Multi-class detection of cherry tomatoes using improved YOLOv4-Tiny

The rapid and accurate detection of cherry tomatoes is of great significance to realizing automatic picking by robots.However,so far,cherry tomatoes are detected as only one class for picking.Fruits occluded by branches or leaves are detected as pickable objects,which may cause damage to the plant or robot end-effector during picking.This study proposed the Feature Enhancement Network Block(FENB)based on YOLOv4-Tiny to solve the above problem.Firstly,according to the distribution characteristics and picking strategies of cherry tomatoes,cherry tomatoes were divided into four classes in the nighttime,and daytime included not occluded,occluded by branches,occluded by fruits,and occluded by leaves.Secondly,the CSPNet structure with the hybrid attention mechanism was used to design the FENB,which pays more attention to the effective features of different classes of cherry tomatoes while retaining the original features.Finally,the Feature Enhancement Network(FEN)was constructed based on the FENB to enhance the feature extraction ability and improve the detection accuracy of YOLOv4-Tiny.The experimental results show that under the confidence of 0.5,average precision(AP)of non-occluded,branch-occluded,fruit-occluded,and leaf-occluded fruit over the day test images were 95.86%,92.59%,89.66%,and 84.99%,respectively,which were 98.43%,95.62%,95.50%,and 89.33% on the night test images,respectively.The mean Average Precision(mAP)of four classes over the night test set was higher(94.72%)than that of the day(90.78%),which were both better than YOLOv4 and YOLOv4-Tiny.It cost 32.22 ms to process a 416×416 image on the GPU.The model size was 39.34 MB.Therefore,the proposed model can provide a practical and feasible method for the multi-class detection of cherry tomatoes.

Effects of Sodium Nitroprussiate on the Metabolites and Key Enzyme Activities of Carbon-nitrogen Metabolism from Seed Germination to Seedling Period of Cherry Tomato

This study was conducted to elucidate the regulating mechanism of sodium nitroprussiate on seed germination and seedling growth of cherry tomato. After the treatment with different concentrations of sodium nitroprusside, the effects on the metabolites and key enzyme activities in carbon-nitrogen metabolism of cherry tomato cuhivar Zhuyun as an experimental material were investigated. The results showed that from seed germination to seedling period, the contents of starch and total nitrogen decreased, but the contents of soluble sugar, reducing sugar, sucrose and soluble protein increased firstly and then decreased; and free amino acids content increased gradually. Sodium nitroprusside made the contents of starch, sucrose and free amino acids higher than CK. From seed germination to seedling period in cherry tomato, the activities of amylase, glutamine synthetase （GS） and sucrose phosphate synthase （SPS） decreased; the activities of nitrate reductase （NR） and glutamate synthase （GOGAT） increased at first and decreased then; and the CK and the 0.25 mmol/L sodium nitroprusside treatments exhibited de- creased sucrose synthase （SS） activity, and the trend was increasing at first and decreasing then after the treatment with 0.50 and 1.00 mmol/L sodium nitroprus- side. Sodium nitroprusside treatment improved amylase activity; and the carbon-nitrogen ratio of the CK increased at first and decreased then, while the values of other treatments tended to decrease. In addition, sodium nitroprusside did not affect seed germination potential and germination rate, but significantly improved biomass accumulation, root length and height of seedlings. These data suggest that sodium nitroprusside could affect the conversion of starch and sugar accumulation, delay the decomposition of total nitrogen and soluble protein, and achieve the effects of accelerating the accumulation of free amino acids, and promoting seed germination and seedling growth, and 0.50 mmol/L sodium nitroprusside has the best effect.

Reduction of Chilling Injury and Ultrastructural Damage in Cherry Tomato Fruits After Hot Water Treatment

The effects of hot water treatment in alleviating chilling injury and reducing ultrastructural damage of mature-green cherry tomatoes （Lycopersicun esculentum cv. cerasiform Alef） were investigated. Mature-green cherry tomato fruits were treated in water at 40℃ or 45℃ for 5 min or 15 min, and then stored at 5℃ for 19 days followed by ripening at 20℃. Water treatment at 40℃ for 15 min increased tolerance of cherry tomato fruits to chilling stress, indicating as low outbreak of skin lesion, high color a＊ value, and low electrolyte leakage. Treated fruits showed typical climacteric respiration and developed normal red color with chlorophyll degradation and lycopene accumulation during ripening, while fruits without treatment failed to develop red color and suffered skin lesion. After 19 days of chilling, heated fruits showed the conversion of chloroplast to chromoplast with the disappearance of thylakoids. Mitochondria and other cell organelles were not adversely affected in treated fruits. However, ultrastructures in pericarp cells in control fruits severely damaged with extensive disorganization of cytoplasm, swelled chloroplasts, distorted and unstacked thylakoids. Chloroplast was the first and most severely impacted organelle by chilling stress. Hot water treatment （40℃ for 15 min） before storage alleviated chilling injury in cherry tomato fruits. The results suggest that chilling injury is related with the damage of cell structure under chilling stress.

Antibacterial Activities of Three Kinds of Plant Extracts against Ralstonia solanacearum of Cherry Tomato

Bacterial wilt has become an important obstacle restricting high quality and high yield of cherry tomato. In this paper, the antibacterial activities of ex- tracts from Allium sativum, Ginkgo biloba and Lygodium japonicum against Ralstonia solanacearum were compared. The results indicated that with the increasing concentrations of three extracts, the antibacterial effect enhanced gradually. The lowest concentrations of three extracts with the inhibitory effects significantly higher than that of pesticide control were 20% A. sativum extract, 40% G. biloba extract and 60% L japonicum extract, and the antibacterial effect of 20% A. sativum extract was significantly higher than those of other two plant extracts. The inhibition zone diameters of R. solanacearum strains B2. 1.2.2, I1.2. 1.1, KS. 1.1.1 and 1.5.3.1.2 were 9.23, 8.30, 8.12 and 9.19 mm, respectively. The antibacterial effects of three plant extracts reached the maximums when the concentration was 100%, but A. sativum extract had the strongest antibacterial effect against test strains. Therefore, A. sativum can be used as the main raw material for development of plant protectant for cherry tomato.

Grafting and Seedling Cultivation Technology of Cherry Tomato for Disease Prevention in Hainan

In order to reduce the occurrence of soil-borne diseases,such as tomato bacterial wilt and Fusarium wilt,and to improve the yield of cherry tomato in Hainan,the paper had summarized grafting and seedling technology of cherry tomato from the aspects of rootstock selection,rootstock seedling cultivation,scion seedling cultivation,preparation before grafting,grafting method and seedling management after grafting.It was found that the technique could significantly improve the yield and disease resistance of cherry tomato.

Design and test of robotic harvesting system for cherry tomato

Harvesting of fresh-eating cherry tomato was highly costly on labor and time.In order to achieve mechanical harvesting for the fresh-eating tomato,a new harvesting robot was designed,which consisted of a stereo visual unit,an end-effector,manipulator,a fruit collector,and a railed vehicle.The robot configuration and workflow design focused on the special cultivating condition.Three key parts were introduced in detail:a railroad vehicle capably moving on both ground and rail was adopted as the robot’s carrier,a visual servo unit was used to identify and locate the mature fruits bunch,and the end-effector to hold and separate the fruit bunch was designed based on the stalk’s mechanical features.The field test of the new developed robot was conducted and the results were analyzed.The successful harvest rate of the robot was 83%,however,each successful harvest averagely needed 1.4 times attempt,and a single successful harvesting cycle cost 8 s excluding the time cost on moving.

Optimization and Experimental Study of Bionic Compliant End-effector for Robotic Cherry Tomato Harvesting

High harvesting success rate is part of the key technologies for robotic cherry tomato harvesting,which is closely related to the structural design of the end-effector.To obtain a high success rate of fruit harvesting,this paper presents a compliant end-effector with bio-inspired tarsus compliant gripper inspired by the structure and mechanics of the tarsal chain in the Serica orientalis Motschulsky.Response Surface Methodology(RSM)based on Box Behnken Design(BBD)technique has been used to optimize the key structural parameters of the bionic compliant end-effector for achieving the expected results in pulling pattern for robotic cherry tomato harvesting.Experiments were designed by maintaining three levels of four process parameters—Length of the Offset Segment Tarsomere(OSTL),Angle of the Inclined Segment Tarsomere(ISTA),Thickness of the Extended Segment Tarsomere(ESTT)and Length of the Extended Segment Tarsomere(ESTL).According to the optimization analysis results,the best parameter combination is OSTL 23 mm,ISTA 14°,ESTT 5.0 mm,ESTL 23 mm.Besides,the harvesting performance of the optimized bionic compliant end-effector was verified by experiments.The results indicated the harvesting success rate of fruits with different equatorial diameters was not less than 76%.