Morpho-molecular and biochemical characterization of sugarcane ( Saccharum Officinarum L. )

Abstract

Pakistan enjoys significant position in sugar world. However cane yield in country is very low, i.e. with 48 tha-1 yield it stands on 47th position amongst 105 cane growing countries. Pakistan has established a strong base of sugar industry with installed capacity of almost 6 million tons sugar production per annum. Due to its high production cost Pakistan can not compete in world sugar trade and less qualitative sugarcane production.

Cane varieties play a pivotal role in improving yield and recovery of sugar cane. The yield of cane is important for economic up lift of growers and sugar industry. This may be noted that Sugar Cane Research Institutes in Pakistan have no cane breeding programme of their own. Cane FUZZ (true seed) of un-known characters is imported from various available resources, including USA and Australia. Since supply of fuzz depends on donor country and un-assured funds availability negatively affect the variety selection programme.

Twenty-six genotypes of sugarcane were characterized on the basis of morphological, biochemical and molecular descriptors for their performance potential. For morphological study different parameters i.e. plant height, cane diameter, cane color, cane attitude, leaf length, leaf width, leaf latitude, number of leaves per plant, leaf color, number of internodes per plant, node size, internodes length and number of tillers per plant were compared. The result of the study indicated that all the genotypes have diversity in different agronomic traits. Stalk height in genotype S-2003-US-114 was significantly shorter than the other genotypes. Stalk diameter of the genotypes compared was also significantly dissimilar. Stalk diameter of genotypes NSG-555 had the maximum values (8.44 cm) followed by CSSG-668 and HSF-240. The genotype CP-77-400 had the longest leaves (157.98 cm) while the genotype NSG-555 had shortest leaves (101.32

cm). Genotypes CP-77-400 had highest leaf width, while genotype S-2003-US-718 had lowest leaf width. SPF-234 had highest leaf numbers as compared to other genotypes. All genotypes exhibited variability in stalk color, node size and number of internodes.

For drought stress different concentrations of polyethylene glycol (PEG) were used. Aim of this study was to determine the antioxidant activity against PEG. The genotype S-2003-US-114 exhibited strong antioxidant activity in the DPPHº (IC50, 35.08±1.25µg/ml) assay. Drought stress imposed at various stages of crop growth resulted in an increase in lipid peroxidation and decrease in membrane stability, CPHS-35 and S-2003-US-694 had the lowest lipid peroxidation (malondialdehyde content) at control and showed highest membrane stability at PEG 12.5%. There was a significant enhancement in the Proline contents and the reduction in Proline oxidase activities under PEG treatment. Drought stress causes an increase in the amino acid and glycine betaine (GB) content. The results indicate that sugarcane possesses potential antioxidant against drought tolerance.

In heat stress experiment the leaves of all genotypes were treated in the oven. The treated leaves were used for the estimation of phenolic contents and the measurement of lipid peroxidation against heat stress. Minimum moisture loss was found in CSSG-668 and CPF-237 and maximum moisture loss was shown by NSG-45 and CO-1148. Maximum phenolic contents were observed in HSF-240 and S-2003-US-778 i,e 65.7 mg GAE/100mL and 58.78 mg GAE/100ml respectively, and minimum were shown by Lho 83-153, CP-43-33, Rb-72 and CO-1148 i,e 32.98, 33.78 mg GAE/100mL, 36.17 and 37.5 mg GAE/100ml respectively. The higher heat tolerant genotypes which were Lho 83-153, CPF-237, HSF-242 and S-2002-US-133 showed higher membrane stability, and maintenance of high fv/fm ratio under heat stress and lower lipid peroxidation of membranes. Hence, the relative tolerance of a genotype to heat stress as reflected

by its lower lipid peroxidation, and higher membrane stability and pigment concentration was found related to the levels of activity of its antioxidant enzymes.

The assays involved different levels of antioxidant action in different juice concentrations of sugarcane genotypes. Radical scavenging abilities were determined by using 2, 2-diphenyl-1-picryl hydrazyl (DPPH)º. In addition the content of phenolics, reducing sugar, non-reducing sugar and brix were measured. The genotypes CPF-237, SPF-234, S-2003-US-778, S-2003-US-718, NSG-60 and CSSG-668 showed high antioxidant activities. The IC50 values of different genotypes of sugarcane varied from 17.04±0.6 to 30.63±0.45 µg/ml indicating the high radical scavenging ability of sugarcane. Cluster analysis showed high variation between the genotypes based on biochemical assays.

The aqueous extracts of leaves of twenty-six genotypes of sugarcane were compared for their antioxidant activity and defensive effect on DNA damage. Phosphomolybdenum reduction assays were used to determine the antioxidant activities in the leaves. Different genotypes of sugarcane showed variable antioxidant properties and demonstrated their ability to protect against DNA damage induced by hydroxyl radicals generated in the Fenton,s reaction. The high antioxidant activity and protection against DNA damage of sugarcane may be partly due to their phenolic and flavonoid contents. It will suggest that the hot water extracts of sugarcane leaves could provide health and functional food effects due to their antioxidant properties.

In molecular studies 53 SSR markers were used. Nei’s genetic distances for SSR, data were determined and relationships between accessions portrayed graphically in the form of a dendrogram. Genetic distance values ranging from 0.69 to 0.98 were observed among the 26 sugarcane genotypes. The shortest genetic distance of 0.69 was recorded between genotypes NSG-555 and CSSG-668, indicating closer relationship of the two genotypes. The most distant

genotypes were HSF-240 and S-2002-US-133, with a genetic distance of 0.98. The marker (SSR) based fingerprints can help breeders to clarify the genetic pedigree of commercial sugarcane genotypes and to evaluate the efficiency of breeding methods.

Studies were carried out for rapid micro propagation of five promising sugarcane genotypes i . e . HSF-242, SPF-213 HSF-240, CP-77-400 and CP-43-33. The optimum multiplication for genotype HSF-240 was obtained at 1.5 mg/l BAP, 0.5 mg/l Kin with 12.6 cm shoot, 11tillers and 8 leaves per plant. Similarly optimum multiplication for genotype CP-77-400 was obtained at 0.5 mg/l BAP and 1.0 mg/l Kinitin, with a maximum of 9 cm shoot length, 1 tiller and 16 leaves. The genotype SPF -213 was obtained at 1.5 mg/l BAP and 0.1 mg/l Kin, with a maximum of 9.6 cm shoot length, 8 tillers and 11leaves. Best multiplication rate for genotype HSF-242 and CP-43-33 was observed at 1.5 mg/l BAP and 0.1 mg/l Kin with a maximum of 13 cm shoot, 8 tillers and 10 leaves per plant . Whereas

1.0 mg/l BAP and 0.1 mg/l Kin produced a maximum of 10 cm shoot, 11 tillers and 12 leaves per plant. Rooting of the plantlets was obtained on half strength MS medi um containing 6% sucrose and various concentrations of IBA. It is investigated that these experiments will help for further selection and multiplication of desirable sugarcane genotypes in changing global environmental perspectives.