Current Status of Early Blight Resistance in Tomato: An Update

Abstract

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.

Microbial community dynamics in the recirculating nutrient solution of tomato plug seedlings cultivated under ebb-and-flow system

“…Additionally, some potentially pathogenic fungi including F. oxysporum and A. alternate, were increased considerably in the nutrient solution or substrate samples. Of them, F. oxysporum can cause Fusarium wilt in tomato, and A. alternate is responsible for many tomato diseases, e.g., stem canker, black mold rot, leaf spot, early blight, and black shoulder disease [33][34][35]. We also identified P. krajdenii, a pathogenic fungus causing petri disease in grapevine [36].…”

VARIATION IN AGGRESSIVENESS AND AFLP AMONG Alternaria solani ISOLATES FROM INDONESIA

“…It is hardly possible to identify tomato and potato germplasm with race-specific resistance since results of genetic studies on resistance to A. solani derived from different donors point to the same conclusion that resistance to the pathogen is expressed quantitatively that is controlled by minor genes (Chaerani et al 2007;Odilbekov 2015;Adhikari et al 2017). Averages of 8 plants × 3 replicates.…”

“…solani is difficult to control since it has a short life cycle, is primarily air borne, has long survival ability in plant debris and soil, and has a wide solanaceaous host range (Chaerani and Voorrips 2006). Host resistance is the most economically and environmentally sound approach over fungicidal spray to restrict early blight incidence in the field, but tomato and potato cultivars with high level of early blight resistance and desirable horticultural traits have not been identified (Gardner and Panthee 2012;Odilbekov 2015;Adhikari et al 2017).…”

“…The occurrence of differential aggressiveness among isolates has led to the conclusion for the presence of physiological races (Bonde 1929). However, the race concept in A. solani has not been widely accepted due to lack of characterized differential varieties (Chaerani and Voorrips 2006;Gannibal et al 2014;Adhikari et al 2017) Genetic variation within A. solani populations has been assessed using various molecular markers which included random amplified polymorphic DNA (RAPD) (Weir et al 1998;Varma et al 2006;Kumar et al 2008;Lourenço Jr et al 2011;Weber and Halterman 2012;Leiminger et al 2013), random amplified microsatellites (RAMS) (van der Waals et al 2004), amplified fragment length polymorphism (AFLP) (Martinez et al 2004;Lourenço Jr et al 2011;Odilbekov et al 2016), and simple sequence repeats (SSRs) (Meng et al 2015), as well as sequence analyses of A. solani genome portion (Lourenço et al 2009;Weber and Halterman 2012). Among different types of molecular markers, AFLP marker has become one of the major methods of choice for studies of genetic diversity because it does not require prior knowledge of genomic sequence and generates a large number of polymorphic loci in a single experiment (Martinez et al 2004;Odilbekov et al 2016).…”

In vitro antimicrobial effect of metallic nanoparticles on phytopathogenic strains of crop plants

“…Another fungal disease is early blight, and yield losses have been estimated at 79% produced by Alternaria solani (Adhikari, Oh, & Panthee, 2017). Also, the bacteria Clavibacter michiganensis (Smith) and Pseudomonas syringae Van Hall are the agents that cause bacterial cankers and bacterial specks on tomatoes (Blank et al, 2016;Kolomiiets, Grygoryuk, Butsenko, & Kalinichenko, 2019).…”