| With the increasing of potato industrial size and products demand, China is becoming the center of potato production, process and trade around Asia and the Pacific. However, potato bruising is being one of the most important constraints in the development of potato industry. In the thesis, the assessment technology including the methodologies for simulation, measurement and classification of bruises, the key factors affecting tuber bruises and forecasting model for tuber bruise were studied. Furthermore, genetic analysis of bruise-induced browning was conducted with a NCD I mating design. Main results are as follows:1. A sensitive, reliable and feasible method was established for potato tuber bruises evaluation by analysis of variance and response surface among five varieties. Simulation of potato tuber bruising. Internal bruise was simulated when velosity and pressure were 6-10 mm?min-1 and 400-500 N respectively. Internal bruise was the most impressible under both 8 mm?min-1 and 420 N. Bruise-induced browning simulation was done by chopping potato tuber into 1 mm slices from terminal bud to base; three slices from the middle of the tuber were freezing for 5 hours before thawed for three hours.Measurement of potato tuber bruising. Skinning degree was determined by the ratio of the skinning site number and the tuber volume (n/V); internal bruise was determined by the relative deformation ratio of the potato tuber under pressing with the velocity of 8 mm?min-1 and the pressure of 420 N; bruise-induced browning was determined by the mean of grey K of two sites, which were midpoints of both sides in the slice.2. Comprehensive evaluation of potato tuber bruises of 104 genotypes by cluster analysis, principle component analysis (PCA) and multivariate analysis of variance (MANOVA). The results showed that the importance of three bruises on potato tuber was skinning>>internal bruise>browning; the best integrated tolerant cluster including 9 processing varieties, 19 table varieties and selection of 9445-93-1 was obtained by cluster analysis. After three kinds of bruises were clustered respectively, NEA303, F70021, Adora and 9445-93-1 were screened out with light-skinning; Mira, Tobique, Fundy, Raritan, Lenape, Desiree and selections of 11901-2, TD41-5, 9401-37-3, 9642-77, 9518-34 were good genotypes with light internal bruise; Gulzow633, Superior, Norchip and 9430-15-1 were good genotypes with low browning. Based on the results from the research, three bruises could be graded into five classes with prominent difference between adjacent ones.3. Key factors affecting potato tuber bruises were determined by regression analysis of 17 parameters of tuber quality and physiology in five selected genotypes. As for skinning, the importance of the key factors were ranked as DM>PAL>Ca2+>TH, and their effects were all positive; as for internal bruise, the importance of the key factors were ranked as Ca2+>K+>PAL>DM>CLA, and their effects were all positive; as for browning, the rank was Ca2+>SP>PPO>PSI>Tyr>CGA, the SP, Tyr and CGA of them were the positive factors, while Ca2+, PPO and PSI were the negative factors. Above all, Ca2+ was the common key factor for potato tuber bruises. Based on the results of analysis, three models were established to forecast skinning, internal bruise and browning respectively: y1=-0.268+0.475 x3+0.00005 x4+0.114 x12 for skinning, y2=-6.428+0.007 x4+12.456 x12-0.002 x14 for internal bruise, and y3=-9.182+1.839 x7+63.968 x11-7.870 x12 for browning.4. Genetic analysis indicated that bruise-induced browning was dominated by both additive and dominant effects. It'sσA2 and hN2 were 159.996 and 0.647 respectively. The traits could be stably transmitted from parents to their progenies and this made it possible to select low-browning genotypes in the offspring. Female parent was more important than male parent in the inheritance of browning trait. |
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