Fruit Drop Research Articles

Duration of fungicide spray program for the control of citrus black spot in sweet orange based on cultivar maturation and orchard age

Citrus black spot (CBS) damage and Phyllosticta citricarpa inoculum tend to increase in old orchards and in late-maturing cultivars of sweet orange. However, CBS control in São Paulo citrus belt is based on standard fungicide program of 180–220 days of fruit protection, regardless of cultivar and orchard age. This study aimed to investigate whether the protection period may be adjusted based on the cultivar maturation and age of orchards intended for juice processing. The efficacy of protection periods of 60, 100, 140, 180, 220 and 260 days was determined by assessing CBS incidence and severity and CBS-related fruit drop in 12 orchards over two seasons. The standard protection period, with 180 days targeted for mid-age and 220 days for old orchards, was the most cost effective for mid-season and late-maturing cultivars. These protection periods resulted in a significant reduction in CBS severity and fruit drop by up to ∼95% and ∼50%, respectively. For early-maturing cultivars, the duration of CBS spray program may be drastically reduced to 60 days for mid-age orchards and to 100 days for old orchards. These protection periods significantly reduced CBS severity and fruit drop by up to ∼92% and ∼50%, respectively. These adjustments in CBS fungicide protection period based on cultivar and orchard age may save up to US$14.3 million per season if adopted throughout the main Brazilian citrus belt. The results of this study allow citrus growers to save inputs, reduce costs, improve the operational efficiency within the farm and contribute to a more sustainable citrus industry.

Trunk Injection of Oxytetracycline for Huanglongbing Management in Mature Grapefruit and Sweet Orange Trees.

Huanglongbing (HLB) is a devastating bacterial disease associated with 'Candidatus Liberibacter asiaticus'. The location of the pathogen within the vasculature of the tree has left growers with limited options for the effective management of the disease. Trunk injection is a crop protection technique that applies therapeutics directly into the xylem of woody tree species and allows for their systemic uptake and transport, which may provide more effective management of vascular diseases such as HLB. In this study, mature 'Valencia' and 'Hamlin' sweet orange (Citrus sinensis) and 'Duncan' grapefruit (C. paradisi) trees were injected with oxytetracycline (OTC) in the spring and/or fall to evaluate the effects of injection timing and response to injection. In addition to seasonal evaluations of tree health and bacterial titer, preharvest fruit drop, yield, and fruit quality were measured at harvest to determine the effects of OTC injection. The benefits associated with injection included a reduction in fruit drop, an increase in fruit yield and fruit size, and improvements in juice quality. However, results varied due to the timing of injection and were not consistent across all three varieties. Residue analysis at different time points after injection suggests that trunk injection effectively delivers therapeutics to mature citrus trees. This study provides fundamental information on the short-term benefits associated with trunk injection of OTC for HLB management in citrus groves. The potential for use of trunk injection at the commercial scale and the possible risks are discussed.

Deciphering the response of thirteen apple cultivars for growth, fruit morphology and fruit physico-chemical attributes during different years

Apple cultivation is one of the most significant means of subsistence in the Kashmir region of the northwestern Himalayas. It is considered as the backbone of the region's economy. Apple cultivation in the region is dominated by a late maturing cultivar “Red Delicious” which usually on maturity causes glut in the market. In order to bring new cultivars in the cultivation, and to expand the maturity season, it is necessary to evaluate the new cultivars on fruit physico-chemical attributes which ultimately decide the market rates before recommending to farmers for cultivars adoption. Therefore, the current study was carried out to evaluate thirteen apple cultivars on physico-chemical attributes over two years, 2017 and 2018 under agro-climatic conditions of Kashmir region The results revealed that cultivars differed significantly in terms of physico-chemical properties. Cultivars with the highest and lowest values for initial fruit set, fruit drop, final fruit retention, and fruit firmness in 2017 did not follow the same trend in 2018. During 2017 and 2018, cultivar Mollie's Delicious possessed the highest fruit length (72.39 mm and 81.45 mm), fruit diameter (81.18 mm and 84.14 mm), and fruit weight (205.85 g and 247.16 g), whereas cultivar Baleman's Cider had the lowest values (50.76 mm and 52.83 mm, 60.10 mm and 62.08 mm, and 71.46 g and 86.94 g), respectively. The harvesting dates were quite spread out during both years of study. Cultivar Mollie's Delicious was harvested the earliest in both years, on August 5th, 2017 and August 8th, 2018. Cultivar Fuji Zehn Aztec was the last cultivar harvested in 2017 on October 2 and in 2018 on October 5. The maximum number of seeds per fruit was noticed in the cultivar Mollie's Delicious (8.34 and 8.71) during both 2017 and 2018, respectively. Cultivar Starkrimson had the fewest seeds per fruit in 2017 (7.11) and 2018 (7.42). Cultivar Baleman's Cider had the highest acidity in 2017 (0.63%) and 2018 (0.52%). In both 2017 (0.25%) and 2018 (0.23%), the Adam's Pearmain cultivar was the least acidic. Cultivar Allington Pippin (16.13 °Brix) and Red Gold (16.73 °Brix) had the highest TSS in 2017 and 2018, respectively, whereas Vance Delicious (12.30 °Brix) and Top Red (10.78 °Brix) had the lowest TSS in 2017 and 2018, respectively. The cultivars Mollie's Delicious and Red Gold had the highest total sugars (11.33 and 11.40%) in 2017 and 2018, respectively. Cultivar Baleman's Cider had the lowest total sugars (9.82%) in 2017 while Top Red (9.78%) in 2018. The cultivar Vance Delicious had the highest ratio of leaves to fruits in 2017 (55.44) and for Shalimar Apple-2 in 2018 (49.65). In 2017, cultivars Fuji Zehn Aztec (29.26) and Silver Spur (24.51), had the fewest leaves per fruit. The highest leaf chlorophyll content was recorded in cultivar Shireen (3.50 and 3.57 mg g−1 fresh weight) during the years 2017 and 2018, respectively. Cultivar Baleman's Cider had the lowest leaf chlorophyll content (2.15 mg g−1 fresh weight) during 2017, while cultivar Allington Pippin (2.09 mg g−1 fresh weight) had the lowest leaf chlorophyll content in 2018. The cultivars Fuji Zehn Aztec, with a yield efficiency of 0.78 kg/cm2 and Silver Spur with a yield efficiency of 1.14 kg/cm2 were the most yield efficient during the years 2017 and 2018, respectively. Cultivar Shalimar Apple-2 was least performing with yield efficiencies of 0.05 and 0.07 kg/cm2 during 2017 and 2018, respectively.The findings suggest that cultivar Mollie's Delicious commercially matures first and has the highest fruit length, diameter, and weight; hence, it can be a good option for cultivation so as to fetch the maximum price in the market when other cultivars are still maturing. Shalimar Apple-2 is precluded for cultivation due to least yield efficiency, whereas cultivars Fuji Zehn Aztec and Silver Spur are recommended to farmers for their higher yield efficiency.

TOXICITY OF COMMONLY USED CHEMICAL INSECTICIDES ON MANGO HOPPER

Mango production in Bangladesh is enormously affected by the infestation of hopper which punctures and sucks sap from tender shoots, inflorescences, and leaves of mango tree, causing non-setting of fruits and dropping of immature fruits. Control of mango hopper in recent days is solely done by synthetic insecticides. This study was conducted in the laboratory during January to October 2022 to know the toxicity of four commonly used insecticides, namely Desis 2.5 EC (Deltamethrin), Ripcord 10 EC (Cypermethrin), Relothrin 10 EC (Cypermethrin), and Sumithion 50 EC (Fenitrothion) on mango hopper. The doses of Desis 2.5 EC, Ripcord 10 EC and Relothrin 10 EC were prepared as 1200, 1000, 750, 500 and 100 ppm, and Sumithion 50 EC solutions were 2500, 2200, 1500, 1000 and 500 ppm. Results showed that the tested insecticides with their recommended doses revealed 51.4±2.5 to 70.6±1.8% mortality of hopper at 4 hours after treatment where Desis 2.5 EC showed the highest mean mortality of the insect. Desis 2.5 EC also showed the lowest LC50 and LC95 values (426.0 and 4331.4 ppm, respectively at 4 hours after treatment) signifying its higher effectiveness compared to other tested insecticides.

Xylem Functionality Is Not a Direct Indicator of Apple Preharvest Fruit Drop

Apple (Malus ×domestica) growers can incur significant economic losses when fruit drop before they can be harvested [preharvest fruit drop (PFD)]. In some years and cultivars, more than 30% of potential yield can be lost. Growers frequently apply plant bioregulators to reduce PFD, either via delay in maturity [aminoethoxyvinylglycine (AVG), 1-methylcycolpropene] or via inhibition in production of cell hydrolysis enzymes in the fruit pedicel [naphthalene acetic acid (NAA)]. Finding a physiological indicator of PFD would allow growers to assess the susceptibility of fruit to PFD. Due to its lignification, xylem is believed to be the last tissue to break down in the fruit pedicel, leading to PFD. To determine whether loss in xylem functionality can be used as an indicator of PFD potential, studies were conducted in 2020 and 2021 with ‘Red Delicious’ treated with AVG (132 µL·L−1), NAA (10 µL·L−1), and an ethylene-producing compound [ethephon (150 µL·L−1 in 2020, 200 µL·L−1 in 2021)] to generate a range of PFD potentials. Xylem functionality was assessed in the fruit cortex. Internal ethylene content (IEC), fruit maturity indices, and PFD rates were quantified weekly throughout the harvest period. Expression of genes encoding for cell hydrolysis enzymes (MdEG1 and MdPG2) was quantified to relate xylem functionality to fruit abscission mechanisms. In 2020 and 2021, AVG reduced PFD compared with the untreated control by decreasing IEC. Although ethephon did not result in higher PFD than untreated fruit, NAA reduced PFD in 2020 but not 2021. For all treatments in both years, there was a linear decrease in xylem functionality throughout the measurement period. Cumulative PFD exponentially decreased as xylem functionality neared zero and the climacteric rise in ethylene began. Concurrent with the rise in IEC and PFD was an increase in the expression of MdEG1 and MdPG2 in the fruit pedicel of the control compared with AVG-treated fruit. AVG-treated fruit lost xylem functionality at a similar rate to the untreated control but had lower expression of MdEG1 and MdPG2. These results indicate that xylem functionality is not a sole direct indicator of PFD. The concurrent increase in PFD and expression of MdEG1/MdPG2 supports previous research indicating that these two genes may serve as potential markers for PFD.

Nano-Biochar Suspension Mediated Alterations in Yield and Juice Quality of Kinnow (Citrus reticulata L.)

Nutrient deficiency negatively affects the yield and quality of citrus fruit. The present experiment was carried out to investigate the improvement in fruit yield and juice quality of Kinnow (Citrus reticulata L.) by foliar application of nano-biochar suspension (NBS). The experiment was carried out in a citrus farmer’s orchard with a history of low fruit yield, using a randomized complete block design. Four NBS treatments, i.e., 0% (control), 1, 3, and 5%, were applied through foliar application at the flowering stage. Foliar application of NBS at 5% and 3% significantly (p < 0.05) improved flowering, fruit retention, fruit set, fruit size, length, weight, diameter, juice volume levels, and minimized fruit dropping. The electrical conductivity of the juice was significantly decreased by increases in NBS concentration. Total dissolved solids increased slightly with treatments as compared to control. However, NBS foliar application did not show significant effects on nitrogen (N), potassium (K), and sodium (Na) leaf contents, but had some effect on phosphorus (P) content. Principal component analysis and a correlation matrix revealed significant (p < 0.05) positive and negative associations among the studied traits. The results of the current experiment showed that all parameters were significantly improved with the application of NBS at 3 and 5%, except that N, K, and Na levels were unaffected. The most encouraging results were achieved at a concentration of 5% NBS. In conclusions, the foliar application of NBS had a significant positive impact on fruit yield and juice quality.

Citrus Canker: A Persistent Threat to the Worldwide Citrus Industry—An Analysis

Citrus canker (CC), caused by one of the most destructive subfamilies of the bacterial phytopathogen Xanthomonas citri subsp. Citri (Xcc), poses a serious threat to the significantly important citrus fruit crop grown worldwide. This has been the subject of ongoing epidemiological and disease management research. Currently, five different forms have been identified of CC, in which Canker A (Xanthomonas citri subsp. citri) being the most harmful and infecting the majority of citrus cultivars. Severe infection symptoms include leaf loss, premature fruit drop, dieback, severe fruit blemishing or discoloration, and a decrease in fruit quality. The infection spreads rapidly through wind, rain splash, and warm and humid climates. The study of the chromosomal and plasmid DNA of bacterium has revealed the evolutionary pattern among the pathovars, and research on the Xcc genome has advanced our understanding of how the bacteria specifically recognize and infect plants, spread within the host, and propagates itself. Quarantine or exclusion programs, which prohibit the introduction of infected citrus plant material into existing stock, are still in use. Other measures include eliminating sources of inoculum, using resistant hosts, applying copper spray for protection, and implementing windbreak systems. The main focus of this study is to highlight the most recent developments in the fields of Xcc pathogenesis, epidemiology, symptoms, detection and identification, host range, spread, susceptibility, and management. Additionally, it presents an analysis of the economic impact of this disease on the citrus industry and suggests strategies to reduce its spread, including the need for international collaboration and research to reduce the impact of this disease on the global citrus industry.

Influence of Different Levels of NAA and 2, 4, 5-T on Fruit Drop, Fruiting, Fruit Retention, Growth and Yield of Indian Ber (Zizyphus mauritiana Lamk.)

The experiment was carried out at Horticulture Garden, Department of Fruit Science, Chandra Shekhar Azad University of Agriculture & Technology, Kanpur (U.P.) during the November 2020- March 2021 and November 2021- March 2022. Sixteen treatments viz. four levels of NAA (0, 20, 30 and 40 ppm) and 2,4,5-T (0, 10, 20 and 30ppm) were studies in a Factorial Completely Randomized Design with three replications. Spraying was done on eleventh November, 2020 in first year and fifteenth November, 2021 in second year at fruit setting stage (Pea Stage) with fine nozzle sprayer in each treatment to give uniform spray on all over the treatment of ber plant. Application of (NAA@40 ppm and 2,4,5-T@30 ppm) significantly maximized initial fruit set (162.00 and 163.66), maximum fruit retention (20.39 and 20.43 percent) and maximum initial fruit set percentage (79.60 and 79.56 per cent). The length and width of fruit was significantly (5.35 and 4.99 cm) and (4.24 and 4.27 cm) respectively increased by application same concentration mention above. The maximum (36.62 and 36.82 g) fruit weight and physical properties of fruits like volume (36.57 and 36.42 cc) recorded under treatment (NAA@40ppm and 2,4,5-T@30ppm). The minimum stone length (0.88 and 0.87 cm), minimum stone diameter (0.88 and 0.87 cm), minimum stone weight (0.65 and 0.66 gm) and specific gravity (0.94 and 0.94 g cc-1) significantly found under (NAA@40 ppm and 2,4,5-T@30 ppm). The yield of ber was significantly increased (39.53 and 40.49) kg per plant, yield per hectare (121.30 and 121.33quintal) with treatment combination (NAA@40ppm and 2,4,5-T@30ppm) both the years of experiment.

Studies on fruit pedicel concerning fruitlet abscission in kinnow mandarin

Fruit drop is a major constraint for the production of kinnow mandarin. The present investigation comparedthe physical, biochemical and anatomical dynamics taking place in abscised and non-abscised fruit pedicelsof Kinnow mandarin at physiological and pathological fruit drop stages. The pedicel parameters (length, girthand weight) were higher in non-abscised than the abscised fruits. The activities of polygalacturonase (4.01μg D-glucose released g-1 FW min-1) and cellulase (4.34 μg D-glucose released g-1 FW min-1) enzymes weresignificantly low in non-abscised as compared to abscised fruit pedicels. The transverse sections of nonabscisedhealthy fruit pedicels revealed intact phloem and long xylem vessels in the vascular tissue. However,pedicels of abscised fruits showed degradation of cells and formation of the abscission zone. Fruit pedicelparameters had positive correlation with mineral nutrients, total soluble sugars and total soluble proteins,however, non-abscised fruit pedicels were negatively correlated with cell wall degrading enzymes. The fruitpedicel health has been found important and positively associated with the diminution in physiological andpathological fruit abscission in kinnow mandarin.

Effects of Plant Growth Regulators Including Micro-nutrients on Fruit Set and Yield of Mandarin in Dhankuta District of Nepal

The study evaluated foliar applications of three plant growth regulators, viz. GA3 @ 20ppm; 2,4-D @ 15ppm; and NAA @ 50ppm; alone and their combinations including three plant micro-nutrients, viz. B @ 0.4% + Zn @ 0.2% + Ca @ 1% in order to determine the best foliar spray of growth hormones and plant nutrients for the increased fruit set and yield of mandarin. The foliar sprays were applied five times, started from full-bloom until late September (pre-harvest stage). The experiments were conducted in Dhankuta, Nepal during 2019 and 2020. The highest bloom fruit set of 6.1% was recorded at the foliar application of GA3 20ppm + NAA @ 50ppm, compared to the control treatment of 4.6%. Likewise, there were significant effects of plant growth regulations and micro-nutrients applications on the fruit drops across the fruit growing periods. The foliar application of GA3 + 2,4-D + micronutrients resulted in the lowest fruit drop during the months of June (63.9%), July (65.9%), and September (20.8%), as opposed to the control treatment's fruit drops of 77.6, 80.4, and 41.5%. In addition, the fruit drops occurred at the foliar sprays of GA3 + 2,4-D were statistically at par with the GA3 + 2,4-D + micro-nutrients. Also, the GA3 + 2,4-D + micronutrient spray treatment had the largest number of fruits (995 nos.) and total fruit weight (64.2 kg) per tree, which were considerably higher than the control by 201.5 and 175.5%, respectively. To sum up, a combined foliar application of gibberellic acid, 2,4-D and micro-nutrients is recommended for improving the fruit set, retention and yield of mandarin.

INFLUENCE OF FOLIAR APPLICATION OF ZINC AND BORON ON FLOWERING AND FRUITING OF MANDARIN (CITRUS RETICULATA BLANCO) AT MYAGDI, NEPAL

A study was conducted during the spring season of 2022 to find out the effect of foliar application of micronutrients (Zinc and Boron) in flowering and fruit setting of mandarin (Citrus reticulata blanco) in Myagdi, Nepal. The experiment was laid out in a factor-randomized complete block design (RCBD) with five treatments and four replications. The treatments consist of foliar application of sole and combined application of Zinc and Boron namely: control (water spray), 0.2% Zn, 0.1% B, 0.15% Zn + 0.05% B, and 0.1% Zn + 0.1% B. Twenty mandarin trees of the same age and height from an orchard were chosen from the north-facing slope. The spray solution was formulated using standard procedures. The foliar application of the micronutrients was done twice, the first application was done days before flowering, and the second application was done after 2 days of full flowering. The data analysis was done using MS Excel and R-stat. Treatments had significant variations in total flowers and hermaphrodite flowers per branch, fruit diameter, fruit set, and fruit drop. Thus, our study showed that foliar spray of Zinc 0.1% + Boron 0.1% was the best for the production of more hermaphrodite flowers, for a higher fruit set percentage, and for a higher fruit retention percentage in Mandarin.

Morpho-anatomical characterization, gene expression and protein cell wall modifications associated with natural finger drop in bananas

Banana (Musa spp.) is one of the main fruits consumed worldwide. However, finger drop, is a physiological disorder that causes many postharvest problems, which eventually reduces market value and consumer acceptance. Therefore, the objective of the study was to evaluate the anatomical changes that occur in the pedicel rupture area (drop zone) of bananas diploids (BB França) and tetraploid (BRS Pioneira) in three ripening stages. The levels of gene expression involved in the natural ripening process and in the development of finger drop, was also investigated. The accumulation of their mRNAs and those of expansin (EXP1), pectate lyase (PEL1) and xyloglucan endotransglucosylase/hydrolase protein (XTH4) genes already isolated from bananas were measured by quantitative polymerase chain reaction in three ripening stages. BB França presented a higher resistance to finger drop due to the presence of some specific morphoanatomical characteristics, such as larger parenchymal cells and greater deposition of lignin. In contrast, there was degeneration of the pedicel parenchymal tissue of the BRS Pioneira genotype, forming large empty spaces during the ripening of the fruits, mainly in stage 6, which contributed to the finger drop. The diploid BB França is a strong candidate for use in banana breeding programs aimed at fruit drop resistance. This will certainly improve the quality of banana varieties. Moreover, PEL1 proved to be an excellent candidate gene for functional studies of finger drop in bananas.

Analysis of damage caused by drop impacts for mulberry fruits: An dropping experiment and numerical simulation

AbstractIn the process of mechanized production of mulberry, falling collision damage is one of the main damage forms, which causes serious damage and accelerates fruit decay. Through the drop collision test and simulation analysis of mulberry fruit, the relationship between drop conditions and fruit damage degree was established, so as to provide reference for reducing fruit falling damage. The drop test is carried out. The relationship between factors and indicators is established. The drop height, fruit plate angle, fruit plate material, and drop direction were taken as factors, and then the energy loss was selected as indicator. The drop process of mulberry fruit is analyzed by numerical simulation, and the maximum stress and deformation of mulberry fruit are analyzed. With the increase of the drop height, the kinetic energy of the fruit increases. When the fruit plate material is pearl cotton, the drop height changes from 200 to 1000 mm, the energy loss of fruit falling increases from 4.42 × 10−0.3 J to 2.14 × 10−0.2 J. When the drop height of fruit is 200 mm, the angle of fruit plate is 30°, and the material of fruit plate is pearl cotton, the minimum energy loss of fruit is 3.39 × 10−0.3 J, the fruit damage was the least. This study can provide a reference to reduce the damage of mulberry fruit in the process of mechanical harvest and transportation.Practical ApplicationsThe existing mulberry harvesting methods are manual harvesting, while the vibration harvesting methods have high harvesting efficiency and serious damage. When the harvesting parts hit the tree trunk, the mulberry fruit will leave the tree and falls onto the fruit‐receiving device in the process of mechanical harvesting. There will be a collision and falling of the mulberry, which may cause serious damage. Therefore, in the process of mulberry fruit harvest, transportation, the falling, and collision damage is the main damage form.At present, there is few research on the drop impact damage test of mulberry fruit. In this study, the effects of mulberry falling direction, fruit plate material and drop height on mulberry damage were discussed by drop experiment. Then, the optimization results were carried out. The change and distribution of stress and strain in the process of collision were analyzed by numerical simulation, and the relationship between falling conditions and damage level was established. It is important to analyze the dynamic characteristics of mulberry in the process of drop. This study can be applied as a reference to reduce mulberry fruit impact damage, and provide a theoretical reference for the design of mulberry vibration harvesting machinery.

Trend during Growth, Development and Quality Attributes of Ber (Zizyphus mauritiana Lamk.) Fruits: A Review

The trends in growth, development and quality attributes of Ber (Zizyphus mauritiana Lamk.) included changes observed during growth and development, namely fruiting behavior, physical properties and biochemical components of the ber fruit at different stages of growth and development. Flowering began in mid-September and ended in mid-November with the peak of the flowering period in mid-October. While the fruit setting was between the third week of September to the first week of December, but the peak fruit initiation period was the last week of September to mid-October. During fruit growth, development and yield attribute the percentage of fruit drop and retention also changes. Ber fruits were harvested in five times collections and the peak yield period was the first week of March. In the physical changes, the study revealed that length, width, weight, volume, pulp weight, and seed weight increased from fruit set to maturity at all stages of growth and development except for specific weight, which first increased in month of mid-November and then decreased when the fruits continued in the harvest phase. The biochemical changes in fruit in terms of total sugars, ascorbic acid, reducing sugars, non-reducing sugars and total sugars increased steadily from fruit set to maturity, when titratable acidity showed a trend decreasing during fruit growth and development.

CPPU and salicylic acid application improved fruit retention, yield, and fruit quality of mango cv. Dusehri

ABSTRACT The present investigation was aimed at assessing the efficacy of N1-(2-chloro-4-pyridyl)-N3-phenylurea (CPPU) and salicylic acid on fruit retention, yield, and quality of mango cv. Dusehri. The research was carried out at the Department of Fruit Science, Punjab Agricultural University, Ludhiana, India. The experiment was conducted simultaneously at two different locations for two cropping seasons during 2019–20 and 2020–21. Fruit retention enhancing treatments of 2,4-Dichlorophenoxyacetic acid (2,4-D) (@20 ppm), CPPU (@5, 10, and 15 ppm), and salicylic acid (@100, 200, and 300 ppm) were applied at pea stage of fruit growth. Experimental plants were observed for various reproductive, yield, and fruit quality parameters. The results indicated that foliar application of CPPU (T6-CPPU @10 ppm) significantly enhanced fruit retention during marble and harvest stages at both locations in both seasons. The novel growth hormone also improved fruit yield, fruit weight, and fruit quality in mango cv. Dusehri. Foliar applied salicylic acid recorded intermediate values for observed parameters. Therefore, foliar application of CPPU can be considered as a better alternative to 2,4-D for fruit drop management of mango.

Incidence Of Citrus Greening Disease In Some Major Khasi Mandarin Growing Areas In Upper Brahmaputra Valley Zone Of Assam

A roving survey was conducted in different districts of Upper Brahmaputra Valley Zone of Assam in order to ascertain the presence of Citrus Greening disease (CGD) and characterization of their causative agents through molecular assays. The typical symptoms observed in field conditions were blotchy mottling, small and upright leaves, yellowing of leaves and chlorosis, pre-mature fruit drop, twig dieback. Disease severity calculated on the basis of the disease rating scale indicated that the severity of CGD in young and matured Khasi mandarin was found to be highest in Jorhat district (33.75%) and Golaghat district (41.26%) respectively. Lowest disease severity of 16.66 per cent was recorded in Dibrugarh district for both young and matured plants. PCR assays of the samples for CGD diagnosis showed that overall 13 out of 44 samples from young and 42 out of 60 samples from matured Khasi mandarin were infected. The desired ~703bp PCR product using the primer pair A2/J5 confirmed the presence of Candidatus Liberibacter asiaticusin the surveyed areas.

Structural characteristics and gel properties of pectin from citrus physiological premature fruit drop

This study is the first to extract and characterize pectin from citrus physiological premature fruit drop. The extraction yield of pectin reached 4.4 % by acid hydrolysis method. The degree of methoxy-esterification (DM) of citrus physiological premature fruit drop pectin (CPDP) was 15.27 %, indicating it was low-methoxylated pectin (LMP). The monosaccharide composition and molar mass test results showed CPDP was a highly branched macromolecular polysaccharide (β: 0.02, Mw: 2.006 × 105 g/mol) with rich rhamnogalacturonan I domain (50.40 %) and long arabinose and galactose side chain (32.02 %). Based on the fact that CPDP is LMP, Ca2+ was used to induce CPDP to form gels. Textural and rheological tests showed that the gel strength and storage modulus of CPDP were higher than commercial citrus pectin (CP) used in this paper due to the lower DM and rich neutral sugar side chains of CPDP. Scanning electron microscope (SEM) results showed CPDP had stable gel network structure.

Differential gene expression analysis and physiological response characteristics of passion fruit (Passiflora edulis) buds under high-temperature stress.

High temperature in summer is an unfavorable factor for passion fruit (Passiflora edulis), which can lead to restricted growth, short flowering period, few flower buds, low fruit setting rate, severe fruit drop, and more deformed fruit. To explore the molecular physiology mechanism of passion fruit responding to high-temperature stress, we use 'Zhuangxiang Mibao', a hybrid passion fruit cultivar, as the test material. Several physiological indicators were measured and compared between high-temperature (average temperature 38 °C) and normal temperature (average temperature 25 °C) conditions, including photosynthesis, chlorophyll fluorescence parameters, peroxidase activity (POD), superoxide dismutase activity (SOD) and malondialdehyde content. We performed RNA-seq analysis combined with biochemistry experiment to investigate the gene and molecular pathways that respond to high-temperature stress. The results showed that some physiological indicators in the high-temperature group, including the net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, transpiration rate, and the maximum chemical quantum yield of photosystemII (PSII), were significantly lower than those of the control group. Malondialdehyde content was substantially higher than the control group, while superoxide dismutase and superoxide dismutase activities decreased to different degrees. Transcriptome sequencing analysis showed that 140 genes were up-regulated and 75 genes were down-regulated under high-temperature stress. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation analysis of differentially expressed genes revealed many metabolic pathways related to high-temperature stress. Further investigation revealed that 30 genes might be related to high-temperature stress, such as chlorophyllide a oxygenase (CAO), glutathione (GSH), WRKY transcription factors (WRKY), and heat shock protein (HSP), which have also been reported in other species. The results of real-time fluorescence quantitative PCR and RNA-seq of randomly selected ten genes are consistent, which suggests that the transcriptome sequencing results were reliable. Our study provides a theoretical basis for the mechanism of passion fruit response to high-temperature stress. Also, it gives a theoretical basis for the subsequent breeding of new heat-resistant passion fruit varieties.

Combination of 1-MCP and modified atmosphere packaging (MAP) maintains banana fruit quality under high temperature storage by improving antioxidant system and cell wall structure

Green-ripe disorder often occurs when banana fruit (Musa AAA group) ripen at high temperature above 25 °C. In this study, the effect of modified atmosphere package (MAP) + 1-methylcyclopropene (1-MCP) treatment on the shelf-life quality of banana after high temperature storage was studied. The results showed that 300 nL L-1 1-MCP treatment combined with MAP could prevent the occurrence of green-ripe disorder in banana stored at high temperature, reduce ethylene production and respiration, then delay senescence and ripening, and reduce disease incidence and finger drop of fruit. Further analysis showed that the combined treatment decreased the content of reactive oxygen species (ROS) and enhanced the activity of defense-related enzymes and antioxidants. By inhibiting the activity of cell-degrading enzymes, the treatment increased lignin and cellulose content and maintained cell wall integrity. In addition, the treatment regulated the contents of endogenous hormones indole-3-acetic acid and abscisic acid, thus delaying the softening of fruit. This work provides a theoretical foundation for the storage and transportation of banana fruit at high temperature.

HUMEDAD RELATIVA Y RADIACIÓN FOTOSINTÉTICAMENTE ACTIVA INFLUYEN EN EL RENDIMIENTO DE FRUTO DE Vanilla planifolia

<em><em></em></em><p><strong>Background:</strong> Fruit yield in vanilla cultivation depends on climatic and genetic factors and management practices; however, studies on the influence of the environment on management systems for vanilla production are still limited. <strong>Objective:</strong> To evaluate the yield of vanilla fruit in three different management systems in correlation with their climate parameters. <strong>Methodology:</strong> 16 fruit yield components were evaluated in at least 10 repetitions; in addition, temperature, relative humidity, photosynthetically active radiation, and accumulated precipitation were recorded during the production cycle. The analysis of variance, Tukey´s test (α=0.05), and canonical correlation between yield components and climate parameters were performed under a randomized complete block design. <strong>Results: </strong>Vanilla fruit yield was influenced by the management system. The intensive system in shade mesh with an inert tutor (Barriles) had the highest yield of three evaluated sites, however, its fruits had lower weight and size than the system in acahual (20 Soles) and shade mesh with a living tutor (Solteros de Juan Rosas). The acahual system had a middle yield and the largest and heaviest fruits. The cultivation in shade mesh with living tutors in Solteros had low yield, attributable to high relative humidity and low photosynthetically active radiation during the cultivation cycle due to excessive shading of living tutors that as a whole could cause low floral induction and environmental stress promoting the development of diseases and premature fruit drop. Nevertheless, the fruits harvested in Solteros had physical characteristics similar to those of acahual (20 Soles). The effect of climate parameters was mainly reflected in inflorescences and fruit density. <strong>Implications:</strong> The incorporation of more study sites and cultivation cycles are necessary to extend the research, however, the information provided may be useful for producers to modify some of their management practices. <strong>Conclusions: </strong>The yield and size of vanilla fruits is influenced by the management system, since the highest yield occurred in the intensive system of shade mesh with inert tutors. The presence of diseases is a factor that could influence low fruit yield. Relative humidity and photosynthetically active radiation are the climate parameters with the greatest influence on fruit yield, particularly on fruits and inflorescences density in vanilla cultivation.<strong></strong></p>