Variation and Probability Grading of Fruit Firmness in Peach Germplasm Resource

Objective The aim was to provide basis for further studies on fruit firmness in peach fruits and the standardization and standardization of peach germplasm resource. [ Method] The analysis of fruit firmness of peach germplasm resource was based on the improved firmness measurement, and the probability grading of characteristics was carried out on peach fruit firmness. [Result] The coefficient of variation of peach fruit firmness with skin was less than that of fruit firmness without skin; the fruit firmness with skin and fruit firmness without skin were both fitted the normal distribution; the probability grading of characteristics were divided into five series based on four points of （X-1. 281 8s）, （X-0. 524 6s）, （X＋0. 524 6s） and （X＋1.281 8s）, so that the probability of 1 -5 were 10%, 20%, 40%, 20% and 10%. [Conclusion] There was more abundant genetic basis in fruit firmness, which held a potential for greater choice.

Overexpression of the apple expansin-like gene MdEXLB1 accelerates the softening of fruit texture in tomato

Fruit firmness is an important quality trait of apple fruit texture,and the pre-harvest ripening period is the key period for the formation of apple fruit texture.Expansin is a cell wall loosing protein family that has four subfamilies:α-expansin(EXPA),β-expansin(EXPB),expansin-like A(EXLA),and expansin-like B(EXLB).In this study,we investigated the key period of pre-harvest texture formation in‘Golden Delicious’apples based on fruit longitudinal diameter,transverse diameter,firmness,tissue structure,respiration intensity,ethylene release rate,and expansin activity.Within the 10 days before harvest,the fruit was found to reach maturity.Semi-quantitative RT-PCR revealed that most of the expansins were expressed at the ripening stage before harvest.The biological function of the EXLB subfamily gene,MdEXLB1,was further identified,and its subcellular localization on the cell wall was confirmed by transient transformation experiments.Compared with the wild type(WT),the transgenic tomato lines overexpressing MdEXLB1 had lower plant height,earlier fruiting period,fewer days for fruit ripening,higher fruit maturity,lower fruit firmness,higher fruit expansin activity,more discrete flesh cell structure,and accelerated fruit ripening process.Overall,this is the first study to propose that the apple EXLB subfamily gene,MdEXLB1,has biological functions and plays an important role in promoting fruit ripening and softening.

Detection of apple firmness with a novel loudspeaker-based excitation device

Firmness is one of the important indices to evaluate the internal quality of fruit.In this study,a noncontact loudspeaker-based detection system was developed to evaluate apple firmness.The structural parameters of the excitation device were modified in the single-factor experiments,and the best combination of structural parameters was that the inner diameter of the gasket was 40 mm;the distance between fruit surface and loudspeaker was 95 mm.Besides,the proper posture style was that the apple was placed with its stem upward.After the modification of the Laser Doppler Vibrometer(LDV)method,the vibration response signals of 48 apples were measured to establish the firmness prediction model.The results showed that the better prediction performance of stiffness was obtained in multiple models.The Back Propagation Neural Network(BPNN)model had the best prediction performance by using parameters of elasticity index(EI),the peak value at the second resonance frequency f_(2)(A_(2)),and peak area S,with a correlation coefficient of prediction(r_(p))of 0.914;root mean square error of prediction(RMSEP)of 0.491 N/mm.Therefore,the proposed detection system is feasible to nondestructively detect apple firmness,which has the potential to be applied in online detection.