), developed from an interspecific cross of upland cotton CRI36 × Egyptian cotton (G. barbadense) Hai7124, was evaluated in 9 replicated field tests. Based on a high-density genetic map with 7709 genotyping-by-sequencing (GBS)-based single-nucleotide polymorphism (SNP) markers, 25 MIC QTLs were identified, including 12 previously described QTLs and 13 new QTLs. Importantly, two stable MIC QTLs (qMIC-D03-2 on D03 and qMIC-D08-1 on D08) were identified. Of a total of 338 genes identified within the two QTL regions, eight candidate genes with differential expression between TM-1 and Hai7124 were identified. Our research provides valuable information for improving MIC in cotton breeding.

Genetic Mapping of the HLA1 Locus Causing Hybrid Lethality in Nicotiana Interspecific Hybrids

Hybrid lethality, a postzygotic mechanism of reproductive isolation, is a phenomenon that causes the death of F1 hybrid seedlings. Hybrid lethality is generally caused by the epistatic interaction of two or more loci. In the genus Nicotiana, N. debneyi has the dominant allele Hla1-1 at the HLA1 locus that causes hybrid lethality in F1 hybrid seedlings by interaction with N. tabacum allele(s). Here, we mapped the HLA1 locus using the F2 population segregating for the Hla1-1 allele derived from the interspecific cross between N. debneyi and N. fragrans. To map HLA1, several DNA markers including random amplified polymorphic DNA, amplified fragment length polymorphism, and simple sequence repeat markers, were used. Additionally, DNA markers were developed based on disease resistance gene homologs identified from the genome sequence of N. benthamiana. Linkage analysis revealed that HLA1 was located between two cleaved amplified polymorphic sequence markers Nb14-CAPS and NbRGH1-CAPS at a distance of 10.8 and 10.9 cM, respectively. The distance between these markers was equivalent to a 682 kb interval in the genome sequence of N. benthamiana.

Keberhasilan dan kompatibilitas penyerbukan sendiri dan silang pada hibridisasi interspesifik ciplukan (Physalis spp)

Tanaman ciplukan digunakan untuk menghasilkan buah segar, bahan baku nutraceutical, dan biofarmasi. Kapasitas genetik ciplukan dapat ditingkatkan dengan hibridisasi interspesifik. Ketidakcocokan adalah masalah yang muncul pada persilangan antarspesies. Tujuan penelitian adalah untuk mempelajari keberhasilan dan kompatibilitas penyerbukan sendiri dan penyerbukan silang hibridisasi interspesifik ciplukan. Penelitian dilaksanakan di Seed and Nursery Industry, Agro Techno Park, Universitas Brawijaya pada bulan Januari sampai Juni 2020. Penelitian menggunakan bahan 5 spesies ciplukan, yaitu Physalis P. angulata, P. peruviana, P. pruinosa, P. pubescens, dan P. ixocarpa. Pola perkawinan dialel digunakan serta pengamatan terhadap hasil penyerbukan diamati. Hasil penyerbukan silang interspesifik memiliki derajat kompatibilitas yang berbeda. Kompatibilitas penyerbukan sendiri pada setiap spesies tinggi. Penyerbukan silang interspesifik P. pubescens (PPB-68154-04) x P. angulata (PAN-69281) kompatibel. Inkompatibilitas parsial terdapat pada penyerbukan silang interspesifik P. angulata (PAN-69281) x P. ixocarpa (PIX-4418-2), P. pubescens (PPB-68154-04) x P. ixocarpa (PIX-4418-2) , P. pruinosa (PPN+3101) x P. angulata (PAN-69281), dan P. pruinosa (PPN+3101) x P. ixocarpa (PIX-4418-2). Inkompatibilitas lengkap terjadi pada penyerbukan silang P. angulata (PAN-69281) x P. pubescens (PPB-68154-04), P. angulata (PAN-69281) x P. pruinosa (PPN+3101), P. pubescens (PPB-68154-04) x P. pruinosa (PPN+3101), P. pruinosa (PPN+3101) x P. pubescens (PPB-68154-04), P. pruinosa (PPN+3101) x P. ixocarpa (PIX-4418-2), P. peruviana (PPV-45311-03) dan P. ixocarpa (PIX-4418-2). Penyerbukan sendiri dan penyerbukan silang yang kompatibel menghasilkan perbedaan pada karakteristik buah dan benih. P. pruinosa (PPN+3101), P. angulata (PAN-69281), dan P. pubescens (PPB-68154-04) menghasilkan jumlah benih yang berbeda pada penyerbukan silang interspesifik.AbstractCiplukan is used as a fresh fruit, nutraceutical raw materials, and biopharmaceuticals. Genetic capacity of ciplukan can be increased by interspecific hybridization. Incompatibility is an issue obtained during the interspecific hybridization. Research objective was to study success rate and compatibility of self-pollination and cross-pollination ciplukan interspecific hybridization. Research was conducted at Seed and Nursery Industry, Agro Techno Park, Universitas Brawijaya from January to June 2020. Physalis P. angulata, P. peruviana, P. pruinosa, P. pubescens, and P. ixocarpa were species included in this study. A diallel mating design pattern was used as well as observations of pollination. Interspecific cross pollination was found to have differing degrees of compatibility. Compatibility of self-pollination in each species is high. Interspecific cross-pollination of P. pubescens (PPB-68154-04) x P. angulata (PAN-69281) is compatible. Partial incompatibilities exist in interspecific cross-pollination of P. angulata (PAN-69281) x P. ixocarpa (PIX-4418-2), P. pubescens (PPB-68154-04) x P. ixocarpa (PIX-4418-2), P. pruinosa (PPN+3101) x P. angulata (PAN-69281), and P. pruinosa (PPN+3101) x P. ixocarpa (PIX-4418-2). Complete incompatibility occurred in cross-pollination of P. angulata (PAN-69281) x P. pubescens (PPB-68154-04), P. angulata (PAN-69281) x P. pruinosa (PPN+3101), P. pubescens (PPB-68154-04) x P. pruinosa (PPN+3101), P. pruinosa (PPN+3101) x P. pubescens (PPB-68154-04), P. pruinosa (PPN+3101) x P. ixocarpa (PIX-4418-2), P. peruviana (PPV-45311-03) and P. ixocarpa (PIX-4418-2). Compatible self-pollination and cross-pollination resulted differences in fruit and seed characteristics. P. pruinosa (PPN+3101), P. angulata (PAN-69281), and P. pubescens (PPB-68154-04) developed different numbers of seeds following interspecific cross-pollination.

Assessment of variability and association for seed yield and yield attributing traits among the interspecific derivatives of greengram x blackgram cross

The present investigation was carried out with 24 progenies in F4 generation of interspecific cross derivatives of Vigna radiata cv. VBN(Gg)2 x Vigna mungo cv. Mash 114 to study the variability and association among the yield and the yield component traits. A set of 24 F4 progenies from the interspecific cross between greengram (VBN(Gg)2) and blackgram (Mash 114) formed the basic genetic material for the present investigation. Variability studies recorded high Phenotypic Coefficient of Variation (PCV) and Genotypic Coefficient of Variation (GCV) for the traits viz., number of branches/ plant, number of clusters/ plant, number of pods/ plant and seed yield /plant. High heritability (h2) along with high genetic advance as per cent of mean (GAM) were recorded for the traits, plant height, number of clusters/ plant, number of pods/ plant and seed yield/ plant. Association studies revealed that the trait number of pods/ plant alone recorded high direct positive effect on seed yield/ plant. The results indicated that high magnitude of variability was present among the interspecific progenies for these traits. The high heritability and genetic advance might be due to presence of additive gene action. Hence selection based on these traits might be effective for genetic improvement among the interspecific progenies of Vigna radiata x Vigna mungo. The study indicates that the trait, number of pods / plant should be given due importance in selection programme for seed yield improvement in the interspecific progenies of greengram and blackgram.

Identification and Validation of QTLs for Macronutrient Contents in Brown and Milled Rice Using Two Backcross Populations between Oryza sativa and O. rufipogon

Mineral malnutrition as a prevalent public health issue can be alleviated by increasing the intake of dietary minerals from major staple crops, such as rice. Identification of the gene responsible for mineral contents in rice would help breed cultivars enriched with minerals through marker-assisted selection. Two segregating populations of backcross inbred lines (BIL) were employed to map quantitative trait loci (QTLs) for macronutrient contents in brown and milled rice, BC1F5, and BC2F4:5 derived from an interspecific cross of Xieqingzao B (Oryza sativa) and Dongxiang wild rice (O. rufipogon). Phenotyping the populations was conducted in multiple locations and years, and up to 169 DNA markers were used for the genotyping. A total of 17 QTLs for P, K, Na, Ca, and Mg contents in brown and milled rice distributed on eight regions were identified in the BC1F5 population, which is explained to range from 5.98% to 56.80% of phenotypic variances. Two regions controlling qCa1.1 and qCa4.1 were validated, and seven new QTLs for Ca and Mg contents were identified in the BC2F4:5 population. 18 of 24 QTLs were clustered across seven chromosomal regions, indicating that different mineral accumulation might be involved in common regulatory pathways. Of 24 QTLs identified in two populations, 16 having favorable alleles were derived from O. rufipogon and 10 were novel. These results will not only help understand the molecular mechanism of macronutrient accumulation in rice but also provide candidate QTLs for further gene cloning and grain nutrient improvement through QTL pyramiding.

Substitution Mapping of a Locus Responsible for Hybrid Breakdown in Populations Derived From Interspecific Introgression Line

Hybrid breakdown, a form of postzygotic reproductive barrier, has been reported to hinder gene flow in many crosses between wild and cultivated rice. Here, the phenomenon of hybrid breakdown was observed as low-tillering (i.e., low tiller number) in some progeny of an interspecific cross produced in an attempt to introduce Oryza meridionalis Ng (W1625) chromosomal segments into Oryza sativa L. ssp. japonica “Taichung 65” (T65). Low-tillering lines were obtained in BC4-derived progeny from a cross between W1625 and “Taichung 65,” but the locus for low-tillering could not be mapped in segregating populations. As a second approach to map the locus for low-tillering, we analyzed an F2 population derived from a cross between the low-tillering lines and a high-yielding indica cultivar, “Takanari.” A major QTL for low-tillering, qLTN4, was detected between PCR-based markers MS10 and RM307 on the long arm of chromosome 4, with a LOD score of 15.6. The low-tillering phenotype was associated with weak growth and pale yellow phenotype; however, low-tillering plant had less reduction of grain fertility. In an F4 population (4896 plants), 563 recombinant plants were identified and the low-tillering locus was delimited to a 4.6-Mbp region between markers W1 and C5-indel3729. This region could not be further delimited because recombination is restricted in this region of qLTN4, which is near the centromere. Understanding the genetic basis of hybrid breakdown, including the low-tillering habit, will be important for improving varieties in rice breeding.

Analysis of the possible cytogenetic mechanism for overcoming hybrid lethality in an interspecific cross between Nicotiana suaveolens and Nicotiana tabacum

Hybrid lethality is a type of reproductive isolation in which hybrids die before maturation, due to the interaction between the two causative genes derived from each of the hybrid parents. The interspecific hybrid of Nicotiana suaveolens × Nicotiana tabacum is a model plant used in studies on hybrid lethality. While most of the progeny produced from such a cross die, some individuals grow normally and mature. Separately, a technique for producing mature hybrids by artificial culture has been developed. However, the mechanism by which hybrids overcome lethality, either spontaneously or by artificial culture, remains unclear. In the present study, we found that some hybrids that overcome lethality, either spontaneously or by artificial culture, lack the distal part of the Q chromosome, a region that includes the gene responsible for lethality. Quantitative polymerase chain reaction results suggested that the distal deletion of the Q chromosome, detected in some hybrid seedlings that overcome lethality, is caused by reciprocal translocations between homoeologous chromosomes. The results showed that chromosomal instability during meiosis in amphidiploid N. tabacum as well as during artificial culturing of hybrid seedlings is involved in overcoming hybrid lethality in interspecific crosses of the genus Nicotiana.