@article{adhikari_siddique_louws_panthee_2023, title={Identification of quantitative trait loci associated with bacterial spot race T4 resistance in intra-specific populations of tomato (Solanum lycopersicum L.)}, volume={18}, ISSN={1932-6203}, url={http://dx.doi.org/10.1371/journal.pone.0295551}, DOI={10.1371/journal.pone.0295551}, abstractNote={Bacterial spot of tomato is a serious disease caused by at least four species and four races of Xanthomonas- X. euvesicatoria (race T1), X. vesicatoria (race T2), X. perforans (race T3 and T4), and X. gardneri, with X. perforans race T4 being predominant in the southeast USA. Practical management of this disease is challenging because of the need for more effective chemicals and commercially resistant cultivars. Identification of genetic resistance is the first step to developing a disease-resistant variety. The objective of this study was to identify quantitative trait loci (QTL) conferring resistance to race T4 in two independent recombinant inbred lines (RILs) populations NC 10204 (intra-specific) and NC 13666 (interspecific) developed by crossing NC 30P x NC22L-1(2008) and NC 1CELBR x PI 270443, respectively. Seven QTLs on chromosomes 2, 6, 7, 11, and 12 were identified in NC 10204. The QTL on chromosome 6 explained the highest percentage of phenotypic variance (up to 21.3%), followed by the QTL on chromosome 12 (up to 8.2%). On the other hand, the QTLs on chromosomes 1, 3, 4, 6, 7, 8, 9, and 11 were detected in NC 13666. The QTLs on chromosomes 6, 7, and 11 were co-located in NC 10204 and NC 13666 populations. The donor of the resistance associated with these QTL in NC 10204 is a released breeding line with superior horticultural traits. Therefore, both the donor parent and the QTL information will be useful in tomato breeding programs as there will be minimal linkage drag associated with the bacterial spot resistance.}, number={12}, journal={PLOS ONE}, publisher={Public Library of Science (PLoS)}, author={Adhikari, Pragya and Siddique, Muhammad Irfan and Louws, Frank J. and Panthee, Dilip R.}, editor={Pandey, Abhay K.Editor}, year={2023}, month={Dec}, pages={e0295551} }
 @article{adhikari_adhikari_timilsina_meadows_jones_panthee_louws_2019, title={Phenotypic and Genetic Diversity of Xanthomonas perforans Populations from Tomato in North Carolina}, volume={109}, ISSN={["1943-7684"]}, url={http://dx.doi.org/10.1094/phyto-01-19-0019-r}, DOI={10.1094/PHYTO-01-19-0019-R}, abstractNote={Bacterial spot caused by Xanthomonas spp. is one of the most devastating diseases of tomato in North Carolina (NC). In total, 290 strains of Xanthomonas spp. from tomato in NC collected over 2 years (2015 and 2016) were analyzed for phenotypic and genetic diversity. In vitro copper and streptomycin sensitivity assays revealed that >95% (n = 290) of the strains were copper tolerant in both years, whereas 25% (n = 127) and 46% (n = 163) were streptomycin tolerant in 2016 and 2015, respectively. Using BOX repetitive element PCR assay, fingerprint patterns showed four haplotypes (H1, H2, H3, and H4) among the strains analyzed. The multiplex real-time quantitative PCR on a subset of representative strains (n = 45) targeting the highly conserved hrcN gene identified Xanthomonas strains from tomato in NC that belonged to X. perforans. Race profiling of the representative strains (n = 45) on tomato and pepper differentials confirmed that ∼9 and 91% of strains are tomato races T3 and T4, respectively. Additionally, PCR assays and sequence alignments confirmed that the copL, copA, copB (copLAB copper tolerance gene cluster), and avrXv4 genes are present in the strains analyzed. Phylogenetic and comparative sequence analyses of six genomic regions (elongation factor G [fusA], glyceraldehyde-3-phosphate dehydrogenase A [gapA], citrate synthase [gltA], gyrase subunit B [gyrB], ABC transporter sugar permease [lacF], and GTP binding protein [lepA]) suggested that 13 and 74% of X. perforans strains from NC were genetically similar to races T3 and T4 from Florida, respectively. Our results provide insights that bacterial spot management practices in tomato should focus on deploying resistance genes to combat emerging pathogenic races of X. perforans and overcome the challenges currently posed by intense use of copper-based bactericides.}, number={9}, journal={PHYTOPATHOLOGY}, publisher={Scientific Societies}, author={Adhikari, Pragya and Adhikari, Tika B. and Timilsina, Sujan and Meadows, Inga and Jones, Jeffrey B. and Panthee, Dilip R. and Louws, Frank J.}, year={2019}, month={Sep}, pages={1533–1543} }
 @article{adhikari_oh_panthee_2017, title={Current Status of Early Blight Resistance in Tomato: An Update}, volume={18}, ISSN={1422-0067}, url={http://dx.doi.org/10.3390/ijms18102019}, DOI={10.3390/ijms18102019}, abstractNote={Early blight (EB) is one of the dreadful diseases of tomato caused by several species of Alternaria including Alternaria linariae (which includes A. solani and A. tomatophila), as well as A. alternata. In some instances, annual economic yield losses due to EB have been estimated at 79%. Alternaria are known only to reproduce asexually, but a highly-virulent isolate has the potential to overcome existing resistance genes. Currently, cultural practices and fungicide applications are employed for the management of EB due to the lack of strong resistant cultivars. Resistance sources have been identified in wild species of tomato; some breeding lines and cultivars with moderate resistance have been developed through conventional breeding methods. Polygenic inheritance of EB resistance, insufficient resistance in cultivated species and the association of EB resistance with undesirable horticultural traits have thwarted the effective breeding of EB resistance in tomato. Several quantitative trait loci (QTL) conferring EB resistance have been detected in the populations derived from different wild species including Solanum habrochaites, Solanum arcanum and S. pimpinellifolium, but none of them could be used in EB resistance breeding due to low individual QTL effects. Pyramiding of those QTLs would provide strong resistance. More research is needed to identify additional sources of useful resistance, to incorporate resistant QTLs into breeding lines through marker-assisted selection (MAS) and to develop resistant cultivars with desirable horticultural traits including high yielding potential and early maturity. This paper will review the current understanding of causal agents of EB of tomato, resistance genetics and breeding, problems associated with breeding and future prospects.}, number={10}, journal={International Journal of Molecular Sciences}, publisher={MDPI AG}, author={Adhikari, Pragya and Oh, Yeonyee and Panthee, Dilip}, year={2017}, month={Sep}, pages={2019} }