Abstract
Sugarcane is an important sugar producing crop in the world and also in Bangladesh. It is a
long duration crop and prone to different abiotic and biotic stresses. These two constrains limit
farmer's interest towards its cultivation. Therefore, it is necessary to develop short duration and
biotic stress tolerance, like stem borer resistance sugarcane genotypes with high yielding
potential of %brix content. In this study attempts have been made to develop desired genotypes
following germplasm screening, creation of somaclonal variants using tissue culture, and
radiation during morphogenesis in tissue culture. Forty sugarcane accessions including local
and exotic were screened for selecting the materials for tissue culture experiment. Four
genotypes (Isd 15, Amrita, HoCP 91-555 and Isd 40) were selected based on their morphophysiological attributes, biochemical attributes and diversity analysis. In the tissue culture
experiment, successful regeneration and somaclonal variations were achieved by using different
concentrations and combinations of phytohormones. BAP (1 mgL-1) and Kn (0.25 mgL-1) were
maintained along with 2, 4-D (3 mgl-1) for maximum shoot regeneration. IBA and NAA (1 mgL1+1 mgL-1) with MS media produced noticeable number of roots in Isd 15 (30 plantlet¹) and
Amrita (13 plantlet1). Regeneration efficacy was influenced by genotypes, in where Isd 15
produced the highest number of shoots (29.6), longest shoots (9.37 cm), maximum roots (22.20),
and longest roots (9.21 cm). The highest rate of mortality (%) of plantlets was found in both
Amrita (78.27%) and Isd 15 (75.75%) at 9 Gy irradiation and it was proportionate to the increase
of radiation dosage. In addition, number of shoots plantlet¹, number of roots plantlet1, length
of shoots and roots were significantly higher in control (0 Gy) than irradiated plantlets (at 3, 6,
and 9 Gy). It has been marked that radiation had significant effect on in vitro growth and
development of sugarcane plantlets. All together 140 tissue culture and irradiated variants were
successfully produced after proper hardening; those were evaluated in a field trial following
Augmented design, where four parental clones were deployed as check. The genotypes
evaluated based on their morpho-physiological attributes, level of insect infestation (%),
biochemical contents (Zinc, iron, and proline) and finally characterized by molecular markers.
There was significant variation among the genotypes in terms of %brix content and insect
infestation (%). The yield contributing parameters cane diameter, stalk length and internode
length was significant and positively correlated with stalk weight. Cane diameter was the prime
yield contributing factor to get higher cane yield followed by internode length and stalk length.
Brix content (%) with >17 was used as the indicator of the maturity, the somaclonal variants
НоСР 91-555R,03 attained brix content >17% at the age of 9/10 months (September/October),
which was selected as short duration genotype. Iron and zinc had negatively correlation with
stem borer infestation. Proline increased the %brix content in cane and positively correlated to
the rate of stem borer infestation. Twenty nine EST-SSR markers targeted to insect tolerance and
short duration in maturity were used, among them four markers were polymorphic and able to
characterize the desired somaclones. EST-SSR31-1 maker confirmed the variants HoCР 91-
555Ro03 was a short duration genotype. EST-SSR markers EST-SSR41-1, EST-SSR41-2 and ESTSSR80 also confirmed the genotypes Isd 40R01, Isd 40R04, and Isd 40R 09 were tolerant
against stem borer. The materials developed in this study could be use as either breeding
materials for future breeding programme to bring both these trait together in a single genotyрe
or could be cultivated in the farmers' field as per their demand.