Radha Jain

Low temperature stress-induced biochemical changes affect stubble bud sprouting in sugarcane (Saccharum spp. hybrid)

A laboratory experiment was conducted to study the effect of low temperature stress on stubble bud sprouting and associated biochemical changes in sugarcane (Saccharum spp. hybrid). At 25°C, stubble bud sprouting was about 80%, whereas at 15 and 6°C, it was 56% and 23%, respectively. In stubble buds, the levels of reducing sugars and acid invertase were low, while IAA, total phenols and proline contents were high at low temperatures, as compared to normal temperature (25°C). Similarly, the specific activities of antioxidant enzymes, viz., catalase and peroxidase in stubble buds were higher at low temperatures than at normal temperature. The results indicate that poor sprouting of stubble buds at low temperatures appears to be due to a reduced availability of reducing sugars concomitant with a lower activity of acid invertase. An increased level of IAA together with toxicity build-up in situ due to an accumulation of total phenols may be responsible for the maintenance of dormancy in stubble buds at low temperatures. On the other hand, higher activities of catalase and peroxidase enzymes may protect stubble buds from an oxidative damage, while proline accumulates to act as an osmoprotectant under low temperature stress.

Assessment of genetic purity of micropropagated plants of sugarcane by isozyme and RAPD analysis

Shoot tip expiants of nine sugarcane varieties(Saccharum species hybrid.), CoLk 8102, CoLk 8001, CoS 767, CoLk 9606, CoLk 9617, CoS 95255, BO 91, CoJ 64 and Co 1148, were established on a solid MS medium containing 0.8% agar, 3% sucrose and 0.05mg/l of IAA, BAP and kinetin. Shoot regeneration has been achieved in liquid MS medium containing 0.5mg/l each of IAA, BAP and kinetin. Multiple shoots were obtained on liquid MS medium containing 0.01mg/l IAA, 0.5mg/l each of 6- benzyl aminopurine (BAP), kinetin and rooting occurred in 1/2 strength liquid MS medium with 5.0 mg/l NAA and 0.01 mg/l each of BAP and kinetin. To detect the genetic purity of in vitro raised plantlets, expression of iso-peroxidases in donor plants andin vitro raised plantlets was compared through native PAGE. Different genotypes showed marked variation regarding number, position and intensity of bands. Micropropagated plantlets showed identical pattern of peroxidases to their parental clones. The genetic stability of micro propagated plantlets was also tested by RAPD analysis. The banding pattern of PCR amplified products from micro propagated plantlets was monomorphic based on RAPD profile in all the varieties. RAPD analysis and peroxidase isozyme pattern confirmed the genetic purity of sugarcane plantlets derivedin vitro.

Expression analysis of genes associated with sucrose accumulation in sugarcane (Saccharum spp. hybrids) varieties differing in content and time of peak sucrose storage.

Sucrose synthesis/accumulation in sugarcane is a complex process involving many genes and regulatory sequences that control biochemical events in source-sink tissues. Among these, sucrose synthase (SuSy), sucrose phosphate synthase (SPS), soluble acid (SAI) and cell wall (CWI) invertases are important. Expression of these enzymes was compared in an early (CoJ64) and late (BO91) maturing sugarcane variety using end-point and qRT-PCR. Quantitative RT-PCR at four crop stages revealed high CWI expression in upper internodes of CoJ64, which declined significantly in both top and bottom internodes with maturity. In BO91, CWI expression was high in top and bottom internodes and declined significantly only in top internodes as the crop matured. Overall, CWI expression was higher in CoJ64 than in BO91. During crop growth, there was no significant change in SPS expression in bottom internodes in CoJ64, whereas in BO91 it decreased significantly. Apart from a significant decrease in expression of SuSy in mature bottom internodes of BO91, there was no significant change. Similar SAI expression was observed with both end-point and RT-PCR, except for significantly increased expression in top internodes of CoJ64 with maturity. SAI, being a major sucrose hydrolysing enzyme, was also monitored with end-point PCR expression in internode tissues of CoJ64 and BO91, with higher expression of SAI in BO91 at early crop stages. Enzyme inhibitors, e.g. manganese chloride (Mn(++) ), significantly suppressed expression of SAI in both early- and late-maturing varieties. Present findings enhance understanding of critical sucrose metabolic gene expression in sugarcane varieties differing in content and time of peak sucrose storage. Thus, through employing these genes, improvement of sugarcane sucrose content is possible.

Sugarcane bud chips: A promising seed material

Sugarcane is normally propagated by stalk cuttings consisting of 2 to 3 bud sett. In conventional system, about 6–8 tons seed cane /ha is used as planting material. Establishing the sugarcane crop using bud chips in place of setts could save about 80% by weight of the stalk material, however this technology has not been scaled up at commercial levels due to poor survival of bud chips under field conditions. Present study is aimed at improving sprouting and establishment of bud chip seed stocks of sugarcane by pre-planting soaking in growth promoting chemicals. Treated bud chips recorded higher bud sprouting, root number, fresh weight of shoot and roots and plant vigor index. Studies have shown that bud chip could be one of the most viable and economical planting material in reducing the cost of sugarcane production.

Nutrient application improves stubble bud sprouting under low temperature conditions in sugarcane

A study was undertaken to enhance the stubble bud sprouting under low temperature conditions by application of calcium (as CaCl2), potassium (as KCl) and manganese (as MnCl2) each at the rate of 0.5% solution. Stubble bud sprouting under controlled condition was about 64.3%, 73%, 68.7% due to calcium, potassium and manganese treatment respectively as compared to untreated check (46.0%). The number of ratoon tillers per stubble, as recorded after 60 days of ratoon initiation, was 157%, 57%, 85.7% more in the calcium, potassium and manganese treatment respectively. Weight of buds, tillers and roots was found maximum with manganese treatment followed by calcium and potassium treatment. Results suggested an improvement in stubble bud sprouting and subsequent regrowth of stubble in winter-initiated ratoon by nutrient application, which may help in enhancing ratoon productivity.

Impact of Heavy Metals on Sugarcane

Sugarcane is one of the most important cash crops in the tropics and subtropics, where it is mainly used to manufacture crystal sugar. It is cultivated between the latitudes of 35°N and 35°S. Theoretically, it has the potential to produce 805 t ha−1 wet cane or 470 t ha−1 dry matter. The highest harvestable sugar cane yield achieved so far is close to 58% of its theoretical yield potential, but efforts are in progress to raise this to 100%. Such efforts include the intensive use of fertilizers, irrigation, effluents, sewage sludge, industrial residues, sugar mill by-products, spent wash, pesticides, and herbicides, besides the use of high-yielding cane varieties to increase cane productivity. All of these efforts (except the use of high-yielding cane varieties) make use of sources that contain heavy metals, which means that these efforts result in increasing levels of heavy metals in soils used to grow sugarcane. These heavy metals are absorbed by the growing sugarcane, where they can reach phytotoxic levels.

Exploiting EST databases for the development and characterisation of 3425 gene-tagged CISP markers in biofuel crop sugarcane and their transferability in cereals and orphan tropical grasses

BackgroundSugarcane is an important cash crop, providing 70% of the global raw sugar as well as raw material for biofuel production. Genetic analysis is hindered in sugarcane because of its large and complex polyploid genome and lack of sufficiently informative gene-tagged markers. Modern genomics has produced large amount of ESTs, which can be exploited to develop molecular markers based on comparative analysis with EST datasets of related crops and whole rice genome sequence, and accentuate their cross-technical functionality in orphan crops like tropical grasses.FindingsUtilising 246,180 Saccharum officinarum EST sequences vis-à-vis its comparative analysis with ESTs of sorghum and barley and the whole rice genome sequence, we have developed 3425 novel gene-tagged markers — namely, conserved-intron scanning primers (CISP) — using the web program GeMprospector. Rice orthologue annotation results indicated homology of 1096 sequences with expressed proteins, 491 with hypothetical proteins. The remaining 1838 were miscellaneous in nature. A total of 367 primer-pairs were tested in diverse panel of samples. The data indicate amplification of 41% polymorphic bands leading to 0.52 PIC and 3.50 MI with a set of sugarcane varieties and Saccharum species. In addition, a moderate technical functionality of a set of such markers with orphan tropical grasses (22%) and fodder cum cereal oat (33%) is observed.ConclusionsDeveloped gene-tagged CISP markers exhibited considerable technical functionality with varieties of sugarcane and unexplored species of tropical grasses. These markers would thus be particularly useful in identifying the economical traits in sugarcane and developing conservation strategies for orphan tropical grasses.

Expression analysis of genes associated with sucrose accumulation in sugarcane under normal and GA3-induced source–sink perturbed conditions

Sugarcane accumulates high amount of sucrose, thus making it one of the important cash crops worldwide. The final destination of sucrose accumulation in sugarcane is sink tissue, i.e., stalk, supplied by the source, i.e., leaf, to fulfill the need of plant growth, respiration, storage, and other metabolic activities. Signals between sink and source tissues regulate sucrose accumulation in sink and possibly the negative feedback from the sink restrains further accumulation in the stalk. However, perturbation of this negative feedback may help to improve sugar yield. This can be achieved by the application of GA3 (Gibberellic acid), a plant growth regulator, known to excite physiological responses and modify the source–sink metabolism through their effect on photosynthesis, which in turn improves sink strength by redistribution of the photoassimilates. In the present study, GA3 applied canes showed prominent increase in invertase activity, at early stage of the application, to provide hexoses. This in turn helped increase the internodal length and cane capacity for additional accumulation of sucrose, thereby increasing sink strength. At maturity, sucrose% and brix% were found higher in middle and top portions of the GA3-applied canes. Expression analysis of various sucrose metabolising genes viz., sucrose phosphate synthase (SPS), sucrose synthase (SuSy), soluble acid invertase, neutral invertase, and cell wall invertase (CWI) was carried out at different growth stages, using quantitative RT-PCR. CWI, which plays key role in phloem unloading in sink tissues, exhibited higher expression in GA3 samples at the elongation stage which decreased with maturity, whereas both SuSy and SPS, involved in regulation of sucrose accumulation, showed a variable level of expression. Thus, GA3 application on cane may improve the sucrose content in stalk and thus assuage maneuvering source–sink dynamics in sugarcane.

Detoxification of Heavy Metals From Soils Through Sugar Crops

Heavy metals can not be destroyed biologically since there is a lack of degradation or change in the nuclear structure of the element. Such metals can only be transformed from one oxidation state or organic complex to another. The methods namely excavation and land fill, thermal treatment, acid leaching and electroreclamation used so for the remediation of heavy metal contamination in soils are not found suitable for practical applications, because of their high cost, low efficiency, large destruction of soil structure and fertility and high dependence on the contaminants of concern, soil properties, site conditions, and so on. On the other hand, phytoremediation in different forms is an emerging technology which is cost-effective, in-situ nonintrusive, esthetically pleasing, ecologically benign, and socially acceptable and has long-term applicability. The technology involves an efficient use of plants to extract, remove, sequester, and/or detoxify or immobilize environmental contaminants in a growth matrix (soil, sediments, water) through natural, biological, chemical or physical activities and processes of the plants. The present communication deals with the phytoremediation/detoxification of heavy metals from soils through sugar crops especially sugar cane, sugar beet, and sweet sorghum. The potential of these sugar crops for phytoremediation of heavy metals from soils is also presented.

Effect of leaf stripping on cane and sugar yield in sugarcane

Effect of leaf stripping +2 levels at monthly intervals starting from August till December on cane yield and commercial cane sugar (CCS) of sugarcane was studied under field conditions. Treatments comprised of whole leaf removal (WLR) and leaf blade removal (LBR). Cane yield showed significant improvement when stripping was performed in the month of August and November and the magnitude was greater with leaf blade removal; 26.1 % and 17.9 % over control in the month of August (LBR) and November (WLR), respectively. CCS % was numerically higher in most of the stripping treatments. Stripping significantly increased CCS (t/ha) in some of the treatments (August, LBR, November WLR and December LBR). The Leaf Area Index (LAI) showed maximum reduction (55.7% and 62%) in the month of November. Results obtained indicated that the effect of LBR was more beneficial than WLR for improving cane and sugar yield and also stripped leaves could be used as animal fodder after 7 month of crop age without affecting sugarcane yield.