Drought is the foremost factor that severely affects growth, yield, and its yield components, and has a great impact on sugarcane productivity globally. Identification of drought-tolerant sugarcane cultivars is very important to mitigate climate-related risks to sustain productivity. Hence, it is critical to assess the pre-bred material with wide genetic diversity for drought tolerance for exploitation in breeding. Seventy-five hybrids with improved germplasm base of Saccharum officinarum, Saccharum spontaneum and Saccharum robustum were evaluated at ICAR-SBI, Coimbatore, under drought and normal conditions for yield and physiological traits, for their response under drought. The membership function value of drought tolerance (MFVD) of 19 traits was used as a comprehensive index for evaluation and selection of sugarcane drought-tolerant types. Mean value of all the traits except infrared and canopy temperature depression decreased under drought condition. Cane yield, single cane weight, cane height, soil plant analysis development, total chlorophyll, crop canopy, leaf area, total dry matter, and cane volume depicted > 25

Nutrient efficient sugarcane varieties are required to sustain the yield under optimal fertiliser application with an aim of reducing environmental pollution and conserving natural resources. In this context, it is essential to evaluate sugarcane genotypes at an early crop growth stage for major nutrient (nitrogen (N), phosphorus (P), and potassium (K)) use efficiency under controlled conditions. Hydroponic culture facilitates evaluating crops under minimal to nil nutrient levels, thus response to varying levels of N, P and K may be observed earlier as compared to field conditions. To identify the deficiency, critical threshold, and sufficiency levels of major nutrients for hydroponic nutrient supplementation, an experiment was conducted by subjecting a popular sugarcane variety Co 86032 (Nayana) to differential levels of N, P and K (0 to 2000 µM). The crop response was analysed through the morpho-physiological traits and nutrient uptake in three-month-old plants. With the Cate-Nelson analysis of relative shoot dry weight (RSDW) vs nutrient uptake, and RSDW vs nutrient supplementation, the critical threshold levels were determined to be 19.41 mg N plant −1 , 4.40 mg P plant −1 , and 12.65 mg K plant −1 , corresponding to hydroponic supplementation of 375.0 µM N, 87.5 µM P, and 175.0 µM K, respectively. Nutrient supplementation below and above the critical threshold were identified as deficiency and sufficiency levels, respectively. Based on the morpho-physiological responses of Co 86032 to varying levels of major nutrients, hydroponic nutrient supplementation for genotypic evaluation under controlled condition was optimised, including deficiency (20.0 µM N, 2.0 µM P, and 10.0 µM K), critical threshold (375.0 µM N, 87.5 µM P, and 175.0 µM K) and sufficiency (2.0 mM N, P and K) levels.

Sugarcane crop is irrigated using surface, overhead, and drip irrigation methods. Increased water use in sugarcane is a major concern around the world, implying the need for water accounting, developing water-efficient hybrids and water-saving agro-techniques for long-term conservation and use of water. “Water Footprint (WF)” is a measure of both direct and indirect water usage accountable for any product and/or process. In praxis, ‘Green Water Footprint’ (GWF) and ‘Blue Water Footprint’ (BWF) are extremely crucial for the restoration of essential ecosystem services (ES), such as sugarcane production. The WF metric was used as a priority tool in our study to evaluate water-efficient sugarcane hybrids, germplasm clones, deficit irrigation scheduling, crop geometry, and water conservation measures. Precise and accurate WF quantification would supplement the decision-making processes for managing available water resources in sugarcane agriculture. In split plot experimental design two research investigations on water management in sugarcane were undertaken at the ICAR-Sugarcane Breeding Institute, Coimbatore, Tamil Nadu, India. The major objective of the research trails was to find out suitable sugarcane hybrids and agronomic management practices to minimise water usage in sugarcane cultivation in water stressed and drought prone areas of tropical India. Our investigation comprised two phases; the first one being assessment of the impact of deficit irrigation scheduling, planting techniques and water conservation measures in sugarcane production, while the second phase dealt with genotypic evaluation under variable irrigation scheduling. Results showed that BWF reduced significantly in the first ratoon crop due to deficit irrigation scheduling coupled with planting of two budded setts and application of sugarcane trash at the rate of 5 t ha −1 . Sugarcane hybrids viz., Co 85019, Co 10026, Co 12009, Co 13014, Co 14002, Co 14025, Co 15015, and Co 15018 were more water efficient, with a lower total WF. Among the germplasm clones, Fiji 55, ISH 111, ISH 107, Pathri, and Gungera exhibited lower GWF, BWF and total WF.

Sugarcane stores sucrose in an aqueous form in the parenchymatous internodal tissues. Juice volume in sugarcane being an indication of the turgidity level of cane, the genotype and environment significantly affects sucrose content in the juice and juice volume. Juice volume, being a measure of the storable aqueous media, might suggest the varietal potential to sustain water content in canes even under severe water deficit condition. Hence, an attempt was made to assess the influence of restricted irrigation regimes on juice volume, sucrose, cane yield and related traits in a field trial involving twenty varieties and three irrigation treatments. The irrigation treatments included I1: full irrigation at recommended interval, with 100% crop evapotranspiration (ET) replacement (control); I2: restricted irrigation at recommended interval, with 50% crop ET replacement (50% by volume) and I3: restricted irrigation at alternate interval, with 50% crop ET replacement (50% by frequency). Juice quality traits at harvest showed significant variation among the treatments as well as genotypes. Juice volume and cane volume showed significant and positive correlation with cane yield, suggesting the possible use of these traits in identifying varieties with high water use efficiency. The juice volume varied from 8173 to 46,627 L ha−1, while cane volume ranged from 60.9 to 157.9 m3 ha−1 in control (I1). In I2, the reduction in juice and cane volume was 45% and 36%, respectively. In I3, the juice volume reduced by 62%, while cane volume reduction was 56% compared to control. Promising varieties such as Co 10026, Co 85019, Co 86249 and Co 86010 exhibited higher juice and cane volume under restricted irrigation treatments.

Rind hardness in sugarcane plays a major role in lodging resistance, and internode borer resistance,screening of sugarcane for rind hardness is essential for reducing yield loss. In order to identify the suitability of soil penetrometer for rapid rind hardness measurement, the rind hardness testing was carried out in two sugarcane clones of different rind hardness variability viz., Co 13003 (hard rind type) and Co 14002 (soft rind type). The investigation was carried out by three methods viz., pendulum type impact test rig, texture analyzer,and soil penetrometer and theresults revealed that thehard rind type Co 13003 sugarcane clone was observed with significantly greater hardness. Significant correlation between the three methods for the rind hardness trait and among the three methods the soil penetrometer method of determination of rind hardness is easy and rapid. Two-way hierarchical cluster analysis of studied biochemical traits has revealed a better classification of hard-rinded and soft-rind sugarcane clones. The Co 13003 was recorded as least susceptible to borers with high rind hardness (>200 psi), along with better fibre. The NG 77 a hard rind type clone was also observed with high lignin compared to soft rind Gungera.

Screening for elite sugarcane genotypes for canopy cover in a rapid and non-destructive way is important to accelerate varietal/clonal selection, and little information is available regarding canopy cover and leaf production, leaf area, biomass production, and cane yield in sugarcane crop. In the present investigation, the digital images of sugarcane crop by using Canopeo software was assessed for their correlation with the physiological and morphological parameters and cane yield production. The results revealed that among the studied parameters, canopy coverage has shown a significantly better correlation with the plant height (0.581 **), leaf length (0.853 **), leaf width (0.587 **), and leaf area (0.770 **) in commercial sugarcane clones. Two-way cluster analysis has led to the identification of Co 0238, Co 86249, Co 10026, Co 99004, Co 94008, and Co 95020 with better physiological traits for higher sugarcane yield under changing climate. Additionally, in another field experiment with pre-breeding, germplasm, and interspecific hybrid sugarcane clones, the canopy coverage showed a significantly better correlation with germination, shoot count, leaf weight, leaf area index, and plant height, and finally with biomass (r = 0.612 **) and cane yield (r = 0.458 **). It has been found that the plant height, total dry matter (TDM), and leaf area index (LAI) had significant correlation with the cane yield, and the canopy cover data from digital images act as a surrogate for these traits, and further it has been observed that CC had better correlation with cane yield compared to the other physiological traits viz., SPAD, total chlorophyll (TC), and canopy temperature (CT) under ambient conditions. Light interception determined using a line quantum sensor had a significant positive correlation (r = 0.764 **) with canopy coverage, signifying the importance of determining the latter in a non-destructive way in a rapid manner and low cost.

The present study was conducted to identify the association of non-destructive rapid estimation of stalk volume by calculation method with water displacement method and to predict the single cane weight by stalk volume. The stalk volume by water displacement method (SVWM) and stalk volume by calculation method (SVCM) were compared for the efficacy of stalk weight determination in sugarcane clones. Results from both methods were similar and a highly significant relationship was found between the two methods (r2 = 0.9092, P < 0.0001). Both protocols provide consistent stalk volume measurements; however, the stalk volume calculation method is preferred for its quick evaluation of a large number of stalks in a rapid way besides its non-destructive nature. The calculation method saved more than 70 seconds for each sample. The stalk weight has shown a significant correlation of r=0.71***, 0.83***, 0.94***, 0.99*** with SH, CD, SVCM and SVWM respectively, while the stalk density (SD) was observed with a negative correlation (r=-0.27ns) with stalk weight. The stalk volume-based predicted stalk weight estimation was observed with high degree of correlation (>0.88***) with the original single cane weight by both the studied methods, thus, measurements of stalk volume based on calculation method which provide simple, rapid, non-destructive field phenotyping of single cane weight in sugarcane crop may be recommended for the sugarcane research.

Advances in sugarcane breeding have contributed significantly to improvements in agronomic traits and crop yield. However, the growing global demand for sugar and biofuel in the context of climate change requires further improvements in cane and sugar yields. Attempts to achieve the desired rates of genetic gain in sugarcane by conventional breeding means are difficult as many agronomic traits are genetically complex and polygenic, with each gene exerting small effects. Unlike those of many other crops, the sugarcane genome is highly heterozygous due to its autopolyploid nature, which further hinders the development of a comprehensive genetic map. Despite these limitations, many superior agronomic traits/genes for higher cane yield, sugar production, and disease/pest resistance have been identified through the mapping of quantitative trait loci, genome-wide association studies, and transcriptome approaches. Improvements in traits controlled by one or two loci are relatively easy to achieve; however, this is not the case for traits governed by many genes. Many desirable phenotypic traits are controlled by quantitative trait nucleotides (QTNs) with small and variable effects. Assembling these desired QTNs by conventional breeding methods is time consuming and inefficient due to genetic drift. However, recent developments in genomics selection (GS) have allowed sugarcane researchers to select and accumulate desirable alleles imparting superior traits as GS is based on genomic estimated breeding values, which substantially increases the selection efficiency and genetic gain in sugarcane breeding programs. Next-generation sequencing techniques coupled with genome-editing technologies have provided new vistas in harnessing the sugarcane genome to look for desirable agronomic traits such as erect canopy, leaf angle, prolonged greening, high biomass, deep root system, and the non-flowering nature of the crop. Many desirable cane-yielding traits, such as single cane weight, numbers of tillers, numbers of millable canes, as well as cane quality traits, such as sucrose and sugar yield, have been explored using these recent biotechnological tools. This review will focus on the recent advances in sugarcane genomics related to genetic gain and the identification of favorable alleles for superior agronomic traits for further utilization in sugarcane breeding programs.

Salinity stress is one major environmental stress that adversely affects cane yield. It interferes with cane growth, development, and crop production. Na+, Ca2+, and Mg2+, Cl−, SO42−, HCO3− ions are the primary sources contributing to the soil salinity. Globally, about 33% of irrigated land and 20% of cultivated land area are salinity-affected. Additionally, salt-affected soil is disseminated at a faster rate annually due to many reasons. Under the changing climate scenario, frequent low precipitation and elevated temperature coupled with high evaporation rate, irrigation with saline water, and faulty agricultural practices lead to twin soil salinity and waterlogging problems, which in tern distressing the cane productivity. Effects of salinity on plant phenotype are characterized by reduced cane germination and cane height (stunted growth) of the crop, reduced leaf area, and finally, a significant reduction in cane yield and sugar content of the crop. When the plant is exposed to salinity stress, there are many changes in physiological traits, such as reduction in plant's ability to absorb water and minerals, partial stomata closure, and ionic toxicity injuries to the plant cell, which ultimately leads to a decrease in the photosynthetic rate, that may be the prime factor responsible for reducing cane growth and development. Many positive changes occur in cell organelles during salinity stress. Changes in cell structure, membrane regulation system, and restoration of plant cell REDOX potential by osmotic adjustment are significant in managing the salinity stress in sugarcane. Complex nature of salinity response hinders many metabolic activities due to the accumulation of many by-products and reactive oxygen species. An increase in ion level of the juice due to salinity can decrease the efficiency of the stalk for sucrose storage, and salinity stress can also decrease the cane photosynthetic rate and translocation of sucrose from leaves to stem. Several management and omics approaches have been successfully employed in sugarcane crops to ensure sustainable cane productivity during salinity stress conditions.

Profuse and synchronized flowering is a prerequisite for breeding crop plants. Sugarcane, known for its highly variable flowering behavior, requires specific photoperiodic regimes. Repeated experiments in photoperiodic chamber (for 3 years) and field trials (for 2 years) were attempted to standardize the physiological interventions required for induction of flowering as well as its synchronization. Flowering was induced in 36 out of 46 clones treated in the photoperiodic chamber with two sets of treatments, commencing with a photoperiod of either 12 h 45 min or 12 h 55 min, followed by declining day length at the rate of 60 s day−1 for 85 and 75 cycles, respectively. Histological studies indicated conversion of vegetative to reproductive bud due to photoperiodic treatments, while temperature was a determining factor for panicle emergence or reversion to vegetative state. In the field trials, night interruption (with lighting for a period of 30 days) followed by post-inductive constant photoperiod of 12 h 40 min delayed flowering by a minimum of 4 days up to 39 days. These experiments confirmed that sugarcane flowering may be manipulated through photoperiodic treatments for the successful hybridization of desired parental clones in breeding programs.

Roots are the primary conductors of water and nutrients and play a vital role in sustaining growth and yield under stressful environments. The study of plant roots poses methodological difficulties in in situ assessment and sampling, which is especially true for sugarcane (Saccharum spp.). Traditional methods during the 1920s documented the genotypic variation in sugarcane root systems, after which few studies were reported on sugarcane root traits per se until recently. In addition to morphology, rhizosphere characteristics, including allelopathic effects and/or affinity for microbial symbiosis, determine plant establishment and survival. Ultimately, root systems define the above-ground productivity of sugarcane. With the impetus for climate-resilient varieties, it is becoming more relevant to explore and utilize the variability in root system traits of sugarcane. This paper describes multipronged approaches for sugarcane root phenotyping, including field excavation by trench sampling, the use of a root core sampler, raised platforms for root sampling, and raising plants under hydroponic culture, employed by a team of scientists at the Indian Council of Agricultural Research-Sugarcane Breeding Institute (ICAR-SBI). Field excavation by trench sampling is imperative to assess the plant roots in their natural growing environment. The use of raised platforms simulating field conditions and a root core sampler are alternative approaches, with a considerable reduction in time, uniform sample size, and less loss of root material. Hydroponic plant culture allows the study of morphology, anatomical features, and rhizosphere biology, including the exudation of organic compounds and microbial interactions. Data generated from different experiments using diverse sampling methods add to the wealth of information on the root system traits of sugarcane.

Sugarcane grown under a wide range of agro-climatic conditions accounts for ~80% of the sugar production worldwide. Since sugarcane productivity is severely affected by abiotic stresses and hence, an experiment was conducted for two consecutive years during 2020 and 2021 on popular sub-tropical sugarcane varieties. The experiment was laid out in two-factorial RBD consisting of nine sugarcane genotypes (Co 98014, Co 0118, Co 0238, Co 05011, Co 06034, Co 09022, Co 12029, Co 15023 and Co 15027) and salinity treatments (Control, ECiw ~ 4, 8 and 12 dS m−1) in 5 replications. Two budded setts were planted in pots and irrigated with saline water of respective levels till formative phase and observed the build-up in electrical conductivity of soil extract (ECse) from 0.48 (control) to 2.99, 4.81 and 7.08; while further saline irrigation increased the ECse values to 4.48, 6.24 and 9.33 dS m−1 in treatments ECiw ~ 4, 8 and 12 dS m−1, respectively. Increase in soil EC decreased plant survival by 24.1, 47.0 and 79.6% under continued irrigation of ECiw ~ 4, 8, 12 dS m−1 with respect to control. Continued saline irrigation caused significant reduction in growth, which was associated with reduction in relative water content (RWC) and gas exchange traits. RWC decreased by 4.91 to 21.9%, chlorophyll content by 8.46 to 32.75%, photosynthetic rate (Pn) by 16.85 to 91.44%, stomatal conductance by 14.96 to 84.25%, transpiration rate by 14.13% to 89.8% and chlorophyll fluorescence by 5.33 to 42.67% from ECiw ~ 4 to 12 dS m−1, respectively. Significant variations in Na+ and K+ ion content was observed under elevated saline condition in roots, leaves and juice extract of genotypes. Na+/K+ ratio, an important trait for screening salinity tolerance, increased in all genotypes as compared to control, the increase was predominant in susceptible varieties. Single cane weight (SCW) was drastically affected by saline irrigation, with a reduction of 36.4, 68.5 and 83.5% at ECiw ~ 4, 8 and 12 dS m−1, respectively as compared to control, with similar declining trend in juice quality. Based on our results, Co 0238, Co 0118 and Co 98014 were tolerant to salinity stress by maintaining higher Pn, lower leaf Na+/K+ ratio, higher SCW and higher juice sucrose content.

Saccharum spontaneum, a wild relative of sugarcane, is highly tolerant to drought and salinity. The exploitation of germplasm resources for salinity tolerance is a major thrust area in India. In this study, we utilized suppression subtractive hybridization (SSH) followed by sequencing for the identification of upregulated transcripts during salinity stress in S. spontaneum clones coming from different geographical regions of India. Our sequencing of the SSH library revealed that 95% of the transformants contained inserts of size 200-1500 bp. We have identified 314 differentially expressed transcripts in the salinity-treated samples after subtraction, which were subsequently validated by quantitative real-time polymerase chain reaction. Functional annotation and pathway analysis revealed that the upregulated transcripts were a result of protein modifications, stress, and hormone signaling along with cell wall development and lignification. The prominently upregulated transcripts included UDP glucose dehydrogenase, cellulose synthase, ribulose, cellulose synthase COBRA, leucine-rich protein, NAC domain protein, pectin esterase, ABA-responsive element binding factor 1, and heat stress protein. Our results is a step forward the understanding of the molecular response of S. spontaneum under salinity stress, which will lead to the identification of genes and transcription factors as novel targets for salinity tolerance in sugarcane.

The productivity of sugarcane is limited by several biotic and abiotic stresses, of which drought is an important environmental stress, causing substantial yield losses especially in tropical parts of the world. The present day sugarcane cultivars are derivatives of interspecific hybrids involving Saccharum officinarum and S. spontaneum and the drought tolerance is governed by S. sponaneum. Of late considerable attention has been given to utilize Erianthus Spp, the related wild genera of Saccharum, shows remarkable levels of drought tolerance under water limited condition. In this study, experiments were conducted to compare the influence of drought on biomass, yield and physiology of commercial and Erianthus introgressed clones. The results showed that the cane yield was reduced 37.98% in commercial clones compared to 24.67% in Erianthus introgressed clones under drought. The highest stress tolerance index (STI) of 1.256 was recorded in the clone CYM 08-922 which is a backcross hybrid involving Erianthus arundinaceus. Significant differences were observed for leaf area index, relative water content, lipid peroxidation and epicuticular wax content among the genotypes and between treatments. Sugar yield was most affected by drought (38.86%) followed by cane yield (33.30%), NMC (26.79%) and single cane weight (22.49%). Cane yield showed a positive and significant correlation with dry biomass under both irrigated (r = 0.303) and drought situations (r = 0.404) and among the physiological parameters, only RWC showed significant and positive correlation with cane yield (r = 0.307). The leaf dry matter was 14.55% higher under drought indicating influence of drought on translocation of dry matter from leaves to canes. Among clones CoM 0265, Co 06022, CYM 08-922, CYM 09-1369 and GU 12-31 showed greater ability to partition dry matter in to canes under drought than the other clones and had higher stress tolerant index. Cane height, number of millable stalks and RWC% showed positive and significant association with cane yield under both drought and irrigated condition and could be important parameters in screening clones under sugarcane improvement programmes.

The Salt Overly Sensitive (SOS) pathway is a crucial ion homeostasis process in crop plants trafficking excess Na+ ions for elimination/sequestration. The SOS pathway genes SOS1 (Na+/H+ antiporter), SOS2 (CIPK), and SOS3 (CBL) associated with ion homeostasis were isolated and characterized in the sugarcane clone Co 85019. The isolated genes had a coding region of 1086, 904, and 636 bp, respectively. A nucleotide blast analysis of the isolated SOS gene sequences showed strong similarity with previous genes found to be involved in the active functioning of the SOS pathway for ion homeostasis conferring salinity tolerance in sugarcane. The analysis of tissue specific gene expression of the identified SOS genes revealed a significant linear increase in the leaves under the first 96 h of salt stress (2.5- to 21.6-fold) in the tolerant genotype Co 85019, while the expression in the roots showed a linear increase up to 48 h and thereafter a gradual decline. The expression of SOS genes in the susceptible genotype (Co 97010) was significantly lower than in the tolerant genotype. Tissue ion content analysis also revealed a differential accumulation of Na+ and K+ ions in the contrasting sugarcane genotypes (Co 85019 and Co 97010) and this corroborates the varied expressions of SOS genes between the tolerant and susceptible varieties under salinity. Genome-wide analysis of identified SOS family genes showed the homologs in Saccharum complex members, Sorghum bicolor and Zea mays, and this verifies a close genetic similarity among these genera.

Temperature extremes are among the major abiotic stresses affecting sugarcane yield and quality. High temperature stress in selected sugarcane clones reduced the total chlorophyll content, SPAD chlorophyll index and photosynthetic efficiency based on fluorescence parameters (Fv/Fm) by 18, 20 and 10% respectively, compared to ambient temperature grown plants. Such transient changes to the photosynthetic machinery caused 30, 15 and 20% reduction in photosynthetic rate, stomatal conductance and intercellular CO concentration respectively, over control. Significant reduction in SPS and SS enzyme activity was noticed due to long term exposure to elevated temperature treatment particularly in sensitive varieties (Co 8021 and Co 0315). Overall, the variation among traits for photosynthetic efficiency based on fluorescence parameters, SPAD chlorophyll index and transpiration rate was significant only under elevated temperature which indicates the effectiveness of using these traits to screen for thermotolerance.

Sugarcane is grown in India in about 4.7 million hectares with a production of 348 million tonnes and sugar output of 32.34 million tonnes during the year 2017–2018. Although cane yield has doubled over the years, it is not so in the case of sugar recovery. Genetic and environmental factors influence sugarcane growth, sucrose accumulation as well as maturity processes. Sucrose in storage compartment of cane stalk is the ultimate balance between synthesis and internal consumption in simple terms; nevertheless, it is stored against a number of complex processes such as respiration loss, demand from growing shoot and root tissues and also the dormant lateral buds apart from pests, diseases and abiotic stress factors. Maturity or ripening in sugarcane is the culmination of diphasic physiological processes occurring in individual internodes. In the first stage of maturation, only about 50% of sucrose is accumulated. Additional sucrose accumulation occurs in the second phase of maturity and is so closely related to ripening. The response of sugarcane to proven ripeners varies with variety, rate of application, physiological stage of the crop and environmental factors before and after ripener application. Decline in recovery is primarily due to crushing of pre-mature canes and delayed harvest of over-mature canes. Sugar recovery is dependent on the juice quality and influenced by factors, viz. moisture stress, light, temperature and nutrient availability. There is wide scope for the use of chemical ripening agents, viz. Ethrel, Glyphosate, Fusilade Super and Gallant Super, which show differential varietal response across locations to either induce ripening or to synchronize ripening with the harvest schedule.

A field experiment was conducted during 2004-2005 crop season with seven promising midlate sugarcane varieties along with the resistant standard (Co 86032) in a strip plot design and evaluated for drought tolerance. The impact of moisture stress on various morphological characters such as plant height, leaf number, leaf area and shoot population was recorded at the termination of water stress in both normal and stressed plants. Drought treatment caused an average reduction of 27.89, 22.91, 27.43 and 17.46% in shoot population, plant height, leaf production and LAI, respectively. Co 99004 and Co 99008 transpired less water and showed relatively higher photosynthetic rate with significant improvement in growth attributes, viz. shoot population, plant height, leaf production and LAI. Yield and its parameters showed remarkable changes due to inadequate water availability during the formative phase. Water stress led to an average reduction in cane and sugar yield to the tune of 36.36% and 40.36% respectively. However, the reduction was comparatively less in Co 99004 and Co 99012 than the resistant standard (Co 86032).

Total chlorophyll content of sugarcane is an important indicator of plant health, directly correlated to the photosynthetic potential of the crop. With recent technological advancements, portable chlorophyll meters have largely replaced biochemical chlorophyll estimation, requiring laborious extraction procedure with solvents like acetone and dimethyl sulphoxide. Chlorophyll meters determine only ‘greenness’ index, which has to be converted into scientifically standard units in order to make the data comprehensive. Prediction models for inter-conversion of chlorophyll units are available for crops like rice, wheat, sorghum, barley, maize, etc., but not for sugarcane till date. In the present study, total chlorophyll content was recorded in diverse sugarcane germplasm and commercial hybrids using both non-destructive and destructive sampling methods. A strong positive correlation was observed between meter readings (SPAD and CCI) with total chlorophyll content estimated using 80% acetone (r = 0.800 and 0.793) and dimethyl sulphoxide (r = 0.915 and 0.868). Regression models for the best fit curve between meter reading and extracted chlorophyll values of the tested sugarcane germplasm and hybrids were non-linear, polynomial equations of the second order. The model developed was validated in an independent experiment wherein sugarcane variety Co 86032 was subjected to increasing nitrogen levels. Highly significant linear regression was found between observed and predicted values of all estimates of total chlorophyll content with almost negligible prediction error. Thus, the model calibrated and validated for sugarcane germplasm and commercial hybrids would be a small yet significant step towards aiding high-throughput phenotyping in sugarcane thereby accelerating crop improvement programmes.