Abstract
Studies were carried out with a view to screening varieties of chili for foot rot resistance and
optimization of Agrobacterium-mediated genetic transformation protocol in chili. For in vitro
regeneration, two types of explants (cotyledon and hypocotyls) of three chili varieties namely
Bogra marich, Balujuri marich and Deshi marich were cultured on different concentrations of
BAP (0.0, 1.0, 3.0 and 5.0 mg/L), NAA (0, 0.3, 0.5, 0.7 and 1 mg/L), IAA (0, 0.1 0.3, 0.5, 0.7
mg/L) as well as IBA (0, 0.3, 0.5, 0.7, 1.0, mg/L) supplemented to MS medium.
Acclimatization of in vitro chili plantlets was performed in different growth media namely
Garden soil and Sand (1:1), Peat soil and Saw dust (1:1), Saw dust (100%), Garden soil (100%)
and Peat soil (100%). Agrobacterium- mediated genetic transformation of chili variety
(Balujuri) was also developed. In addition, chili genotypes were screened for resistance to
Sclerotium rolfsii. RAPD analysis was also done for observing the genetic diversification of the
studied ten chili genotypes. Chili genotypes screened for selection of resistance to Sclerotium
rolfsii exerted that inoculation of Sclerotium rolfsii at early flowering and at peak fruiting stages
showed 100% infection within 6-7 day of inoculation. Uninoculated plants did not develop any
symptoms. It revealed the absence of any resistance against S. rolfsii in the tested ten chili
genotypes. The experiment also revealed that foot/collar rot could occur at any growth stage of
chili. In RAPD study, four primers (OPА11, ОРВ03, OPB04 and OPB17) which gave
reproducible and distinct polymorphic amplified products were selected for evaluation of
diversity across all the genotypes. The highest percentage of polymorphic loci (14.29%) was
found in Matal marich and Biroli city marich which gave 3 polymorphic loci whereas the lowest
percentage (9.52%) of polymorphic loci were observed both in Ausadhebra which gave 2
polymorphic loci. Gene diversity (h) across all varieties and genotypes for all loci was 0.6834.
Ausadhebra showed the lowest (0.0465) gene diversity. The study revealed Balujuri marich was
superior to Bogra and Deshi marich in terms of callus induction, shoot induction, days to shoot
initiation, number of shoots/explant, days to callus initiation, number of shoots/callus, shoot
elongation and shoot length. Cotyledon explants were better than hypocotyls in terms of callus
induction, shoot induction and shoot elongation. BAP at 5.0 mg/L was the best hormonal
concentrations for producing the highest performances of callus induction (%), shoot induction (%), days to shoot initiation and number of shoots/explant. On the other hand the highest shoot
elongation (%) and shoot length were found in 1.0 mg/L BAP and 0.1 mg/L IAA. NAA at 0.5
mg/L was recorded as the best for callus induction (%), shoot induction (%), days to shoot
initiation and number of shoots/explant, whereas NAA at 0.3 mg/L was the best in terms of per
cent callus induction and days to callus initiation. IAA at 0.3 and 0.1 mg/L was recorded as the
best ones in terms of shoot induction (percent shoot induction, days to shoot initiation, number
of shoots/callus) and shoot characters (shoot elongation and shoot length), respectively.
Between the two types of explants (namely shoot tip based shoot and callus mediated shoot)
used, per cent root initiation was significantly different between the two studied explants and
shoot tip based shoot ensured maximum root initiation. Acclimatization study revealed that
96.25% plantlets were established successfully when plantlets were transplanted on the soil
media consisting of equal amount of Sawdust and Peat soil. Agrobacterium-mediated genetic
transformation of chili revealed that the highest GUS positive transgenic callus was obtained
from cotyledon explants (2.75) and the hypocotyls explants gave the lowest number (2.25) GUS
positive transformants. The highest number and percentage (3.50 and 58.34 %, respectively) of GUS +ve callus were obtained from cotyledon explants when they were immersed in
Agrobacterium suspension for 15 min followed by co-cultivation for 48 hrs. The present study
is the first step towards establishing a successful regeneration and genetic transformation
protocol of chili and provides a possible system towards genetic improvement of the crop.