Search Results (93)

Background: Avocado is an important economic fruit tree that requires a lot of nitrogen (N) to support growth and development. Nitrate transporter (NRT) gene family plays an essential role in N uptake and use in plants. However, no systematic identification of the NRT gene family has been reported in avocado. Methods: Bioinformatic analysis was used to identify and characterize the NRT gene family in avocado. The five N additions (29.75, 59.50, 119.00, 178.50, and 238.00 mg/L N) were used to identify the N requirement of avocado seedlings based on physiological indexes, while RNA-seq was conducted to analyze the response of PaNRTs under low-N and high-N conditions. Results: Sixty-one members of the NRT gene family were identified and dispersed on 12 chromosomes in avocado. Many cis-regulatory elements (CREs) related to phytohormonal and stress response were found in the PaNRTs promoter regions. The avocado leaves in N3 have the highest activities of N-assimilating enzymes and N content as well as the lowest activities of antioxidant enzymes. Thus, 29.75 mg/L and 119.00 mg/L were chosen as low-N supply and normal-N supply for transcriptome analysis. The transcriptome analysis showed that PaNRT1.11, PaNRT1.22, PaNRT1.32, PaNRT1.33, PaNRT1.38, and PaNRT1.52 and PaNRT1.56 among PaNRT1 members were up-regulated under normal-N condition in the leaves or roots, suggesting that these genes might affect N absorption under nitrate-sufficient conditions in avocado. RT-qPCR analysis found the relative expression patterns of selected genes among four samples were consistent with transcriptome data, suggesting that transcriptome data were reliable. Conclusions: This study would provide valuable information for identifying the functions of the NRT gene family in avocado. Full article

Actinobacteria, especially the genus Streptomyces, have been shown to be potential biocontrol agents for phytopathogenic bacteria. Bacteria spot disease caused by Xanthomonas spp. may severely affect chili pepper (Capsicum annuum) crops with a subsequent decrease in productivity. Therefore, the objective of the study was to isolate rhizospheric actinobacteria from soil samples treated by physical methods and evaluate the inhibitory activity of the isolates over Xanthomonas. Initially, soil samples collected from avocado tree orchards were treated by dry heat air and microwave irradiation; thereafter, isolation was implemented. Then, antibacterial activity (AA) of isolates was evaluated by the double-layer agar method. Furthermore, the positive/negative effect on AA for selected isolates was evaluated on three culture media (potato-dextrose agar, PDA; yeast malt extract agar, YME; and oat agar, OA). Isolates were identified by 16S rRNA sequence analysis. A total of 198 isolates were obtained; 76 (series BVEZ) correspond to samples treated by dry heat and 122 strains (series BVEZMW) were isolated from samples irradiated with microwaves. A total of 19 dry heat and 25 microwave-irradiated isolates showed AA with inhibition zones (IZ, diameter in mm) ranging from 12.7 to 82.3 mm and from 11.4 to 55.4 mm, respectively. An increment for the AA was registered for isolates cultured on PDA and YME, with an IZ from 21.1 to 80.2 mm and 14.1 to 69.6 mm, respectively. A lower AA was detected when isolates were cultured on OA media (15.0 to 38.1 mm). Based on the 16S rRNA gene sequencing analysis, the actinobacteria belong to the Streptomyces (6) and Amycolatopsis (2) genera. Therefore, the study showed that microwave irradiation is a suitable method to increase the isolation of soil bacteria with AA against Xanthomonas sp. In addition, Streptomyces sp. BVEZ 50 was the isolate with the highest IZ (80.2 mm). Full article

Companion cropping offers a potential solution to the challenges of sustainable agriculture, such as optimizing resource use and reducing reliance on chemical inputs. The problem of achieving higher yields while maintaining environmental health remains critical. This practice enhances natural resource conservation, improves fertilization, and optimizes nutrient cycling through the balanced use of chemical and organic sources. Studies, such as those involving tree tomato and Hass avocado, have demonstrated a significant yield increase compared to monocultures, underscoring the viability of this practice. In addition to their environmental benefits, companion crops provide economic advantages by allowing producers to harvest multiple products simultaneously, thereby strengthening food security and the rural economy. This study evaluated three levels of fertilization and interactions between fruit trees at different altitudes, observing differential behavior in the variables evaluated. The combination of cape gooseberry and blackberry showed significantly positive results, with more leaves and fewer pests, demonstrating the benefits of companion plants. A trend towards the combined use of chemical and organic fertilizers was observed, a potential strategy to reduce costs and improve crop growth. The results indicated that the UF system (P. peruviana and P. vulgaris) had the highest plant height, while TF (tree tomato and bean) showed the best stem perimeter development. The incidence of pests was also significant, with Trialeurodes vaporarioum being most prevalent in the P. peruviana companion. These findings support companion cropping as a viable and promising strategy for more efficient and sustainable agriculture, offering both environmental and economic benefits. Full article

The increasing incidence of heat stress due to global climate change poses a significant challenge to avocado (Persea americana) cultivation, particularly in regions with intense solar radiation. This review evaluates sun protection strategies, focusing on the efficacy of different sunscreen products such as kaolin, titanium dioxide, and calcium oxide in mitigating thermal stress in avocado trees. The application of these materials was shown to reduce leaf and fruit surface temperatures, improve photosynthetic efficiency, and enhance fruit quality by preventing sunburn and dehydration. Despite these benefits, challenges remain, including the optimal timing and dosage of application, and the potential residue impacts on fruit marketability. The review emphasizes the need for ongoing research to develop more effective formulations and to integrate these sun protection strategies with other agronomic practices. The role of extension services in educating producers about the proper use of these technologies is also highlighted as crucial for the successful adoption of sun protection measures in avocado farming. Full article

In the absence of comparative real estate data in the market segment of the property to be estimated, the appraiser may resort to income capitalization to estimate the market value. Often, however, the choice of which rate to apply is affected by subjective and arbitrary assessments. The estimation result can therefore be inaccurate and rather unclear. However, the Remote Segments Approach (RSA), through appropriate adjustments on the original values, prices, and incomes detected in the remote segments, makes it possible to arrive at an appraisal result consistent with estimative logic and real estate valuation standards. The proposed application illustrates the estimation of the market value of a specialized fruit orchard of avocado, which is to be considered new in relation to other fruit species already present in the reference area. The adjustments required by the RSA are solved with the General Appraisal System (GAS), defining the difference matrix based on relevant characters common to all segments considered. The application is carried out by comparing the segment in which the orchard being estimated falls (subject) with other remote market segments in which prices and incomes constituted by other tree crops are collected. The market value of the subject is derived by making adjustments to the prices and incomes observed in the remote segments of comparison with a comparison function constructed through relevant characters common to the segments considered. The comparison function makes it possible to arrive at the determination of the capitalization rate to be used in estimating the value of the fruit orchard by income approach. While it is based on the comparison of segments, the approach followed allows for a value judgment consistent with the estimation comparison and capable of providing a solution less conditioned by the appraiser’s expertise in the presence of particularly pronounced limiting conditions. Full article

Plants generate a range of physiological and molecular responses to sustain their growth and development when suffering heat stress. Avocado is a type of tropical fruit tree with high economic value. Most avocado cultivars delete, wither, or even die when exposed to heat stress for a long time, which seriously restricts the introduction and cultivation of avocados. In this study, samples of a heat-intolerant variety (‘Hass’) were treated under heat stress, and the transcriptomics and metabolomics were analyzed, with the expectation of providing information on the variety improvement and domestication of avocados. The differentially expressed genes identified using transcriptome analysis mainly involved metabolic pathways such as plant hormone signal transduction, plant–pathogen interaction, and protein processing in the endoplasmic reticulum. Combined transcriptome and metabolome analysis indicated that the down-regulation of Hass.g03.10206 and Hass.g03.10205 in heat shock-like proteins may result in the reduced Trehalose and Sinapoyl aldehyde content. Metabolomics analysis results indicated that the decrease in Trehalose and Sinapoyl aldehyde content may be an important factor for heat intolerance. These results provide important clues for understanding the physiological mechanisms of adaptation to heat stress in avocados. Full article

Crop residue decomposition is fundamental for ecosystems, influencing carbon cycling, organic matter accumulation, and promoting plant development through nutrient release. Therefore, this study aimed to ascertain the rate of decomposition of four commonly cultivated crops (alfalfa, maize, avocado, and eucalyptus) along the northern coast of Lima (Huaral) and in the Ancash Mountain range (Jangas) areas. Decomposition rates were assessed using mass loss from decomposition bags measuring 15 × 10 cm, filled with 10–15 g of material tailored to each species, and buried at a depth of approximately 5 cm. Sampling occurred every three months over a year, totaling four sampling events with three replicates each, resulting in ninety-six experimental units. The findings demonstrate that the decomposition rates and the release of nutrients were markedly greater in Huaral for maize and avocado. In contrast, these rates were notably elevated in Jangas for alfalfa and eucalyptus. The leaf litter of avocado and eucalyptus (tree) had periods of accumulation and release of heavy metals such as Cd. The initial C/N ratio was one of the main factors related to the nutrient decomposition rate; in contrast, there were no significant relationships with soil properties at the study sites. Full article

Carbohydrate levels are important regulators of the growth and yield of tree crops. Current methods for measuring foliar carbohydrate concentrations are time consuming and laborious, but rapid imaging technologies have emerged with the potential to improve the effectiveness of tree nutrient management. Carbohydrate concentrations were predicted using hyperspectral imaging (400–1000 nm) of leaves of the evergreen tree crops, avocado, and macadamia. Models were developed using partial least squares regression (PLSR) and artificial neural network (ANN) algorithms to predict carbohydrate concentrations. PLSR models had R² values of 0.51, 0.82, 0.86, and 0.85, and ANN models had R² values of 0.83, 0.83, 0.78, and 0.86, in predicting starch, sucrose, glucose, and fructose concentrations, respectively, in avocado leaves. PLSR models had R² values of 0.60, 0.64, 0.91, and 0.95, and ANN models had R² values of 0.67, 0.82, 0.98, and 0.98, in predicting the same concentrations, respectively, in macadamia leaves. ANN only outperformed PLSR when predicting starch concentrations in avocado leaves and sucrose concentrations in macadamia leaves. Performance differences were possibly associated with nonlinear relationships between carbohydrate concentrations and reflectance values. This study demonstrates that PLSR and ANN models perform well in predicting carbohydrate concentrations in evergreen tree-crop leaves. Full article

Avocado fruits are considered unusual because of the large amounts of oil and seven-carbon (7-C) carbohydrates (mannoheptulose and perseitol) in the fruit’s flesh and skin. The fruit may be held on the tree unripe until required for marketing, and in some producing regions, this may extend past the next flowering period. This prolonged period on the tree is associated with increased oil content and decreased 7-C carbohydrates. There has been relatively less research into soluble hexose sugars and starch. In this research, the inter-relationships between fruit maturation, storage, and ripening have been investigated for both 7-C and six-carbon non-structural carbohydrates using ‘Hass’ fruit harvested from the same trees between 11 and 14 months after flowering. Significant differences were identified in both fruit flesh and skin for most compounds, affected by maturity, storage, and ripening. It is concluded that the non-structural carbohydrate composition of ‘Hass’ fruit is variable, with significant changes occurring associated with maturation, storage, and ripening. The compositions of the flesh and skin tissues are not consistently proportionate. Maturation provides the initial baseline composition from which any further change through storage or ripening can occur. The changes with maturation appear to be associated with the tree’s phenology, with tree-to-tree differences in the timing or degree of change. Full article

The productivity of many tree crops is limited by low yield, partly due to high rates of fruitlet abscission during early fruit development. Early studies suggested that cross-pollinated fruitlets may be selectively retained during fruit development, although paternity testing of fruitlets to test this hypothesis was technically challenging. We used MassARRAY genotyping to determine the effects of pollen parentage on fruitlet retention and fruit quality of Hass avocado. We identified the paternity of abscised and retained fruitlets at 6 and 10 weeks, and mature fruit at 36 weeks, after peak anthesis. We measured the embryo mass, pericarp mass, total mass and nutrient concentrations of fruitlets, and the seed mass, flesh mass, total mass, diameter, length, nutrient concentrations and fatty-acid composition of mature fruit. The percentages of progeny on the tree that were cross-fertilised increased from 4.6% at 6 weeks after peak anthesis to 10.7% at fruit maturity. Only 1.0% of freshly abscised fruitlets on the ground at 10 weeks after peak anthesis were cross-pollinated even though 6.5% of retained fruitlets on the tree were cross-pollinated. At this stage, cross-pollinated fruitlets had similar nutrient concentrations to self-pollinated fruitlets, but they had higher total contents of P, K, Al, Ca, Fe, Mn and Zn due to having greater fruitlet mass. At maturity, cross-pollinated fruit were 6% heavier and had 2% greater diameter than self-pollinated fruit, without significant differences in flesh nutrient concentrations or fatty acid composition. The results demonstrate that Hass avocado trees selectively retain cross-pollinated fruitlets, which are larger than self-pollinated fruitlets and ultimately produce larger mature fruit. Avocado growers can increase fruit size and yield by improving the opportunities for cross-pollination, possibly by closely interplanting type A and type B cultivars and introducing more beehives into orchards. Full article

Avocado tree wilt is a disease caused by Phytophthora cinnamomi Rands. Recently, this disease has been associated to Pythium amazonianum, another causal agent. Avocado tree wilt is being currently controlled with synthetic fungicides that kill beneficial microorganisms, polluting the environment and leading to resistance problems in plant pathogens. The current research work aims to provide alternative management using extracts from Proboscidea parviflora W. and Phaseolus lunatus L. to control the development of mycelia in P. amazonianum in vitro. Raw extracts were prepared at UAAAN Toxicology Laboratory, determining the inhibition percentages, inhibition concentrations and inhibition lethal times. Several concentrations of the plant extracts were evaluated using the poisoned medium methodology, showing that both extracts control and inhibit mycelial development, in particular P. lutatus, which inhibits mycelial growth at concentrations lower than 80 mg/L, being lower than P. parviflora extracts. These extracts are promising candidates for excellent control of Pythium amazonianum. Full article

Bioconversion in biorefineries is a way to valorize residues from agriculture and food processing. Pretreatment is an important step in the bioconversion of lignocellulosic materials, including crop residues. This Special Issue includes nine articles on several pretreatment and bioconversion approaches applied to different agricultural residues and food-processing by-products. The materials addressed in this collection cover straw from wheat, rye, and miscanthus, olive tree pruning residue, almond shells and husks, avocado waste, sweet sorghum bagasse, soybean meal, and residues of non-edible oilseeds. Full article

Grafting, the careful selection of rootstocks and scions, has played a crucial role maintaining Chilean avocado fruit quality standards in a scenario in which climate change and drought-related issues have considerably decreased avocado fruit production in the last fifteen years. The historical use of seedling rootstocks in Chile has experienced a recent shift towards clonal rootstocks, driven by the potential to produce more consistent and predictable crops. This research aims to compare Hass avocado plants grafted on Mexicola seedling and Dusa^® clonal rootstocks in a soilless and protected system using (i) a differential expression analysis of root and leaf samples and (ii) a fruit transcriptomic and metabolomic integration analysis to improve our understanding of rootstock–scion interaction and its impact on avocado tree performance and fruit quality. The results demonstrated that no significant transcriptomic and metabolomic differences were identified at fruit level in the ready-to-eat (RTE) stage for Hass avocado fruit from both rootstocks. However, Hass avocados grafted on the clonal rootstock showed greater aerial growth and slightly increased fruit size than the seedling rootstock due to the enrichment of cell wall-remodeling genes as revealed in leaves and fruit at harvest stage. Full article

Mango is one of the main subtropical crops growing in southern Spain. Spanish mango fruit production can be efficiently transported to the rest of Europe, and these mangoes are very appreciated for their quality and flavour. However, postharvest rots have been detected in stored mango fruits, making their commercialization difficult. The causal agents associated with such rot symptoms have been isolated and identified. Because the mango crops used to share the same growing area with avocado crops, fungal presence on surrounding asymptomatic avocado fruits was also analysed to detect potential cross infections. Artificial inoculation with Neofusicoccum parvum and N. mediterraneum was able to reproduce rot symptoms in mango but was also able to induce rots in avocado fruits. To approach a biological control strategy against these rot-producing fungi, two very well-known antagonistic biocontrol bacteria, Pseudomonas chlororaphis PCL1606, and Bacillus velezensis UMAF6639, were tested. The obtained results revealed that both bacteria can control the fungal rots on stored mango and avocado fruits under controlled conditions. Additionally, the strain B. velezensis UMAF6639 showed the ability to persist on the fruit surface of adult commercial trees in experiments under open field conditions, helping to prevent the appearance of these postharvest diseases. Full article

Avocado is an evergreen tree that exhibits protogynous dichogamy and displays a massive flower production, characterized by a high abscission of unfertilized flowers and developing fruitlets, ultimately leading to a low final fruit set. A common practice to improve avocado pollination involves introducing honey bee (Apis mellifera L.) hives during the flowering season. To evaluate the extent of inadequate pollination in avocado, the effect of different beehive densities on the percentage of flowers receiving pollen during the female flower stage was examined for seven years in an experimental orchard located in Southern Spain. A total of 17,288 flowers were observed under the microscope for this purpose. Additionally, pollen deposition was evaluated in five “Hass” avocado commercial orchards under different management strategies situated in the Malaga province (3960 flowers). The results obtained reveal that the percentage of flowers with pollen at the end of the female stage ranged from 2.85 (0.13% fruits retained at the end of June) in orchards without honey bee hives to 4.34 (0.11% fruits retained) in orchards in which 10 beehives per ha were placed. This percentage increased significantly to 13.79 after introducing 24 honey beehives per ha (0.21% fruits retained). Furthermore, the percentage of pollinated flowers in the commercial orchards remained below 15% even in those orchards in which pollen donors and honey bee hives were present. Thus, insufficient pollination could be considered as a primary limiting factor in avocado production under Mediterranean climates. Enhancing pollinator diversity and increasing their numbers could be a viable strategy to improve the percentage of avocado flowers receiving pollen during the female stage. Full article