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Response to infection with Xcc. strain CH 31 in parents (N: B. nigra and B: B. rapa), interspecific hybrid (F 1 ), the first backcross plant (BC 1 ), and the second backcross plants (BC 2-1 and BC 2-2 )
Source publication
Black rot is a bacterial disease of Brassica rapa caused by Xanthomonas
campestris pv. campestris (Xcc.). Sources of resistance to this disease within B. rapa are insufficient and control measures are limited, making the development of resistant breeding lines extremely important.
Certain lines of B. nigra exhibit very high resistance to Xcc. For t...
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xBrassicoraphanus line BB#5, a new synthetic intergeneric hybrid between Brassica rapa L. ssp. pekinensis and Raphanus sativus L. var. rafiphera induced by N-methyl-N-nitroso-urethane mutagenesis in microspore culture, shows high seed fertility and morphological uniformity. Dual-color fluorescence in situ hybridization (FISH) using SS and 45S rDNA...
Citations
... In previous studies, the stability amongst the three genomes in Brassica was B > A > C, and the non-homologous pairing of B with A and C was observed. Moreover, abnormal chromosome behaviour was also found in some allodiploid hybrids AB and AC including the frequent occurrence of lagged chromosome phenomenon, chromosome bridge, uneven distribution and asynchronous meiosis, which showed the irregular meiosis of hybrids, leading to the inviability of pollen grains (Cui et al. 2012;Sheng et al. 2012). In this study, the synthetic allodiploid B. juncea hybrids exhibited similar phenotypes, with high pollen abortion. ...
Key message
Imbalanced chromosomes and cell cycle arrest, along with down-regulated genes in DNA damage repair and sperm cell differentiation, caused pollen abortion in synthetic allodiploid Brassica juncea hybrids.
Abstract
Interspecific hybridization is considered to be a major pathway for species formation and evolution in angiosperms, but the occurrence of pollen abortion in the hybrids is common, prompting us to recheck male gamete development in allodiploid hybrids after the initial combination of different genomes. Here, we investigated the several key meiotic and mitotic events during pollen development using the newly synthesised allodiploid B. juncea hybrids (AB, 2n = 2× = 18) as a model system. Our results demonstrated the partial synapsis and pairing of non-homologous chromosomes concurrent with chaotic spindle assembly, affected chromosome assortment and distribution during meiosis, which finally caused difference in genetic constitution amongst the final tetrads. The mitotic cell cycle arrest during microspore development resulted in the production of anucleate pollen cells. Transcription analysis showed that sets of key genes regulating cyclin (CYCA1;2 and CYCA2;3), DNA damage repair (DMC1, NBS1 and MMD1), and ubiquitin–proteasome pathway (SINAT4 and UBC) were largely downregulated at the early pollen meiosis stages, and those genes involved in sperm cell differentiation (DUO1, PIRL1, PIRL9 and LBD27) and pollen wall synthesis (PME48, VGDH11 and COBL10) were mostly repressed at the late pollen mitosis stages in the synthetic allodiploid B. juncea hybrids (AB). In conclusion, this study elucidated the related mechanisms affecting pollen fertility during male gametophyte development at the cytological and transcriptomic levels in the synthetic allodiploid B. juncea hybrids.
... The colchiploid hybrids restored partial pollen fertility, while the non-colchiploid hybrids were all male sterile. Pollen fertility as low as 2.77% (Sharma et al., 2017) and 0-4% (Dey et al., 2015) in B. oleracea × B. carinata, 28% in B. rapa × B. nigra (Sheng et al., 2012). Besides, giant pollen were also reported from the Cauliflower × Ethiopian mustard Griffiths 2004), in B. napus × B. carinata, B. juncea × B. carinata andB. ...
... juncea × B. napus (Mason et al., 2011). The low pollen fertility increased slightly in the subsequent backcross progenies as was observed by previous works (Sheng et al., 2012;Dey et al., 2015). ...
Multiple R-gene is required to achieve strong resistance against clubroot, a disease caused by Plasmodiophora brassicae in Cabbage (Brassica oleracea, 2n=18, CC). Most of the R-genes were identified in Chinese cabbage (B. rapa, 2n=20, AA), which could be transferred to cabbage via inter interspecific hybridization. We present a breeding scheme to transfer six major CR-loci namely, Crr1, Crr2, Crr3, CRa, CRb and CRc from Chinese cabbage line, LCR36 to cabbage line, Plimio. Approximately, 48% of the interspecific hybrid embryos were rescued, of which chromosomes of 48.15% colchiploid plants were successfully doubled. The hybridity of the colchiploid interspecific hybrids were confirmed by diagnostic sub-genome specific Conserved Ortholog Set (COS) markers, ploidy level, pollen fertility and meiotic chromosome number analyses. Backcross generations are characterized by very low seed set (0.57-1.33% success rate) in backcrossed generations (using Plimio as the recurrent parent). Marker assisted selection using the six CR-loci specific markers identified the resistant plants in F1 and backcross generations. MAS and bioassay test of BC2F2 plants revealed that plants having all six R-loci are resistant to clubroot. Development of subsequent backcross generations are in progress. More number of back-crosses and/or embryo rescue will be performed to ensure sufficient seed set. The success so far is the first report of successful introgression of multiple R-genes via interspecific hybridization in the initial backcrossed generations, indicating that an elite cabbage line having strong resistance to clubroot can be produced upon the completion of the breeding scheme.
... Similarly, the interspecific hybrid also displayed 1.09% of bands of nonparental origin. The non-inheritance of parental bands as well as hybrid specific bands were documented earlier in several plant species such as zoysia (Xuan et al. 2008), peanut (Ren et al. 2010), coffee (Mishra et al. 2011b) and Brassica (Sheng et al. 2012) using SRAP markers and could be ascribed to the result of DNA recombination, mutation or random segregation of heterozygous chromosomes during meiosis. ...
Natural hybridization is a common phenomenon in plants and considered to be a driving force of biodiversity and evolution. In coffee spontaneous hybridization between two different species is earlier documented. Here we investigated the morphological, molecular and physiological characteristics of a natural tetraploid interspecific coffee hybrid involving allopolyploid Coffea arabica and diploid C. excelsa species. The formation of the tetraploid hybrid was postulated on account of the production of unreduced female gametes in C. excelsa. In our findings, most morphological characters of the interspecific hybrid were found to be intermediate between the putative parental species, but the young leaf colour was found to be distinctively transgressive. Sequence-related amplified polymorphism marker analysis unequivocally supported the involvement of C. excelsa and C. arabica in hybrid formation. The gas exchange parameters, chlorophyll fluorescence parameters were compared between the hybrid and parents which revealed that the interspecific hybrid had the significantly higher substomatal CO2 concentration and non-photochemical quenching compared to parents. This tetraploid interspecific hybrid encompassing the genome of two divergent species could be of ascertainable importance in arabica coffee breeding program.
... On the contrary, Dey et al. (2015) reported F 1 sterility which later showed slight fertility in BC 1 progenies (0-4%) in the entire cross combinations of B. oleracea botrytis group × B. carinata as well as its reciprocal crosses. Sheng et al. (2012) reported semi-fertile interspecific hybrids of B. rapa × B. nigra with increased mean pollen fertility(28%) of BC 1 along with high level of resistance against black rot disease.Whereas, Hansen and Earle (1995) reported fertile resistant hybrids developed by protoplast fusion between rapid-cycling B. oleracea and a highly resistant B. napus line to X. campestris pv. campestris in order to transfer resistance to Xcc identified in B. carinata (PI 199947: previously identified as B. napus) to B. oleracea. ...
Black rot caused by Xanthomonas campestris pv. campestris (Xcc) is a very important disease of cauliflower (Brassica oleracea botrytis group) resulting into 10–50% yield losses every year. Since there is a dearth of availability of resistance to black rot disease in B. oleracea (C genome), therefore exploration of A and B genomes was inevitable as they have been reported to be potential reservoirs of gene(s) for resistance to black rot. To utilize these sources, interspecific hybrid and backcross progeny (B1) were generated between cauliflower “Pusa Sharad” and Ethiopian mustard “NPC-9” employing in vitro embryo rescue technique. Direct ovule culture method was better than siliqua culture under different temperature regime periods. Hybridity testing of F1 inter-specific plants was carried out using co-dominant SSR marker and Brassica B and C genome-specific (DB and DC) primers. Meiosis in the di-genomic (BCC) interspecific hybrid of B. oleracea botrytis group (2n = 18, CC) × B. carinata (2n = 4x = 34, BBCC) was higly disorganized and cytological analysis of pollen mother cells revealed chromosomes 2n = 26 at metaphase-I. Fertile giant pollen grain formation was observed frequently in interspecific F1 hybrid and BC1 plants. The F1 inter-specific plants were found to be resistant to Xcc race 1. Segregation distortion was observed in BC1 generation for black rot resistance and different morphological traits. The At1g70610 marker analysis confirmed successful introgression of black rot resistance in interspecific BC1 population. This effort will go a long way in pyramiding gene(s) for resistance against black rot in Cole crops, especially cauliflower and cabbage for developing durable resistance, thus minimize dependency on bactericides.
... Brassica species contains three genomes: B. rapa (AA), B. oleracea (CC), and B. nigra (BB), in which the A and C genomes have relatively higher homology than the A and B genomes (Song et al., 1995;Attia and Robbelen, 1986). Therefore, the frequency of hybridisation is very low due to the difficulty in haploid chromosome pairing in meiosis and successful wide hybrids between B. rapa (AA) and B. nigra (BB) are very rare (Attia and Robbelen, 1986;Sheng et al., 2012;Srivastav et al., 2004). ...
The DA1 gene family is plant-specific and Arabidopsis DA1 regulates seed and organ size, but the functions in soybeans are unknown. The cultivated soybean (Glycine max) is believed to be domesticated from the annual wild soybeans (Glycine soja). To evaluate whether DA1-like genes were involved in the evolution of soybeans, we compared variation at both sequence and expression levels of DA1-like genes from G. max (GmaDA1) and G. soja (GsoDA1).
Sequence identities were extremely high between the orthologous pairs between soybeans, while the paralogous copies in a soybean species showed a relatively high divergence. Moreover, the expression variation of DA1-like paralogous genes in soybean was much greater than the orthologous gene pairs between the wild and cultivated soybeans during development and challenging abiotic stresses such as salinity. We further found that overexpressing GsoDA1 genes did not affect seed size. Nevertheless, overexpressing them reduced transgenic Arabidopsis seed germination sensitivity to salt stress. Moreover, most of these genes could improve salt tolerance of the transgenic Arabidopsis plants, corroborated by a detection of expression variation of several key genes in the salt-tolerance pathways.
Our work suggested that expression diversification of DA1-like genes is functionally associated with adaptive radiation of soybeans, reinforcing that the plant-specific DA1 gene family might have contributed to the successful adaption to complex environments and radiation of the plants.
