Browsing by Subject "Mango"

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    Physiological and molecular mechanisms of fruitlet abscission in mango
    (2015) Hagemann, Michael Helmut; Wünsche, Jens Norbert
    Compared to the typical high initial fruit set of mango (Mangifera indica L.), only a small share of those fruits reach harvest-maturity. This extensive fruitlet drop is a major yield-limiting factor, leading to substantial economic losses for mango growers world-wide. The numerous causes of fruitlet drop include infections with pests or diseases and unsuitable environmental or crop management conditions. Due to the high impact of fruitlet drop for mango production, the overall objective of this study was to further the understanding of the underlying mechanisms and to develop strategies for reducing fruitlet drop in mango. Different experimental approaches have been applied to reduce mango fruitlet drop, however, almost as numerous methods have been used for data interpretation, which makes the comparison of data between studies difficult. Therefore a model was developed for defining the timely pattern of fruitlet drop more generally, thus allowing inter-study comparisons of results. The model was tested and validated by monitoring the fruitlet drop in different management systems: traditional monocropping orchard versus 1) intercropping; 2) irrigation; and 3) plant growth regulator applications, respectively. The timely pattern of fruitlet drop was best described with a sigmoid function, which also formed the basis for defining the post-bloom, the midseason and the pre-harvest fruitlet drop stage. Results of the crop management evaluation show that intercropping of maize with mango has no detrimental effect on fruitlet drop. Irrigation resulted in approximately three times higher fruit retention compared with the non-irrigated control. A single application of 40 ppm 1 naphthaleneacetic acid at the end of the post-bloom drop stage resulted consistently in the highest fruit retention. The developed model permits for example the evaluation the treatment efficacies during midseason drop or yield forecasting at the beginning of the pre-harvest stage. It was suggested that especially during the midseason drop stage tree resources are limited, which results in inter-organ concurrence and subsequently induces fruitlet drop. This is supported by the current findings that during midseason drop mango trees show low rates of photosynthesis, which indicates drought stress. Such stress can induce ethylene-dependent fruitlet abscission. Therefore the ethylene releasing substance ethephon was used in order to study the onset and time-dependent course of fruitlet abscission. The results show that ethephon at a concentration of 7200 ppm (ET7200) is a reliable abscission inducer. The experiment was extended using ethephon at an additional concentration of 600 ppm (ET600). Both ethephon treatments reduced significantly the capacity of polar auxin transport (PAT) in the pedicel at 1 day after treatment (DAT) and thereafter compared to untreated pedicels. The transcript levels of the ethylene receptor genes MiETR1 and MiERS1 were significantly upregulated already at 1 DAT in the ET7200 while only at 2 DAT in the ET600 when compared to the control fruitlets. Specifically, a significant increase of MiETR1 in the pericarp at 2 DAT and of MiERS1 in the pedicel at 2 and 3 DAT was induced by ET600. In contrast, both genes were significantly upregulated in both tissues, except MiETR1 in the pedicel, at 1 DAT and thereafter by ET7200. The last parameter that significantly changed in response to the ethephon treatments was the concentration of sucrose in fruitlet pericarps, which was reduced at 2 DAT compared to control fruitlets. Based on these results, it is postulated that the ethephon-induced abscission process commences with a reduction of the PAT capacity in the pedicel, followed by an upregulation of ethylene receptors and finally a decrease of the sucrose concentration in the fruitlets. Ethylene receptors are key elements of abscission and other processes of the plants life cycle. Therefore the ethylene receptors were further studied at the molecular level in mango. Additionally to the previously known receptors MiETR1 and MiERS, two novel versions of the MiERS1 were identified in mango. These receptor genes, MiERS1m and MiERS1s, translate into truncated proteins with deletions of functional domains and show different expression patterns compared to MiERS1. The receptors were further studied through transient expression of fluorescent fusion proteins in the leaves of the model plant tobacco. All receptors are localized at the endoplasmic reticulum. Specific dimerization assays via bi-molecular fluorescence complementation indicate, that MiERS1m can dimerize with itself and with MiERS1, but not with MiETR1. In contrast, no dimerization of MiERS1s with the other receptors could be detected.
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    The effect of picking time and postharvest treatments on fruit quality of mango (Mangifera indica L.)
    (2012) Vu, Hai Thanh; Wünsche, Jens Norbert
    Mango production in Northern Vietnam is mainly in the upland areas. The two locally grown cultivars are ?Tron? and ?Hoi? with limited yearly production due to poor traditional crop management practices by ethnic minorities. Both cultivars possess excellent fruit aroma and taste properties, yet there is a need to further improve fresh fruit quality to meet high domestic demand and consumer expectations in the market place, thereby exploiting more products of preferred quality. Assessment of quality parameter and consumer preference can assist to precisely determine optimum harvest time and suitable storage regime for a given cultivar. Furthermore, specific postharvest treatments such as applications of hot water, 1-MCP or ethrel for manipulating fruit ripening and shelf-life may help to enhance economic returns and thus to make mango production in the long term more profitable. The research work on both cultivars was carried out on farmer orchards near the township of Yen Chau, Son La Province, Vietnam, in 2007, 2008 and 2009. The research objectives were to (1) monitor internal and external fruit quality changes in relation to varying select picks throughout the harvest period and to a range of storage temperatures; (2) investigate the effect of 1-MCP on various fruit ripening parameters for maintaining fruit quality and extending shelf-life; (3) evaluate applications of aqueous ethrel solution in cool storage for accelerating fruit ripening; and (4) assess the responses of several external fruit criteria to hot water treatments and subsequent cool storage. At each select pick, fruit was immediately taken to the laboratories at Hanoi University of Agriculture for fruit quality assessment at harvest, and following various postharvest treatments, ex-store. Chemical analyses of fruit tissue samples were performed at the University of Hohenheim. Various physicochemical quality parameters such as fruit weight, skin disorder, skin and flesh colour, flesh firmness, total soluble solids concentration, titrable acidity, as well as concentrations of soluble sugars, starch, vitamin C and carotenoids were evaluated. The results of the first part indicated that key quality criteria for determining the optimal harvest time of ?Tron? and ?Hoi? were determined. ?Hoi? fruit was at best quality when harvested late, preferably in the 2nd or 3rd pick, whereas 1st pick fruit was relatively immature with less than 8% total soluble solid concentration and did not properly ripen when stored at 12ºC. In contrast, ?Tron? fruit should be picked early in the harvest period since the 3rd pick with tree-ripened fruit was only suitable for direct local marketing without storage time. The results also indicated that ?Tron? fruit of the 1st and 2nd pick and ?Hoi? fruit of 2nd and 3rd pick continued the ripening process to full maturity when stored at 12ºC. Consequently, fruit from these picks were suitable for distant markets when handled within 5-10 days at 20ºC or up to 20 days at 12ºC. Generally, ?Hoi? had a greater postharvest potential than ?Tron? but ex-store fruit quality of both cultivars was best with flesh firmness ranging from 70.5 to 96.1 N, skin hue angle from 71.4º to 85.4º, flesh hue angle from 70.1º to 78.5º and total soluble solid concentration from 16.8 to 19.6%. The results of the second part clearly showed that 1-MCP is a useful tool to delay fruit ripening and in particular softening of both cultivars during the postharvest period. Both cultivars treated with 1000 nL?L-1 1-MCP delayed considerably the decrease in TA, skin and flesh hue angle as well as the loss of flesh firmness in the 1st and 2nd pick for about 10 days of storage at 12ºC compared to control. Both cultivars were more sensitive to 1-MCP applications in 1st rather than the 2nd pick. In addition, 1-MCP applications were more effective on ?Tron? fruit than ?Hoi? fruit. The results of the third part indicate that 0.8% ethrel accelerated fruit ripening on fruit from the 1st pick of both cultivars while stored at 12ºC. Ex-store fruit quality was acceptable and met consumer preference. The efficacy of ethrel application on ?Hoi? fruit was greater than that on ?Tron? fruit. The results of the fourth part showed that the degree of skin disorder was considerably decreased when ?Tron? and ?Hoi? fruit were treated with either 48ºC or 50ºC water for 6 min and stored at 12ºC. This treatment delayed skin colour development of ?Hoi? when compared to other treatments. In conclusion, this study demonstrates that lack of proper whole chain fruit quality management systems is the key factor for the limited production of mangoes in Northern Vietnam. Improved fruit quality management can result in more consistent and higher quality particularly for distant markets. Based on the results of this work, ?Tron? and ?Hoi? fruit should be harvested using well-defined and recommended harvest quality indices and thereafter undergo appropriate postharvest management systems to attain higher fruit quality. This will help farmers to better manipulate fruit ripening processes, to deliver high quality fruit to the market and to achieve greater returns and thus livelihoods.
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    Untersuchungen zur Eignung von Mangoschalen (Mangifera indica L.) in der Tierernährung und deren Einfluss auf die zootechnische Leistung sowie verdauungsphysiologische und mikrobiologische Parameter bei Absetzferkeln
    (2016) Brucker, Lisa; Zentek, Jürgen
    This study was conducted to test the suitability of mango peels in the feeding of weaned piglets according to different investigations. The methodical work was divided into three sections. At first short term incubations with feces from sows together with different carbohydrates were carried out. After 24 h of incubation under anaerobic conditions the fermentation pattern was analyzed according to the produced bacterial metabolites. Moreover, semi-continuous long term incubations with cecum content from piglets together with mango peels or apple pectin were examined to determine the influence on the fermentation pattern over a longer period. The results of both incubation techniques showed, that there was an influence of the substrate on the amount of produced bacterial metabolites. The results of the short term incubations revealed differences that were achieved by the addition of the various substrates compared to the negative control in almost all measured parameters. Thereby the reduction of the pH-value after the addition of apple or mango pectin was due to an increased acetic acid concentration. The incubation of mango peels for 24 hours showed results comparably to the addition of apple pectin (p = 0.579). In the long term incubations the addition of mango peels to the fermenter caused only little changes of the fermentation parameters. The addition of mango peels resulted in the highest butyric acid levels (p = 0.002), and also higher valeric acid levels (p = 0.002) were detected compared to apple pectin. However, the addition of mango peels into the system of the long term incubation did not differ in the acetic acid content or the pH-value compared to the control group. The second methodical part of the present study constitutes infection experiments with the permanent cell line IPEC-J2. The aim was to determine possible effects of plant extracts on the protection of IPEC-J2 cells against enterotoxic E. coli bacteria via flow cytometry analysis. The results of these infection experiments showed validated effects (p = 0.029) of mango pectin compared to the positive control, with a reduction in the number of E. coli associated IPEC-J2 cells by 56.1%. The third section included a feeding trial to analyse intestinal parameters of a total of 50 weaned piglets in five groups over a period of four weeks. To ascertain the performance data another feeding trial was carried out with a total of 100 weaned piglets over a trial period of six weeks. The feeding trial was conducted to examine the effects of a one- and two-percent dosage of mango peels, resp. apple pectin on digestibility and microbiology parameters. The acquired data included the determination of the apparent ileal digestibility as well as the total tract digestibility and the analysis of different bacterial metabolites. This included the content of short chain fatty acids, lactate, ammonia and biogenic amines as well as phenols and indoles. Furthermore, the influence of the experimental diets on defined groups of the microbiota was examined on a molecular biological level. In addition, the substrate utilization of the microbiota was measured based on fecal samples and the use of BIOLOG MT2 plates. The results of the in vitro studies verified the fermentation of mango peels by the porcine microbiota with a corresponding change in the fermentation pattern. The mango pectin, which is present in mango peels, showed a protective effect on IPEC-J2 cells against an E. coli infection. In general, the feeding experiment showed scarce differences between the five experimental groups. In the effect of mango peels resp. apple pectin on the determined contents of bacterial metabolites, some numerical differences in the examined sections of the GIT could be detected. These differences appeared particularly in the ileal sections of the GIT, with the result that the majority of mango peels or apple pectin might already be metabolized praecaecal resulting in fewer changes in the bacterial groups of microbiota and their metabolites in the large intestine. In contrast to these results, a reduced proteolytic activity of the microbiota in the large intestine was detected in the experimental groups C and E. A certain part of the so far undigested carbohydrates left in these groups could be accountable for these findings, since they could be used as an energy source. In the present study, no adverse effects by the addition of mango peels or apple pectin in an experimental diet of weaned piglets were detected. Therefore it can be assumed that the investigated dosage showed a good tolerability. This suggests that the use of dried mango peels in the feeding of weaned piglets is possible and can result in a positive effect on the gut health.