Fruit Tree Crops Research Articles

Comparing Apples and Oranges: Advances in Disease Resistance Breeding of Woody Perennial Fruit Crops.

Apple and citrus are perennial tree fruit crops that are vital for nutritional security and agricultural economy and to achieve the Sustainable Development Goals of the United Nations. Apple scab and fire blight, along with Huanglongbing, canker, and tristeza virus, stand out as their most notorious diseases and annually destabilize fruit supply. An environmentally sound approach to managing these diseases is improving tree resistance through breeding and biotechnology. Perennial fruit tree germplasm collections are distributed globally and offer untapped potential as sources of resistance. However, long juvenility, specific pollination and flowering habits, and extensive outcrossing hinder apple and citrus breeding. Advances in breeding approaches include trans- and cis-genesis, genome editing, and rapid-cycle breeding, which, in addition to conventional crossbreeding, can all facilitate accelerated integration of resistance into elite germplasm. In addition, the global pool of available sources of resistance can be characterized by the existing genetic mapping and gene expression studies for accurate discovery of associated loci, genes, and markers to efficiently include these sources in breeding efforts. We discuss and propose a multitude of approaches to overcome the challenges of breeding for resistance in woody perennials and outline a technical path to reduce the time required for the ultimate deployment of disease-resistant cultivars.

A Sustainable Approach Based on Sheep Wool Mulch and Soil Conditioner for Prunus domestica (Stanley Variety) Trees Aimed at Increasing Fruit Quality and Productivity in Drought Conditions

In the context of extreme climate change, experts in fruit production face a significant challenge in developing new strategies aimed at increasing the productivity of fruit tree crops. In order to investigate the changes in various horticultural indices (production, tree growth, and development) as well as the quality of plum fruits, sheep’s wool mulch, a cornstarch-based soil conditioner, and a combination of the two were applied in a Stanley plum orchard. In parallel, an experimental control variation was used. The results showed that the methods used had a substantial impact on fruit yield, size, and weight, with the best results obtained when mulching with sheep’s wool and soil conditioner. Plum fruits from mulching with sheep wool + soil conditioner exhibited the greatest total phenol concentration (1.30 ± 0.09 mg GAE/g dw), followed by the reference sample at 1.16 ± 0.09 mg GAE/g dw. The antioxidant capacity assessed using the three different methods provided favorable results for the experimental variant, sheep wool + soil conditioner. The results indicate that using the three experimental versions increased the fruit yield with 27% (sheep’s wool mulch) and with, 37% (sheep wool + soil conditioner) on average compared to that of the control group, while also improving the fruit quality. The fruit weight increased with 17.26% (cornstarch-based soil conditioner) and with 48.90% (sheep wool + soil conditioner) compared to that of the control, and the fruit size increased with 5% in two experiments (sheep’s wool mulch and a cornstarch-based soil conditioner) with 19% (sheep wool + soil conditioner), compared to the control group.

Transcriptome and weighted gene co-expression network analyses reveal key genes and pathways involved in early fruit ripening in Citrus sinensis

BackgroundThe fruit ripening period is an important target trait in fruit tree crop breeding programs. Thus, citrus tree breeders seek to develop extreme early ripening cultivars that allow optimization of citrus maturation periods. In this study, we explored the regulatory network involved in fruit ripening in Citrus sinensis using the ‘Newhall’ navel orange variety and its early-ripening mutant, ‘Gannanzao’. This research will provide a basis for further research on important signaling pathways, gene functions and variety breeding of Citrus sinensis related to fruit ripening period.ResultsPhysiological analyses suggested that early fruit ripening in ‘Gannanzao’ is regulated by early accumulation of abscisic acid (ABA), persistently high levels of jasmonic acid (JA), and higher sucrose content in the pericarp. Pericarp samples from ‘Gannanzao’ and ‘Newhall’ navel oranges were sampled for RNA sequencing analysis at 180, 200, and 220 days after flowering; 1430 differentially expressed genes (DEGs) were identified. Functional enrichment analysis indicated that these DEGs were mainly enriched in the plant hormone signal transduction and sugar metabolism pathways, as well as other pathways related to fruit ripening. Important DEGs associated with fruit ripening in ‘Gannanzao’ included genes involved in ABA and JA metabolism and signal transduction, as well as sugar metabolism. Weighted gene co-expression network analysis showed that the deep pink module had the strongest correlations with ABA content, JA content, and early ripening. Based on gene functionality and gene expression analyses of 37 genes in this module, two candidate hub genes and two ethylene response factor 13 (ERF13) genes (Cs_ont_5g000690 and Cs_ont_5g000700) were identified as key genes regulated by ABA and JA signaling. These findings will help to clarify the mechanisms that underlie early citrus fruit ripening and will lead to the development of excellent genetic resources for further breeding of extreme early-ripening varieties.ConclusionsThrough analyses of the ‘Newhall’ navel orange cultivar and its early-ripening mutant ‘Gannanzao’, we identified genes involved in ABA and JA metabolism, signal transduction, and sugar metabolism that were related to fruit ripening. Among these, two ERF13 genes were inferred to be key genes in the regulation of fruit ripening. These findings provide insights into the genetic architecture related to early fruit ripening in C. sinensis.

Evaluation of an Attract-and-Kill Strategy Using Long-Lasting Insecticide Nets for the Management of the Brown Marmorated Stink Bug in Northern Italy.

The brown marmorated stink bug (BMSB), Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), is causing extensive economic losses in tree fruit crops. Including attract-and-kill (AK) strategies targeting BMSBs in an integrated pest management framework could reduce the amounts of insecticides sprayed and benefit growers, consumers and the environment. This study evaluated the effectiveness of an area-wide AK strategy across an intensive fruticulture region of Northern Italy, comparing four paired pear sites with and without two AK stations ha-1. These stations consisted of long-lasting insecticide-treated nets containing alpha-cypermethrin, baited with the BMSB aggregation pheromone and synergist. BMSB abundance was estimated using black-standing monitoring traps, and fruit damage upon harvest was recorded across all sites. The AK stations did not decrease the BMSB abundance nor the fruit damage, while after harvest significantly lower BMSB captures were detected in the AK sites compared to the control sites. Whilst the lures' efficacy was corroborated by this research, the killing method requires improvement and refinement.

A data platform for real-time monitoring and analysis of the brown marmorated stink bug in Northern Italy

The brown marmorated stink bug (Halyomorpha halys) is one of the main insect pest species causing economic damage to several agricultural commodities worldwide and one of the worst threats to tree fruit crops in northern Italy, especially in the Emilia-Romagna region. Previous efforts in implementing H. halys surveillance at the regional level were mainly focused on studying the H. halys phenology, but they were not designed to provide a public service. In this paper, we propose a data-driven approach to support the application of Integrated Pest Management strategies against H. halys. The proposal is based on the experience of a three-year project in which a network of monitoring traps has been deployed throughout the whole Emilia-Romagna region and a data platform has been implemented to enable the real-time tracking of H. halys occurrence and distribution, integrating these information with multiple data sources, and analytical capabilities through a public website. Besides the real-time pest surveillance, the data platform allowed us to increase our understanding about H. halys seasonal invasion dynamics and the main factors contributing to its spread. The results will help individual growers in protecting their crops and the whole region in promoting more efficient usage of insecticides and more sustainable and healthy agricultural productions.

Continuous Plant-Based and Remote Sensing for Determination of Fruit Tree Water Status

Climate change poses significant challenges to agricultural productivity, making the efficient management of water resources essential for sustainable crop production. The assessment of plant water status is crucial for understanding plant physiological responses to water stress and optimizing water management practices in agriculture. Proximal and remote sensing techniques have emerged as powerful tools for the non-destructive, efficient, and spatially extensive monitoring of plant water status. This review aims to examine the recent advancements in proximal and remote sensing methodologies utilized for assessing the water status, consumption, and irrigation needs of fruit tree crops. Several proximal sensing tools have proved useful in the continuous estimation of tree water status but have strong limitations in terms of spatial variability. On the contrary, remote sensing technologies, although less precise in terms of water status estimates, can easily cover from medium to large areas with drone or satellite images. The integration of proximal and remote sensing would definitely improve plant water status assessment, resulting in higher accuracy by integrating temporal and spatial scales. This paper consists of three parts: the first part covers current plant-based proximal sensing tools, the second part covers remote sensing techniques, and the third part includes an update on the on the combined use of the two methodologies.

Comparative Physio-Biochemical and Transcriptome Analyses Reveal Contrasting Responses to Magnesium Imbalances in Leaves of Mulberry (Morus alba L.) Plants.

Magnesium (Mg) deficiency is a major factor limiting the growth and development of plants. Mulberry (Morus alba L.) is an important fruit tree crop that requires Mg for optimal growth and yield, especially in acid soils. However, the molecular mechanism of Mg stress tolerance in mulberry plants remains unknown. In this study, we used next-generation sequencing technology and biochemical analysis to profile the transcriptome and physiological changes of mulberry leaves under different Mg treatments (deficiency: 0 mM, low: 1 mM, moderate low: 2 mM, sufficiency: 3 mM, toxicity: 6 mM, higher toxicity: 9 mM) as T1, T2, T3, CK, T4, T5 treatments, respectively, for 20 days. The results showed that Mg imbalance altered the antioxidant enzymatic activities, such as catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD), and non-enzymatic, including soluble protein, soluble sugar, malondialdehyde (MDA), and proline (PRO), contents of the plant. The Mg imbalances disrupted the ultrastructures of the vital components of chloroplast and mitochondria relative to the control. The transcriptome data reveal that 11,030 genes were differentially expressed (DEGs). Genes related to the photosynthetic processes (CAB40, CAB7, CAB6A, CAB-151, CAP10A) and chlorophyll degradation (PAO, CHLASE1, SGR) were altered. Antioxidant genes such as PER42, PER21, and PER47 were downregulated, but DFR was upregulated. The carbohydrate metabolism pathway was significantly altered, while those involved in energy metabolism processes were perturbed under high Mg treatment compared with control. We also identified several candidate genes associated with magnesium homeostasis via RT-qPCR validation analysis, which provided valuable information for further functional characterization studies such as promoter activity assay or gene overexpression experiments using transient expression systems.

Variations in Fruit Ploidy Level and Cell Size between Small- and Large-Fruited Olive Cultivars during Fruit Ontogeny.

Olive (Olea europaea L.) is one of the major oil fruit tree crops worldwide. However, the mechanisms underlying olive fruit growth remain poorly understood. Here, we examine questions regarding the interaction of endoreduplication, cell division, and cell expansion with olive fruit growth in relation to the final fruit size by measuring fruit diameter, pericarp thickness, cell area, and ploidy level during fruit ontogeny in three olive cultivars with different fruit sizes. The results demonstrate that differences in the fruit size are related to the maximum growth rate between olive cultivars during early fruit growth, about 50 days post-anthesis (DPA). Differences in fruit weight between olive cultivars were found from 35 DPA, while the distinctive fruit shape became detectable from 21 DPA, even though the increase in pericarp thickness became detectable from 7 DPA in the three cultivars. During early fruit growth, intense mitotic activity appeared during the first 21 DPA in the fruit, whereas the highest cell expansion rates occurred from 28 to 42 DPA during this phase, suggesting that olive fruit cell number is determined from 28 DPA in the three cultivars. Moreover, olive fruit of the large-fruited cultivars was enlarged due to relatively higher cell division and expansion rates compared with the small-fruited cultivar. The ploidy level of olive fruit pericarp between early and late growth was different, but similar among olive cultivars, revealing that ploidy levels are not associated with cell size, in terms of different 8C levels during olive fruit growth. In the three olive cultivars, the maximum endoreduplication level (8C) occurred just before strong cell expansion during early fruit growth in fruit pericarp, whereas the cell expansion during late fruit growth occurred without preceding endoreduplication. We conclude that the basis for fruit size differences between olive cultivars is determined mainly by different cell division and expansion rates during the early fruit growth phase. These data provide new findings on the contribution of fruit ploidy and cell size to fruit size in olive and ultimately on the control of olive fruit development.

Design, integration, and field evaluation of a robotic blossom thinning system for tree fruit crops

AbstractThe United States (US) apple industry relies heavily on semi‐skilled manual labor force for essential field operations such as training, pruning, blossom and green fruitlet thinning, and harvesting. Blossom thinning is one of the crucial crop‐load management practices to achieve desired crop load, fruit quality, and return bloom. While several techniques such as chemical and mechanical thinning are available for large‐scale blossom thinning, such approaches often yield unpredictable thinning results and may damage the canopy, spurs, and leaf tissue. Hence, growers still depend on laborious, labor‐intensive, and expensive manual hand blossom thinning for desired thinning outcomes. This research presents a robotic solution for precision blossom thinning in apple orchards using a deep learning‐based computer vision system, a six‐degrees‐of‐freedom UR5e robotic manipulator, and an electrically actuated miniature end‐effector. The integrated robotic system was evaluated in a commercial apple orchard which showed promising results for targeted and selective blossom thinning. Two thinning approaches, center and boundary thinning, were investigated to evaluate the system's ability to remove varying proportions of flowers from apple flower clusters. During boundary thinning, the end‐effector was actuated around the cluster boundary, while center thinning involved end‐effector actuation only at the cluster centroid for a fixed duration of 2 s. Field evaluation results showed that the boundary thinning approach thinned 67.2% of flowers from the targeted clusters with a cycle time of 9.0 s per cluster, whereas the center thinning approach thinned 59.4% of flowers with a cycle time of 7.2 s per cluster. Upon further improvement for commercial adoption, the proposed system could help address problems faced by apple growers with current hand, chemical, and mechanical blossom thinning approaches.

Genome-Wide Analysis of the Xyloglucan Endotransglucosylase/Hydrolase (XTH) Gene Family: Expression Pattern during Magnesium Stress Treatment in the Mulberry Plant (Morus alba L.) Leaves.

Mulberry (Morus alba L.), a significant fruit tree crop, requires magnesium (Mg) for its optimal growth and productivity. Nonetheless, our understanding of the molecular basis underlying magnesium stress tolerance in mulberry plants remains unexplored. In our previous study, we identified several differential candidate genes associated with Mg homeostasis via transcriptome analysis, including the xyloglucan endotransglucosylase/hydrolase (XTH) gene family. The XTH gene family is crucial for plant cell wall reconstruction and stress responses. These genes have been identified and thoroughly investigated in various plant species. However, there is no research pertaining to XTH genes within the M. alba plant. This research systematically examined the M. alba XTH (MaXTH) gene family at the genomic level using a bioinformatic approach. In total, 22 MaXTH genes were discovered and contained the Glyco_hydro_16 and XET_C conserved domains. The MaXTHs were categorized into five distinct groups by their phylogenetic relationships. The gene structure possesses four exons and three introns. Furthermore, the MaXTH gene promoter analysis reveals a plethora of cis-regulatory elements, mainly stress responsiveness, phytohormone responsiveness, and growth and development. GO analysis indicated that MaXTHs encode proteins that exhibit xyloglucan xyloglucosyl transferase and hydrolase activities in addition to cell wall biogenesis as well as xyloglucan and carbohydrate metabolic processes. Moreover, a synteny analysis unveiled an evolutionary relationship between the XTH genes in M. alba and those in three other species: A. thaliana, P. trichocarpa, and Zea mays. Expression profiles from RNA-Seq data displayed distinct expression patterns of XTH genes in M. alba leaf tissue during Mg treatments. Real-time quantitative PCR analysis confirmed the expression of the MaXTH genes in Mg stress response. Overall, this research enhances our understanding of the characteristics of MaXTH gene family members and lays the foundation for future functional genomic study in M. alba.

Zanzibar’s spice forests: Restoring the Spice Islands

Spice farming in Zanzibar has been integral to the country’s culture, history and economy but in recent decades, Zanzibar’s role in the global spice trade has diminished as declining market prices and government interference have pushed many farmers to convert spice forests into monoculture farms. Community Forests International (CFI) and Community Forests Pemba (CFP) have been working since 2015 to re-establish these diverse agroforest ecosystems and restore farmers’ livelihoods. Unlike monoculture farming, spice forests offer better economic incentives, ecological sustainability, and equality for women, and have the potential to restore a resilient spice-farming economy that is ecologically and socially sustainable. By revitalising local and indigenous knowledge, including from Tanzania, agroforestry practices are being implemented by small-scale Zanzibari farmers to grow a mix of timber, fruit and spice tree crops. This has enabled farmers to improve their household nutrition, increase their crop yields and diversify their income streams, ensuring energy, food and income security. The use of agroforestry practices in spice forests has also promoted structural and ecological diversity, regenerated soil health, enhanced carbon stores, and ensured resilience against climate change. Stories of individual farmers, Saidi Khalifa and Kibano Omar Kibano, exemplify how landscapes and lives can be positively transformed when spice forests are restored to replace monoculture farms with training and support from CFP. The story of Bimajo Masoud Juma also exemplifies how CFP has promoted agroforestry to empower women to have an independently earned income, ensuring their economic independence. CFP is also working with farmers to create stronger cooperative models that would enable them to sell directly to international buyers. The global organic spice market is expanding, so farmers involved in these sustainable and organic agroforestry practices are well-positioned to thrive.

Microsatellite Sequence Polymorphisms Reveals Substantial Diversity in Caribbean Breadfruit [Artocarpus altilis (Parkinson) Fosberg] Germplasm

Breadfruit [Artocarpus altilis (Parkinson) Fosberg] is recognized as a tropical fruit tree crop with great potential to contribute to food and nutrition security in the Caribbean and other tropical regions. However, the genetic diversity and germplasm identification in the Caribbean and elsewhere are poorly understood and documented. This hampers the effective conservation and use of the genetic resources of this tree crop for commercial activities. This study assessed the genetic identity, diversity, ancestry, and phylogeny of breadfruit germplasm existing in the Caribbean and several newly introduced accessions using 117 SNPs from 10 SSR amplicon sequences. The results showed that there was high and comparable genetic diversity in the breadfruit germplasm in the Caribbean, and the newly introduced breadfruit accessions were based on nucleotide diversity (πT) 0.197 vs. 0.209, respectively, and nucleotide polymorphism (θW) 0.312 vs. 0.297, respectively. Furthermore, the existing Caribbean breadfruit accessions and the newly introduced breadfruit accessions were statistically genetically undifferentiated from each other (p < 0.05). Ancestry and phylogeny analysis corroborated the genetic relatedness of these two groups, with accessions of these groups being present in both main germplasm clusters. This suggests that the existing Caribbean breadfruit germplasm harbors a higher level of genetic diversity than expected.

Fungicide ingestion reduces net energy gain and microbiome diversity of the solitary mason bee

Fungicides are frequently used during tree fruit bloom and can threaten insect pollinators. However, little is known about how non-honey bee pollinators such as the solitary bee, Osmia cornifrons, respond to contact and systemic fungicides commonly used in apple production during bloom. This knowledge gap limits regulatory decisions that determine safe concentrations and timing for fungicide spraying. We evaluated the effects of two contact fungicides (captan and mancozeb) and four translaminar/plant systemic fungicides (cyprodinil, myclobutanil, penthiopyrad, and trifloxystrobin) on larval weight gain, survival, sex ratio, and bacterial diversity. This assessment was carried out using chronic oral ingestion bioassays where pollen provisions were treated with three doses based on the currently recommended field use dose (1X), half dose (0.5X), and low dose (0.1X). Mancozeb and penthiopyrad significantly reduced larval weight and survival at all doses. We then sequenced the 16S gene to characterize the larvae bacteriome of mancozeb, the fungicide that caused the highest mortality. We found that larvae fed on mancozeb-treated pollen carried significantly lower bacterial diversity and abundance. Our laboratory results suggest that some of these fungicides can be particularly harmful to the health of O. cornifrons when sprayed during bloom. This information is relevant for future management decisions about the sustainable use of fruit tree crop protection products and informing regulatory processes that aim to protect pollinators.

Integrative Analysis of Oleosin Genes Provides Insights into Lineage-Specific Family Evolution in Brassicales.

Oleosins (OLEs) are a class of small but abundant structural proteins that play essential roles in the formation and stabilization of lipid droplets (LDs) in seeds of oil crops. Despite the proposal of five oleosin clades (i.e., U, SL, SH, T, and M) in angiosperms, their evolution in eudicots has not been well-established. In this study, we employed Brassicales, an economically important order of flowering plants possessing the lineage-specific T clade, as an example to address this issue. Three to 10 members were identified from 10 species representing eight plant families, which include Caricaceae, Moringaceae, Akaniaceae, Capparaceae, and Cleomaceae. Evolutionary and reciprocal best hit-based homologous analyses assigned 98 oleosin genes into six clades (i.e., U, SL, SH, M, N, and T) and nine orthogroups (i.e., U1, U2, SL, SH1, SH2, SH3, M, N, and T). The newly identified N clade represents an ancient group that has already appeared in the basal angiosperm Amborella trichopoda, which are constitutively expressed in the tree fruit crop Carica papaya, including pulp and seeds of the fruit. Moreover, similar to Clade N, the previously defined M clade is actually not Lauraceae-specific but an ancient and widely distributed group that diverged before the radiation of angiosperm. Compared with A. trichopoda, lineage-specific expansion of the family in Brassicales was largely contributed by recent whole-genome duplications (WGDs) as well as the ancient γ event shared by all core eudicots. In contrast to the flower-preferential expression of Clade T, transcript profiling revealed an apparent seed/embryo/endosperm-predominant expression pattern of most oleosin genes in Arabidopsis thaliana and C. papaya. Moreover, the structure and expression divergence of paralogous pairs was frequently observed, and a good example is the lineage-specific gain of an intron. These findings provide insights into lineage-specific family evolution in Brassicales, which facilitates further functional studies in nonmodel plants such as C. papaya.

First report of Spiroplasma citri associated with disease symptoms in field-grown hemp (Cannabis sativa L.) in the Pacific Northwest.

Hemp (Cannabis sativa L.) is grown for cannabinoid oil production in Oregon. During the 2021 and 2022 growing seasons, plants with leaf curling, puckering, chlorotic mosaic, fasciation, and vein clearing were observed in disease surveys of Oregon hemp fields (Fig. 1). Symptoms were present on 1-10% of 2-4-month-old plants in fields located in Benton, Clackamas, Deschutes, Jackson, Josephine, Lane, Linn, Marion, Morrow, and Polk counties between July and September. Leaf and stem samples were collected from 38 symptomatic plants. Symptoms resembled those caused by beet leafhopper-vectored (BLH, Circulifer tenellus Baker) curtovirus or phytoplasma infection. Therefore, total nucleic acids were extracted (Dellaporta et al. 1983) from leaf material, and PCR conducted on all 38 samples to detect curtovirus coat proteins (BCTV-1/2 primers; Rondon et al. 2016) and 16S rRNA of phytoplasmas (nested primers P1/P7 followed by FU/RU; Lorenz et al. 1995). No curtoviruses or phytoplasmas were detected in any samples. Spiroplasma citri is also transmitted by BLH, so PCR was conducted with primers targeting the putative P89 adhesin gene and spiralin gene of S. citri (Yokomi et al. 2008). For all samples, PCR using P89F/R primers resulted in a 707 bp amplicon, and a 675 bp amplicon with Spiralin-f/r primers. PCR products were purified with ExoSapIT (Applied Biosystems, Waltham, MA), and two representative samples (ScH1; ScH2) were Sanger sequenced (EuroFins, Lancaster, PA) in the forward and reverse direction. Pairwise aligned P89 sequences were found to be 99 to 100% (ScH1: 633/637 bp; ScH2: 654/654 bp) identical to S. citri accession KT377386. Aligned/span>spiralin sequences were found to be 99 to 100% (ScH1: 661/664 bp; ScH2: 647/647 bp) identical to S. citri accession CP013197 in the NCBI GenBank Database. All sequences were deposited into GenBank (accession no. OQ969983, OQ992766, OQ969984, OQ969986). Frozen leaf material from one sample was used to culture S. citri according to Lee and Davis (1984). Leaf tissue was surface sterilized for 60 s in 1% NaOCl in 70% ethanol, cut into pieces in LD8 broth, and incubated for 25 min at 25˚C. The solution was passed through a 0.45um filter and incubated for 14 days at 30°C with constant shaking (150 rpm). Then, cultures were centrifuged for 2 min at 12,000 rpm to pelletize, resuspended in 100µL sterile distilled water and passed through a 0.2um filter. From this culture, 2 µL of broth was used as template for both the P89F/R and Spiralin-f/r primer sets. Amplicons were purified and sequenced as above (accession nos. OQ969982, OQ969985). Leaf tissue from both representative samples (ScH1 and ScH2) were positive for S. citri using double antibody sandwich ELISA (Agdia, Inc., Elkhart, IN) following manufacturer instructions. These results from sequencing, culturing, and ELISA testing indicate the hemp samples were infected with S. citri. To our knowledge this is the first report of disease symptoms in hemp associated with S. citri in Oregon and the Pacific Northwest. Infection by S. citri can limit yield by reducing photosynthetic capability of the plant and distortion of plant growth. Other pathogens like curtoviruses and phytoplasmas have also been detected in hemp in Oregon and the U.S. (Hu 2021; Rivedal et al. 2022), and the addition of S. citri associated with disease symptoms indicates a need for BLH management research. This discovery has implications for arid regions with other S. citri hosts including cruciferous plants, carrots, and tree fruit crops, all of which were grown near the sampled hemp fields in this study.

Evaluation of weed control efficacy and crop safety of the PPO-inhibiting herbicide tiafenacil in California orchard cropping systems

Abstract Tiafenacil is registered in the United States for use in annual crops such as corn and soybean, but not on orchard crops. Field studies were conducted to determine orchard crop safety and efficacy of tiafenacil on important California orchard weeds. To evaluate crop safety, tiafenacil was applied at 74, 148, and 222 g ai ha−1 alone and with 38 g ai ha−1 of tolpyralate three times per year at the base of almond, pistachio, prune, and walnut trees. The first treatment was applied 2 mo after the trees had been transplanted. In all four tree crop experiments, treatments were applied once in May 2020, then three times again during the winter of 2021 and 2022 at 21-d treatment intervals. There were no visual foliar injury symptoms or treatment-related effects on tree trunk diameter change even at the highest tested rate of tiafenacil applied seven times over three growing seasons. In a separate study of weed control, in most instances, tiafenacil applied at 12 g ai ha−1 performed similarly to that of tiafenacil plus glufosinate. Control of glyphosate-resistant hairy fleabane with tiafenacil applied alone at 25 g ai ha−1 was 65% by 14 d after treatment. Tiafenacil applied at 50 g ai ha−1 to hairy fleabane performed similarly to glufosinate plus glyphosate. In a greenhouse study, tiafenacil applied at 12 g ha−1 provided 95% to 100% control of barnyardgrass and junglerice, and there was no significant difference between tiafenacil applied alone or with glufosinate. Saflufenacil applied alone or in a mixture with glufosinate was not as effective as the tiafenacil treatments for grass weed control. Based on experiments conducted over three growing seasons in four tree fruit and tree nut crops, tiafenacil crop safety appeared to be acceptable even at up to 2- or 3-fold the expected use rate.

Расчет поливной нормы при капельном орошении древесно-плодовых культур в садовых насаждениях

Purpose: to develop the methodology for calculating irrigation rate for drip irrigation of tree-fruit crops, ensuring the formation of moistened soil contours in soil space with the required geometric and moisture parameters. Materials and methods. The empirical basis for the methodology development was the materials of the author's research devoted to determining the geometric dimensions (parameters) of soil moisture contours. The working hypothesis of the study involved determining the water supply rate for one emitter, one tree-fruit plant and a number of crops in the plantation, with further determining drip irrigation rate per unit area of drip-irrigated agricultural land, taking into account the number of drip micro-water outlets located on it. Results and discussion. When determining the geometric parameters of moisture contours and water supply rate, the main soil and technological parameters of drip irrigation and contour formation (physical clay content in soil, its lowest moisture capacity and bulk density, levels of pre-irrigation and after-irrigation soil moisture, specified depth soil profile moistening and dripper consumption) were considered as influence factors. The dependencies obtained by the author make it possible to determine the linear, areal and volumetric dimensions of local moisture contours and water supply rate, which, under appropriate conditions of drip irrigation, ensures the formation of a local, initially formed moisture contour with the required soil wetting depth in the soil layer. A study of the proposed methodology showed a deviation of the predicted parameters from the experimental soil moisture contours within ±10.0 %. Conclusions. A methodology allowing determining the irrigation rate for drip irrigation of agricultural land as the sum of the water supply rates of all drip water outlets irrigating 1 hectare of agricultural land with practical accuracy has been developed.

Расчет поливной нормы при капельном орошении древесно-плодовых культур в садовых насаждениях

Purpose: to develop the methodology for calculating irrigation rate for drip irrigation of tree-fruit crops, ensuring the formation of moistened soil contours in soil space with the required geometric and moisture parameters. Materials and methods. The empirical basis for the methodology development was the materials of the author's research devoted to determining the geometric dimensions (parameters) of soil moisture contours. The working hypothesis of the study involved determining the water supply rate for one emitter, one tree-fruit plant and a number of crops in the plantation, with further determining drip irrigation rate per unit area of drip-irrigated agricultural land, taking into account the number of drip micro-water outlets located on it. Results and discussion. When determining the geometric parameters of moisture contours and water supply rate, the main soil and technological parameters of drip irrigation and contour formation (physical clay content in soil, its lowest moisture capacity and bulk density, levels of pre-irrigation and after-irrigation soil moisture, specified depth soil profile moistening and dripper consumption) were considered as influence factors. The dependencies obtained by the author make it possible to determine the linear, areal and volumetric dimensions of local moisture contours and water supply rate, which, under appropriate conditions of drip irrigation, ensures the formation of a local, initially formed moisture contour with the required soil wetting depth in the soil layer. A study of the proposed methodology showed a deviation of the predicted parameters from the experimental soil moisture contours within ±10.0 %. Conclusions. A methodology allowing determining the irrigation rate for drip irrigation of agricultural land as the sum of the water supply rates of all drip water outlets irrigating 1 hectare of agricultural land with practical accuracy has been developed.

Are Tahiti Limes Profitable in South Florida? A Deterministic and Stochastic Budget Analysis

ABSTRACTTahiti limes were an important fruit tree crop in South Florida until the late 1990s. Several factors contributed to the demise of the Florida lime industry, namely the impact of hurricane Andrew in 1992 and the arrival of Citrus Canker (CC) in 1995. The Florida lime industry was then eradicated in the early 2000s to protect the main commercial citrus industry from CC. This article focuses on the financial viability of reintroducing Tahiti lime production in South Florida. A total of 20 Tahiti lime scion/rootstock combinations were evaluated under endemic CC and Citrus Greening (CG) conditions. We created a deterministic and a stochastic budget to evaluate the feasibility of reintroducing Tahiti limes in South Florida that incorporated yields from experimental plots. We also implemented a financial analysis, that included net present value (NPV) and internal rate of return (IRR) estimations, for a 20-year period with the Tahiti lime/citrus macrophylla (TL/CM), the best performing scion/rootstock combination. Our findings indicated that Tahiti lime production in South Florida was not financially feasible; we obtained a negative NPV from both the deterministic and stochastic budgets. We conclude with a discussion of potential scenarios for the Tahiti lime industry in the US and on lessons for other crops that face similar production challenges.

Mapping fruit tree dynamics using phenological metrics from optimal Sentinel-2 data and Deep Neural Network

Accurate and up-to-date crop-type maps are essential for efficient management and well-informed decision-making, allowing accurate planning and execution of agricultural operations in the horticultural sector. The assessment of crop-related traits, such as the spatiotemporal variability of phenology, can improve decision-making. The study aimed to extract phenological information from Sentinel-2 data to identify and distinguish between fruit trees and co-existing land use types on subtropical farms in Levubu, South Africa. However, the heterogeneity and complexity of the study area—composed of smallholder mixed cropping systems with overlapping spectra—constituted an obstacle to the application of optical pixel-based classification using machine learning (ML) classifiers. Given the socio-economic importance of fruit tree crops, the research sought to map the phenological dynamics of these crops using deep neural network (DNN) and optical Sentinel-2 data. The models were optimized to determine the best hyperparameters to achieve the best classification results. The classification results showed the maximum overall accuracies of 86.96%, 88.64%, 86.76%, and 87.25% for the April, May, June, and July images, respectively. The results demonstrate the potential of temporal phenological optical-based data in mapping fruit tree crops under different management systems. The availability of remotely sensed data with high spatial and spectral resolutions makes it possible to use deep learning models to support decision-making in agriculture. This creates new possibilities for deep learning to revolutionize and facilitate innovation within smart horticulture.