Evaluation of tomato genotypes for resistance to bud necrosis disease caused by groundnut bud necrosis virus (GBNV)

Abstract Bud necrosis disease has emerged as the major threat for tomato cultivation throughout the Asia, including India. Several strategies are being explored for the management of the disease and its vector thrips. Of the available, the most effective and practical way to manage the tospoviral diseases is to adopt resistant cultivars. However, work on development of resistant cultivars/hybrids to bud necrosis disease is very limited, due to the non-availability of resistant sources. Hence, in the present investigation, forty tomato genotypes comprising of nine different species were evaluated using two different GBNV isolates maintained at Indian Institute of Agricultural Research (IARI), New Delhi and at Indian Institute of Horticultural Research (IIHR), Bengaluru, under glasshouse conditions through mechanical sap transmission. Evaluated genotypes exhibited differential response in terms of symptom expression from mild chlorosis to severe bud necrosis, toppling and death of plants post GBNV infection. The genotypes which showed resistance and moderately resistance responses under glasshouse conditions were screened further under natural epiphytotic conditions along with two susceptible checks (PKM-1 and Pusa Ruby) at both the locations in all the three cropping seasons. Under field evaluation, only three genotypes (IIHR-2988, IIHR-2901 and IIHR-1940) were found to be resistant and three more (IIHR-2953, IIHR-2809 and IIHR-2101) were found to be moderately resistant, while the remaining thirty-four genotypes were turned out to be susceptible or highly susceptible. Maximum disease incidence (40%) under field conditions was recorded in the kharif crop. Significant difference was observed in the host response/severity to the two different isolates of GBNV, except in the resistant and moderately resistant lines. Furthermore, there was a high correlation between the findings of glasshouse and field-based screening, yet these results are to be validated further by thrips inoculation. Out of the nine different species of tomato evaluated, only S. chilense, S. peruvianum, and the advance breeding lines derived from them were showing resistance or moderately resistance response to GBNV. The resistant lines identified in the present investigation can be utilized to study the genetics of resistance and for the development of molecular markers linked to GBNV resistance, which subsequently will help to incorporate the resistant genes into several elite backgrounds of tomato.