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Sugarcane (Saccharum officinarum L.) is an important crop for sugar and bioenergy worldwide. The increasing greenhouse gas emission and global warming during climate change result in the increased frequency and intensity of extreme weather events. Climate change is expected to have important consequences for sugarcane production in the world, especially in the developing countries because of relatively low adaptive capacity, high vulnerability to natural hazards, and poor forecasting systems and mitigating strategies. Sugarcane production may have been negatively affected and will continue to be considerably affected by increases in the frequency and intensity of extreme environmental conditions due to climate change. The degree of climate change impact on sugarcane is associated with geographic location and adaptive capacity. In this paper, we briefly reviewed sugarcane response to climate change events, sugarcane production in several different countries, and challenges for sugarcane production in climate change in order for us to better understand effects of climate change on sugarcane production and to propose strategies for mitigating the negative impacts of climate change and improving sugarcane production sustainability and profitability.

Yield and profitability of sugarcane (a complex hybrid of Saccharum spp.) grown on sand soils are much lower than on organic soils in Florida owing to biotic and abiotic stresses. A greenhouse study was conducted using a sand soil to identify effects of water deficit stress (WS) during sugarcane early growth on leaf photosynthetic components, plant growth, and dry matter accumulation. Treatments included two sugarcane genotypes (CP 01‐2390 and CP 80‐1743) and two water regimes (well watered [WW] and WS). All plants were well watered before initiating WS. Water was withheld from the WS pots when plants reached seven to eight leaves on the primary stem. During the WS treatment, plant growth and leaf photosynthetic components were measured. Final green leaf area (GLA) and shoot biomass were determined at the end of the experiment. Water stress depressed leaf relative chlorophyll level (SPAD), stomatal conductance (gs), leaf net photosynthetic rate (Pn), transpiration rate (Tr), transpiration use efficiency (TUE) of photosynthesis, and GLA, resulting in reduced shoot biomass. CP 01‐2390 was superior to CP 80‐1743 in most measured physiological and growth traits under the WW and WS conditions, suggesting that selection of genotypes with tolerance to WS while improving irrigation management will improve sugarcane yields on sand soils. Physiological and growth traits, such as SPAD, gs, Pn, Tr, TUE, GLA, tillering, and stalk length, may be useful for early detection of WS and for evaluation of sugarcane genotypes in the stress tolerance.

Measurements of nonstructural carbohydrates (NSC) in plant tissues are important to estimate plant organ resources available for plant growth and stress tolerance or for feed value to grazing animals. A popular commercially available assay kit used to detect glucose with a light-sensitive dye reaction was recently discontinued and replaced by a test-tube-scale glucose kit (GAHK-20) that assays glucose through enzymatic coupled reactions and the formation of reduced nicotinamide adenine dinucleotide. The objective of this study was to develop a microplate assay method that uses the GAHK-20 to quantify forage NSC composition. A laboratory microplate enzymatic method was developed for the new glucose kit and evaluated for rapidly assaying NSC components, including glucose, fructose, sucrose, fructan, and starch in 11 species of cool-season perennial grasses. By standard addition, dilution, and temporal tests of enzyme reactions, we found that this microplate enzymatic assay is a rapid and reliable method to quantify NSC composition in grass forage samples. The microplate method allows analysis of many samples per day and considerably improved time and reagent use efficiencies, especially for a large number of samples. In addition to forage, this method should be suitable for measuring NSC concentrations in fresh or dry tissues of a variety of other plant samples.

A pot study was conducted to investigate influences of salinity on sugarcane (Saccharum spp.) plant growth, leaf photosynthesis, and other physiological traits during tillering and stalk elongation. Treatments included two commercial sugarcane cultivars (Canal Point (CP) 96-1252 and CP 00-1101) and an Erianthus with five different soil salt concentrations (0 [Control], 38, 75, 150, and 300 mM of NaCl added). Growth (tillers, plant height, and nodes) and physiological (leaf net photosynthetic rate [Pn], stomatal conductance [gs], intercellular CO2 concentration, and leaf water soluble sugar concentrations) characters were determined during the experiment. Responses of sugarcane growth, photosynthesis, and photoassimilate translocation to salinity depended on soil salt concentration. Plant height was the most sensitive while the number of nodes was the most tolerant to soil salinity among the three growth traits measured. CP 96-1252 differed from CP 00-1101 significantly in response of shoot:root ratio to high salt concentration. Leaf Pn of plants treated with the 38 mM salt did not differ from that of the control plant, but plants treated with the 75, 150, and 300 mM salt had 12.7, 18.7, and 35.3% lower leaf Pn, respectively, than the control. The low leaf Pn due to salinity was associated with not only the decrease in gs, but also the non-stomatal factors. Results of leaf sugar composition and concentrations revealed that high salt concentration also depressed photoassimilate translocation from leaves to other plant tissues. These findings are important for better understanding of some physiological mechanisms of salinity influence on sugarcane growth and yields.

The selection of sugarcane genotypes with high sucrose content and good ratooning ability (RA) is an important objective of the Canal Point breeding program to improve the current profitability levels of the Florida sugarcane industry. In this study, thirteen test sugarcane genotypes and three checks were evaluated in three sand locations, Pahokee Produce Inc. (PP), Townsite farm (TS), and Lykes Brothers Inc. (PF), during three crop cycles (plant cane, first ratoon, and second ratoon). Multi-environment best linear unbiased predictors (BLUPs) were highly significant for commercially recoverable sucrose (CRS) and not significant for cane yield (CY) among genotypes. The ANOVA based on the RA values produced significant genotypic effects but a reduced RA diversity among the genotypes. The simultaneous selection for BLUP_CRS, BLUP_CY yield, and RA identified CP 14-4165 and CP 13-2340 as the most outstanding genotypes. The BLUP_GGE biplots method showed that the PP location was the most discriminative for BLUP_CY, whereas the TS was the ideal location. For BLUP_CRS, the three locations had similar abilities to discriminate genotypes and were positively and strongly correlated. The which-won-where graph indicated that CP 13-2340 showed the highest BLUP_CRS levels in TS and PP locations, while CP 14-4165 and CP 14-4588 were the top genotypes in the PF location. The results suggest that selecting genotypes with high CRS values is possible without compromising the genotype discrimination for CY. CP 14-4165 and CP 13-2340 are resistant to most diseases and genetically diverse.

Plant reproduction is highly vulnerable to global climate change components such as carbon dioxide concentration ([CO₂]), temperature (T), and ultraviolet-B (UV-B) radiation. The objectives of this study were to determine the effects of season-long exposure to treatments of [CO₂] at 360 (control) and 720 [micro]mol mol⁻¹ (+CO₂), temperature at 30/22 °C (control) and 38/30 °C (+T) and UV-B radiation 0 (control) and 10 kJ m⁻² d⁻¹ (+UV-B) on flower and pollen morphology, pollen production, germination, and tube lengths of six soybean genotypes (D 88-5320, D 90-9216, Stalwart III, PI 471938, DG 5630RR, and DP 4933RR) in sunlit, controlled environment chambers. The control treatment had 360 [micro]mol mol⁻¹ [CO₂] at 30/22 °C and 0 kJ UV-B. Plants grown either at +UV-B or +T, alone or in combination, produced smaller flowers with shorter standard petal and staminal column lengths. Flowers so produced had less pollen with poor pollen germination and shorter tube lengths. Pollen produced by the flowers of these plants appeared shrivelled without apertures and with disturbed exine ornamentation even at +CO₂ conditions. The damaging effects of +T and +UV-B were not ameliorated by +CO₂ conditions. Based on the total stress response index (TSRI), pooled individual component responses over all the treatments, the genotypes were classified as tolerant (DG 5630RR, D 88-5320: TSRI >-790), intermediate (D 90-9216, PI 471938: TSRI <-790 to >-1026), and sensitive (Stalwart III, DP 4933RR: TSRI <-1026). The differences in sensitivity identified among genotypes imply the options for selecting genotypes with tolerance to environmental stresses projected to occur in the future climates.

Leaf reflectance has been used to estimate crop leaf chemical and physiological characteristics. Sugarcane (Saccharum spp.) leaf N, C, and chlorophyll levels are important traits for high yields and perhaps useful for genotype evaluation. The objectives of this study were to identify sugarcane genotypic variation in leaf hyperspectral reflectance, leaf chemical (chlorophyll, N, and C), and yield (juice sucrose content, commercial recoverable sucrose [CRS], cane yield in tonnes of cane per hectare [TCH], and sucrose yield in tonnes of sucrose per hectare [TSH]) traits and to determine relationships between leaf reflectance and these chemical and yield traits. In Stage II of the Canal Point, FL, sugarcane cultivar development program, we measured spectral reflectance and chemical traits on three leaves of the top visible dewlap from each of 87 genotypes in December 2008 and 208 and 124 genotypes in May, July, September, and October 2009 and 2010, respectively. Yield traits were determined on mature plants. Genotypic variation of leaf reflectance mainly occurred in 540 to 1200 nm. Leaf relative chlorophyll, N, C, and C to N ratio varied among genotypes and during the growing season. Highly significant calibrations were developed for leaf chemical traits using leaf reflectance (P < 0.0001). Correlations of juice sucrose, CRS, TCH, and TSH with leaf reflectance were poor. Measurement of leaf reflectance is a promising tool for estimating leaf chemical traits but not for predicting yield traits across a large number of diverse genotypes in early selection stages of a sugarcane breeding program.

Sugarcane (Saccharum spp.) brown rust (caused by Puccinia melanocephala Syd. & P. Syd.) was first reported in the United States in 1978 and is still one of the great challenges for sugarcane production. A better understanding of sugarcane genotypic variation in response to brown rust will help optimize breeding and selection strategies for disease resistance. Brown rust ratings were scaled from non-infection (0) to severe infection (4) with intervals of 0.5 and routinely recorded for genotypes in the first clonal selection stage of the Canal Point sugarcane breeding program in Florida. Data were collected from 14,272 and 12,661 genotypes and replicated check cultivars in 2012 and 2013, respectively. Mean rust rating, % infection, and severity in each family and progeny of female parent were determined, and their coefficients of variation (CV) within and among families (females) were estimated. Considerable variation exists in rust ratings among families or females. The families and female parents with high susceptibility or resistance to brown rust were identified and ranked. The findings of this study can help scientists to evaluate sugarcane crosses and parents for brown rust disease, to use desirable parents for crossing, and to improve genetic resistance to brown rust in breeding programs.

Trinexapac-ethyl (Moddus) is known as a plant growth regulator widely used in sugarcane to boost sugar yield and improve harvest efficiency. The objectives of this study were to investigate responses of sugarcane growth, physiology and yield components to application of Moddus in grand growth phase and to determine differences in plant response to Moddus™ among sugarcane cultivars. The experiment was conducted in 2 years with plant cane crop of three cultivars (CP 00–1101, CP 01–1372 and CP 05–1526) and two Moddus™ treatments [an unsprayed check and a two-time application of Moddus™ (0.4 L ha −1 each time) at 149 and 215 days after planting]. The field trail was laid out as a split-plot design (Moddus™ treatments as main plots and cultivars as sub-plots). Plant growth and physiological measurements were taken in June–August and yield data were collected in mid-December. A novel finding was that cultivar and Moddus™ interactions were significant in leaf relative chlorophyll level (SPAD reading), mean stalk weight, cane yield, commercial recoverable sucrose (CRS) and sucrose yield. Moddus™ application increased the SPAD readings of CP 01–1372 and CP 05–1526, but did not affect that of CP 00–1101. Neither leaf photosynthetic rate nor leaf N responded to Moddus™, but Moddus™ reduced normalized difference vegetation index and stalk length. Moddus™ application in grand growth phase decreased sucrose yield of CP 00–1101, but increased sucrose yield of CP 05–1526 because of high stalk weight and CRS. Therefore, the Moddus™ application for improving seed-cane quality and yield should depend on cultivars and their growth behavior.

Leaf N and chlorophyll (Chl) concentrations of cotton (Gossypium hirsutum L.) are important indicators of plant N status. Laboratory determinations of plant tissue N are time consuming and costly. Measurements of leaf reflectance may provide a rapid and accurate means of estimating leaf N and Chl. Studies were conducted to determine the relationships between leaf hyperspectral reflectance (400-2500 nm) and Chl or N concentration in field-grown cotton. One study consisted of four N rates of 0, 56, 112, and 168 kg N ha(-1), and another study consisted of four mepiquat chloride (MC) rates of 0, 0.59, 1.17, and 2.34 L MC ha(-1). Chlorophyll and N concentrations and reflectance of uppermost, fully expanded mainstem leaves were measured throughout the growing seasons. Reflectance at 556 and 710 nm increased significantly as N fertilizer rate decreased. Averaged across years and sampling dates, the percentage increase in reflectance at these two wavelengths was 8, 10, and 19% greater in the 112, 56, and 0 kg N ha(-1) treatments, respectively, compared with the 168 kg N ha(-1) treatment. The effect of MC on leaf reflectance was more complex than the N effect. In both the N and MC studies, a linear relationship was found between leaf N and a simple ratio of leaf reflectance at 517 and 413 nm (R517/R413) (r2 = 0.65-0.78***). Leaf Chl concentration was associated closely with reflectance ratios of either R789/R915 or R789/R915 (r2 = 0.67-0.76***). Our results suggest leaf reflectance can be used for real-time monitoring of cotton plant N status and N fertilizer management in the field.