Selection efficiency and genetic and biochemical bases of resistance to bacterial wilt in tomato
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Date
1985
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Department of Olericulture, College of Horticulture, Vellanikkara
Abstract
Bacterial wilt (Pseudomona solanacearum E.F. Smith) is a major disease of tomato. Attempts were made to improve a reportedly resistant line CL 32d-0-1-19 GS for higher fruit weight and better plant type through four selection methods – mass, pureline, single seed descent and bulk. Genetic and biochemical bases of resistance were also studied. Resistance of the evolved line was tested in vivo and in vitro. Mass, pureline and SSD methods of selection were effective to improve fruits/plant, locules/fruit, yield/plant and fruit weight. SSD method resulted in higher realized genetic gain for fruits/plant (30.97) locules/fruit (0.5) and yield/plant (1.05 kg). Higher genetic advance and high realized heritability were recorded for days to first harvest in SSD selections. Mass selection had higher realized heritability (0.95) for fruits/plant and high realized heritability (0.65) and realized genetic gain (0.5) for locules/fruit. Fruit weight was improved through pure- line selection. Selections based on trait combination fruits/plant, yield/plant and plant height significantly effected higher locules/fruit (4.2). Selection based on trait combination fruits/plant, yield/plant, locules/fruit and plant height were the earliest to flower (59 days). Days to first harvest were significantly reduced (96 days) through selections based on fruit/plant and yield/plant followed by yield/plant and plant height (98 days). Fruit weight was significantly improved by selections based on yield/plant and locules/fruit (58.5 g). Selections based on yield/plant had high realized heritability (0.59) and realized genetic gain (22.0 g) for fruit weight. Fruit weight was significantly improved by selections based on yield/plant and locules/fruit under SSD method (62.4 g). Transgressive segregants appeared through selection based on yield/plant and locules/fruit. SSD selections had the lowest incidence of wilt (9.86%). Multi- locational trails revealed a survival of 89.5% of plants under normal disease stress. Evaluation of generations from LE79 (CL 32d-0-1-1-1-19GS) x Pusa Ruby Cross indicated a monogenic and incompletely dominant type of gene action for wilt resistance. There was no association between yellow gel colour around the seed and disease resistance. No close linkage between resistance and a fewer locules/fruit was observed. The resistant line (LE79-CL 32d-0-1-1-1-1-19 GS) had higher total and higher root content of Pusa Ruby. - tomatine than the susceptible line - Tomatine content increased and maintained at a higher level in resistant line eventhough the infection progressed consequent to artificial inoculation. Pusa Ruby wilted seven days after inoculation. Total phenol content was higher in roots of Pusa Ruby before and after inoculation. The wilted plants of Pusa Ruby had higher content in root and shoot. The O.D. phenols content was more in the resistant line before and after inoculation. Vitamin C content was also more in roots of LE79 before and after inoculation. A higher ratio of phenols and -tomatine: total phenols, -tomatine: O.D. -tomatine: vitamin C were found in roots of LE79 before inoculation. The wilted plants of Pusa Ruby had lower ration of -tomatine: total phenols and -tomatine: vitamin C. a higher increase in O.D. phenols and vitamin C content on infection was observed in resistant line. The ratio of vitamin C: total phenols was higher in roots of LE79 before infection and the ratio increased in both the lines initially on infection and then decreased but to a greater extent in Pusa Ruby. A higher increase in vitamin C content compared to total phenol was observed in LE79 on infection. A low ratio of total phenol: O.D. phenol was related to resistance in LE79. Inoculation in vitro confirmed the resistance of LE79 to Vellanikkara isolate of Pseudomonas solanacearum E.F. Smith. Grafting of suspectible scion on LE79 delayed wilting of scion even on artificial inoculation.
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