Leaf pruning intensities at flowering of banana (Musa AAA,cv. Grande Naine) did not influence fruit green and yellow life and quality

This study examined the effects of leaf pruning intensities at flowering on the green and yellow life and fruit quality of bananas (Musa AAA, cv. Grande Naine). The fruit from banana plants that retained 7, 9, 11 and 13 leaves after pruning were packed in carton boxes of 13.7 kg and stored in a cold room at 14 °C for 21 days to simulate transportation conditions. During this period, eight visual evaluations of fruit peel colour were made. Next, fruits were induced to commercial ripening using ethylene at 100 μl/ml. Four evaluations (every 2 days) on fruit firmness, soluble solids, titratable acidity, fruit weight and peel colour were made to assess fruit yellow life. No interaction between evaluations and number of leaves retained was found for pulp firmness, soluble solid percentage, fruit acidity, fruit weight and maturation grade. The fruit green life and peel colour was similar for plants retaining different number of leaves. After the application of ethylene, there were no differences in fruit firmness (P > 0.62), percentage of soluble solids (P > 0.24) nor in the percentage of acidity (P > 0.32). No difference in fruit weight (P > 0.07) and ripening grade (P > 0.17) were observed among plants retaining different number of leaves. The results suggest that in tropical commercial banana plantations, producing for international markets, it is possible to defoliate the banana plants to seven leaves at flowering without causing a reduction on the green and yellow life and quality of fruit.     

应用PCR技术快速检测柑桔溃疡病的研究

应用PCR检测柑桔溃疡病，所用引物为5′TTGGTG TCGTCGCTTGTAT 3′和5′CACGGGTGCAAAAAATCT 3′。从病样的叶片、果皮和枝皮抽提溃疡病菌核酸进行PCR扩增，其产物经琼脂糖凝胶电泳，产生大约220bp的特征条带，与纯培养溃疡病菌的PCR产物一致。试验比较两种核酸抽提方法，微量快速抽提法的灵敏度明显高于高盐抽提法。有症状病样品的不同部位均能检测到溃疡病；病株的无症状叶片、果皮、枝皮有部分检测到病菌。病果园健康植株大多数检测不到病菌，少数植株PCR产物电泳条带较弱。取样量以10～20mg为宜。该PCR技术可用于快速检测柑桔溃疡病。     

Seasonal changes of mineral nutrients and phenolics in pomegranate (Punica granatum L.) fruit

Pomegranate fruit is an important source of potentially healthy bioactive compounds and mineral nutrients. Changes in total phenolic compound, concentrations, and levels of macronutrients (P, K, N, Mg, Ca and Na) and micronutrients (Zn, Cu, Mn, Fe and B) in arils and peel of pomegranate fruit were recorded from 10 days after full bloom until harvest. Total phenolics levels increased at early stage of growth both in peel and arils of fruit, but thereafter generally decreased during maturation and reached to 3.70 and 50.22 mg g⁻¹ of dry weight in arils and peel, respectively, at harvest. The amount of total phenolics in peel was markedly higher than arils of pomegranate fruit. The concentration of most elements in arils and peel decreased during fruit growth and development. At harvest the relative order of concentration of macronutrients both in arils and peel was K > N > Ca > P > Mg > Na. The concentration of most micronutrients was greater in the arils than in the peel especially in early season. The relative order of concentration of micronutrients in arils was B > Fe > Zn > Cu > Mn. The accumulation of all the macro- and microelement within the fruit also increased during fruit growth and development. These results provide important data on total phenolics and macro- and micronutrient changes during fruit growth and development, emphasizing that pomegranate fruit can be a good source of bioactive compounds and minerals.     

Yield prediction in intercropped versus monocropped citrus orchards

Pooled data analysis for intercropped versus monocropped citrus orchards showed superiority of monocultured (68.5 kg tree⁻¹) over intercropped (51.4 kg tree⁻¹) orchards. But, intercrop specific analysis revealed that citrus orchards with legumes as intercrop (soybean and chickpea), produced significantly (p < 0.05) higher fruit yield (72.2 kg tree⁻¹) compared to orchards without intercrops (68.5 kg tree⁻¹). These legume-based intercropped orchards maintained much higher levels of leaf nutrient (2.35% N, 0.13% P, 2.08% K, 86.5 ppm Fe, 71.1 ppm Mn, 22.2 ppm Cu, and 22.0 ppm Zn) than the orchards without intercrops (2.29% N, 0.13% P, 2.47% K, 79.2 ppm Fe, 63.8 ppm Mn, 21.7 ppm Cu, and 23.2 ppm Zn). Intercrop yield prediction through regression models in relation to leaf nutrient status were further investigated.     

Reduction of apple tree height (Malus domestica Borkh) cv. Ultra Red Gala/MM111 does not decrease fruit yield and quality

In Chile, like in other countries, a high percentage of apple (Malus domestica Borkh) orchards are grafted on vigorous or semi-vigorous rootstocks. The need to decrease the amount of labor involved and increase efficiency has motivated this study on the effect of reducing the height of cv. Ultra Red Gala/MM111 trees in a commercial orchard in the Maule Region of Chile. Apple trees were planted in 2003, and their tree heights were adjusted to 2.5, 3.0 and 3.6 m prior to blooming in 2006. The reduction of plant height from 3.6 m to 2.5 m determined a significant reduction in canopy volume (26% and 29% in 2007/2008 and 2008/2009, respectively), but no differences were detected in leaf area index (LAI) and the photosynthetic active radiation (PAR) transmitted through the canopy. However, a higher proportion of the canopies of the shorter trees had over 30% of incident PAR, the threshold for the production of good fruit quality and flower-bud differentiation. There were no differences in fruit production among plant heights, accumulating 131 tonnes ha⁻¹ in the three growing seasons. Over the three seasons, the shortest plants (2.5 m) required 19, 57 and 42% less labor time at harvest, respectively, than the plants maintained at a height of 3.6 m. There were no evident differences in fruit quality among the treatments; flesh firmness varied between 73.0 and 74.0 N, soluble solids between 11.6 and 12.6°Brix, mean weight between 180 and 200 g, and the percentage of red coloring exceeded 59% of the Premium fruit in the three growing seasons. Our results suggest that it is possible to manage plants with reduced height on semi-vigorous rootstocks and thus reduce the time necessary for harvesting, without affecting fruit yield and quality.     

Isolation of a citrus ethylene-responsive element binding factor gene and its expression in response to abiotic stress,girdling and shading

Information about citrus ethylene-responsive element binding factor (ERF) genes and their functions in fruit ripening or in stress tolerance is still scarce. In the present study, one of ERF genes, CitERF was isolated from fruit of Citrus unshiu with a maximal putative open reading frame encoding 207 amino acids. The deduced protein contains a region rich in acidic amino acids, an AP2/ERF domain and a KRRK nuclear localization signal. It belongs to group B of Class I in the ERF subfamily in which MdERF2 (Malus × domestica ethylene-response factor 2) and PsERF1b (Prunus salicina ethylene-response factor 1b) were involved in the progress of fruit ripening. CitERF mRNA level in fruit peel and pulp increased obviously along with fruit ripening. However, its expression could be reduced significantly by treatments of total shading and fruit-bear-shoot girdling plus defoliation during fruit ripening. As for the response to abiotic stresses, CitERF expression was found to be induced continuously during the treatment of 10% polyethylene glycol. On the other hand, it could be induced to high level at 1 h after the treatment of 4 °C or 250 mM NaCl and then declined continuously. Taken together, the results suggested that CitERF may play an important role in some biological processes during fruit ripening and in improving tolerance to drought, low temperature and salt stress.     

柑橘锈螨为害‘沃柑’果皮的结构变化和挥发油成分分析

柑橘锈螨广泛分布于世界各大柑橘产区,为害柑橘果实后形成黑皮果。以‘沃柑’正常果和锈螨为害果为试验材料,采用扫描电镜、顶空固相微萃取-气质联用等技术分析2种试验材料在微观结构和挥发油成分方面的差异。结果表明:柑橘锈螨为害‘沃柑’果皮引起表皮出现龟裂,果皮微观结构被破坏。‘沃柑’正常果皮共检测出75种成分,包括萜烯烃类(65.89%)、醇类(6.94%)、酯类(3.59%)、醛类(2.89%)、烷烃类(1.02%)、酸类(0.40%)、酮类(0.58%)、酚类(0.29%),分别有20、19、15、8、4、3、3、3种成分;柑橘锈螨为害果共检测出79种成分,其中萜烯烃类(59.86%)、酯类(4.04%)、醇类(3.59%)、醛类(2.61%)、烷烃类(1.58%)、酸类(0.76%)、酮类(0.33%)、醚类(0.07%)、酚类(0.03%)分别有18、21、18、8、2、1、7、3、1种成分,2种试验材料的挥发油成分在种类及含量上存在差异。表明柑橘锈螨为害造成柑橘果皮结构和成分差异,可为研究柑橘果实抗黑皮果机理提供理论参考。     

柑桔园防护林的生态效应及效益研究

研究认为,防护林的主要气象效应是减少风速,调节温度,提高湿度和减少蒸发。有防护林桔园比无防护林桔园其冬季落叶率减少7.0—15.5％,冻害指数减少6.5—25.7％,树高增加38.5—72.4％,冠径增加6.0—80.7％,柑桔产量增加20—30％。     

提高我国柑桔果实品质的探讨

柑桔(Citrus Linn)是一种热带和亚热带植物,它是我国南方重要的经济作物。柑桔的产量和品质与多种因子相联系。这些因子是:生产对象、环境因子和人为因子。本文讨论了柑桔品质与上述因子之间的相互关系,以及提高我国柑桔果实品质的方法。为了提高我国柑桔果实的品质,作者建议:(1)选择生态环境适宜的地区栽培柑桔;(2)选育和推广柑桔良种;(3)采取各种有效措施改造桔园生态环境,诸如搞好桔园基本建设,营造桔园防护林和应用合理的栽培技术等。     

Yield and fruit quality of ‘Gala’ and ‘Fuji’ apple trees protected by white anti-hail net

Covering apple orchards with nets protects them from hailstorms but this changes the amount and quality of the light supplied to the trees. This study was carried out to assess the effects of shade provided by white protection net on yield and fruit quality of apple orchards in Southern Brazil, along three growing seasons (2002/2003, 2003/2004, and 2004/2005). ‘Gala’ and ‘Fuji’ apple trees (on MM111 rootstock, raised as slender spindles, with a spacing of 5.5 m × 3 m) were left uncovered (control trees) or covered with white net. The white net reduced the photosynthetically active radiation (λ = 400–700 nm) accumulated over the trees’ canopy along a day by 18.4%, leading to a higher leaf chlorophyll content in both cultivars, and a higher specific leaf area in ‘Gala’. The shade provided by the net did not affect yield and increased fruit average weight in both cultivars. At harvest, the number of seeds per fruit and severity of russet were not affected by netting in both cultivars, as well as the incidence of watercore in ‘Fuji’. The main beneficial effects of the white net were the reduced incidence of sunburn on ‘Gala’, reduced incidence of bitter pit during cold storage in both cultivars, and reduced incidence of apple scab at harvest and of decay after cold storage in ‘Fuji’. Fruit fly damage in ‘Gala’ (assessed in one season) was reduced by netting. However, netting affected negatively some fruit quality attributes. ‘Gala’ and ‘Fuji’ apples from trees protected by the net had a poor skin color (pale blush and a more intense green background color) at harvest. The net reduced flesh firmness and SSC, and increased the starch index of ‘Gala’ apples at harvest, and reduced flesh firmness and SSC, assessed after cold storage and shelf life, in fruits of both cultivars.     

Responses of fruit growth,quality, and productivity to crop load in apple cv. Ultra Red Gala/MM111

The effects of three crop load densities (4, 6 and 8 fruit per cm² of the cross-section of each tree branch, BCSA) on fruit growth, yield, fruit quality and vegetative growth were studied in apples (Malus × domestica Borkh) Ultrared Gala/MM111, from the fourth leaf (2006–2007 season) to the sixth (2008–2009 season). The maximum fruit growth rate was reached between 90 and 108 days after full bloom (DAFB), with values above 2.6 g day⁻¹. Accumulated yields to the sixth leaf reached 181, 157 and 123 Mg ha⁻¹ in the high, medium and low crop loads, respectively. Mean fruit weight decreased with increasing fruit crop load but the yields of fruit weight over 194 g were similar in all crop loads; the highest crop load exceeded the lowest crop load by 18.8 and 27.5 Mg ha⁻¹ of fruit weight of more than 172 and 154 g, respectively. The yields of harvested fruit exceeding 75% with red coloring did not show major differences, while fruit classified as 50–75% with red coloring were less common in the low crop load. No major differences were found at the end of the study in vegetative growth in the different seasons, nor in plant size. The reduction in mean fruit weight and in the percentage of fruit with good coloring was compensated by the increase in yields, thus not resulting in an effective reduction in the quality of the harvested fruit. The level of plant development reached with a semi-vigorous rootstock and high fruit loads allowed obtaining high fruit yield earlier and of good quality.     

Optimising quality-parameters of apple cv. ‘Pigeon’ by adjustment of nitrogen

To improve the productivity and quality of the apple cultivar ‘Pigeon’ the influence of 5 fertigation levels (14, 42, 70, 112, 224 mg N/l) and 3 widths of herbicide strip (0.2, 0.5, 1.0 m) were investigated on growth, yield and post-harvest quality/colour development of fruit. ‘Pigeon’ apples are picked when ca. 20% of the fruit skin has turned red, the fruit are then exposed to a sunning period on the orchard floor of 2–3 weeks to enhance red colour development (80% red skin); however the internal quality deteriorates during this period. Fruit drop occurs if fruit are left on the tree to develop colour. This study focused on how to reduce the length of the post-harvest sunning period to maximise both colour development and fruit quality. It was demonstrated that 14 mg N/l resulted in a low yield, small fruit, low vegetative growth, and low N content in leaf dry matter, but good fruit colour development. Excessive N fertigation (224 mg N/l) did not produce the significantly highest yield or the largest fruit, but it did enhance vegetative growth and resulted in less fruit colouration. N fertigation influenced optimal picking date; higher N fertigation delayed the time of picking, and increased the incidence of green fruit. Fruit from the high-N treatments required more days of post-harvest sunning to obtain the comparable red skin colour than fruit from the lower N-treatments. However, when all treatments were picked at ca. 20% fruit coloration it was not possible to reduce the length of post-harvest sunning period by N-supply. Most of the post-harvest colour development occurred within the first 6–9 days following harvest; colour developed on both sides but was enhanced on the shade side of the fruit. The shade side of the fruit had a greater potential for better red colour development than the blush side of the fruit.     

Reflective materials under hailnet improve orchard light utilisation,fruit quality and particularly fruit colouration

The increase in hailstorms, possibly due to climate change, has led to installation of hailnets in fruit orchards worldwide. This is associated with poorer fruit quality, particularly fruit colouration, which is determined by the light conditions viz diminishing light intensities and shorter day length in the autumn. To overcome these adverse effects of hailnets, five materials were examined as possible ground covers as to their light reflection and the subsequent effect on fruit quality including fruit colouration, using a 9-year-old apple orchard cv. ‘Gala Mondial’ on M9 under black hailnet near Bonn. The ground covers included the woven white plastic Extenday^R/Daybright™, the kaolin-coated, bio-degradable paper UniSet O™ and the aluminium-coated plastic Mylar™ and Svensson ILS Alu™; the latter is a white plastic interwoven with aluminium strips used as energy saving screen in greenhouses. The ground covers were spread in the alleyways 4–5 weeks before anticipated harvest; adjacent uncovered grass strips under the hailnet served as control. Light reflection, measured perpendicular at 1 m height in the alleyways at the time of fruit colouration, was 79–80% by Extenday^R/Daybright™, 75% by UniSet O™, 68% by Mylar™ and 58% by Svensson Alu ILS™. Apple fruit with any of the reflective ground covers ripened 2–3 days earlier without affecting internal fruit quality and sugar as indicative of taste. The reflective ground covers under black hailnet improved the proportion of well-coloured class I fruit relative to the control (uncovered grass) by an averaged 9%. Economic analysis showed that Extenday^R, with an expected lifetime of ten years (based on 4–6 weeks spread time per year) under hail nets in North-Western Europe, scored best based on 45 t ha⁻¹ yield in cv. ‘Gala Mondial’ and 0.40 € kg⁻¹ farm-gate price, resulting in 200 € ha⁻¹ net return. Manual labour for spreading and retrieving the ground covers had the major share of the overall gross cost and offers scope for improvement by mechanisation.     

Long term fertilization effects on ‘Rio Red’ grapefruit yield and shape on a heavy textured calcareous soil

Fertilizer recommendations for citrus production on heavier textured, calcareous soils increase with the age of the tree up to 168 kg N ha⁻¹ year⁻¹ from a soluble source in one or two applications. Such practices may be inefficient and could cause detrimental effects on fruit quality. A variety of fertilization practices are used in South Texas, and additional evaluation is needed. Rates and sources of nitrogen (N), phosphorus (P), and a commercial program consisting of both a soil component containing organic acids and a foliar component were evaluated on grapefruit production for 6 years. Increasing rate of N application increased leaf nutrient concentration, grapefruit yield, and affected fruit shape as indicated by a decrease in the equatorial:polar diameter (E:P) ratio. Since the response to increasing N application by the E:P ratio was linear while grapefruit yield was quadratic, high N application has a negative effect on fruit shape beyond the level of increasing total yield. Phosphorus application had no effect on any parameter measured, even though soil testing indicated soil P levels were below those at which a P response would be expected. Comparisons between granular 21-0-0 applied broadcast and liquid N-32 injected in a band in the soil at the drip line showed an increase in the number of fruit per tree, but no differences in yield. The ‘Actagro’ program greatly improved available soil P levels and increased the juice brix:acidity ratio, but did not affect grapefruit yield. Phosphorus availability may therefore be a factor in improving grapefruit juice quality. The soil profile within the citrus root zone was found to contain large amounts of inorganic N, but availability of this residual N was limited since yield responses occurred at the N application rates applied in this study. The amount of N contained in the fruit harvested was a small fraction, roughly 5–10%, of the residual amount in the soil. While N uptake in the fruit increased with N fertilizer application, the increase in N taken up relative to the amount applied averaged 42%.     

Phenotypic variations in fruits and selection potential in Sclerocarya birrea subsp. birrea

The domestication of indigenous fruits through agroforestry is seen as one of the important issues in the transformation in the way in which land is used within rural areas. A study of the variation in fruit traits is also important as it is a prerequisite for cultivar development in the domestication process. Following an aridity gradient, phenotypic variation was assessed in fruits of Sclerocarya birrea subsp. birrea, native to West African semi-arid areas. Fruits were collected from 42 trees of various diameters in agroforestry parklands from the dry and semi-humid Sudanian zones. They were partitioned into peel, flesh and pit. Each fruit was labelled and its components were measured and weighted. The overall mean fruit mass was 18.58 ± 0.24 g (mean ± SE) but fruits from the population in the drier zone were significantly larger (19.90 ± 0.37 g vs 17.02 ± 0.24 g; P < 0.001). The results showed a strong correlation between fruits and their components (P < 0.05). Tree diameter was very weakly correlated with fruit traits. There was a high level of variation in fruit characteristics and components within and between populations. The within-population variation accounted for the greatest part (67–100%) of the total variation. Many trees, mainly from the drier zones, showed superior phenotypic traits. Five groups of trees which represented different fruit morphotypes were identified for various prospective exploitations. The results strongly support the implementation of preliminary practical conservation action and domestication of S. birrea in West Africa.     

Climatic conditions affect the texture and colour of Cavendish bananas (Grande Naine cultivar)

Relationships between natural production conditions (soil and climate) and physical fruit traits (texture and colour) were studied in Martinique to fuel discussions on creating a label for bananas from the French West Indies. Bananas produced at six sites, under very different conditions, during three different periods of the year, were harvested at the same temperature sum and ripened under identical conditions. The peel of green bananas harvested during the hot humid season was not as hard as that of bananas harvested during the cool dry season. In ripe bananas, an increasing correlation was noted between the rainfall level and fruit firmness (R = 0.88) and peel hardness (R = 0.80). This correlation could explain why bananas produced during the dry season were less firm and, conversely, those produced in highland areas, where rainfall is highest, were firmer. In ripe bananas, a decreasing correlation was also noted between the mean daily temperature and the fruit yellowness (R = 0.84). This interaction could be responsible for the yellower colour of mountain banana pulp and of bananas harvested during the coolest seasons. The green life of bananas harvested during the hot humid season was shorter than that of bananas harvested during the dry and intermediate seasons.     

广东柑桔潜叶蛾种群动态及放秋梢适期研究

调查了同一年中３个柑桔园及同一柑桔园连续３年柑桔潜叶蛾的卵量消长动态；并在不使用农药无人为干预的苗圃内连续一年调查潜叶蛾幼虫密度、叶片受害率及幼虫自然死亡率。发现潜叶蛾在广州及其附近地区７月下旬至８月上旬，即一年中气温最高期间，有一个短暂的卵量低谷。利用此低谷期在正常挂果园促放秋梢，不喷杀虫剂或只喷一次杀虫剂，新梢虫叶率均在受害允许界限以内。在广东省多年多点推广应用，均取得高效、低成本、少污染的效益。     

Improving the fruit yield and quality of cucumber by grafting onto the salt tolerant rootstock under NaCl stress

To investigate the feasibility of using salt tolerant rootstock to increase fruit yield and quality of cucumber under NaCl stress, a greenhouse experiment was carried out to determine fruit yield, leaf relative water content, fruit quality, and mineral composition of cucumber plants (Cucumis sativus L. cv. Jinchun No. 2), either self-grafted or grafted onto the commercial salt tolerant rootstock Figleaf Gourd (Cucurbita ficifolia Bouche) and Chaofeng Kangshengwang (Lagenaria siceraria Standl). Plants were grown in a substrate culture (peat:vermiculite:perlite = 1:1:1, v/v) and irrigated with half-strength Hoagland solutions containing 0, 30, or 60 mM NaCl. The results showed that salinity significantly reduced fruit yield of cucumber owing to a decrease both in mean fruit weight and fruit number. Rootstock had no significant effect on leaf relative water content. Plants grafted onto Figleaf Gourd and Chaofeng Kangshengwang had higher fruit number, marketable and total fruit yield than those of self-grafted plants under 0, 30, and 60 mM NaCl, which could be attributed to, at least in part, the higher K⁺ but lower Na⁺ and/or Cl⁻ contents in the leaves. Salinity improved fruit quality by increasing fruit dry matter, soluble sugar, and titratable acidity contents of all the plants, but had no significant effect on vitamin C content. In comparison to the self-grafted plants, plants grafted onto Figleaf Gourd and Chaofeng Kangshengwang had an overall improved fruit quality under NaCl stress owing to an increase in contents of soluble sugar, titratable acidity, and vitamin C, and a decrease in the percentage of non-marketable fruit and Na⁺ and/or Cl⁻ contents of fruits in comparison to the self-grafted plants, mainly under 60 mM NaCl. Overall, it is suggested that the use of salt tolerant rootstock could provide a useful tool to improve fruit yield and quality of cucumber under NaCl stress.     

Nitrogen best management practice for citrus trees: II. Nitrogen fate,transport, and components of N budget

Soils in central Florida citrus production region are very sandy, hence are vulnerable to leaching of soluble nutrients and chemicals. The objective of this study was to develop nitrogen (N) and irrigation best management practices for citrus in sandy soils to maintain optimal crop yield and quality, and to minimize N leaching below the rootzone. A replicated plot experiment was conducted in a highly productive 20+ year-old ‘Hamlin’ orange [Citrus sinensis (L.) Osbeck] trees on ‘Cleopatra mandarin’ [(Citrus reticulata Blanco)] rootstock grove located on a well drained Tavares fine sand (hyperthermic, uncoated, Typic Quartzipsamments) in Highland County, FL. Nitrogen rates (112–280 kg ha⁻¹ year⁻¹) were applied as fertigation (FRT), water soluble granular (WSG), a combination of 50% FRT and 50% WSG, and controlled release fertilizer (CRF). Tensiometers were used to monitor the soil moisture content at various depths in the soil profile as basis to optimize irrigation scheduling. Fruit yield and quality and nutritional status of the trees were reported in a companion paper. Soil solution was sampled at 60, 120, and 240 cm depths under the tree canopy using suction lysimeters. Concentrations of NO₃-N in the soil solution at 240 cm deep, which is an indicator of NO₃-N leaching below the tree rootzone, generally remained below the maximum contaminant limit (MCL) for drinking water quality (10 mg L⁻¹) in most samples across all N sources and rates, but for few exceptions. Total N in the fruit was strongly correlated with fruit load, thus, at a given N rate N removal by the fruit was lower during years of low fruit yield as compared to that during the years of high fruit yield. Furthermore, there was a strong linear relation between N and K in the fruit. This supports the need to maintain 1:1 ratio between the rates of N and K applications. In a high fruit production condition, the N in the fruit accounted for about 45% of the total N input on an annual basis. Fifteen percent of the total N input at 280 kg N ha⁻¹ year⁻¹ was not accounted for in the citrus N budget, which could be due to leaching loss. This estimate of potential leaching was very close to that predicted by LEACHM simulation model. The improved N and irrigation management practices developed in this study contributed to an improved N uptake efficiency and a reduction in N losses.     

Changes in antioxidants and fruit quality in hot water-treated ‘Hom Thong’ banana fruit during storage

The effects of hot water treatment on antioxidants and fruit quality were investigated in banana fruit of cv. Gros Michel (Musa acuminata, AAA Group, locally called cv. Hom Thong) by immersing fruits in hot water (50 °C) for 10 min, before storage at 25 °C for 10 days or 14 °C for the first 8 days followed by storage at 25 °C for the second 8 days until ripening. Quality parameters including peel color and pulp firmness indicated that hot water treatment helped to delay banana fruit ripening at both storage conditions. Hot water treatment decreased the levels of hydrogen peroxide (H₂O₂) and malonydialdehyde (MDA) during storage at 25 °C. Glutathione (GSH and GSSG) contents and the ratio of GSH/GSSG during fruit approaching ripening were significantly induced in hot water-treated fruits while ascorbic acid (AA) contents were slightly increased. In addition, the combined treatment increased free phenolics and flavonoids during storage. Results suggest that hot water treatment has led to an induction of antioxidants in banana fruits as indicated by an increase of antioxidants and a decrease of H₂O₂ during ripening, and all of which result in a delayed ripening of banana fruit.