PhD

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.