Preharvest Elicitors as a Tool to Enhance Bioactive Compounds and Quality of Both Peel and Pulp of Yellow Pitahaya (Selenicereus megalanthus Haw.) at Harvest and during Postharvest Storage.

Yellow pitahaya is a tropical fruit that has gained popularity in recent years. Natural elicitors are compounds that can stimulate the resistance and quality of fruits. The objective of this study was to evaluate the effects of natural elicitors, methyl salicylate (MeSa), methyl jasmonate (JaMe), salicylic acid (SA) and oxalic acid (OA) at concentrations of 0.1 mM (MeSa and JaMe) and 5 mM (SA and OA), applied to the yellow pitahaya fruits under greenhouse conditions. After full blossom, four applications were made with a frequency of 15 days. At the time of harvest and after storage, the following variables were evaluated: firmness (whole fruit), total soluble solids (TSS), total acidity (TA), phenolics and carotenoids (in the pulp), while phenolics, carotenoids, macronutrients and micronutrients were determined in the peel. The results showed MeSa advanced the fruit maturation, according to higher TSS, lower TA and firmness than MeJa-treated fruits, for which a delayed ripening process was shown. All treatments induced a higher polyphenolic concentration during storage. Regarding the alternative use of the peel as a by-product, the application of natural elicitors significantly increased the content of polyphenols, carotenoids, macronutrients and micronutrients in the peel, especially MeSa, which can be used as a bioactive compound in the food industry. In conclusion, the results indicate that natural elicitors can be an alternative to improve the quality and shelf life of yellow pitahaya fruits.

Trends in research on cacti: the food of the future.

Cacti are a distinguished group of plants that stand out for their great nutritional values, diverse uses, and unique morphology, allowing them to grow and thrive under different conditions such as dry, xeric, and even low-temperature environments. The world is going through significant climate changes that are affecting the agriculture system. Therefore, sustainable and multifunctional crops, as many species of the Cactaceae family are, might be a good alternative in the near future. In this work, the uses of cacti in human food were analyzed through a scientific prospection from the point of view of their temporal and spatial distribution and potential uses. Brazil is the country with more publications related to the scope of this work, followed by Mexico. The presence of cacti in these countries can influence their interest in these species, which might reflect the results encountered in this study. The uses and ethnobotanical applications of cacti vary in different countries worldwide. Cactus is consumed fresh (in salads), in preparations (jams and sweets), and juices, being also present in traditional dishes in countries like Mexico. This study emphasizes cacti's importance in people's diets and ongoing world changes. Their ability to thrive even in hot environments with low water resources will lead to a greater focus on these species in the upcoming years. Furthermore, these plants have great flavor and contain several beneficial chemical compounds with desirable nutritional and health properties. Therefore, knowledge dissemination combined with technological innovations will allow greater use of these multifunctional species for human consumption. © 2024 Society of Chemical Industry.

Comparative analysis of floral transition and floral organ formation in two contrasting species: Disocactus speciosus and D. eichlamii (Cactaceae).

KEY MESSAGE: Contrasting morphologies in Disocactus are the result of differential development of the vegetative and floral tissue where intercalary growth is involved, resulting in a complex structure, the floral axis. Species from the Cactaceae bear adaptations related with their growth in environments under hydric stress. These adaptations have translated into the reduction and modification of various structures such as leaves, stems, lateral branches, roots and the structuring of flowers in a so-called flower-shoot. While cacti flowers and fruits have a consistent structure with showy hermaphrodite or unisexual flowers that produce a fruit called cactidium, the developmental dynamics of vegetative and reproductive tissues comprising the reproductive unit have only been inferred through the analysis of pre-anthetic buds. Here we present a comparative analysis of two developmental series covering the early stages of flower formation and organ differentiation in Disocactus speciosus and Disocactus eichlamii, which have contrasting floral morphologies. We observe that within the areole, a shoot apical meristem commences to grow upward, producing lateral leaves with a spiral arrangement, rapidly transitioning to a floral meristem. The floral meristem produces tepal primordia and a staminal ring meristem from which numerous or few stamens develop in a centrifugal manner in D. speciosus and D. eichlamii, respectively. Also, the inferior ovary derives from the floral meristem flattening and an upward growth of the surrounding tissue of the underlying stem, producing the pericarpel. This structure is novel to cacti and lacks a clear anatomical delimitation with the carpel wall. Here, we present a first study that documents the early processes taking place during initial meristem determination related to pericarpel development and early floral organ formation in cacti until the establishment of mature floral organs.

Unraveling the development behind unisexual flowers in Cylindropuntia wolfii (Cactaceae).

BACKGROUND: In certain unisexual flowers, non-functional sexual organs remain vestigial and unisexuality can be overlooked leading to the ambiguous description of the sexual systems. Therefore, to accurately describe the sexual system, detailed morphological and developmental analyses along with experimental crosses must be performed. Cylindropuntia wolfii is a rare cactus endemic to the Sonoran Desert in southern California and northern Baja California that was described as gynodioecious by morphological analysis. The aims of our project include accurately identifying the sexual system of C. wolfii using histological and functional studies and characterizing the developmental mechanisms that underlie its floral development. METHODS: Histological analyses were carried out on different stages of C. wolfii flowers and controlled crosses were performed in the field. RESULT: Our results identified C. wolfii to be functionally dioecious. The ovule and anther development differed between staminate and pistillate flowers. In vivo pollen germination tests showed that the pollen of staminate and pistillate flowers were viable and the stigma and style of both staminate and pistillate flowers were receptive. This suggests that there are no genetic or developmental barriers in the earlier stages of pollen recognition and pollen germination. CONCLUSIONS: Despite being functionally dioecious, we observed that functionally pistillate individuals produced fruits with a large number of aborted seeds. This implies that not only does this species have low reproductive success, but its small population sizes may lead to low genetic diversity.

Soil Microbial Communities Altered by Titanium Ions in Different Agroecosystems of Pitaya and Grape.

Titanium (Ti) is an element beneficial to plant growth. Application of titanium to roots or leaves at low concentrations can improve crop yield and performance. However, the effect of titanium ions on the bulk soil microbial community of planted crops remains unclear. This study aimed to explore the effects of titanium on soil bacterial and fungal communities. Field surveys were conducted to determine the effect of titanium ions on bulk soil microbial communities in pitaya and grape plantations of Panzhihua and Xichang areas, respectively. Full-length 16S rRNA and internal transcribed spacer (ITS) amplicon sequencing were performed using PacBio Sequel to further explore the composition and structure of soil microbiota. The application of titanium ions significantly altered the composition and structure of soil microbiota. Root irrigation with titanium ions in pitaya gardens reduced the diversity of soil fungi and bacteria. However, the decline in bacterial diversity was not statistically significant. Meanwhile, foliar spray of titanium ions on grapes greatly reduced the soil microbial diversity. The bulk soil microbiota had a core of conserved taxa, and titanium ions significantly altered their relative abundances. Furthermore, the application of titanium increased the interaction network of soil fungi and bacteria compared with the control group. Thus, titanium ions potentially improve the stability of the soil microbial community. IMPORTANCE Pitaya and grape are important cash crops in the Panzhihua and Xichang areas, respectively, where they are well adapted. Titanium is a plant growth-promoting element, but the interaction between titanium and soil microorganisms is poorly understood. Titanium ions are still not widely used for growing pitaya and grape in the two regions. Thus, we investigated the effects of titanium ions on soil microbial communities of the two fruit crops in these two regions. Microbial diversity decreased, and the community structure changed; however, the addition of titanium ions enhanced cooccurrence relationships and improved the stability of the community. This study provides a basis for the importance of titanium ion application in crop cultivation.

An Integrative Transcriptomic and Metabolomic Analysis of Red Pitaya (Hylocereus polyrhizus) Seedlings in Response to Heat Stress.

Red pitaya (Hylocereus polyrhizus) is a significant functional food that is largely planted in Southeast Asia. Heat stress (HS) induced by high temperatures is likely to restrict the growth and survival of red pitaya. Although pitaya can tolerate temperatures as high as 40 °C, little is known of how it can withstand HS. In this study, the transcriptomic and metabolomic responses of red pitaya seedlings to HS were analyzed. A total of 198 transcripts (122 upregulated and 76 downregulated) were significantly differentially expressed after 24 h and 72 h of exposure to 42 °C compared with a control grown at 28 °C. We also identified 64 differentially accumulated metabolites in pitaya under HS (37 increased and 27 decreased). These differential metabolites, especially amino acids, organic acids, and sugars, are involved in metabolic pathways and the biosynthesis of amino acids. Interaction network analysis of the heat-responsive genes and metabolites suggested that similar pathways and complex response mechanisms are involved in the response of pitaya to HS. Overexpression of one of the upregulated genes (contig10820) in Arabidopsis, which is a homolog of PR-1 and named HuPR-1, significantly increased tolerance to HS. This is the first study showing that HuPR-1 plays a role in the response of pitaya to abiotic stress. These findings provide valuable insights that will aid future studies examining adaptation to HS in pitaya.

Genome-Wide Identification of Aquaporin Gene Family in Pitaya Reveals an HuNIP6;1 Involved in Flowering Process.

Aquaporins (AQPs) are essential membrane proteins involved in seed maturation and germination, stomata movement, photosynthesis, and regulation of plant flowering processes. Pitaya flowers are open at night and wither at daybreak, which shows an obvious circadian rhythm. In this study, a comprehensive genome-wide analysis of AQPs in Hylocereus undantus was conducted to screen key genes associated with flowering processes. A total of 33 HuAQP genes were identified from the H. undantus genome. The 33 HuAQPs were grouped into four subfamilies: 10 PIPs, 13 TIPs, 8 NIPs, and 2 SIPs, which were distributed on 9 out of 11 pitaya chromosomes (Chr) (except for Chr7 and Chr10). Results from expression profiles showed that HuNIP6;1 may be involved in pitaya's floral opening. HuNIP6;1 was localized exclusively in the cell membrane. Overexpression of HuNIP6;1 in Arabidopsis thaliana significantly promoted early flowering through regulating negative flowering regulators of MJM30, COL9, and PRR5, suggesting that HuNIP6;1 plays key roles in regulating flowering time. The present study provides the first genome-wide analysis of the AQP gene family in pitaya and valuable information for utilization of HuAQPs.

Episodic recruitment in the saguaro cactus is driven by multidecadal periodicities.

Each year, an individual mature large saguaro cactus produces about one million seeds in attractive juicy fruits that lure seed predators and seed dispersers to a 3-month feast. From the million seeds produced, however, only a few will persist into mature saguaros. A century of research on saguaro population dynamics has led to the conclusion that saguaro recruitment is an episodic event that depends on the convergence of suitable conditions for survival during the critical early stages. Because most data have been collected in Arizona, particularly in the surroundings of Tucson, most research has relied on a limited amount of environmental variation. In this study, we upscaled this knowledge on saguaro recruitment to a regional scale with a new method that used the inverse-growth modeling of 1,487 saguaros belonging to 13 populations in a latitudinal gradient ranging from arid desert to tropical thornscrub forest in Sonora, Mexico. Using generalized linear and additive mixed models, we created two 110-yr-long saguaro recruitment curves: one driven only by previous size, and the second driven by size, drought, and soil structure. We found evidence that saguaro recruitment is indeed episodic, with periodicities of 20-30 yr, possibly related to strong El Niño Southern Oscillation events. Our results suggest that saguaros rely on multidecadal periodic pulses of good beneficial years to incorporate new individuals into their populations. Inverse-growth modeling can be used in a wide variety of plant species to study their recruitment dynamics.

Effect of shade and precipitation on germination and seedling establishment of dominant plant species in an Andean arid region, the Bolivian Prepuna.

Germination and seedling establishment are two critical processes in the life cycle of plants. Seeds and seedlings must pass through a series of abiotic and biotic filters in order to recruit as members of their communities. These processes are part of the regeneration niche of the species. In arid regions, the regeneration niche is frequently associated to facilitation by shade. Facilitation is a positive interaction between plants, in which one of them acts as a benefactor (the nurse) of the other (the beneficiary). The result of this interaction can be reflected in the increased growth, survival, and/or reproduction of the beneficiary plant. In this study, we determined experimentally the effect of shade and irrigation on the germination and early survival of dominant species of a semi-arid Andean region, the Bolivian Prepuna. An experiment with Acacia feddeana, Prosopis ferox, Cercidium andicola (woody species), Parodia maassii, and Oreocereus celsianus (cactus species) was carried out at an experimental garden in La Paz, Bolivia, with a bifactorial design, considering shaded and unshaded pots, subjected to two irrigation treatments (≈50 and 80 mm of rainfall during the whole study period). Microenvironmental conditions did not affect the seed germination of the woody species. However, they showed differences in seedling survival: A. feddeana survived better under shade, whereas P. ferox and C. andicola survived better without shade. Cercidium andicola, compared to P. ferox, was more affected by shade and low irrigation. Although germination success of cacti was low, both species germinated better under shade and with high irrigation. These results showed differences in the regeneration niche of dominant species of the Prepuna which may favor their coexistence and which may be characteristic of other dry Andean regions.

Identification and characterization of the EXPA7, EXPA18 and EXT10 genes in Turbinicarpus lophophoroides (Werderm.) Buxb. & Backeb; and their expression analysis in the root under abiotic stress.

Expansin and extensin are proteins involved in resistance to various abiotic stresses by processes of cell wall modification and in the formation and elongation of the hairy root. They are located in several organs of the plant included root epidermis. Turbinicarpus lophophoroides is a cactus model to studies these genes in adventitious and transformed roots. In this study, we identified and characterized the expansin7, expansin18 and extensin10 genes in T. lophophoroides. Bioinformatic analysis indicated that the expansin sequences contained the motifs: HTFYG, HFD, YRR, VPC and YW; and certain conserved cysteine (C) residues. Regarding extensin10, the sequence contains the conserved SPPPP (SP4), YYS and YV motifs. The expression analysis in adventitious and transformed roots under osmotic stress (300 mM mannitol), heat (37 °C) and cold (4 °C); shows a higher expression of TlExpA18 in both roots, a decrease in TlExpA7 in transformed roots and a null expression in TlExt10 in both roots. In addition, a morphological comparison of the maturation/differentiation zone, meristem and cap between adventitious and transformed roots by SEM was performed, finding differences in the quantity and length of the hairy roots and the shape of the root cap. Overall, the study concluded that TlExpA18 and TlExpA7 belong to expansin family and TlExt10 belong to extensin family. The expression characteristics of TlExpA18, TlExpA7 and TlExt10 will facilitate the investigation of its function in stress response and other physiological processes in T. lophophoroides.

An AP2/ERF Gene, HuERF1, from Pitaya (Hylocereus undatus) Positively Regulates Salt Tolerance.

Pitaya (Hylocereus undatus) is a high salt-tolerant fruit, and ethylene response factors (ERFs) play important roles in transcription-regulating abiotic tolerance. To clarify the function of HuERF1 in the salt tolerance of pitaya, HuERF1 was heterogeneously expressed in Arabidopsis. HuERF1 had nuclear localization when HuERF1::GFP was expressed in Arabidopsis protoplasts and had transactivation activity when HuERF1 was expressed in yeast. The expression of HuERF1 in pitaya seedlings was significantly induced after exposure to ethylene and high salinity. Overexpression of HuERF1 in Arabidopsis conferred enhanced tolerance to salt stress, reduced the accumulation of superoxide (O2∙) and hydrogen peroxide (H2O2), and improved antioxidant enzyme activities. These results indicate that HuERF1 is involved in ethylene-mediated salt stress tolerance, which may contribute to the salt tolerance of pitaya.

Transcriptomic analysis reveals hub genes and subnetworks related to ROS metabolism in Hylocereus undatus through novel superoxide scavenger trypsin treatment during storage.

BACKGROUND: It was demonstrated in our previous research that trypsin scavenges superoxide anions. In this study, the mechanisms of storage quality improvement by trypsin were evaluated in H. undatus. RESULTS: Trypsin significantly delayed the weight loss and decreased the levels of ROS and membrane lipid peroxidation. Transcriptome profiles of H. undatus treated with trypsin revealed the pathways and regulatory mechanisms of ROS genes that were up- or downregulated following trypsin treatment by gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes pathway (KEGG) enrichment analyses. The current results showed that through the regulation of the expression of hub redox enzymes, especially thioredoxin-related proteins, trypsin can maintain low levels of endogenous active oxygen species, reduce malondialdehyde content and delay fruit aging. In addition, the results of protein-protein interaction networks suggested that the downregulated NAD(P) H and lignin pathways might be the key regulatory mechanisms governed by trypsin. CONCLUSIONS: Trypsin significantly prolonged the storage life of H. undatus through regulatory on the endogenous ROS metabolism. As a new biopreservative, trypsin is highly efficient, safe and economical. Therefore, trypsin possesses technical feasibility for the quality control of fruit storage.

Transcriptomic analysis of flower induction for long-day pitaya by supplementary lighting in short-day winter season.

BACKGROUND: Pitayas are currently attracting considerable interest as a tropical fruit with numerous health benefits. However, as a long-day plant, pitaya plants cannot flower in the winter season from November to April in Hainan, China. To harvest pitayas with high economic value in the winter season, it is necessary to provide supplementary lighting at night to induce flowering. To further explore the molecular regulating mechanisms of flower induction in pitaya plants exposed to supplementary lighting, we used de novo RNA sequencing-based transcriptomic analysis for four stages of pitaya plants subjected to light induction. RESULTS: We assembled 68,113 unigenes in total, comprising 29,782 unigenes with functional annotations in the NR database, 20,716 annotations in SwissProt, 18,088 annotations in KOG, and 11,059 annotations in KEGG. Comparisons between different samples revealed different numbers of significantly differentially expressed genes (DEGs). A number of DEGs involved in energy metabolism-related processes and plant hormone signaling were detected. Moreover, we identified many CONSTANS-LIKE, FLOWERING LOCUS T, and other DEGs involved in the direct regulation of flowering including CDF and TCP, which function as typical transcription factor genes in the flowering process. At the transcriptomic level, we verified 13 DEGs with different functions in the time-course response to light-induced flowering by quantitative reverse-transcription PCR analysis. CONCLUSIONS: The identified DEGs may include some key genes controlling the pitaya floral-induction network, the flower induction and development is very complicated, and it involves photoperiod perception and different phytohormone signaling. These findings will increase our understanding to the molecular mechanism of floral regulation of long-day pitaya plants in short-day winter season induced by supplementary lighting.

Cacti for production of metabolites: current state and perspectives.

The Cactaceae family is native from the American continent but is distributed in the arid and semiarid regions worldwide. Cacti exhibit different morphological (succulent body, extended root system, presence of spines, thick waterproof epidermis) and physiological adaptations (crassulacean acid metabolism) that allow growth in adverse conditions intolerable for most C3 and C4 crops. In addition, these plants produce a wide range of secondary metabolites involved in defense mechanism against biotic and abiotic stresses. The present review focused on the content of alkaloids, phenolic compounds, and terpenes present in cacti plants. Data were limited to those compounds clearly characterized by chromatographic and/or spectrometric techniques in both globular and columnar cacti. Additional information about their pharmacological or biological activities, validated by in vitro or in vivo assays, is also presented. Data revealed that the level of some chemical constituents could give value added to these species from a nutritional, pharmacological, and biological point of view.

Optimizing the use of spineless cactus in the finishing diet of lambs: physicochemical properties and sensory characteristics of meat.

BACKGROUND: The use of spineless cactus in finishing diets for lambs improves the carcass quality. However, data about its influence on meat traits is very scarce. The effects of spineless cactus inclusion in the finishing diet of lambs at four levels (0, 150, 300 and 450 g kg-1 of dry matter, DM) in replacement of Tifton hay on the physicochemical and sensory properties of meat were studied. RESULTS: The spineless cactus modified the chemical composition increasing the protein (P < 0.001) and the fat (P < 0.01) contents of meat, presenting the greatest values in lambs fed diets with 150 and 300 g kg-1 (DM) replacing levels, respectively. However, the spineless cactus did not influence the growth performance from 23.7 to 37.3 kg of body weight (on average). In addition, colour parameters of the meat were not affected by the inclusion of spineless cactus in the finishing diet of lambs, resulting in mean values of 37.55, 14.96 and 8.49 for lightness, redness and yellowness, respectively. There were no statistical differences among treatments for cooking loss and shear force, with mean values of 34.8% and 14.8 N, respectively. Finally, the sensorial properties were not affected by the inclusion of spineless cactus in the finishing diet of lambs. CONCLUSION: Spineless cactus could be included up to the level of 300 g kg-1 DM in the finishing diets of lambs to increase the fat content of meat without compromising its sensorial properties. However, further studies about the fatty acid composition of meat from lambs fed diets containing spineless cactus are necessary. © 2019 Society of Chemical Industry.

Metabolic Profiling of Pitaya (Hylocereus polyrhizus) during Fruit Development and Maturation.

Pitaya (Hylocereus polyrhizus) has attracted much interest from consumers as it is a novelty fruit with high nutrient content and a tolerance to drought stress. As a group of attractive pigment- and health-promoting natural compounds, betalains represent a visual feature for pitaya fruit quality. However, little information on the correlation between betalains and relevant metabolites exists so far. Currently, color (Commission International del'Eclairage, CIE) parameters, betalain contents, and untargeted metabolic profiling (gas chromatography-time-of-flight-mass spectrometry, GC⁻MS and liquid chromatography tandem mass spectrometry, LC⁻MS) have been examined on 'Zihonglong' fruits at nine different developmental stages, and the variation character of the metabolite contents was simultaneously investigated between peel and pulp. Furthermore, principal component analysis (PCA) and partial least-squares discriminant analysis (PLS-DA) were used to explore metabolite profiles from the fruit samples. Our results demonstrated that the decrease of amino acid, accompanied by the increase of sugars and organic acid, might contribute to the formation of betalains. Notably, as one of four potential biomarker metabolites, citramalic acid might be related to betalain formation.

Enhanced production and identification of antioxidants in in vitro cultures of the cacti Mammillaria candida and Turbinicarpus laui.

Cacti are an important source of metabolites but present limitations for their commercial exploitation, like slow growth and a decrease of wild populations. An alternative to obtain their biocompounds without affecting the natural environment are the in vitro culture techniques. We established in vitro cultures from Mammillaria candida Scheidweiler and Turbinicarpus laui Glass and Foster and used different stresses to increase metabolites and antioxidant activity. The cultures were exposed to 1.25% polyethylene glycol to induce a moderate drought stress, 50 g L-1 sucrose to generate an osmotic stress, chitosan (1.25 to 5 mg mL-1) to simulate a biotic attack, or to UV light. Chitosan was the best elicitor improving 1.5 times the concentration of phenolics, 9 to 10 times the content of flavonoids and betalains, and 16% the antioxidant activity in M. candida suspensions. In T. laui suspensions, this elicitor duplicates the flavonoids content and antioxidant activity. The antioxidant levels in elicited suspensions increased 5 to 10 times in relation to plant tubercles. Eleven compounds were identified in M. candida suspensions being digalloyl rhamnoside and epicatequin gallate the most abundant; in the T. laui suspensions, 16 compounds were detected and the most abundant were 17-decarboxi neobetanin and derivatives of luteolin. Thus, cacti in vitro culture is an efficient system to obtain high level of metabolites of biological interest.

Comparative volatile compounds and primary metabolites profiling of pitaya fruit peel after ozone treatment.

BACKGROUND: Ozone treatment can effectively inhibit fruit decay in many fruits during postharvest storage. However, little information is available for pitaya fruit. RESULTS: Ozone treatment significantly reduced the decay rate and induced the enzyme activities of peroxidase and polyphenol oxidase, and also reduced the levels of reactive oxygen species. In total, 103 metabolites were detected and changed the content after ozone treatment, including 54 primary metabolites and 49 aromatic compounds. After significance and importance analysis, 37 metabolites were important. Some metabolites were induced by peel senescence to respond to senescence stress, including d-fructose, d-glucose, mannose, inositol, galactonic acid, ethanedioic acid and stearic acid. Some metabolic products of peel senescence were reduced by ozone treatment, including d-arabinose, glucaric acid, galacturonic acid, 1-hexanol, 4-ethylcyclohexanol, ß-linalool, palmitoleic acid and 2-hydroxy-cyclopentadecanone. Some metabolites induced by ozone treatment might play a vital role in delaying the senescence and decay, including malic acid, succinic acid, pentenoic acid, eicosanoic acid, 2-hexenal, hexanal, 2-heptenal, 4-heptenal, 2-octenal and nitro m-xylene. CONCLUSION: Ozone treatment significantly reduced decay and prolonged shelf-life without reducing fruit quality. In total, 37 metabolites might play an important role in ozone delayed fruit decay. © 2018 Society of Chemical Industry.

Growth of cactus pear cv. Miúda under different salinity levels and irrigation frequencies.

Soil and water salinity are considered the main limiting factors of plant production. This work aimed to evaluate the influences of irrigation frequency and soil salinity on the development of cactus pear cv. Miúda (Nopalea cochenillifera Salm Dyck). The experiment was conducted in factorial arrangement of four salinity levels: 0.3 (control), 0.5 (low), 1.5 (medium) and 3.6 (high salinity) (ds m-1), associated with four irrigation frequencies (each 7, 14, 21 and 28 days) and two soil textures (sandy and sandy loam) in a randomized block design with four replicates. One cladode was planted in each polyethylene pot containing 10 kg of soil. The soil texture influenced some of the morphological characteristics of the cactus pear, so that plants grown in sandy loam soil yielded higher number of cladodes (9.47) and higher productivity (62.1 g plant-1). The sandy soil produced plants with fewer cladodes (4.50). Irrigation water with a salinity level of 3.6 ds m-1 and an irrigation frequency of 7 days showed higher soil electrical conductivity (48.65 dS m-1) and plants with a higher damage (5.0) and lower productivity (32.51 g plant-1), indicating a low tolerance of the cv. Miúda to salt stress.

Transcriptomics insights into the genetic regulation of root apical meristem exhaustion and determinate primary root growth in Pachycereus pringlei (Cactaceae).

Many Cactaceae species exhibit determinate growth of the primary root as a consequence of root apical meristem (RAM) exhaustion. The genetic regulation of this growth pattern is unknown. Here, we de novo assembled and annotated the root apex transcriptome of the Pachycereus pringlei primary root at three developmental stages, with active or exhausted RAM. The assembled transcriptome is robust and comprehensive, and was used to infer a transcriptional regulatory network of the primary root apex. Putative orthologues of Arabidopsis regulators of RAM maintenance, as well as putative lineage-specific transcripts were identified. The transcriptome revealed putative orthologues of most proteins involved in housekeeping processes, hormone signalling, and metabolic pathways. Our results suggest that specific transcriptional programs operate in the root apex at specific developmental time points. Moreover, the transcriptional state of the P. pringlei root apex as the RAM becomes exhausted is comparable to the transcriptional state of cells from the meristematic, elongation, and differentiation zones of Arabidopsis roots along the root axis. We suggest that the transcriptional program underlying the drought stress response is induced during Cactaceae root development, and that lineage-specific transcripts could contribute to RAM exhaustion in Cactaceae.