Background: Acetolactate synthase (ALS)-inhibiting herbicides amidosulfuron (Hoestar) is an efficient gametocide that can induce male sterility in rapeseed (Brassica napus L.). We conducted an integrated study of cytological, transcriptomic, and physiological analysis to decipher the gametocidal effect of amidosulfuron.Results: In the first several days after exposure to amidosulfuron at a gametocidal dose of ca. 1 μg per plant, the plants showed the earliest symptoms including short retard of raceme elongation, slight chlorosis on leaf, and decrease of photosynthesis rate. Chloroplasts in leaf and anther epidermis, and tapetal plastids were deformed. Both tapetal cell and uni-nucleate microspore showed autophagic vacuoles and degenerated quickly. The amidosulfuron treatment caused reduction of photosynthetic rate and the contents of leaf chlorophyll, soluble sugar and pyruvate, as well as content alteration of several free amino acids in the treated plants. A comparison of transcriptomic profiling data of the young flower buds of the treated plants with the control identified 142 up-regulated and 201 down-regulated differential expression transcripts with functional annotations. Down-regulation of several interesting genes encoding PAIR1, SDS, PPD2, HFM1, CSTF77, A6, ALA6, UGE1, FLA20, A9, bHLH91, and putative cell wall protein LOC106368794, and up-regulation of autophagy-related protein ATG8A indicated functional abnormalities about cell cycle, cell wall formation, chloroplast structure, and tissue autophagy. Ethylene-responsive transcription factor RAP2-11-like was up-regulated in the flower buds and ethylene release rate was also elevated. The transcriptional regulation in the amidosulfuron-treated plants was in line with the cytological and physiological changes.Conclusions: The results suggested that metabolic decrease related to photosynthesis and energy supply are associated with male sterility induced by amidosulfuron. The results provide insights into the molecular mechanisms of gametocide-induced male sterility and expand the knowledge on the transcriptomic complexity of the plants exposure to sulfonylurea herbicide.

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The efficiency of a novel gametocide amidosulfuron, 1-(4, 6-dimethoxypyrimidin-2-yl) -3-mesyl (methyl) sulfamoylurea, was evaluated on rapeseed (Brassica napus L.). Double application of 0.09-0.12 g/ha amidosulfuron at the uni-nucleate stage of longest buds and 12 days later, made 97.4-100% plants male-sterile in seventeen out of 20 cultivars tested. The shrunken anthers could not release pollen or produced only dysfunctional pollen grains that could not be stained by aceto carmine. The treatment also caused 10-30% reduction on seed setting in comparison to the controls. The purity of hybrid seed from crosses of ÔC161 · HuayeÕ and ÔZhongshuang No.2 · HuayeÕ based on amidosulfuron was 99.8% and 100.0%, respectively. The results suggested that amidosulfuron is an efficient gametocide for B. napus.

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Background Acetolactate synthase (ALS)-inhibiting herbicide tribenuron-methyl (TBM) is an efficient gametocide that can cause rapeseed ( Brassica napus L.) to become male sterile and outcrossing. To find the reason the TBM treatment leads to male sterility, an integrated study using cytological, physiological, and transcriptomic methods was conducted. Results Some temporary symptoms, including the discoloration of young leaves and a short halt of raceme elongation, were observed in the rapeseed plants exposed to TBM at an application rate of 1 μg per plant. Both chloroplasts in young leaves and plastids in anthers were deformed. TBM also reduced the leaf photosynthetic rate and the contents of chlorophyll, soluble sugar and pyruvate. Both the tapetal cells and uni-nucleate microspores in the treated plants showed large autophagic vacuoles, and the tissue degenerated quickly. A transcriptomic comparison with the control identified 200 upregulated and 163 downregulated differential expression genes in the small flower buds of the TBM treatment. The genes encoding functionally important proteins, including glucan endo-1,3-beta-glucosidase A6, QUARTET3 (QRT3), ARABIDOPSIS ANTHER 7 (ATA7), non-specific lipid-transfer protein LTP11 and LTP12, histone-lysine N-methyltransferase ATXR6, spermidine coumaroyl-CoA acyltransferase (SCT), and photosystem II reaction centre protein psbB, were downregulated by TBM exposure. Some important genes encoding autophagy-related protein ATG8a and metabolic detoxification related proteins, including DTX1, DTX6, DTX35, cytosolic sulfotransferase SOT12, and six members of glutathione S-transferase, were upregulated. In addition, several genes related to hormone stimulus, such as 1-aminocyclopropane-1-carboxylate synthase 8 ( ACS8 ), ethylene-responsive factor ERF1A, ERF1, ERF71, CRF6, and RAP2-3 , were also upregulated. The transcriptional regulation is in accordance with the functional abnormalities of pollen wall formation, lipid metabolism, chloroplast structure, ethylene generation, cell cycle, and tissue autophagy. Conclusion The results suggested that except for ALS, the metabolic pathways related to lipid metabolism, pollen exine formation, photosynthesis and hormone response are associated with male sterility induced by TBM. The results provide new insight into the molecular mechanisms of inducing male sterility by sulfonylurea. Electronic supplementary material The online version of this article (10.1186/s12870-019-1722-1) contains supplementary material, which is available to authorized users.

BackgroundFor most cruciferous plants, which are known as important crops and a number of weeds, hybrid breeding is hampered by the unavailability of a pollination control system. Male sterility induced by a gametocide can be useful for the utilization of plant heterosis.ResultsThe gametocidal effect of sulfonylurea herbicide tribenuron-methyl was tested across seventeen cruciferous species or subspecies including Brassica juncea, B. carinata, B. oleracea ssp. capitata, B. oleracea ssp. acephala, B. rapa ssp. pekinensis, B. rapa ssp. chinensis, B. rapa ssp. parachinensis, B. nigra, Orychophragmus violaceus, Matthiola incana, Raphanus sativa, Sisymbrium altissimum, Eruca sativa, Sinapis alba, Sinapis arvensis, Capsella bursa-pastoris and Camelina sativa. The plants of 23 cultivars in these species or subspecies were foliar sprayed with 10 ml of 0.2 or 0.4 mg/L of tribenuron-methyl before the vacuolated microspore formed in the largest flower buds; the application was repeated ten to twelve days afterwards. Tribenuron-methyl exposure significantly changed the flowering phenology and reproductive function. The treated plants demonstrated a one to four day delay in flowering time and a shortened duration of flowering, as well as other slight phytotoxic effects including a reduction in plant height and floral organ size. Approximately 80% to 100% male sterility, which was estimated by both pollen staining and selfing seed-set rate, was induced in the plants. As a result, plants were rendered functionally able to out-cross, with an average 87% and 54% manually pollinated seed-set rate compared to the corresponding controls at the 0.2 mg/L and 0.4 mg/L doses, respectively.ConclusionsThe results suggested that male reproductive function was much more sensitive to tribenuron-methyl exposure than female function. This sulfonylurea herbicide has a promising use as the gametocide for hybrid production in cruciferous plants.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-017-1019-1) contains supplementary material, which is available to authorized users.

Powdery mildew (PM), caused by Erysiphe cruciferarum, is an epidemic of oil rapeseed (Brassica napus L.) growing worldwide, but PM resistant germplasm is rare in this species. We screened 102 accessions of B. napus and other cruciferous species and found an Ethiopian mustard (Brassica carinata) cultivar 'White flower' immune to PM in both the field and greenhouse. Outcrossing in the female parent 'White flower' was promoted by using a chemical gametocide tribenuron-methyl, to obtain hybrid seeds of distant hybridization with an elite B. napus cultivar 'Zhongshuang11'. Three true F 1 hybrids with B. carinata cytoplasm were obtained without using embryo rescue, which showed complete male sterility and light yellow petals. The hybrid plants and the progenies derived from backcrossing were validated using morphological traits, seed quality, and molecular markers. Five lines in the BC 1 F 3 generation, named 'W7-1', 'W7-4', 'W7-6', 'W8-1', and 'W8-3', and one BC 2 F 2 line 'W3PS-1', whose young leaf was yellow green, were identified to be resistant or moderately resistant to PM. The seed quality and some morphological traits of these lines resembled the parent 'Zhongshuang11', indicating that the resistance gene(s) has been preliminarily introduced into B. napus.

With the rapid development of next-generation sequencing (NGS), multi-omics techniques have been emerging as effective approaches for crop improvement. Here, we focus mainly on addressing the current status and future perspectives toward omics-related technologies and bioinformatic resources with potential applications in crop breeding. Using a large amount of omics-level data from the functional genome, transcriptome, proteome, epigenome, metabolome, and microbiome, clarifying the interaction between gene and phenotype formation will become possible. The integration of multi-omics datasets with pan-omics platforms and systems biology could predict the complex traits of crops and elucidate the regulatory networks for genetic improvement. Different scales of trait predictions and decision-making models will facilitate crop breeding more intelligent. Potential challenges that integrate the multi-omics data with studies of gene function and their network to efficiently select desirable agronomic traits are discussed by proposing some cutting-edge breeding strategies for crop improvement. Multi-omics-integrated approaches together with other artificial intelligence techniques will contribute to broadening and deepening our knowledge of crop precision breeding, resulting in speeding up the breeding process.