Marker-assisted identification of Meloidogyne incognita and Phytophthora infestans resistant elite indeterminate tomato lines for protected cultivation

To mitigate the effect of root-knot nematode and late blight disease on tomato yield, multiple disease-resistant indeterminate lines were developed and evaluated for resistance to root-knot nematode, Phytophthora late blight and horticultural traits. Among the total thirty-three lines developed, eight lines (LBNR 6-5-1, LBNR 52-5-5, LBNR 77-1-1, LBNR 229-6-4, LBNR 300-1-9, LBNR 300-7-1LBNR 311-2-8 and LBNR 447-2-2) were found promising for both the pathogens, during screening at nursery stage. These eight lines were then evaluated for horticultural traits in root-knot nematode-infested polyhouse. The resistance of these selected lines was again confirmed conventionally as well as using molecular markers specific to Mi and Ph genes. Six lines viz., LBNR 6-5-1, LBNR 52-5-5, LBNR 77-1-1, LBNR 229-6-4, LBNR 300-1-9 and LBNR 300-7-1 confirmed resistance against nematode and possessed Mi 1.2 gene.The nematode-resistant lines also caused 24.78-43.43 per cent reduction in soil nematode population during crop season, over the initial soil nematode population as compared to susceptible lines. For late blight disease, three lines, LBNR 6-5-1, LBNR 52-5-5 and LBNR 229-6-4 exhibited high level of resistance and also possessed both Ph2 and Ph3 genes while two lines, LBNR 77-1-1 and LBNR 300-7-1 showed a resistant reaction. Three lines, LBNR 6-5-1, LBNR 229-6-4 and LBNR 52-5-5 were identified with multiple disease resistance along with superior horticultural traits. The resistant tomato lines with better horticultural traits identified in the current study could be further exploited for commercial purposes in nematode-infested soils or can be used as a parent in tomato improvement programme.