PhD

Brinjal shoot and fruit borer is one of the most devastating pests of brinjal.
It is a major bottle neck in the cultivation of egg plant. Identification of resistant
sources and transfer of these genes into the high yielding varieties is an important
step in mitigating the damage caused by this pest. Keeping the above facts in
view, the present investigation entitled “Breeding brinjal (Solanum melongena L.)
for resistance to brinjal shoot and fruit borer” was taken up in the Department of
Plant Breeding and Genetics from Sept 2017- April 2021.
Thirty one accessions belonging to eight different species of Solanum
were evaluated in the field for resistance to brinjal shoot and fruit borer during
Aug- Nov 2018. The treatments showed significant difference for all the
characters studied. The highest number of primary branches was observed in
IC618034 belonging to S. virginianum and the lowest number was observed in
IC618035 belonging to Solanum melongena. Infestation of shoots by borer
started nearly 7th week after transplanting. The number of damaged shoots was
highest in Surya. The per cent shoot infestation ranged from 0 to 75 per cent. The
wild accessions were resistant to brinjal shoot and fruit borer and only the
melongena lines exhibited considerable damage. The extent of per cent fruit
damage ranged from 0 per cent in the wild accessions to 64.67 per cent in Arka
Neelkanth. Yield per plant and marketable yield per plant was highest in Vengeri.
Based on the observation from the screening experiment conducted during
August –November 2018, eleven accessions were evaluated further for a
confirmatory screening during March- July 2020. As there was considerable
infestation by borer, artificial inoculation was not carried out. There was
significant difference among the treatments for the characters studied. Highest
yield per plant and marketable yield per plant was observed in Vengeri. Lowest
yield was observed in IC624241 and IC624239. Yield loss was highest in Ponni
and lowest in IC624239. The resistance index developed by Mishra et al. (1988)
was followed to classify the accessions. The accessions IC618035, IC618044,
IC624241, Arka Kusumkar and Vengeri were graded as resistant (1-10 %) with
respect to per cent shoot damage. Based on the extent the of fruit damage, the
accessions IC618035, IC618044 and IC624239 and Arka Kusumkar were graded
as moderately resistant (11-20%). IC624241 and Vengeri were graded as resistant
(0-10%). Haritha, Surya, Arka Keshav, Ponni and Arka Neelkanth were graded as
highly susceptible (>40 %).
The biophysical, anatomical and biochemical basis of resistance was
elucidated in the selected accessions. Trichomes in Solanum sps. were stellate in
shape with six trichome strands forming one asterisk. Trichome density on calyx
was negatively and significantly correlated with shoot damage while trichome
density on leaf was positively and significantly correlated with shoot damage.
Pericarp thickness, fruit breadth, total sugar content and total nitrogen content
were positively and significantly correlated with per cent fruit damage. Total
phenol content showed a significant negative correlation with the per cent fruit
infestation. The resistant lines IC618035, IC618044, IC624241, Arka Kusumkar
and Vengeri were characterized by thick epidermis and cuticle, dense and
compact cortex and cambium, well developed vascular bundles and small pith.
IC618044, IC624241, IC618035, Arka Kusumkar and Vengeri falling
under the resistant and moderately resistant category were selected as testers to
cross with highly susceptible lines Haritha, Ponni and Arka Neelkanth. The
twelve hybrids and parents were screened in the field along with the hybrid
‘Neelima’ as check during Dec 2020- April 2021 to check the per cent infestation
of brinjal shoot and fruit borer. On the basis of per cent fruit infestation the
hybrids Haritha x JRPH IC624241 and Ponni x IC624241 were graded as
immune. Haritha x IC618044, Haritha x IC618035, Ponni x IC618035 and Ponni
x Vengeri were graded as resistant. The hybrids Haritha x Vengeri , Haritha x
Arka Kusumkar, Ponni x IC618044 and Neelima were graded as moderately
resistant. Ponni x Arka Kusumkar was graded as tolerant. The hybrid Arka
Neelkanth x IC618035 Arka Neelkanth x IC618044 were graded as highly
susceptible.
L x T analysis revealed that Vengeri can be considered as a good
combiner with respect to per cent shoot damage, yield per plant and marketable
yield per plant. While Arka Kusumkar is a good combiner with respect to number
of fruits per plant, number of damaged fruits and per cent fruit damage. Among
the lines, Ponni can be considered as a good combiner in terms of yield and
marketable yield. Ponni x Vengeri can be considered to be superior as it exhibited
high positive heterosis over the mid parent, better parent as well as the
commercial check for yield as well as marketable yield and high negative
heterosis for per cent shoot and fruit damage. Almost all the hybrids exhibited
negative heterosis for per cent shoot and fruit damage. Ponni x Vengeri was
ranked as ‘one’ on the basis of organoleptic evaluation conducted with a panel of
ten judges.
DNA fingerprinting of the superior F1 hybrids and the respective parents
done using nineteen ISSR markers revealed that Arka Neelkanth was unique in a
way that it produced 10 bands for UBC 836. Comparing other hybrids highest
number of bands for UBC 868, UBC 816, UBC 836 and ISSR 08 were produced
by Arka Neelkanth. UBC 826 was used to identify bands common in hybrids and
parents in Haritha x IC618044, Haritha x Arka Kusumkar, Ponni x Arka
Kusumkar and Arka Neelkanth x IC618044. The bands similar in parents and
hybrids were identified in all the hybrids except Ponni x IC624241.
Superior hybrids viz., Ponni x Vengeri, Ponni x Arka Kusumkar and
Haritha x Vengeri can be evaluated further. Mapping populations can be
developed from the segregating generations to develop functional markers for
resistance to brinjal fruit and shoot borer.