Thursday, December 12, 2019
Genomic Disease Resistance to Late Blight of Tomato-myassignmenthelp
Question: Discuss about theGenomic Disease Resistance to Late Blight of Tomato. Answer: Tomato or Solanum lycopersicum is a very vital vegetable crop in the world. According to the recent estimation, about 4.6 million ha of tomatoes are grown per year around the world, producing over 126million mt (Straquadine, Baig and Mukhtar 2017). Apart from being the second most important vegetable crop, tomatoes are also considered as a model species of plant for many of the genetic studies associated with stress tolerance, fruit quality or several other psychological traits. Furthermore, to meet with the demands for tomatoes, they are also grown in the greenhouse. Due to great economic contribution of tomatoes in the field of agriculture, there is plentiful interest in making use of the genomic tools in order to ameliorate the tomato and grow more new varieties of it. May times, the production of tomatoes are hindered by several fungal diseases such as late blight, fusarium wilt, early blight, verticilium wilt, septoria leaf spot, etc (Ohara et al. 2015). Among all; the late blight is the most critical one. It is one of the most vital foliar fungal disease in tomatoes. It is the same fungus, which created the destructive loss of potatoes in the year 1845 in Europe. It limits the tomato production. Late blight of tomato is considered as one of the most infamous diseases in the field of agriculture (Jung et al. 2015). It is acclaimed as the root of the famous Irish potato famine of the mid nineteenth century that has resulted in the demise of more than two million people in Ireland. The disease in fact spurred the exposure of the study of plant pathology. During his studies to understand the root cause of late blight, Anton deBary, the botanist demonstrated that a fungal-like growth on the blighted plants was the reason behind it. This had led other scientists and botanists to investigate on other bacteria and fungi that were related to plant diseases and along with the expansion of the Kochs postulates for initiating pathogenicity, causal pathogens of several plant diseases have been identified. The late blight is originated by oomycete pathogen called the Phytophthora infestans (Zuluaga et al. 2016). It in fact is fundamentally a pathogen of tomatoes and potatoes. However, it has also been known to infect the other adherents of the plant family of Solanaceae. It is also significant for having both sexual and asexual life. However, the disease is also referred to as community disease as it has the ability to circulate or spread speedily from one field to another under right weather conditions. It is mostly favored by humid, foggy or raining conditions and cool temperature. It quickly ruins the entire crop and supplies a good source of infections for the other plants. Hence, it is very important for the gardeners to understand the fact that the disease of tomato late blight is not like the other usual tomato diseases. The other diseases causes very limited damage but Late blight in fact, kills the plants completely and is highly infectious and communicable. Late blight is one of the known destructive diseases of tomatoes in the world. Because of the emergence of the very new and aggressive isolates of Phytophthora infestans, identification of new genomic diseases resistance to Late Blight is a top most priority in breeding of tomatoes. The term phytophthora is a Latin term, which means plant destroyer (Lazebnik et al. 2017). The tissues of the infected plants die and the outbreak grow and spread rapidly as the pathogen has the ability to produce a large number of wind-dispersed spores. If once a plant gets infected, it is bound to destroy. Its occurrence in a garden may even affect the other gardens as well and this is due to wind dispersion of the spores. From the popular Irish famine, there has been a high amount interest of the researchers in the disease of late blight. At first, it they studied the affect of the same in potatoes but later the study was held in tomatoes as well. The three major genetic disease resistances against LB include Ph-1, Ph-2 and the Ph-3 (Luan et al. 2018). These resistances have been charted to the tomato chromosomes 7, 10 and 9 respectively. The Ph-1 is a single dominant gene that provides resistance in order to trace the race T-0, but it was speedily mastered by the new races of pathogen. It was portrayed to the very distant end of the chromosome 7 by making use of morphological markers but it has been reported that there was no molecular marker that was related with this resistance gene. The Ph-2 on the other hand is a single insufficient-dominant gene that was portrayed to the very lower end of the prolonged arm of the tomato chromosome 10. It supplies limited resistance to various isolates of the rac e T-1. Ph-3 was primarily discovered in the accessions of S. pimpinellifolium- L3708 and L3707 in Taiwan (Siedl Johnson, Jordan and Gevens 2014). At present, Ph-3 is the most useful among the three major genetic disease resistances. It benefits insufficient dominant resistance against wide array of Phytophthora infestans tomato isolates including the ones that overcomes both Ph-1 and Ph-2. It has been portrayed to the very lower end of the prolonged arm of the tomato chromosome 9 and near the RFLP marker- TG591. Ph-3 has been portrayed in the 0.5cM genomic area of the long arm of chromosome 9 in between the P55 and Indel_3 molecular markers. In addition to these, there are several reports on the quantitative resistance to the late blight as well as the QTLs (Quantitative trait loci) that are related to it. In a study, the reciprocal backcross (BC) populations that are derived from the Solanum habrochaites x Solanum lycopersicum were evaluated by using three kinds of copied disease essays i.e. whole-plant, field and detached-leaflet (Haggard, Johnson and Clair 2015). The linkage maps were developed for each of the BC population by making use of RFLPS. The resistance QTLs was spotted on all of the twelve tomato chromosomes by using interval mapping. Someof the Phytophthora infestansresistance QTLs were identified in the tomato tallied with the chromosomal locations of earlier charted QTLs and the R genes in potato for resistance toPhytophthora infestans, which suggests functional conservation of the resistance in theSolanaceae. Tomato is the one of the most consumed vegetable crops in the world but the emergence of the late blight is considerably limiting its production worldwide. The QTL analysis and the molecular markers analysis works that are executed so far has been very competent for detecting the resistance gene or genes on the genome of the tomatoes and to accomplish marker-assisted choice for few fungus related diseases. As the whole genome succession of tomato is available now, it will be very useful for advancing the molecular breeding through smoothing the positional cloning and marker-assisted selection. References: Haggard, J.E., Johnson, E.B. and Clair, D.A.S., 2015. Multiple QTL for horticultural traits and quantitative resistance to Phytophthora infestans linked on Solanum habrochaites chromosome 11.G3: Genes, Genomes, Genetics,5(2), pp.219-233. Jung, J., Kim, H.J., Lee, J.M., Oh, C.S., Lee, H.J. and Yeam, I., 2015. Gene-based molecular marker system for multiple disease resistances in tomato against Tomato yellow leaf curl virus, late blight, and verticillium wilt.Euphytica,205(2), pp.599-613. Lazebnik, J., Tibboel, M., Dicke, M. and Loon, J.J., 2017. Inoculation of susceptible and resistant potato plants with the late blight pathogen Phytophthora infestans: effects on an aphid and its parasitoid.Entomologia Experimentalis et Applicata,163(3), pp.305-314. Luan, Y., Cui, J., Li, J., Jiang, N., Liu, P. and Meng, J., 2018. Effective enhancement of resistance to Phytophthora infestans by overexpression of miR172a and b in Solanum lycopersicum.Planta,247(1), pp.127-138. Ohara, T., Ishida, Y., Kudou, R., Kakibuchi, K., Akimitsu, K., Izumori, K. and Tajima, S., Kagawa University and Mitsui Agro Chemicals Inc, 2015.Plant disease control agent comprising D-tagatose as active ingredient, and plant disease control method. U.S. Patent 9,125,409. Seidl Johnson, A.C., Jordan, S.A. and Gevens, A.J., 2014. Novel resistance in heirloom tomatoes and effectiveness of resistance in hybrids to Phytophthora infestans US-22, US-23, and US-24 clonal lineages.Plant Disease,98(6), pp.761-765. Straquadine, G.S., Baig, M.B. and Mukhtar, M., 2017. Journal of Experimental Biology and Agricultural Sciences.Journal of Experimental Biology. Zuluaga, A.P., Vega?Arregun, J.C., Fei, Z., Matas, A.J., Patev, S., Fry, W.E. and Rose, J.K., 2016. Analysis of the tomato leaf transcriptome during successive hemibiotrophic stages of a compatible interaction with the oomycete pathogen Phytophthora infestans.Molecular plant pathology,17(1), pp.42-54.