Study On The Causes And The Control Method Of Spongy Tissue Of Fruit Disorder In Mango(Mangifera Indica L.)

Spongy tissue of mango fruit is a kind of physiological disorders which affected theedible quality of fruit and caused very seriously economic losses. It occurs in most ofmajor mango growing areas of the world. Because of disease fruit appearance no symptomor obvious symptom, it may not determine and distinguish disease and normal fruits by thefruit appearance symptom at harvest. At the same time, it brings great difference to studyits occurring and developing process. Although it has been done many works to researchspongy tissue of mango fruit at abroad for long, identification of the causes has not beenpossible as there are poor correlations between the outbreak of internal flesh disorder andspecific factors, it has still not good methoid to control its occurring. Mango fruit disorderhave not caused concern and regard as our mango commercial production developing isnow at early stages and lacks standards and specifications to sell mango fruit at the market.Therefore, researching the causes and occurring law of spongy tissue of mango fruit atpresent and controlling its occurring have not only important strategically significance atour production and development of mango, but also important reference value at academicresearch. So, we have formulated this study to investigate the fruit disorder character,occurring laws, and determine the changes of mineral elements and physiology andbiochemistry of fruit interior from the correlations between the outbreak of spongy tissuedisorder and specific factors. The main results of this research as follows:1. Symptom characters and occurring laws of spongy fissure disorder of Zihua mangofruit(1).Survey result of symptom characters of spongy fissure disorder of Zihua mangofruit showed there is distinct traits which it occurs middle or bottom part(seldom top part)of disease fruit. First symptom is one or more small and white dot, which develop tobecome a hollow small cavity, dry or water-soaked, hollow edge white or non-white,whereafter small cavity enlarge continually, which one or more small cavity joint a wohole,to become Large spongy cavity, and has water-soaked around disease part. It woulddetermine disease fruit before 10 days at harvest. From the initial to the late symptom divide three grades, it appears a continuous developing state. Based on temporal andspatial differences in symptom development within the fruit, it has obvious distinction ascompared with soft nose, jelly seed, stem-end cavity and internal flesh breakdown.Therefore, spongy tissue disorder of fruit is testified to be a independent disorder.(2).Spongy tissue incidence of Zihua mango fruit is relationship with fruit maturitydegree, which occurs much higher frequency before 10 days at harvest. The higher the fruitmaturity degree, the seriouser the disease and the higher the index of disease. Spongytissue disorder of Zihua mango fruit is testified to be happen a disorder before harvest, andit is not occurred disease at the storage period.(3). There were very remarkable relationship between spongy tissue incidence andfruit size, which included single fruit weight, fruit length and width as well as index of fruitshape. There indices have very obvious coherence. The correlation efficiency analysisshowed significance at P＜0.01 or P＜0.05.(4). At the same tree parameter, spongy tissue incidence decreased as the number ofsingle tree fruit numbers growing, and increased as the average weight of single fruit rising.In other words, it is directly proportion with the number of single tree fruit, and inverseproportion with the average weight of single fruit. Hill fruit garden compared with flat fruitgarden, the former disorder incidence is lower than the later.(5). Relationship between spongy tissue incidence with stock has not been reported bynow. This research investigated four different stocks in Guangxi province for four years,and first showed that spongy tissue incidence of Zihua mango fruit had not related withstocks.(6). Investigated the spongy tissue incidence of fourteen mango cultivars in Guangxiprovince, only two cultivars of Zihua and Guire 82 mango have spongy tissue disorder, theothers of twelve cultivars have not discoveried spongy tissue disorder. The result showedthat spongy tissue disorder was related with the character of cultivar itself. Otherwise, theothers of twelve cultivars have determined jelly seed, soft nose and internal fleshbreakdown and so on respectively. It showed that different disorders were related withspecial cultivar.(7). Spongy tissue disorder of Zihua mango fruit has occurred before harvest, which it would not occur new disease fruit at the storage period after harvest. But at the naturestorage process after harvest, symptom of diseased fruits would become more seriously asthe time of fruit maturity need much longer. With the ethrel treatment, as fruit maturitytime would become shorter, which symptom development of diseased fruits would controlat the storage process, the indices of disease is lower.2. Initial study on ISSR in the ealtivars and disease ealtivars identification in mango(1) The main cultivars and species of Guanxi mango tested by ISSR could bedistinguished from each other, indicating that ISSR-PCR was an effective method forcultivar identification of Guanxi mangoes, and the genetic diversity of mango cultivars inGuanxi was clarifield by comaring 74 polymorphic loci.(2) Of the 42 ISSR primers screened 9 specific primers were selected in our analysisfor 8 susceptible to fruit disorder and 12 free from fruit disorder mango cultivars. Theywere distinguished from each other. Cluster analysis indicated that 20 mango cultivarscould be clustered into two groups on the dendrogram. 8 mango cultivars (susceptible tofruit disorder) were clustered into a group, while 12 mango cultivars (free from fruitdisorder) were clustered into another group. It was testified that they had very closerelationship each other on the heredity of 8 mango cultivars (susceptible to fruitdisorder). At the same time, it was also showed that ISSR-PCR was a identification methodfor susceptible to fruit disorder and free from fruit disorder mango cultivars. It couledprovide a aid method for screened against disorder disease while we will breed new mangocultivars, and prevent to occur fruit disorder from the way of breeding cultivar.3. Non-destructive inspection technology of spongy tissue disorder of Zihua mango fruit flesh(1). Non-destructive inspection technology of spongy tissue disorder of Zihua mango fruit wasresearched by the difference of weight and proportion. It was not distinguished both normal fruit andspongy tissue fruit as their difference was too small at the weight and proportion. To adopt the methodsof correlation between single fruit weight and length and width, the difference of fruitproportion, we would not distinguish exactly normal fruit and spongy tissue fruit fromexperiment fruits. As a result, methods of two did not adapt to determine spongy tissue fruit.(2). Determining mango fruits by X-rays technology we can see the internal seed stateof fruit. Because of limits of X-rays intension as well as effects of seed and the seed shell, we can not see the cavity state of internal flesh. But if we would decrease rays intensionmake large machine becoming small machine, and combine with computer imagetechnology. Maybe, it will become a practical and good method for non-destructive inspection.4. Changes of the main enzymes of occurring process on spongy tissue disorder inZihua mango fruit(1). Changes of proto pectin and the main enzymes of occurring process on spongytissue disorder in Zihua mango fruit were determined this paper. The result showed that thecontent of water soluble pectin, the activity ofα-amylase, pectinase(PE),polygalacturonase(PG) and cellulase(CMC) were increased at different time, and thecontent of proto pectin was decreased. When the activity ofα-amylase was rising, the starchwas waterd byα-amylase, cell stress declined, which led to the distortion of cell and tissue.Second, the activity of PE and PG increased, which led to the solution of pectin on cellwall. Finally, the activity of CMC rose, and cellulose was dismissed, which furtherpromoted and dismissed transit structure of cellulose- half cellulose-pectin on cell wall,and led to the cavity of fruit occurring. This process carded on again and again, and thecavity continued extension, which each orther connected, and the last led to the spongytissue formed.(2). With single treatment ofpectinase, CMC and EGTA, as well as mixing treatmentsof pectinase+CMC,α-amylase+pectinase+CMC, EGTA+pectinase+CMCrespectively to induce fruit disorder, they induced parallel symptom of spongy tissue andinternal flesh breakdown disorder. It was indirectly testified that Ca,α-amylase, pectinaseand CMC generated to act at the developing process on spongy tissue disorder. Therefore,we can guess the mechanism of mango fruit disorder according to literature data and ourresearch results.5. The relationship both spongy tissue incidence and mineral elements(1).Ground playing Ca fertilizer, trunk high-pressure injection Caand KCl treatments,it decreased the spongy tissue incidence to a certain extent. It testified that Ca deficiencywas a factor of inducing spongy tissue disorder. When Ca content was normal, the level ofK content was the main factor of inducing disease. But single playing Ca and K fertilizer,they were not restrainted all effectually spongy tissue disorder. Therefore, DRIS indices analysis showed that Ca and K elements were factors to affect spongy tissue disorder, butthey were not unique factor. Ca,K,N,P and Mg elements would affect spongy tissuedisorder incidence.(2). Soil applying fertilizer of N, K and NPK mixing treatments increased the spongytissue disorder incidence, but different treatments had difference to affect spongy tissuedisorder incidence, of soil applying KCl treatment, its incidence was the highest. So, thechanges of Ca,K and N elements had also close relationship with spongy tissue disorderincidence except for Ca element. DRIS indicies analysis showed again that the elements ofinducing spongy tissue disorder incidence in fruit were not single, but also the results ofCa,K,N,P,B and Mn et al. elements synthetical balance. The experiment result showedalso that elements synthetical balance was complex because it would be affected from thefactors of fertilizer types, playing time, soil, tree and fruit growing itself et al.