Evaluation Of The Texture Properties Of Melon(Cucumis Melo L.) Germplasms And Expression Analysis Of Related Enzyme Genes

Texture property of melon fruit is one of the most important factors that impact itstotal quality. Nowadays, more and more studies on texture property of all kinds ofcrops are available, but overall reports on melon texture is rare, especiallycomparisons on different melon germplasms. In this study,14melon materials from6types and5varieties, makuwa，conomon，inodorus，reticulatus and cantaloupensisthat have conferential texture properties were examined on different levels, frommacroscopic physico-logical traits, cellular level microscope observation, tomolecular level enzymes and enzyme genes expression analysis, main results were asfollows,1. Both TPA and puncture test were suitable for textural analysis of melonmaterials, and texture parameters were correlated to each other. Among14melonmaterials, TB, YJC and Queen had the best fraturity taste, which were widely loved,their stiffness parameter was between500.00~650.00N/sec, TPA hardness wasbetween2000.00~2250.00g, and chewiness was between300.00~400.00.2. Charentais from var. cantaloupensis had the most typical ethylene burst, theethylene production rate of mature stage was47.4times of immature stage; at thesame time, its hardness, chewness and stiffness decreased to14.5%,6.9%and17.8%of immature stage, respectively. The expression of CmPG1、CmEXP1and CmACO1increased to10.13,2.83and138.50of immature stage, respectively. Enzyme activitiesof PG, Cx and β-Gal increased to1.58,1.75and1.46-fold of immature stage,respectively. In comparison to3-6and20-5, during the maturation and senescence ofCharentais from var. cantaloupensis, the expression of enzyme β-Gal and geneCmACO1were significantly higher, other than that, the rate of fruit texture parametersdecreasing, cell walls fusing and wrinkling, ethylene production, as well as the rate ofpH and SSC increasing were much higher.3. The expression of CmEXP1was the most highest during the immature stage,maybe it was associated with softing activating. The expression of CmACO1usuallyoccurred at mature and senenscence stages. Enzyme PG and Cx showed a significantincrease in var. makuwa,3-6and20-5during their maturation; The expression ofenzyme β-Gal was the highest at immature stage in var. makuwa, the peak was earlier than enzyme PG and Cx, but it had no significant difference among threemature stages of3-6, which had the biggest flesh hardness.4. According to microscopy observation, fruit cell size and composition wereclosely related to flesh hardness measured by TPA and puncture tests. Bigger cells,loose arrangements, plicated cell walls and dissolved cell walls all resulted in lowerflesh hardness.5. According to principle component analysis, the contribution of PC1and PC2were37.6%and22.8%, respectively. PC1was able to distinct melon materials withdifferential texture properties, while PC2was associated with fruit development level.3-6and20-5was positioned at the positive side of PC1, due to their relatively higertexture properties, they maintained lower expression ofβ-Gal, pH, ethylene releaserate and respiration rate.