25 Jun 2024
Citrus Fruit Drop

PGR For Controlling Pre-Harvest Fruit Drop And Improving Quality of Kinnow

A field trial was conducted to evaluate the effect of PGR (2, 4-D, NAA and GA3) at different concentrations on fruit drop and enhancement in fruit quality of Kinnow. Three sprays of PGR viz. 2, 4-D, NAA and GA3 were given to the Kinnow plants as per the treatment concentrations from initiation of flowering to before harvesting. The results revealed that among all the PGR’s tried at different concentrations, spray of 2, 4-D @ 30 ppm was the most promising in reducing the fruit drop in Kinnow as fruit physical and chemical characters were found to be superior as compared to all other treatments. There was an enhancement in the fruit size with the application of 2, 4-D @ 30 ppm, which led to an overall increase in the yield of Kinnow.

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25 Jun 2024

Short-term effects of cover crops on soil properties and the abundance of N-cycling genes in citrus agroecosystems

Limited information is available on the influence of cover crops (CCs) on soil nutrient cycling and the abundance of bacterial and archaeal communities, nitrogen (N)-fixers, nitrifiers, and denitrifiers in tree crops. We examined the effect of replacing the traditional weedy inter-row middle of a commercial citrus orchard in Florida with two different mixtures of CCs: legumes and non-legumes (LG + NL) and non-legumes only (NL). A no-treatment/grower standard was used as a control (GSC). After one year of CCs, the use of NL and LG + NL CCs significantly increased soil carbon (C) availability in the row middles compared to GSC as shown by increases in permanganate oxidizable C, and to a lesser extent, soil organic matter. Treatment with LG + NL significantly increased soil ammonium content compared to the NL and GSC treatments. Improved C cycling in soils treated with CCs was related to increased abundance of bacteria and archaea. Changes in the size of the soil N pool were accompanied by increases in the abundance of N-fixation (nifH) and nitrification (amoA) genes in soils treated with LG + NL, likely due to greater N-mineralization and N-fixation by legumes.

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25 Jun 2024
Huanglongbing infected orange trees

Identification of citrus greening based on visual symptoms: A grower’s diagnostic toolkit

Citrus greening is one of the world’s most serious diseases of citrus that affects all cultivars and causes the systematic death of trees worldwide. The disease is caused mostly by the bacteria Candidatus Liberibacter species. The wind, rain, and touch of infected workers cannot transmit this infectious disease. The Asian Citrus Psyllid (ACP), a minuscule insect, is one of the main vectors that transmit the disease by feeding on citrus leaves. Citrus greening management is also quite expensive since no successful treatment for the cure has been found, except to remove all affected vegetables from healthy crops to eliminate the bacterial spread.

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25 Jun 2024
Citrus Black Spot

The Effects of Postharvest Treatments and Sunlight Exposure on the Reproductive Capability and Viability of Phyllosticta citricarpa in Citrus Black Spot Fruit Lesions

Citrus black spot (CBS) is caused by Phyllosticta citricarpa, which is classified as a quarantine organism in certain countries whose concerns are that CBS-infected fruit may be a pathway for introduction of the pathogen. This study evaluated the reproductive capability and viability of P. citricarpa under simulated conditions in which the whole fruit, peel segments, or citrus pulp with CBS lesions were discarded. Naturally infected ‘Midknight’ Valencia orange and ‘Eureka’ lemon fruit, either treated using standard postharvest sanitation, fungicide, and wax coating treatments or untreated, were placed into cold storage for 5 weeks (oranges at 4 °C and lemons at 7 °C). Thereafter, treated and untreated fruit were incubated for a further 2 weeks at conditions conducive for CBS symptom expression and formation of pycnidia. The ability of pycnidia to secrete viable pycnidiospores after whole fruit and peel segments or peel pieces from citrus pulp were exposed to sunlight at warm temperatures (±28 °C) and ±75% relative humidity levels was then investigated.

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24 May 2024
Citrus flower

Demonstration of a Change in Nitrogen Metabolism Influencing Flower Initiation in Citrus

Changes in the leaf NH3-NH4 + content were monitored during floral induction in Citrus. Five-year-old rooted cuttings of ‘Washington’ navel orange (Citrus sinensis) were induced to flower by subjecting the trees to 8 weeks of low temperature, 8-h day (500 μE m−2 s−1) at 15–18°C/16-h night at 10–13°C and by transferring them afterwards to 12-h day (500 μE m−2 s−1) at 24°C/12-h night at 19°C. Maximum bloom occurred 4 weeks after the transfer to the warmer temperature. The number of flowers and the NH3–NH4 + content of leaves increased significantly (p < 0.05 and P < 0.01, respectively) with the length of the low temperature treatment. Sixteen-year-old ‘Frost Lisbon’ lemon trees (Citrus limon) on ‘Troyer’ citrange rootstocks (C. sinensis × Poncirus trifoliata) under commercial production were subjected to water-deficit stress of increasing severity.

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24 May 2024
Effect of different salinity levels

Salinity Level Influenced Morpho-physiology and Nutrient Uptake of Young Citrus Rootstocks

Soil and irrigation water salinity are major limiting factor to citrus industry in arid environments. The objective of this study was to assess the effects of different salt stress levels on growth and ion uptake of three-month-old citrus rootstocks; sour orange (Citrus aurantium) and Volkamer lemon (Citrus volkameriana). Six levels of NaCl-salinity were used, 0.7 (control), 2, 4, 8, 12 and 15 dS m-1. Salinity increment from 2.0 to 15.0 dS m-1 significantly reduced seedlings height, stem diameter, leaf area, root dry weight, leaf relative water content, chlorophyll content index and chlorophyll fluorescence by one to three folds. In addition, leaf and root N concentration reduced by 10%–50%, P 6%–50%, K 8%–47%, Ca+2 7%–51% and Mg+2 7%–50% when salt stress in the irrigation water increased from 2.0 to 15.0 dS m-1.

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26 Apr 2024
Foster Grapefruit

Effect of harvesting method on quality and storability of grapefruits

The effect of harvesting method on fruit quality and storability of the pink-fleshed ‘Foster’ grapefruits, at 18±1°C and 85%-90% r.h., was evaluated. The traditional method, using a hooked pole, was compared with an improved technique, where the picking pole was equipped with a long cloth sleeve held open by a ring for collecting the harvested fruits.

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26 Apr 2024
Pomelo

Influence of Water Stress in Autumn on Flower Induction and Fruiting in Young Pomelo Trees

Young pomelo trees grown in concrete pots in a plastic house were water-stressed for different durations from early September to late December, 1990. The cyclical stress treatments were established by withholding water from the potted trees until the leaf water potentials reached -24 to -28 bars (7 to 13 days after irrigation) at which time they were re-irrigated. Maximum day and minimum night temperatures in the plastic house were adjusted to about 25° and 10°C, respectively, from early December, 1990, to early April of the following year.

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