Abstract
The experiments were carried out at Biotechnology Laboratory and farm of Bangladesh
Sugarcrop Research Institute (BSRI), Ishurdi, Pabna, Bangladesh during 2012-2013, 2013-
2014 and 2014-2015 cropping seasons for in vitro plant regeneration of tropical sugarbeet
and evaluate the genetic fidelity as well as field performance of regenerated plants over
their parents. Tropical cultivars of sugarbeet CS 0327, CS 0328, HI 0044, HI 0473, Shubhra
and Cauvery were used for plantlet regeneration and field evaluation. On the basis of
different shoot characters cultivar HI 0044 was most responsive for shoot regeneration
which produced highest number of shoot (96.67%), shoot per explant (2.50) and shoot
length (4.31 cm) cultured in medium containing BAP 1.0 mgl-1 + NAA 0.5 mgl-1.
Different explants viz. shoot tip, hypocotyl, cotyledon, leaf and leaf petiole were also
incubated on the same medium. Explant shoot tip produced the highest shoot (93.33%)
and shoot length (4.40 cm) while leaf petiole explant produced the highest number of
shoot per explant (3.67). Among five concentrations of BAP and two explants the highest
shoot induction% was found in medium containing 1.0 mgl-1 of BAP for both types of
explants. The highest number of rooted plant was found in half strength MS medium
supplemented with 2.0 mg1-1 NAA from genotype HI 0044 and lowest from genotype CS
0328. MS media containing 0.1 mgl-1 NAA + 1.0 mgl-1 TDZ produced the highest per cent
callus (93.67) as well as highest amount of callus (1.43 g) under the explant ofof hypocotyl.
This treatment combination also produced the highest number of shoot per callus and
longest shoot. The highest per cent explants induced callus (94.33%) in MS medium
fortified with 1.0 mg1-1 2, 4-D + 1.0 mgl-1 BAP by the leaf petiole explant. Out of eighteen
primers, four primers OPG03, UBC283, UBC431 and UBC467 generated 37 distinct bands
among them 36 bands were polymorphic and percentage of polymorphic loci was
97.92%. The average gene diversity across all varieties for all loci studies was 0.2399.
High level of Nei's gene diversity value was found 0.4986 and the lowest one was found
0.0000. The value of the highest genetic distance (0.903) was found among sugarbeet
genotypes CS 0328 vs Shubhra, CS 0328 vs CC-Shubhra-6 and CS 0328 vs CC-Shubhra-7.
The lowest value (0.000) was observed in genotypes H10044, HIO473, Shubhra and
Cauvery vs their somaclones. Dendogram based on Nei's (1972) genetic distance using
the segregated nineteen genotypes into two main clusters. Eighteen of them were formed
cluster and the remaining one genotype CC-Shubhra-7 was in cluster 2. The developed
somaclones and their parents on field evaluation exhibited variation regarding different
yield attributes. Cultivar CS 0328 produced the highest beet yield (tha-¹) but HI 0044
consisted higher sugar content. All regenerated somaclones produced lower yield and
higher sugar compared to their parents and matured earlier compared to their parents.
From the above findings, it could be concluded that genotype HI 0044 would be high
responsive for in vitro regeneration and high sugar production. The variation assessed
among genotypes by RAPD markers could be used in future breeding program for
tropical sugarbeet improvement while in vitro regeneration protocol developed has the
potential use in improvement of the species through genetic transformation.