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The ratoon crop occupies approximately 40% of the total area of sugarcane crop in tropical India. The main reason for the lower average cane productivity is the yield decline in ratoon crops (40 - 50 t/ha) despite the release of the high yielding varieties and advanced cane production technology. The physiological factors associated with ratooning performance and the variation in growth and yield were studied in 11 sugarcane varieties in two cycles of one plant and two ratoon crops each. The first ratoon and second ratoon crop showed 17.0% and 28.1% reduction in tiller production and 15.5% and 15.7% reduction in NMC, respectively, over plant crop. The differences in growth parameters between the plant and ratoon crops at the formative phase were lesser than that of grand growth and maturity phases. Varieties Co 86032, Co 97008, Co 95020 Co 99004 and Co 2000-10 showed better physiological efficiency in terms of plant height, shoot population, leaf size, TDMP, partitioning efficiency, chlorophyll content and nitrate reductase activity and significantly higher yield components such as NMC, SCW, cane length, internodal length as well as cane yield compared to other varieties. The higher reduction in ratoon yield in Co 99008, Co 94012, Co 8021 and Co 97009 (>35.00% reduction) was due to higher reduction in tiller production associated with stunted plant growth and root system, reducetion in individual leaf size and LAI, TDMP, total chlorophyll content, NMC, internodal length and SCW. The results obtained indicated that the plant height, TDMP, stem partitioning, leaf size, total chlorophyll content, SCW, cane length and cane girth were highly associated with yield of first and second ratoon crops than that of plant crop. Therefore the difference in the association between physiological parameters with yield of plant and ratoon crops therefore decides the ratooning potential of the crop.

The comparative responses of photosynthesis, growth, dry matter accumulation leaf water (< l ) and osmotic (S) potentials were investigated in contrasting genotypes of sugarcane. Photosynthetic rate, transpiration rate and < l did not differ significantly among genotypes in the formative stage of crop growth (60-150 days of crop age). Leaf < l showed consistent difference among the clones due to salinity treatment. During grand growth stage (150-240 days of crop age), the photosynthetic rate, transpiration rate (t) and < l decreased due to salinity treatment. Dry biomass accumulation was severely affected and biomass allocation towards stem reduced drastically in sensitive types. The reduction in ultimate sink size as revealed by cane length and stem biomass was in accordance with the tolerance potential of the clones.

Sugarcane ( Saccharum spp.) is a special crop plant that underwent anthropogenic evolution from a wild grass species to an important food, fodder, and energy crop. Unlike any other grass species which were selected for their kernels, sugarcane was selected for its high stem sucrose accumulation. Flowering in sugarcane is not favored since flowering diverts the stored sugar resources for the reproductive and developmental energy needs. Cultivars are vegetatively propagated and sugarcane breeding is still essentially focused on conventional methods, since the knowledge of sugarcane genetics has lagged that of other major crops. Cultivar improvement has been extremely challenging due to its polyploidy and aneuploidy nature derived from a few interspecific hybridizations between Saccharum officinarum and Saccharum spontaneum, revealing the coexistence of two distinct genome organization modes in the modern variety. Alongside implementation of modern agricultural techniques, generation of hybrid clones, transgenics and genome edited events will help to meet the ever-growing bioenergy needs. Additionally, there are two common biotechnological approaches to improve plant stress tolerance, which includes marker-assisted selection (MAS) and genetic transformation. During the past two decades, the use of molecular approaches has contributed greatly to a better understanding of the genetic and biochemical basis of plant stress-tolerance and in some cases, it led to the development of plants with enhanced tolerance to abiotic stress. Hence, this review mainly intends on the events that shaped the sugarcane as what it is now and what challenges ahead and measures taken to further improve its yield, production and maximize utilization to beat the growing demands.

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A pot culture experiment was conducted to study the influence of salt stress on growth and yield component of four sugarcane varieties viz., C 92038, Co 85004, Si 94050 and Co 85036. The result of the study reveals that the growth parameter viz., LAI, LAD and CGR, RGR and SGR indicated that the derivation of LAI, CGR and SGR are the reliable growth parameters for assessing the genotypes for salt tolerance, as resistant genotypes Co 85004 and C 92038 performed better because of higher CGR, and SGR in present study. The important yield parameters viz., number of stalk per-1 , stalk length, number of inter nodes, inter nodal length, cane diameter and single cane weight were found to be affected under salt stress condition, which leads in overall yield reduction of 38.56 per cent in T 2. However the extent of reduction was less in GA 3 treated plants (18.50 %). Under salinity condition, the reduction in yield was less in C 92038 and Co 85004 (29.81 and 28.00 %) and it was found to be maximum in Co 85036 and Si 94050 (47.82 and 47.36 %). Irrespective of the genotypes, supplementing GA 3 (150 ppm) as sett treatment and foliar application play role on imparting salt tolerance in terms of getting better growth and cane yield.

Impact of elevated temperature on physiological and biochemical changes were evaluated in 5 commercial sugarcane genotypes and 2 wild species clones at two different growth phases. The study revealed that heat stress decreased chlorophyll content, chlorophyll stability index (CSI), SPAD value, maximum quantum efficiency of PSII photochemistry (Fv/Fm ratio), leaf gas exchange parameters, relative water content (RWC), and activities of nitrate reductase (NR), sucrose-metabolizing enzymes (SPS, SS, AI, NI) in all the genotypes and species clones. In contrast, elevated temperature induced an increase in proline, total phenolics content (TP), antioxidant enzyme activities (SOD and POX), lipid peroxidation (LP), membrane injury index (MII) and soluble sugar content in all clones. Principal component analysis based on physiological heat tolerance indexes could clearly distinguish sugarcane genotypes into three heat tolerance clusters. Noteworthy in comparison to the heat-sensitive varieties, sugarcane genotype that possessed higher degrees of heat tolerance Co 99004 displayed higher chlorophyll content, CSI, antioxidant enzyme activities, NR activity, RWC, total phenols, sucrose-metabolizing enzymes, soluble sugar content and leaf gas exchange and lower level of lipid peroxidation and membrane injury index.