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Cultivated gerbera (Gerbera hybrida; Asteraceae) is an economically important flower worldwide. It is also used as a model plant for studying flower development and understanding biosynthesis of secondary metabolites. Genetic variation in cultivated gerbera is narrow; therefore, increased genetic variation is much needed for further improvement of gerbera. Polyploidization has played an extremely important role in the diversification, evolution, domestication and breeding of many plant species. In this study, tetraploids were induced by treating the apical meristems of gerbera seedlings with colchicine. The nuclear DNA content of tetraploid gerbera was increased to 10.41 pg/2C from 5.22 pg/2C. Induced tetraploids had larger, fewer stomata and wider, thicker leaves than diploids, resulting an increased leaf index. With tetraploidization, flower scapes became thicker, flowers were larger, ray florets became wider, and the center eye (composed of disc florets) was larger. Induced tetraploids showed lower but still high pollen stainability and are expected to be quite fertile and be able to serve as parents for production of triploids. Some of the morphological changes associated with induced tetraploidy, including larger flowers, thicker ray florets, larger eyes and/or thicker scapes, will be beneficial for gerbera flower quality and vase life, while other changes such as stomatal size and density and thicker leaves may change and improve gerbera tolerance to stresses. Induced gerbera tetraploids may be valuable for breeding, genetic research and increasing genetic diversity in gerbera.
Krishna Bhattarai; Abdul Kareem; Zhanao Deng. In vivo induction and characterization of polyploids in gerbera daisy. Scientia Horticulturae 2021, 282, 110054 .
AMA StyleKrishna Bhattarai, Abdul Kareem, Zhanao Deng. In vivo induction and characterization of polyploids in gerbera daisy. Scientia Horticulturae. 2021; 282 ():110054.
Chicago/Turabian StyleKrishna Bhattarai; Abdul Kareem; Zhanao Deng. 2021. "In vivo induction and characterization of polyploids in gerbera daisy." Scientia Horticulturae 282, no. : 110054.
Background RNA sequencing has been widely used to profile genome-wide gene expression and identify candidate genes controlling disease resistance and other important traits in plants. Gerbera daisy is one of the most important flowers in the global floricultural trade, and powdery mildew (PM) is the most important disease of gerbera. Genetic improvement of gerbera PM resistance has become a crucial goal in gerbera breeding. A better understanding of the genetic control of gerbera resistance to PM can expedite the development of PM-resistant cultivars. Results The objectives of this study were to identify gerbera genotypes with contrasting phenotypes in PM resistance and sequence and analyze their leaf transcriptomes to identify disease resistance and susceptibility genes differentially expressed and associated with PM resistance. An additional objective was to identify SNPs and SSRs for use in future genetic studies. We identified two gerbera genotypes, UFGE 4033 and 06–245-03, that were resistant and susceptible to PM, respectively. De novo assembly of their leaf transcriptomes using four complementary pipelines resulted in 145,348 transcripts with a N50 of 1124 bp, of which 67,312 transcripts contained open reading frames and 48,268 were expressed in both genotypes. A total of 494 transcripts were likely involved in disease resistance, and 17 and 24 transcripts were up- and down-regulated, respectively, in UFGE 4033 compared to 06–245-03. These gerbera disease resistance transcripts were most similar to the NBS-LRR class of plant resistance genes conferring resistance to various pathogens in plants. Four disease susceptibility transcripts (MLO-like) were expressed only or highly expressed in 06–245-03, offering excellent candidate targets for gene editing for PM resistance in gerbera. A total of 449,897 SNPs and 19,393 SSRs were revealed in the gerbera transcriptomes, which can be a valuable resource for developing new molecular markers. Conclusion This study represents the first transcriptomic analysis of gerbera PM resistance, a highly important yet complex trait in a globally important floral crop. The differentially expressed disease resistance and susceptibility transcripts identified provide excellent targets for development of molecular markers and genetic maps, cloning of disease resistance genes, or targeted mutagenesis of disease susceptibility genes for PM resistance in gerbera.
Krishna Bhattarai; Ana Conesa; Shunyuan Xiao; Natalia A. Peres; David G. Clark; Saroj Parajuli; Zhanao Deng. Sequencing and analysis of gerbera daisy leaf transcriptomes reveal disease resistance and susceptibility genes differentially expressed and associated with powdery mildew resistance. BMC Plant Biology 2020, 20, 1 -17.
AMA StyleKrishna Bhattarai, Ana Conesa, Shunyuan Xiao, Natalia A. Peres, David G. Clark, Saroj Parajuli, Zhanao Deng. Sequencing and analysis of gerbera daisy leaf transcriptomes reveal disease resistance and susceptibility genes differentially expressed and associated with powdery mildew resistance. BMC Plant Biology. 2020; 20 (1):1-17.
Chicago/Turabian StyleKrishna Bhattarai; Ana Conesa; Shunyuan Xiao; Natalia A. Peres; David G. Clark; Saroj Parajuli; Zhanao Deng. 2020. "Sequencing and analysis of gerbera daisy leaf transcriptomes reveal disease resistance and susceptibility genes differentially expressed and associated with powdery mildew resistance." BMC Plant Biology 20, no. 1: 1-17.
Lantana (Lantana camara L., Verbenaceae) is an important ornamental crop, yet can be a highly invasive species. The formation of unreduced female gametes (UFGs) is a major factor contributing to its invasiveness and has severely hindered the development of sterile cultivars. To enrich the genomic resources and gain insight into the genetic mechanisms of UFG formation in lantana, we investigated the transcriptomes of young ovaries of two lantana genotypes, GDGHOP-36 (GGO), producing 100% UFGs, and a cultivar Landmark White Lantana (LWL), not producing UFGs. The de novo transcriptome assembly resulted in a total of 90,641 unique transcript sequences with an N50 of 1692 bp, among which, 29,383 sequences contained full-length coding sequences (CDS). There were 214 transcripts associated with the biological processes of gamete production and 10 gene families orthologous to genes known to control unreduced gamete production in Arabidopsis. We identified 925 transcription factor (TF)-encoding sequences, 91 nucleotide-binding site (NBS)-containing genes, and gene families related to drought/salt tolerance and allelopathy. These genomic resources and candidate genes involved in gamete formation will be valuable for developing new tools to control the invasiveness in L. camara, protect native lantana species, and understand the formation of unreduced gametes in plants.
Ze Peng; Krishna Bhattarai; Saroj Parajuli; Zhe Cao; Zhanao Deng. Transcriptome Analysis of Young Ovaries Reveals Candidate Genes Involved in Gamete Formation in Lantana camara. Plants 2019, 8, 263 .
AMA StyleZe Peng, Krishna Bhattarai, Saroj Parajuli, Zhe Cao, Zhanao Deng. Transcriptome Analysis of Young Ovaries Reveals Candidate Genes Involved in Gamete Formation in Lantana camara. Plants. 2019; 8 (8):263.
Chicago/Turabian StyleZe Peng; Krishna Bhattarai; Saroj Parajuli; Zhe Cao; Zhanao Deng. 2019. "Transcriptome Analysis of Young Ovaries Reveals Candidate Genes Involved in Gamete Formation in Lantana camara." Plants 8, no. 8: 263.
Bacterial spot (BS), caused by four species of Xanthomonas: X. euvesicatoria, X. vesicatoria, X. perforans and X. gardneri in tomato (Solanum lycopersicum L.) results in severe loss in yield and quality by defoliation and the appearance of lesions on fruits, respectively. The combined industry standard for BS control (foliar applications Actigard® rotated with copper plus mancozeb) does not offer sufficient protection, especially when weather conditions favor disease spread. Development of tomato cultivars with BS resistance is thus an important measure to minimize losses. Hypersensitive and non-hypersensitive resistance has been identified in different wild accessions and cultivated tomato relatives and has been transferred to cultivated tomato. However, complete resistance is yet to be obtained. With the advent of next generation sequencing and precise genome editing tools, the genetic regions that confer resistance to bacterial spot can be targeted and enriched through gene pyramiding in a new commercial cultivar which may confer higher degree of horizontal resistance to multiple strains of Xanthomonas causing bacterial spot in tomato.
Sadikshya Sharma; Krishna Bhattarai. Progress in Developing Bacterial Spot Resistance in Tomato. Agronomy 2019, 9, 26 .
AMA StyleSadikshya Sharma, Krishna Bhattarai. Progress in Developing Bacterial Spot Resistance in Tomato. Agronomy. 2019; 9 (1):26.
Chicago/Turabian StyleSadikshya Sharma; Krishna Bhattarai. 2019. "Progress in Developing Bacterial Spot Resistance in Tomato." Agronomy 9, no. 1: 26.
Impatiens downy mildew (IDM) is a devastating disease to garden impatiens. A good understanding of IDM resistance in New Guinea impatiens is essential for improving garden impatiens resistance to this disease. The present study was conducted to sequence, assemble, annotate and compare the leaf transcriptomes of two impatiens cultivars differing in resistance to IDM, reveal sequence polymorphisms and identify candidate genes for IDM resistance. RNA-Seq was performed on cultivars Super Elfin® XP Pink (SEP) and SunPatiens® Compact Royal Magenta (SPR). De novo assembly of obtained sequence reads resulted in 121,497 unigenes with an average length of 1156 nucleotides and N50 length of 1778 nucleotides. Searching the non-redundant protein and non-redundant nucleotide, Swiss-Prot, Kyoto Encyclopedia of Genes and Genomes and Clusters of Orthologous Groups and Gene Ontology databases, resulted in annotation of 57.7% to 73.6% of the unigenes. Fifteen unigenes were highly similar to disease resistance genes and more abundant in the IDM-resistant cultivar than in the susceptible cultivar. A total of 22,484 simple sequence repeats (SSRs) and 245,936 and 120,073 single nucleotide polymorphisms (SNPs) were identified from SPR and SEP respectively. The assembled transcripts and unigenes, identified disease resistance genes and SSRs and SNPs sites will be a valuable resource for improving impatiens and its IDM resistance.
Krishna Bhattarai; Weining Wang; Zhe Cao; Zhanao Deng. Comparative Analysis of Impatiens Leaf Transcriptomes Reveal Candidate Genes for Resistance to Downy Mildew Caused by Plasmopara obducens. International Journal of Molecular Sciences 2018, 19, 2057 .
AMA StyleKrishna Bhattarai, Weining Wang, Zhe Cao, Zhanao Deng. Comparative Analysis of Impatiens Leaf Transcriptomes Reveal Candidate Genes for Resistance to Downy Mildew Caused by Plasmopara obducens. International Journal of Molecular Sciences. 2018; 19 (7):2057.
Chicago/Turabian StyleKrishna Bhattarai; Weining Wang; Zhe Cao; Zhanao Deng. 2018. "Comparative Analysis of Impatiens Leaf Transcriptomes Reveal Candidate Genes for Resistance to Downy Mildew Caused by Plasmopara obducens." International Journal of Molecular Sciences 19, no. 7: 2057.
Cultivated tomato has been in existence for about 400 years and breeding activities have been conducted for only eight decades. However, more than 10,000 tomato cultivars have already been developed. Ninety-one tomato genotypes were characterized for twenty-one morphological traits using developmental, vegetative, and fruit traits. Correlation, principal component, and cluster analysis between the traits were carried out. Higher correlations between fruit traits including fruit shape, fruit size, and fruit types were observed. These correlations indicate that specific fruit types require specific traits like branched inflorescence and a greater number of fruits per inflorescence are beneficial only for smaller fruit sizes like cherry and grape tomatoes. Contrastingly, traits like determinate growth habit and fruit maturity are preferred in all fruit types of tomato for better cultivation practices and longer production duration and hence showed lower correlations. Principal component analysis clustered tomato genotypes into three main clusters with multiple subgroups. Similar tomato genotypes were placed into one or more clusters confirming the results from correlation analysis. Involvement of private breeding programs in cultivar development has increased the competition on introgression of novel and desired traits across new cultivars. Understanding the diversity present in modern cultivars and potential traits identification in related wild species can enhance tomato diversity and improve quality and production.
Krishna Bhattarai; Sadikshya Sharma; Dilip R. Panthee. Diversity among Modern Tomato Genotypes at Different Levels in Fresh-Market Breeding. International Journal of Agronomy 2018, 2018, 1 -15.
AMA StyleKrishna Bhattarai, Sadikshya Sharma, Dilip R. Panthee. Diversity among Modern Tomato Genotypes at Different Levels in Fresh-Market Breeding. International Journal of Agronomy. 2018; 2018 ():1-15.
Chicago/Turabian StyleKrishna Bhattarai; Sadikshya Sharma; Dilip R. Panthee. 2018. "Diversity among Modern Tomato Genotypes at Different Levels in Fresh-Market Breeding." International Journal of Agronomy 2018, no. : 1-15.
Tomato (Solanum lycopersicum) is the second most important vegetable crop in the world. Bacterial spot (BS) of tomato, caused by four species of Xanthomonas: X. euvesicatoria, X. vesicatoria, X. perforans and X. gardneri, results in severe loss in yield and quality due to defoliation and formation of lesions on fruits, respectively. Currently management practices do not offer effective control under conditions of high disease pressure. Thus, developing BS resistance is a critical priority for tomato growers in order to minimize crop losses. Sixty-three advanced tomato breeding lines, heirlooms and wild tomato lines with diverse genetic backgrounds were screened under greenhouse and field conditions for BS resistance using X. perforans race T4, which was found to be a prevalent race in North Carolina. Race T4 isolate 9 was used to inoculate the plants by spraying, and disease severity was measured using the Horsfall–Barratt scale. Tomato lines 74L-1W(2008), NC2CELBR, 081-12-1X-gsms, NC22L-1 (2008) and 52LB-1 showed resistance to BS in the field and/or greenhouse trials. These lines were derived from S. pimpinellifolium L3707. Screening L3707 followed by development of a mapping population and mapping resistance genes might be useful for breeding resistance against BS in future breeding programmes.
Krishna Bhattarai; Frank Louws; J. D. Williamson; D. R. Panthee. Resistance to Xanthomonas perforans race T4 causing bacterial spot in tomato breeding lines. Plant Pathology 2017, 66, 1103 -1109.
AMA StyleKrishna Bhattarai, Frank Louws, J. D. Williamson, D. R. Panthee. Resistance to Xanthomonas perforans race T4 causing bacterial spot in tomato breeding lines. Plant Pathology. 2017; 66 (7):1103-1109.
Chicago/Turabian StyleKrishna Bhattarai; Frank Louws; J. D. Williamson; D. R. Panthee. 2017. "Resistance to Xanthomonas perforans race T4 causing bacterial spot in tomato breeding lines." Plant Pathology 66, no. 7: 1103-1109.
Krishna Bhattarai; Frank J. Louws; John D. Williamson; Dilip R. Panthee. Diversity analysis of tomato genotypes based on morphological traits with commercial breeding significance for fresh market production in eastern USA. Australian Journal of Crop Science 2016, 10, 1098 -1103.
AMA StyleKrishna Bhattarai, Frank J. Louws, John D. Williamson, Dilip R. Panthee. Diversity analysis of tomato genotypes based on morphological traits with commercial breeding significance for fresh market production in eastern USA. Australian Journal of Crop Science. 2016; 10 (8):1098-1103.
Chicago/Turabian StyleKrishna Bhattarai; Frank J. Louws; John D. Williamson; Dilip R. Panthee. 2016. "Diversity analysis of tomato genotypes based on morphological traits with commercial breeding significance for fresh market production in eastern USA." Australian Journal of Crop Science 10, no. 8: 1098-1103.
Horticulture Research is a new Open Access, fully peer-reviewed journal which will publish the best and most interesting research focusing on all major horticultural crops from around the world.
Krishna Bhattarai; Frank Louws; John D Williamson; Dilip R Panthee. Differential response of tomato genotypes to Xanthomonas-specific pathogen-associated molecular patterns and correlation with bacterial spot (Xanthomonas perforans) resistance. Horticulture Research 2016, 3, 1 .
AMA StyleKrishna Bhattarai, Frank Louws, John D Williamson, Dilip R Panthee. Differential response of tomato genotypes to Xanthomonas-specific pathogen-associated molecular patterns and correlation with bacterial spot (Xanthomonas perforans) resistance. Horticulture Research. 2016; 3 (1):1.
Chicago/Turabian StyleKrishna Bhattarai; Frank Louws; John D Williamson; Dilip R Panthee. 2016. "Differential response of tomato genotypes to Xanthomonas-specific pathogen-associated molecular patterns and correlation with bacterial spot (Xanthomonas perforans) resistance." Horticulture Research 3, no. 1: 1.