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The objective of this study was to set up a plant micropropagation facility to mass propagate sugarcane, energy cane, and related clonally propagated species. An efficient methodology for micropropagation of energy cane and perennial grasses using temporary immersion bioreactors was developed. Several different methods of tissue culture initiation, multiplication, and rooting were evaluated for several varieties of sugarcane (Saccharum officinarum L.) and sugarcane-related species such as Erianthus spp., Miscanthus spp., and Sorghum spp. × sugarcane hybrids, all from a germplasm collection. Apical meristem cultures were initiated for all genotypes that were micropropagated, when liquid or semisolid Murashige and Skoog (MS) medium was used, which was supplemented with 0.1–0.2 mg L−1 BAP, 0.1 mg L−1 kinetin, 0–0.1 mg L−1 NAA, and 0–0.2 μg L−1 giberellic acid. These cultures produced shoots between 4 and 8 wk after initiation. Shoot regeneration from leaf rolls or immature inflorescences was observed as early as 4 wk after initiation. Shoot multiplication was successful for all genotypes cultured in MS medium with 0.2 mg L−1 BAP and 0.1 mg L−1 kinetin. Energy cane had a significantly higher combined multiplication rate when grown under four or five LED lamps than when grown under three LED lamps, or under fluorescent lights in a growth chamber. The addition of 2 mg L−1 NAA produced faster and better rooting in all of the genotypes tested. Shoots produced well-developed roots after one cycle of 15–21 d in the bioreactors. The maximum number of plantlets produced per bioreactor was 1080. Plantlets developed a vigorous root system and were ready to be transplanted into the field after 2 mo. A protocol was standardized for different energy cane clones that were recommended for their biomass production and cell wall composition. Different tissues were used to speed up or facilitate tissue culture initiation. Visual assessment of micropropagated plants in the field did not show any off-types, based on gross morphological changes of plant morphology or disease reaction, compared to plants of the same genotype derived from a traditional propagation method (stem cuttings). This is the first report of energy cane and Miscanthus spp. micropropagation using the SETIS bioreactor.

Roots impact plants’ capacity to absorb water and nutrients and thus play a vital role in tolerance to drought, salinity, and nutrient stress. In tomato (Solanum lycopersicum) breeding programs, wild tomato species have been commonly used to increase disease resistance and fruit quality and yield. However, tomato has seldom been bred for water/nutrient use efficiency or resilience to abiotic stress. Meanwhile, little knowledge of the genetic control of root traits in tomato is available. In this study, a mapping population consisting of 181 F2 progenies derived from a cross between an advanced breeding line RvT1 (S. lycopersicum) and a wild species Lche4 (Solanum cheesmaniae) was evaluated for root and shoot traits in the greenhouse. Root phenotypes were studied for the early seedling stage. Heritability estimates show that root traits are moderately or highly heritable. Root mass was highly correlated with root size (length, surface area, and volume). Shoot mass and chlorophyll content (SPAD) were moderately correlated with root mass and size. Genotyping-by-sequencing was applied to discover single nucleotide polymorphism (SNP) markers. Seven hundred and forty-two SNPs were successfully mapped, and a medium-dense linkage map was created that covered 1319.47 centimorgans (cM) with an average distance of 1.78 cM between adjacent markers. Using composite interval mapping, multiple quantitative trait loci (QTL) mapping and nonparametric mapping, 29 QTLs were identified for 12 root and shoot traits on eight chromosomes. Those QTLs of major and minor effect were involved in the differences among the F2 population. Two QTL hotspot regions associated with root mass, size, shoot mass and SPAD were identified on chromosomes 1 and 4, which was consistent with the correlation among traits. Five QTLs for shoot length and eight QTLs for SPAD were accounting for 40.01% and 55.53% of the phenotypic variation. Two QTLs were associated with 18.26% of the total variation for specific root length. The wild parent Lche4 has been characterized as a potential genetic donor of higher specific root length and might be a good parent to modify the root system of cultivated tomato.

Demand for Asian vegetables is rising rapidly due to changing demographics and increasing consumer awareness of their health benefits. However, growers are not familiar with growing these “foreign” crops due to insufficient technical information regarding suitable cultivars for different regions, production schedules, disease and pest susceptibility, and postharvest management. The objective of this study was to conduct trials in different production systems and climate regions to demonstrate the potential of growing Asian vegetables in Texas. We conducted preliminary trials of nine leafy greens in the open field, high tunnel, and greenhouse (container and hydroponic production) to explore the suitability and potential for year-round production. We also conducted field trials for warm season crops in the open field in different climate zones. Results indicated that for cool season leafy greens, open field production has a limited growing season, high tunnel has the potential to extend the growing season, while greenhouse may provide year-round production using soilless substrate container culture or hydroponic system. For warm season crops, early planting is recommended for high yield. Additional research is warranted in different regions to test more species and cultivars and optimize the production system of high-performing cultivars to maximize production and profitability.

Green nanotechnology is rapidly expanding in sustainable precision agriculture that promises to revolutionize food production. In the present study, nanoparticles (NPs) were synthesized using a gre...

Effects of environmental and management factors on the diversity and abundance of rhizosphere microbes in unmanaged ecosystems are well established. However, there is limited information about these interactions in vegetable cropping systems. In this two-year field study, we used organic amendments (humic substances, HS) and water supply (deficit irrigation) as soil management factors to characterize changes in bell pepper rhizosphere microbial population under two distinct soil types (clay and sandy). Path analysis revealed that soil type was the main factor constructing the microbial population. Clay soil indirectly increased bacterial biomass through the changes in root length, soil pH, P and K contents, while increased fungal biomass was linked with the enhanced above-ground plant yield. As organic inputs, HS had long-term positive influences on soil microbial activity through improvements in soil organic carbon content, which was also positively correlated with bacterial population. Water input became a less influential factor – deficit irrigation indirectly decreased fungal biomass but increased soil respiration through the reduction in pepper yield. These findings provide a better understanding of external factors controlling the abundance of rhizosphere microbiota under intensively managed cropping systems, and potential strategies to improve beneficial microbial diversity and soil health.

Biomass sorghum ( (L.) Moench) is widely recognized for its high biomass yield potential, high efficiency in converting solar energy into biomass, and high efficiency in water use for biofuel production. Therefore, it could be a sustainable alternative to traditional food/feed crops in south Texas. The objectives of this investigation were to: (1) quantify the growth response and dry biomass productivity of a forage sorghum hybrid (Pioneer 877F) and two high-biomass sorghum hybrids (Blade ES 5140 and Blade ES 5200) in south Texas, (2) determine the radiation use efficiency (RUE) and water use efficiency (WUE) of the sorghum hybrids over two years, and (3) identify variations in WUE and water used among the hybrids. The experiments were conducted at the Texas A&M AgriLife Research Center at Weslaco, Texas, during the 2015 and 2016 growing seasons. There were significant differences among hybrids during the two years in dry biomass, RUE, and WUE. The highest productivities and efficiencies were observed in the biomass hybrids. Blade ES 5200 produced an average dry biomass of 32.8 Mg ha-1 with a leaf area index (LAI) of 6.0 m2 m-2, RUE of 4.92 g MJ-1, and WUE of 6.98 kg m-3. In contrast to the biomass hybrids, the forage hybrid produced the lowest yields. The average dry biomass observed was 20.9 Mg ha-1 with an LAI of 2.6 m2 m-2, RUE of 3.52 g MJ-1, and WUE of 4.28 kg m-3. Our results show that biomass sorghum hybrids can produce up to 66% more biomass than forage hybrids, and they have potential for producing as much as 33 Mg ha-1 with 530 mm of water using drip irrigation in south Texas. Keywords: Biomass sorghum, Crop growth rate, Radiation use efficiency, Water use efficiency.

Melon is one of the most popular fruits worldwide and has been bred into various cultivars. RNA-sequencing using healthy melon fruit was performed to determine differences in gene expression among cultivars. Unexpected RNA-seq results revealed that viruses asymptomatically infected fruits at a high frequency (16 of 21 fruits examined were infected) and that viral transcripts highly accumulated in comparison with host transcripts (15 %–75 % of total reads). Their nucleotide sequences and phylogenetic analyses indicated that more than 10 novel isolates of tobacco ringspot virus (TRSV) were found in melon fruits. Asymptomatic infection with TRSV on melon fruits was confirmed by both immunoblot and RT-PCR analyses. Numerous isolates of TRSV generated and maintained in melon fields, and this is likely due to their asymptomatic infections. This TRSV melon isolate infected Nicotiana benthamiana plants with stunting and yellowing symptoms. This is the first report of frequent and asymptomatic infection of TRSV in consumable melon fruits.

The sensory and functional quality attributes of muskmelons (Cucumis melo L.), such as flavor, sweetness, color, and texture, determine consumer preferences. Genetic makeup primarily regulates these traits, but environmental factors such as soil type, irrigation, and temperature affects yields and quality. Here, we investigated variation in quality traits of diverse melon cultigens (advanced breeding lines or cultigen) grown in multiple locations (California, Texas, Georgia, Arizona, and North Carolina) across the United States. Mesocarp sugar and carotenoid concentrations varied significantly as a function of production location and cultigen. Multivariate analyses revealed significant cultigen, location, and interactive effects on fruit quality. The highest sugar content was found in a honeydew melon cultigen (HD-150; 83.1 ± 2.36 mg/g) grown in Georgia and the Western Shipper type cantaloupe (F-39; 70.8 ± 2.85 mg/g) grown in North Carolina compared to the other cultigens. The Tuscan type (Da Vinci) grown in Texas and Georgia had the highest β-carotene concentrations (29.1 ± 3.37 and 33.6 ± 1.73 µg/g, respectively) compared to the other cultigens. These observations, showing that cultivar and location significantly influenced melon phytochemical composition, will help melon breeding programs improve the sensory and functional qualities of melons and identify suitable cultivars for specific environments to maximize fruit quality.

Plants represent a safe and cost-effective platform for producing high-value proteins with pharmaceutical properties; however, the ability to accumulate these in commercially viable quantities is challenging. Ideal crops to serve as biofactories would include low-input, fast-growing, high-biomass species such as sugarcane. The objective of this study was to develop an efficient expression system to enable large-scale production of high-value recombinant proteins in sugarcane culms. Bovine lysozyme (BvLz) is a potent broad-spectrum antimicrobial enzyme used in the food, cosmetics and agricultural industries. Here, we report a novel strategy to achieve high-level expression of recombinant proteins using a combinatorial stacked promoter system. We demonstrate this by co-expressing BvLz under the control of multiple constitutive and culm-regulated promoters on separate expression vectors and combinatorial plant transformation. BvLz accumulation reached 1.4% of total soluble protein (TSP) (10.0 mg BvLz/kg culm mass) in stacked multiple promoter:BvLz lines, compared to 0.07% of TSP (0.56 mg/kg) in single promoter:BvLz lines. BvLz accumulation was further boosted to 11.5% of TSP (82.5 mg/kg) through event stacking by re-transforming the stacked promoter:BvLz lines with additional BvLz expression vectors. The protein accumulation achieved with the combinatorial promoter stacking expression system was stable in multiple vegetative propagations, demonstrating the feasibility of using sugarcane as a biofactory for producing high-value proteins and bioproducts.

Grafting with vigorous rootstocks could offer tomato growers in Texas sustainable and efficient option to achieve reliable yield across a range of production systems and locations. Genotypes (G) of grafted and non-grafted tomato were grown in different environments (E) in the 2017 and 2018 spring seasons. The objectives of the study were to (i) evaluate the effects of production system and grafting on tomato yield traits, (ii) determine the size of genotypic and genotype by environment interaction (G × E) variance components, and (iii) evaluate the relative stability of tested genotypes for yield and its components across production environments. In 2017, genotypes were non-grafted ‘TAMU Hot Ty’ (TAM) and ‘Tycoon’ (TY) and each grafted on commercial tomato rootstocks ‘Estamino’ (TAM/ES, TY/ES) and ‘Multifort’ (TAM/MU, TY/MU) while in 2018, TAM and ‘HM1823’ (HM) were grafted on ‘Estamino’ (TAM/ES, HM/ES) and ‘Multifort’ (TAM/MU, HM/MU). Testing environments were high tunnel (HT) and open-field (OF) in Uvalde in 2017 while in 2018, these were HT and OF in Lubbock (LU-HT, LU-OF), Overton (OV-HT, OV-OF), Uvalde (UV-HT, UV-OF), and Weslaco (WE-HT, WE-OF). Total and marketable yields, fruit number per plant, and average fruit weight were significantly affected by E, G, and G × E interaction. Environmental component contributed 71–86% to the total variation for all these traits, while genotype explained 1.5–10.8%, and the contribution of G × E ranged between 4.3 to 6.7%. Estimation of the univariate statistic parameters and genotype plus genotype × environment (GGE) biplot analysis indicated that HM/MU and HM/ES were the most stable graft combination with the highest total and marketable yields, while TAM/ES was very unstable for yields across test environments. TAM/MU was stable but with yield lower than the grand mean. These results suggest that high tomato yields could be consistently achieved with grafted combination (HM/MU and HM/ES) especially under high tunnel production system across the regions of Texas.

Seed priming uses treatments to improve seed germination and thus potentially increase growth and yield. Low-cost, environmentally friendly, effective seed treatment remain to be optimized and tested for high-value specialty crop like watermelon (Citrullus lanatus) in multi-locations. This remains a particularly acute problem for triploids, which produce desirable seedless watermelons, but show low germination rates. In the present study, turmeric oil nanoemulsions (TNE) and silver nanoparticles (AgNPs) synthesized from agro-industrial byproducts were used as nanopriming agents for diploid (Riverside) and triploid (Maxima) watermelon seeds. Internalization of nanomaterials was confirmed by neutron activation analysis, transmission electron microscopy, and gas chromatography-mass spectrometry. The seedling emergence rate at 14 days after sowing was significantly higher in AgNP-treated triploid seeds compared to other treatments. Soluble sugar (glucose and fructose) contents were enhanced during germination in the AgNP-treated seeds at 96 h. Seedlings grown in the greenhouse were transplanted at four locations in Texas: Edinburg, Pecos, Grapeland, and Snook in 2017. At Snook, higher yield 31.6% and 35.6% compared to control were observed in AgNP-treated Riverside and Maxima watermelons, respectively. To validate the first-year results, treated and untreated seeds of both cultivars were sown in Weslaco, Texas in 2018. While seed emegence and stand establishments were enhanced by seed priming, total phenolics radical-scavenging activities, and macro- and microelements in the watermelon fruits were not significantly different from the control. The results of the present study demonstracted that seed priming with AgNPs can enhance seed germination, growth, and yield while maintaining fruit quality through an eco-friendly and sustainable nanotechnological approach.

The seasonal dynamics of energycane biomass accumulation has major implications in designing optimized cellulosic biomass production and logistics systems. The objectives of this study are to: 1) quantify the growth and biomass dynamics of selected energycane genotypes along the Texas Gulf Coast and 2) estimate the yield penalty and nitrogen removal of different just-in-time harvesting schemes. Field experiments were conducted in three sites along the Texas Gulf Coast with four energycane genotypes. Biomass accumulation varied greatly among genotypes, but relative biomass growth, expressed as a proportion of each genotype's end of season biomass, was similar across years and genotypes for a particular site. On a calendar time basis, relative biomass growth curve became steeper at higher latitudes, indicating a shorter growing season, a narrower harvesting window, and a greater biomass yield penalty for early season harvest. Estimated biomass yield penalties for early August harvest were 60, 44, and 32% of the biomass at crop maturity for the northernmost, intermediate and southernmost site, respectively. Early harvesting of the same amount of biomass tends to remove more nitrogen due to higher organ nitrogen concentration. Combination of organ types harvested also greatly impacts nitrogen removal. Retaining leaf blade materials in the field would remove less nitrogen as compared to harvesting all organs, but will require greater harvesting area. Results from this study highlight the need for a systematic approach to integrate critical time- and site-dependent biomass growth characteristics of energycane in optimizing biomass production and supply logistics.

Zinc is essential for the synthesis of amino acids, carbohydrates, and proteins, which are directly related to the chemical composition of raw coffee (Coffea arabica L.) beans, and it may influence the quality of the beverage. This study aimed at evaluating the influence of Zn doses on the chemical composition of coffee beans and beverage quality. Increased Zn availability in the growth medium maximized attributes related to beverage quality, such as polyphenol oxidase activity, color index, and contents of sucrose, caffeine, and trigonelline, reaching maximum values in plants with Zn leaf contents within the sufficiency range of 8.0 to 12.7 mg kg⁻¹. Zinc doses lower or higher than the one that provided maximum quality (∼2 μmol L⁻¹ in nutrient solution) increased the attributes related to loss of beverage quality, such as content of total phenols, 5-caffeoylquinic acid, leached K, and electrical conductivity. Zinc supply influences the quality of coffee beans, having a positive effect on polyphenol oxidase activity, color index, and contents of sucrose, caffeine, and trigonelline. Adequate Zn doses reduce total phenol content, 5-caffeoylquinic acid, leached K, and electrical conductivity. The leaf contents, which related to the minimum or maximum points of the quality attributes studied, varied between 8.0 and 12.7 mg Zn kg⁻¹.

Sugarcane is among the most efficient crops in converting solar energy into chemical energy. However, due to its complex genome structure and inheritance, the genetic and molecular basis of biomass yield in sugarcane is still largely unknown. We created an F2 segregating population by crossing S. officinarum and S. spontaneum and evaluated the biomass yield of the F2 individuals. The F2 individuals exhibited clear transgressive segregation in biomass yield. We sequenced transcriptomes of source and sink tissues from 12 selected extreme segregants to explore the molecular basis of high biomass yield for future breeding of high-yielding energy canes. Among the 103,664 assembled unigenes, 10,115 and 728 showed significant differential expression patterns between the two extreme segregating groups in the top visible dewlap leaf and the 9th culm internode, respectively. The most enriched functional categories were photosynthesis and fermentation in the high-biomass and the low-biomass groups, respectively. Our results revealed that high-biomass yield was mainly determined by assimilation of carbon in source tissues. The high-level expression of fermentative genes in the low-biomass group was likely induced by their low-energy status. Group-specific expression alleles which can be applied in the development of new high-yielding energy cane varieties via molecular breeding were identified.

The nutritional quality of many fruits and vegetables is regulated by pre-harvest management factors that can be manipulated to attain desired quality standards. In this study, the impact of seed nanopriming on the phytochemical composition of watermelon was studied. Seeds of two watermelon varieties namely: River Side (diploid) and Maxima (triploid) treated with two nanomaterials (silver nanoparticle and turmeric nanoemulsion) along with untreated seeds were grown in five locations over two seasons. Physico-chemical properties and phytochemical profiles were assessed after mature fruits were harvested and stored at 23 °C for 0, 10, and 20 d. Key physico-chemical characteristics that were impacted by storage included fruit weight, rind thickness, pH, and soluble solid content. Similarly, levels of health-promoting compounds such as carotenoids, l -citrulline, and total ascorbic acid were maintained and/or enhanced in watermelons after 10 d of storage compared to untreated fruits at harvest. However, l -citrulline (10.40 g/kg) and total ascorbic acid (57.52 g/kg) was significantly reduced in watermelons after 20 d of storage (8.6 and 19.09 g/kg, respectively) regardless of treatment and location (p

High temperatures and drought are common stresses limiting crop growth and productivity in subtropical regions where citrus are produced. In addition to impacts on physiological processes such as transpiration, photosynthesis, and respiration, excessive solar radiation can also reduce fruit productivity by inducing physiological disorders such as sunburn. This study evaluated the effects of radiation reflectants and anti-transpirants on leaf physiology, and fruit sunburn in grapefruit trees (Citrus x paradisi Macfs. cv. Rio Red) in south Texas during the 2016 and 2017 growing seasons. Two calcium-based reflectants, and a methene/pinolene-based anti-transpirant were foliar applied to fruit-bearing trees. Reflectants reduced fruit and leaf temperatures by 0.2&deg, C and 0.21&deg, C, respectively, while the anti-transpirant treatments increased fruit and leaf temperature by approximately 0.83&deg, C and 0.2&deg, C relative to the controls. Stomatal conductance decreased by 1.3% and 3.3%, respectively, in response to the reflectant treatments, while anti-transpirant treatments resulted in decreased stomatal conductance (8.3%) relative to the controls. More sunburned fruit were found in anti-transpirant treated trees in both years (6% and 8.2% for 2016 and 2017) and the reflectant treatments reduced sunburn incidence by 4.9% and 1.8% in those years. These observations indicate that reflectant applications could be a viable strategy to mitigate heat/radiation stress and sunburn in grapefruit.

Severe virus-like symptoms consisting of mosaic, distortion, yellowing, and brittleness were observed on papaya plants in a 20-ha orchard in South Texas during the 2014–15 growing season. Incidence of symptomatic plants increased from ∼40 to 100% within 6 months of the outbreak; the most severely affected plants were stunted, and fruit yield and quality were reduced compared with asymptomatic plants. The orchard papaya plant virome was explored using the Illumina NextSeq 500 platform and results were validated by Sanger DNA sequencing of complete viral genomes obtained by PCR amplification. The combined results revealed the presence of Papaya ringspot virus (PRSV; Potyvirus), Lettuce chlorosis virus (LCV; Crinivirus), and Tomato yellow leaf curl virus-IL (TYLCV-IL; Begomovirus). The RT-PCR analyses of leaves from 51 randomly sampled papaya plants indicated the presence of PRSV, LCV, and TYLCV-IL in 100, 39.2, and 15.7% of the samples, respectively. Plants infected with PRSV, in combination with LCV and/or TYLCV-IL, exhibited more severe symptoms compared with plants infected with PRSV alone. Furthermore, successful whitefly-mediated transmission of TYLCV-IL and LCV was accomplished by exposing virus-free papaya seedlings to viruliferous Bemisia tabaci (Genn.) under greenhouse conditions. The results of this study document a new host record for LCV and the first successful whitefly-mediated transmission of TYLCV-IL and LCV to papaya. As a perennial crop, infected papaya serving as an over-seasoning reservoir for TYLCV-IL and LCV, presents a new challenge to viral disease management in papaya orchards.

Melon (Cucumis melo L.) is an important diploid crop with a wide variety of flavors due to its distinct aromatic volatile organic compounds (VOC). To understand the development of VOC profiles during fruit development, we performed metabolomic and transcriptomic analysis of two cantaloupe varieties over the course of fruit development. A total of 130 metabolites were detected in fruit samples, and 449014207 reads were mapped to the melon genome. A total of 4469 differentially expressed genes in fruits were identified and used to visualize the transition of VOC and transcriptomic profiles during the fruit development. A shift of VOC profiles in both varieties was observed from early-fruit profiles enriched in C5-C8 lipid-derived VOCs to late-fruit profiles abundant in C9 lipid-derived VOCs, apocarotenoids, and esters. The shift coincided with the expression of specific isoforms of lipid and carotenoid metabolizing enzymes as well as transcription factors involved in fruit ripening, metabolite regulation, and hormone signaling.

The influence of spectral light on leaf quality and phytochemical contents and composition of aroma compounds in coriander leaves grown for fresh use under photo-selective nets; pearl net [40% shading; and 3.88 blue/red ratio; 0.21 red/far red ratio; photosynthetic radiation (PAR) 233.24 (μmolm(-2)s(-1))] and red net [40% shading and 0.57 blue/red ratio; 0.85 red/far red ratio; 221.67 (μmolm(-2)s(-1))] were compared with commercially used black nets [25% shading; 3.32 blue/red ratio 0.96 red/far red ratio; 365.26 (μmolm(-2)s(-1))] at harvest and after 14days of storage. Black nets improved total phenols, flavonoid (quercetin) content, ascorbic acid content, and total antioxidant activity in coriander leaves at harvest. The characteristic leaf aroma compound decanal was higher in leaves from the plants under the red nets at harvest. However, coriander leaves from plants produced under red nets retained higher total phenols, flavonoids (quercetin) and antioxidant scavenging activity 14days after postharvest storage (0°C, 10days, 95% RH and retailers' shelf at 15°C for 4days, 75% RH). But production under the pearl nets improved marketable yield reduced weight loss and retained overall quality, ascorbic acid content and aroma volatile compounds in fresh coriander leaves after postharvest storage. Pearl nets thus have the potential as a pre-harvest tool to enhance the moderate retention of phytochemicals and saleable weight for fresh coriander leaves during postharvest storage.

This study illustrates the effects of light quality as influenced by photo-selective shade nets (red, yellow, and pearl with 40% shade) and the widely used commercial black net (25% shade) on overall retail quality and phytochemical contents of three lettuce (Lactuca sativa L.) varieties (two green varieties, Ashbrook and Aquarell, and a red variety, Exbury) at after postharvest storage. Variety-specific responses were observed with respect to different coloured shade nets with regards to the accumulation of β-carotene, ascorbic acid, flavonoids (kaempferol, isorhamnetin, quercetin, myricetin, anthocyanin), and antioxidant activity at harvest. Growing var. Ashbrook under the pearl net improved the ascorbic acid and myricetin contents after postharvest storage. Var. Exbury (red) produced under the black net showed higher retention of ascorbic acid, and anthocyanin contents after postharvest storage. Also pearl net production improved the β-carotene content after postharvest storage in var. Aquarell...

Grapefruits grown under organic or conventional systems were analyzed for 6,7-dihydroxybergamottin (DHB) and flavanones using HPLC, and DPPH activity and ORAC using a micro-plate reader. Grapefruits harvested in November 2008 (E-1) and February 2010 (E-2) were stored at room temperature (RT) and 9 °C for four weeks. Higher levels of DHB were observed in conventional grapefruits during the second (4.7 ± 0.2 μg/g), third (1.5 ± 0.2 μg/g) and fourth (2.5 ± 0.2 μg/g) week of storage at room temperature in E2. Among flavonoids analyzed, narirutin (666.7 ± 33.9 μg/g), neohesperidin (17.5 ± 1.3 μg/g), didymin (75.5 ± 5.6 μg/g) and poncirin (130.8 ± 10.4 μg/g) levels were significantly higher (P⩽0.05) in organic grapefruits over conventional grapefruits at harvest and storage in E-1. Although DPPH levels were moderately correlated with grapefruit flavanone content, variability in the individual flavanone activity was pronounced, resulting in non-significant differences in antioxidant activity between organic and conventional grapefruits.

Subtropical and tropical climates are becoming more vulnerable to drought and salinity problems. Of the crops produced in these climates, citrus is especially sensitive to increasing salinity. In times of water scarcity and periodic drought alternative water sources that may be lower in quality may be required for irrigation, leading to reduced yield unless a mechanism of increasing salinity tolerance is found. The salinity tolerance of citrus rootstocks differs depending on species and cultivar in their ability to exclude or sequester toxic ions. Identifying rootstocks that are more salt tolerant is important to citrus production in susceptible areas. ‘Olinda’ Valencia trees budded to three rootstocks (sour orange [SO], C22, and C146) and the ungrafted rootstocks were subjected to 6 months of saline irrigation. Simulated brackish water at 1, 3, 5, and 10 dS m −1 along with a 0 dS m −1 control were used to irrigate trees over the course of the study. Throughout this time period chlorophyll fluorescence, stomatal conductance, electrolyte leakage, and SPAD were measured to identify how trees responded to different levels of salinity stress. Chlorophyll fluorescence, stomatal control, and SPAD decreased with increased salinity, while electrolyte leakage increased. These responses were more pronounced in grafted trees than ungrafted trees. C22 and C146 rootstocks showed more tolerance to increases in salinity than the SO rootstocks. The ‘Olinda’ Valencia scion reduces rootstock tolerance to salinity, however, trees grafted to the C22 and C146 rootstocks showed more salinity tolerance than those grafted to SO rootstocks. This study emphasizes that both rootstock and scion should be considered when selecting trees for saline conditions.

Identifying the rates of nitrate absorption by almond plants under water stress is important for improving nitrogen use efficiency in almond orchards. This study aimed to determine the rates of nitrate absorption by almond plants subjected to short-term water stress and no water stress, and the kinetic NO3− absorption parameters in well-watered three-year-old almond plants. Two assays were performed. In the first, fourteen plants arranged in completely randomized design received nutrient solutions with water potentials (Ψw) of 0.0, −0.2, −0.4 and −0.7 MPa and containing 1.2 mmol l−1 KNO3. We accessed the NO3− depletion in these solutions over an 8-h interval and estimated regression curves of the quantity of nitrate in the nutrient solution (Q) as a function of time (t). Subsequently nitrate uptake rates were calculated. Water loss; nitrate reductase activity; nitrate and total N of the sap; nitrate concentration of leaf dry matter; and nitrate and nitrite concentration of root dry matter were, either, evaluated. The second assay was performed the same way of the first one, with four well-watered plants submitted to 0.3 mmol l−1 KNO3 as initial concentration, and allowed estimating NO3− absorption parameters Vmax, Km and Cmin. We observed a linear decrease in the nitrate content of the containers receiving 1.2 mmol l−1 of NO3− over a period of 8 h. In this concentration, the rates of NO3− uptake ranged from 1.11 to 3.43 μmol g−1 h−1 and decreased in low water potentials at the root medium. Root nitrate reductase activity followed the same trend of nitrate absorption. In the low NO3− concentration range, the absorption showed a Michaelis–Menten pattern, being the kinetic parameters of NO3− absorption 1.15 ± 0.27 μmol g−1 h−1, 28.81 ± 4.12 μmol l−1 and 17.93 ± 1.1 μmol l−1 for Vmax, Km, and Cmin, respectively. We concluded that NO3− uptake of almonds is affected by short periods of water stress, with harmful effects occurring at Ψw below −0.18 MPa.

Okra (Abelmoschus esculentus [L.] Moench) is an important fresh market vegetable crop in southern Texas, U.S.A. In fall 2018, an investigation was conducted to identify the agent(s) of a virus-like disease outbreak on a 4.9-ha okra (cv. Clemson Spineless) farm in Hidalgo Co., Texas. By mid-growing season, disease incidence was 100%, which led to total crop loss. Symptoms—foliar yellow mosaic, bleaching, and vein clearing—were reminiscent of those caused by begomoviruses (Begomovirus, Geminiviridae). Leaves collected from 10 randomly distributed symptomatic plants were subjected to total DNA isolation (Dellaporta et al. 1983) and rolling cycle amplification (RCA) (TempliPhi 100 Amplification Kit, GE Healthcare Biosciences). The RCA product was used as a template for PCR amplification of a diagnostic fragment of the DNA-A (Wyatt and Brown 1996) and DNA-B (Rojas et al. 1993) components and full-length alphasatellites (Bull et al. 2003) and betasatellites (Briddon et al. 2002). The expected-size amplicon corresponding to each of the four targets was obtained from all 10 samples, except the betasatellite, for which half of the expected ∼1,350-bp product resulted. Amplicons were cloned into the pJET1.2 plasmid vector, and inserts of the expected sizes were Sanger sequenced (n ≥ 3 per event). BLASTn searches of GenBank revealed an unexpectedly complex begomovirome, consisting of the monopartite cotton leaf curl Gezira virus (CLCuGV), cotton leaf curl Gezira alphasatellite (CLCuGA; Colecusatellite, Alphasatellitidae), cotton leaf curl Gezira betasatellite (CLCuGB; Betasatellite, Tolecusatellitidae), and the bipartite okra yellow mosaic Mexico virus (OkYMMV). Viral genome-, component-, and satellite-specific abutting primers were designed and used to PCR amplify the corresponding molecule from two RCA products in two different labs, followed by cloning and bidirectional Sanger sequencing of ≥3 clones per event. The complete genome sequences were analyzed comparatively with corresponding GenBank sequences of each genomic DNA segment using SDT1.2 (Muhire et al. 2014). The OkYMMV DNA-A of 2,613 nt (GenBank MN027195 to 96) and DNA-B of 2,594 nt (MN027197 to 98), each shared 99.5 and 99.7% maximum identity, respectively, with the DNA-A (HM035059) and -B (HM035060) of OkYMMV-[US:TX:09] from okra plants in Texas (Hernandez-Zepeda et al. 2010). The complete monopartite genome sequence of the CLCuGV okra isolates (MN027199 to 202) was 2,764 nt and shared 99.5 to 99.6% maximum identity with an isolate of CLCuGV from hollyhock plants in Jordan (CLCuGV-[JO:Hol:09]: GU945265). The closest relative of the CLCuGA okra isolate, of 1,354 nt (MN027203 to 05), was CLCuGA-[IL:IsSq-C171:11] (KT099176) from whiteflies collected from squash plants in Israel, at 99% identity. Several approaches by two independent laboratories to clone and sequence a full-length CLCuGB, involving restriction digestion from total DNA or RCA (n = 2) and/or PCR amplification with abutting primers designed based on the full-length CLCuGB sequences (AF397217, KT099178), yielded only “defective-sized” CLCuGB molecules of 676 to 730 nt (MN027206 to 220). The betasatellite half-mers lacked the βC1 coding region while sharing 96 to 99% identity with CLCuGB-[EG:OK03:02] (AF397217) from okra plants in Egypt and CLCuGB-[IL:IsSq-C9:11] (KT099178) from whiteflies. This is the first U.S. report of CLCuGV and its associated alphasatellite and betasatellite, which are endemic to Africa (Idris and Brown 2000). More recently, members of the CLCuGV-satellite complex have been reported in the African Sahel, Arabian Peninsula and Middle East, and Pakistan (Idris et al. 2014; Tahir et al. 2011; Tiendrebeogo et al. 2010). The source of this Old World CLCuGV-satellite complex into New World okra plants is unknown, but its introduction via infected plants or viruliferous whiteflies transported into southern Texas, with its intensive cotton and vegetable production, is plausible. Spread of this complex poses a serious threat because U.S. cotton and vegetable varieties harbor no resistance to CLCuGV.

Photoselective shade netting technology is an emerging agrotechnological concept, which aims at combining physical crop protection with different filtrations of solar radiation. They are based on the incorporation of various chromatic additives, light dispersive and reflective elements into the netting materials during manufacturing. Postharvest quality of fresh produce is influenced by environmental conditions that include light, average temperature, minimum temperature, and night–day temperature difference. Photoselective shade nets have been shown to influence yield and quality parameters of fresh produce, their impacts on functional properties of vegetables after postharvest storage has not been fully investigated. Therefore, this chapter illustrates the effect of different colored photoselective shade nets (pearl, red, and yellow) in comparison to the commercially used black net on vegetables, such as tomatoes and sweet overall quality parameters (weight, SSC, and TA), bioactive compounds (ascorbic acid, total phenols, flavonoids, β-carotene, and lycopene contents), antioxidant scavenging activity, volatile aroma compounds at harvest and after postharvest storage.

Micronutrients perform specific and essential functions in plant metabolism, and their deficiency may lead to metabolic disturbances that affect coffee production and quality beverage. In Brazil, the B, Cu, and Zn are the main micronutrients, and these are provided by soil or foliar fertilization, frequently with low recovery efficiency. This work objected verifying the feasibility of supplying of B, Cu, and Zn via insertion of tablets in the orthotropic branch of Coffea arabica, as well as to evaluate the coffee plant response in terms of productivity and quality of the beverage. Adult plants received B, Cu, and Zn, each micronutrient alone or combined with the other two, by foliar fertilization or by tablets inserted in the trunk base. The productivity, cupping quality, and some chemical indicators of beans quality were evaluated in two crop seasons. Boron, copper, and zinc supplied by foliar spray or solid injections in the trunk influenced the chemical composition and quality of the coffee beans, characterized by the cupping test and the levels of caffeine, trigonelline, sucrose, glucose, arabinose, mannose, 3-caffeoylquinic acid, 5-caffeoylquinic acid, polyphenol oxidase activity, and total phenolic compounds. Copper and zinc were equivalent in either form of supply regarding the production and quality of coffee.

Yields, water use efficiency and economic returns (net farm revenues) of biomass sorghum [Sorghum bicolor (L.) Moench] were investigated over two years (2012 and 2014) under limited water resource conditions. Energy sorghum was grown under four water supply regimes: rain-fed (or dry-land, level 1), 50% (level 2), 75% (level 3) and 100% (level 4) of crop evapotranspiration rates (% ETc). Biomass yields ranged from 5.8 to 16.6 Mg ha−1 (dry weight) after 126 days of growth. Average water use efficiencies ranged from 3.95 kg m−3 to 23.4 kg m−3. Net return was approximately 410 $ ha−1 with water depths above 400 ha-mm. These results suggest that it is possible to obtain more than 60 Mg ha−1 of sorghum biomass (wet basis) with at least 425 mm of water. While biomass yield under irrigation was greater than rain-fed conditions, there were no significant differences among irrigation treatments. Biomass chemical composition did not differ significantly among water treatments suggesting that biofuel quality would not be affected by water deficits.

This study was designed to characterize morphological, physiological and molecular responses of sugarcane genotypes to a simulated water deficit stress. Two genotypes (TSP05-4: Drought-tolerant; TCP02-4589: Drought-sensitive) were subjected to a 20-day water deficit treatment and an 8-day recovery period. Leaf photosynthesis (Pn), transpiration rate (E), stomatal conductance (Gs), leaf greenness index (SPAD) and variable-to-maximum chlorophyll a fluorescence ratio (Fv/Fm), were evaluated before, during and after water deficit. Root-to-shoot ratio (R/S), stalk height (SH), diameter (SD) and stalk weight (SW) were evaluated at the end of the experiment. Real-time RT-PCR confirmed seven differentially-expressed transcript-derived fragments (TDFs) identified by cDNA-AFLP. Pn rates were similar between the genotypes under well-watered conditions. However, under water deficit, TSP05-4 had higher Pn rates. SPAD, Fv/Fm and R/S were also generally higher in TSP05-4, regardless of soil moisture status. Water deficit-induced reductions in SH and SW were greater in TCP02-4589 than in TSP05-4. Three TDFs showing sequence similarities to genes encoding a putative expressed pentatricopeptide, a protein kinase CK2 regulatory subunit CK2β3, and a glucose-6-phosphate/phosphate translocator 2 were identified in TCP02-4589. One TDF similar to a drought-inducible protein was identified in TSP05-4. Recovery of physiological processes and gene expression patterns to the water stress levels was fast. Key words: Differential gene expression, water deficit stress, re-watering, Saccharum spp.

Postharvest responses of red ('HTSP-3') and yellow ('Celaya') sweet pepper fruit yield, quality parameters and bioactive compounds (to three types of photo-selective nets and a standard black net) were investigated in this study. Red and yellow peppers produced under the black net retained higher β-carotene, lower total phenolic contents and showed deep red and orange colour after storage. Both peppers produced under the pearl net retained a higher ascorbic content, antioxidant scavenging activity, fruit firmness and also reduced weight loss after storage. Red and yellow peppers grown under pearl and yellow nets resulted in a higher percentage of marketable fruit, after storage. Red pepper grown under the yellow net showed a higher number of odour active aroma compounds in the fruit, while black nets significantly affected the synthesis of odour active aroma compounds during storage. Sensory analysis indicated a preference for red pepper fruits after storage from plants grown under pearl nets.

Selection of the proper irrigation method will be advantageous to manage limited water supplies and increase crop profitability. The overall objective of this study was to evaluate the effect of subsurface drip irrigation (SDI) and furrow irrigation on onion yield and irrigation use efficiency. This study was conducted in two locations, a commercial field and a field located at the Texas A&M AgriLife Research Center in Weslaco, TX. This study was conducted as a split-plot design for both sites with two treatments (SDI and furrow irrigation) and three replications per treatment. The total onion yield obtained with the SDI systems was more than 93% higher than the yield obtained with furrow irrigation systems. The large onion size was 181% higher for the SDI system than the furrow system in both sites. The colossal size yield was also higher. At one site colossal yield was 206% higher than furrow, while at another site furrow yielded no colossal onions and SDI had some production. It was concluded that drip irrigation systems more than double yields and increased onion size while using almost half of the water. This was due to SDI allowing for more frequent and smaller irrigation depths with higher irrigation efficiency than furrow irrigation systems.

Government support uncertainty, scarce yield information, and the inherent risk in bioeconomic phenomena are some of the deterrents faced by investors in the nascent cellulosic biofuel industry. A financial probabilistic model was developed to contrast the economic feasibility of producing cellulosic biofuels from energy cane and sweet sorghum using three technologies: hydrolysis, pyrolysis, and gasification. Hydrolysis and pyrolysis proved feasible (showed possibilities of a positive net present value) without government support and conditioned to stochastic feedstock yields and biofuel prices. Gasification was feasible with government support. Improved feedstock and biofuel productivity would considerably raise the feasibility probabilities for hydrolysis and pyrolysis without government support.

As population and agricultural pressure on high quality fresh water resources increases, it becomes more important to identify rootstocks and production techniques that allow the usage of lower quality water in irrigated agriculture. Water of 0, 1, 3, 5 and 10 dS m −1 salinity was applied to grafted (with Olinda Valencia ( Citrus sinensis var. Olinda) scion) and ungrafted sour orange ( Citrus aurantium L.), C22, and C146 ( Citrus sunki Hort. Ex Tan. × Poncirus trifoliata L. Raf. ‘Swingle’) trees to evaluate the effect of grafting and rootstock variety on salinity tolerance. Grafted rootstocks had a lower survival rate at higher salinity concentration than ungrafted trees and effects were dependent upon tree variety. Height growth rate and standing leaf area of grafted citrus trees declined with increased salinity concentrations while the response of ungrafted and grafted citrus trees was variety dependent. Mortality increased and standing leaf area decreased with increasing tissue Na + and Cl − concentrations. Mortality in response to salinity was greater in grafted rootstocks than mortality of ungrafted trees. Overall, C22 and C146 rootstocks and ungrafted trees were found to be more tolerant of saline conditions than grafted SO rootstock or ungrafted SO trees.

Bioactive compounds in plant-derived foods provide essential human health benefits. However, the content and types of bioactive compounds may vary based on genetic and environmental factors. The present study examined the impacts of cultivar, fruit maturity stage (mature versus immature), and growing season (2008, 2009) on the concentration of bioactive compounds in diverse pungent and non-pungent peppers. Significant interactions were observed among cultivars, maturity stages, and growing seasons. Mature peppers generally had the highest content of ascorbic acid (782.0–2305.3 μg/g FW in 2008 and 693.5–2817.2 μg/g FW in 2009), and capsaicinoids (115.5–338.9 μg/g FW in 2008 and 93.8–326.3 μg/g FW in 2009) compared to immature peppers. Paprika-type peppers generally had the highest contents of ascorbic acid and flavonoids especially in mature fruits, while capsaicinoids were higher in all mature stage peppers. Flavonoid concentrations varied considerably depending on cultivar and maturity stage. Total phenolics were also significantly higher in mature fruits compared to immature peppers in both years. A positive correlation between total phenolics and DPPH radical scavenging activity was observed. This indicates that the health beneficial components in peppers could also vary as a function of cultivar, fruit developmental stage and production season. The genetic variability in bioactive compounds found in this study constitutes a useful genetic base for improving the nutrient quality of peppers.

Grapefruit heterocyclic oxygenated compounds have demonstrated antimicrobial and cytotoxic properties; purifying these compounds is essential for systematic biological studies to elucidate their bioactive properties. In the current study, a new method was used to isolate and purify coumarins from grapefruit oil and peels. Grapefruit oil was fractionated into volatile and non-volatile fractions (NVFs) by vacuum distillation. The NVF was further partitioned into hexane soluble and hexane insoluble fractions (HIFs). Then, the NVF–HIF composite was subjected to a hyphenated chromatography and separations were performed using a C-18 reversed phase column to yield several compounds. Additionaly, grapefruit peel was extracted with hexane and five compounds were purified using a normal phase silica column using hyphenated chromatography. Structures of the purified compounds were elucidated by 1 H and 13 C attached proton test (APT) NMR spectral data and identified as pranferin ( 1 ), meranzin ( 2 ), bergapten ( 3 ), dihydroxybergamottin ( 4 ), and marmin ( 9 ). Compounds ( 5–8 ) were later identified as heptamethoxy flavone, auraptene, osthol and nobilitin by comparing retention times in HPLC and mass spectra. With this method, it was possible to selectively separate major compounds from minor bioactives prior to hyphenated chromatography. This approach of solvent partitioning and rapid hyphenated chromatography proved highly effective in isolating several compounds, including pranferin from grapefruit oil.

Genetic diversity is present in the Capsicum genus for fruit size, shape, color, length, firmness, flavor, and even concentrations of different phytochemicals. Our goal in this study was to gain a better understanding of the relative ease of incorporating these characteristics into an improved cultivar evaluating a combination of 29 F1 paprika and serrano pepper (Capsicum annuum) hybrids along with 19 of their respective parents. Genotypes were grown and evaluated at the Texas AgriLife Research Center in Weslaco in the spring of 2008. Results confirmed our hypotheses that paprika type material have higher ascorbic acid (AA) and flavonoid (quercetin and luteolin) concentrations, while serrano peppers have higher expression of capsaicinoids (capsaicin and dihydrocapsaicin). We were also able to identify how productive certain hybrid combinations were at expressing a significant amount of positive heterosis for particular traits. From our Pearson's correlation analyses, we were able to identify the existence of a significant association between such comparisons as fruit weight with fruit diameter, fruit weight with fruit length, and fruit diameter with fruit length. Interestingly, we were also able to identify the presence of a significant association between such comparisons as ascorbic acid with fruit weight, ascorbic acid with fruit length, ascorbic acid with fruit diameter, total flavonoids with fruit weight, and total flavonoids with fruit length. This information, henceforth, allowed us to acknowledge the amount of variability present between these comparisons. In all, our results were able to reveal how effective certain combinations of parent material are toward production of F1 offspring exhibiting improved fruit traits and elevated phytochemical concentrations. Ideally, these results will serve as benchmarks for breeders interested in development of improved lines for these traits.

Fruit cracking is an important disorder that can cause severe loss of marketable yield and revenue in the muskmelon (Cucumis melo) fruit industry. The physiological and environmental factors causing cracking are poorly understood. Although generally considered a physiological disorder caused by fluctuating environmental conditions, current evidence indicates that this disorder also has a genetic as well as a genotype × environment component. Certain cultivars are more susceptible than others, but wide fluctuations in irrigation, temperature, and nutrition during late fruit maturation stages appear to predispose fruit to cracking. This article summarizes the current state of our understanding of the causes of fruit splitting in muskmelons.

The Asian citrus psyllid preferentially feeds and exclusively reproduces on young, newly emerged flush shoots of citrus. Asian citrus psyllid nymphs feed and complete their life stages on these flush shoots. Recent studies conducted under greenhouse conditions have shown that the transmission rates of ‘Candidatus Liberibacter asiaticus’ (CLas), the putative causal agent of huanglongbing disease of citrus, are enhanced when flush shoots are present. However, it is unclear if CLas acquisition by migrant adult Asian citrus psyllids is similarly enhanced. To address this knowledge gap, cohorts of Asian citrus psyllid adults were allowed 1-wk acquisition access period (AAP) on flushing and nonflushing shoots of qPCR-tested symptomatic (CLas+) and asymptomatic (CLas–) 10-yr-old sweet orange trees under field conditions. After the AAP, they were tested for CLas by qPCR. Progeny Asian citrus psyllid adults that emerged 4 wk post-AAP were similarly retrieved and tested. Eighty percent of flushing and 30% of nonflushing CLas+ trees produced infective Asian citrus psyllid adults, indicating that flush shoots have greater potential to be inoculum sources for CLas acquisition. Concomitantly, 21.1% and 6.0% infective adults were retrieved, respectively, from flushing and nonflushing CLas+ trees, indicating that Asian citrus psyllid adults acquire CLas more efficiently from flush shoots relative to mature shoots. In addition, 12.1% of infective Asian citrus psyllid adult progeny were obtained from 70% of flushing CLas+ trees. Significantly lower mean Ct values were also obtained from infective adults retrieved from flushing relative to nonflushing trees. The results underscore the role of flush shoots in CLas acquisition and the need to protect citrus trees from Asian citrus psyllid infestations during flush cycles.

Studies were conducted to relate the influence of the physical characteristics, leaf nutrient content and phloem sap amino acid concentration of citrus flush shoots on the densities of various Diaphorina citri life stages. Adult D. citri preferentially selected young shoots for feeding and numbers of D. citri immatures were positively correlated with flush shoot softness. Young flush shoots had higher concentrations of macro and micro nutrients relative to mature ones and this was associated with higher densities of all D. citri life stages. All D. citri life stages were positively correlated with higher nitrogen-carbon (N:C), nitrogen:sulfur (N:S) and nitrogen:calcium (N:Ca) ratios in leaf tissue, while densities of adults were negatively related to calcium, manganese and boron levels. Concentrations of total and essential amino acids were highest in phloem sap of young expanding flush shoots in both grapefruit and lemon, but dramatically declined as flush shoots matured. The sulfur-containing amino acids cystine, methionine and taurine occurred only in younger flush shoots. In contrast, cystathionine was only present in phloem sap of mature shoots. These results clearly indicate that young citrus flush shoots are a nutritionally richer diet relative to mature shoots, thus explaining their preference by D. citri for feeding and reproduction. Conversely, tissue hardness and the lower nutritional quality of mature flush shoots may limit oviposition and immature development. The data suggest that both physical characteristics and nutritional composition of flush shoots and their phloem sap are important factors regulating host colonization and behavior of D. citri, and this interaction can impact the dynamics and spread of HLB in citrus groves.

SUMMARYThe relationships between physiological variables and sugarcane productivity under water deficit conditions were investigated in field studies during 2005 and 2006 in Weslaco, Texas, USA. A total of 78 genotypes and two commercial varieties were studied, one of which was drought-tolerant (TCP93-4245) and the other drought-sensitive (TCP87-3388). All genotypes were subjected to two irrigation regimes: a control well-watered treatment (wet) and a moderate water-deficit stress (dry) treatment for a period of 90 days. Maximum quantum efficiency of photosystem II (Fv/Fm), estimated chlorophyll content (SPAD index), leaf temperature (LT), leaf relative water content (RWC) and productivity were measured. The productivity of all genotypes was, on average, affected negatively; however, certain genotypes did not suffer significant reduction. Under water deficit, the productivity of the genotypes was positively and significantly correlated with Fv/Fm, SPAD index and RWC, while LT had a negative correlation. These findings suggest that genotypes exhibiting traits of high RWC values, high chlorophyll contents and high photosynthetic radiation use efficiency under low moisture availability should be targeted for selection and variety development in programmes aimed at improving sugarcane for drought prone environments.