Automatic strawberry leaf scorch severity estimation via faster R-CNN and few-shot learning

Using deep learning to estimate strawberry leaf scorch severity often achieves unsatisfactory results when a strawberry leaf image contains complex background information or multi-class diseased leaves and the number of annotated strawberry leaf images is limited. To solve these issues, in this paper, we propose a two-stage method including object detection and few-shot learning to estimate strawberry leaf scorch severity. In the first stage, Faster R-CNN is used to mark the location of strawberry leaf patches, where each single strawberry leaf patch is clipped from original strawberry leaf images to compose a new strawberry leaf patch dataset. In the second stage, the Siamese network trained on the new strawberry leaf patch dataset is used to identify the strawberry leaf patches and then estimate the severity of the original strawberry leaf scorch images according to the multi-instance learning concept. Experimental results from the first stage show that Faster R-CNN achieves better mAP in strawberry leaf patch detection than other object detection networks, at 94.56%. Results from the second stage reveal that the Siamese network achieves an accuracy of 96.67% in the identification of strawberry disease leaf patches, which is higher than the Prototype network. Comprehensive experimental results indicate that compared with other state-of-the-art models, our proposed two-stage method comprising the Faster R-CNN (VGG16) and Siamese networks achieves the highest estimation accuracy of 96.67%. Moreover, our trained two-stage model achieves an estimation accuracy of 88.83% on a new dataset containing 60 strawberry leaf images taken in the field, which indicates its excellent generalization ability.     

红薯水提物对外来入侵植物喜旱莲子草生长的化感影响

从植物化感作用的角度,探索利用具有较高经济价值的本地植物或伴生的本地物种对入侵植物进行抑制和清除,是一种控制外来入侵植物行之有效的方法。本研究以本地作物红薯和入侵植物喜旱莲子草为试验对象,探究红薯不同部位(根、茎、叶)3个浓度(0.025、0.05、0.1 g·mL^-1)的水提物对喜旱莲子草的化感作用。以形态学指标(无性系小株个数、节数、叶片数、叶面积、株高、总干重和根数)、化感响应指数、性状比值(肉质化程度、根冠比、比叶面积、叶生物量比、茎生物量比、根生物量比)、新生叶片中过氧化氢酶(CAT)、过氧化物酶(POD)、丙二醛(MDA)、超氧化物歧化酶(SOD)等作为衡量红薯对喜旱莲子草根状茎生长影响程度的参数。结果表明: 1)不同浓度不同部位红薯水提物对喜旱莲子草生长有不同影响。0.1 g·mL^-1根水提物显著抑制所有形态学指标,除总干重和根数外,其他形态学指标均随不同部位水提物浓度的升高而显著降低。2)所有处理的综合化感响应指数均为负值,说明红薯水提物对喜旱莲子草各指标具有负效应,抑制其正常生长。在所有处理中,0.1 g·mL^-1根水提物的化感抑制作用最强,化感响应指数为-0.73,其次为0.1 g·mL^-1茎水提物和0.05 g·mL^-1根水提物,化感响应指数均为-0.44。3)从性状比值可以看出,红薯水提物对肉质化程度、根冠比、比叶面积和叶生物量比有显著抑制作用,而对茎生物量比和根生物量比无显著性影响。4)红薯水提物显著增加新生叶片中丙二醛含量,显著降低超氧化物歧化酶含量,但对过氧化氢酶和过氧化物酶无显著影响。表明红薯水提物对喜旱莲子草根状茎生长有显著抑制作用。     

An improved Faster R-CNN model for multi-object tomato maturity detection in complex scenarios

Accurate detection of tomato maturity is significant in automatic tomato picking. Although there are many detection methods, they are often sensitive to occlusion, overlap, uneven illumination, and other complex factors, leading to a limited performance in complex environment scenes. To address this problem, this study designed an improved Faster R-CNN model named MatDet for tomato maturity detection. First, MatDet used ResNet-50 as the backbone to improve the representation ability and robustness of the model. Second, RoIAlign was used to obtain more precise bounding boxes in the feature mapping stage. Third, a Path Aggregation Network (PANet) was introduced to address the difficulty of detecting tomato maturity in complex scenarios. Experimental results showed that the proposed model achieved the best detection results in terms of branch occlusion, fruit overlapping and illumination influence under complex scenarios. Specifically, the mean average precision (mAP) of the proposed algorithm is 96.14%, which is better than that of common object detection models. Through many multi-angle comparative experiments, it was confirmed that our method can overcome complex factors such as branch occlusion, fruit overlap and light influence, and achieve the best detection effect. Meanwhile, this research has certain theoretical and practical significance for the intelligent and precise picking of tomatoes, thereby promoting the directional cultivation of crops such as fruits and vegetables, and providing technical support for the development of ecological monitoring technology and ecological planting.     

Agroinfection of sweet potato by vacuum infiltration of an infectious sweepovirus

Sweepovirus is an important monopartite begomovirus that infects plants of the genus Ipomoea worldwide. Development of artificial infection methods for sweepovirus using agroinoculation is a highly efficient means of studying infectivity in sweet potato. Unlike other begomoviruses, it has proven difficult to infect sweet potato plants with sweepoviruses using infectious clones. A novel sweepovirus, called Sweet potato leaf curl virus-Jiangsu (SPLCV-JS), was recently identified in China. In addition, the infectivity of the SPLCV-JS clone has been demonstrated in Nicotiana benthamiana. Here we describe the agroinfection of the sweet potato cultivar Xushu 22 with the SPLCV-JS infectious clone using vacuum infiltration. Yellowing symptoms were observed in newly emerged leaves. Molecular analysis confirmed successful inoculation by the detection of viral DNA. A synergistic effect of SPLCV-JS and the heterologous betasatellite DNA-β of Tomato yellow leaf curl China virus isolate Y10 (TYLCCNV-Y10) on enhanced symptom severity and viral DNA accumulation was confirmed. The development of a routine agroinoculation system in sweet potato with SPLCV-JS using vacuum infiltration should facilitate the molecular study of sweepovirus in this host and permit the evaluation of virus resistance of sweet potato plants in breeding programs.     

四川间作地区作物高度、覆盖度和叶面积指数的动态变化

为研究间作系统的作物参数,于2005年在四川间作地区进行了作物高度、覆盖度和叶面积指数的时间变化研究.结果表明:作物的高度、覆盖度和叶面积指数随时间变化很大;玉米的最大高度是177 cm,最大覆盖度(86%)出现在花期,最大叶面积指数是1.96;红苕的最大和最小株高分别为22和12 cm,最大覆盖度(73%)出现在薯块膨大期,最大叶面积指数为1.79.与玉米间作时,红苕所有作物参数均受玉米影响.在玉米-红苕间作系统中,最危险的侵蚀期是玉米收获后至红苕覆盖度最大期.     

甘薯丛枝病植原体的PCR检测

以报道的植原体 (Phytoplasma)16SrDNA基因保守序列为依据,设计合成了两对引物对R16mF2/ R16mR2和R16F2/ R16R2,以甘薯丛枝病（SPWB）带病植株的叶脉中提取的DNA为模板,应用聚合酶链式反应（PCR）技术和巢式PCR（Nested- PCR）技术对甘薯丛枝病病原进行分子检测。结果表明PCR扩增出了1.5　kb的特异片段,在PCR基础上的巢式PCR扩增出了1.2　kb的特异片段。灵敏度实验显示该方法所需PCR模板DNA量为0.1073　ng/μl,在PCR基础上的巢式PCR可以将灵敏度提高约10000倍,所需模板DNA仅为0.01073　pg/μl,在甘薯丛枝病的检测中是一种快速、灵敏、可靠的方法。     

甘薯丛枝病植原体的PCR检测

以报道的植原体（Phytoplasma)16SrDNA基因保守序列为依据,设计合成了两对引物对R16mF2/R16mR2和R16F2／R16R2,以甘薯丛枝病（SPWB）带病植株的叶脉中提取的DNA为模板,应用聚合酶链式反应（PCR）技术和巢式PCR（Nested-PCR)技术对甘薯丛枝病病原进行分子检测。结果表明PCR扩增出了1．5kb的特异片段,在PCB基础上的巢式PCR扩增出了1．2kb的特异片段,灵敏度实验显示该方法所需PCR模板DNA量为0．1073ng/ul在PCR的基础上的巢度PCR可以将灵敏度提高约10000倍,所需模板DNA仅为0．01073pg/ul,在甘薯丛枝病的检测中是一种快速,灵敏,可靠的方法。     

Overexpression of barley nicotianamine synthase 1 confers tolerance in the sweet potato to iron deficiency in calcareous soil

Background and aims

Iron (Fe) is an essential micronutrient for all higher organisms. Fe is sparingly available in calcareous soils and Fe deficiency is a major agricultural problem worldwide. Nicotianamine (NA) is a metal chelator involved in metal translocation in plants. Sweet potato is an attractive crop that can grow in poor soil and thus is useful for planting in uncultivated soil. In addition, the sweet potato has recently been suggested as a source of bioethanol. Our aim is to increase NA concentration in sweet potato to ameliorate Fe deficiency.

Method

Sweet potato plants expressing the barley NA synthase 1 (HvNAS1) gene under the control of CaMV 35S promoter were produced by Agrobacterium-mediated transformation.

Results

The transgenic sweet potato exhibited tolerance to low Fe availability when grown in calcareous soil. The level of tolerance to low Fe availability was positively correlated with the HvNAS1 expression level. The NA concentration of the transgenic sweet potato leaves was up to 7.9-fold greater than that of the non-transgenic (NT) plant leaves. Furthermore, the Fe and zinc concentrations were 3- and 2.9-fold greater, respectively, in transgenic sweet potato than in NT plant leaves.

Conclusions

Our results suggest that increasing the NA concentration of sweet potato by overexpression of HvNAS1 could significantly improve agricultural productivity and energy source.

     

Sucrose Phosphate Synthetase from Various Plant Origins

Some properties of sucrose-P synthetases obtained from various plant tissues, including sweet potato roots, potato tubers and leaves of barley, rape and ladino clover were studied. The specific enzyme activity of the sucrose-P synthetase from sweet potato roots was much lower than that of the sucrose synthetase of the other tissues. The enzyme activity decreased gradually as the roots developed. The optimum pH did not differ between enzyme preparations from sweet potato roots and barley leaves. Manganese chloride exhibited a marked stimulative effect on the sucrose-P synthetase from sweet potato roots and potato tubers, whereas it was inhibited the barley leaf enzyme.

Kinetic studies of sucrose-P synthetase showed that the behavior of the enzyme to the substrates did not differ in the enzyme sources examined. The substrate saturation curve of the enzyme with respect to fructose-6-P was sigmodal in shape, giving a straight line with a slope of 1.35~1.5 (n value) in a plot of the data using the empirical Hill equation. On the other hand, enzymes from all the various tissues exhibited a hyperbolic substrate saturation curve for UDP-glucose, obeying the ordinary Michaelis-Menten type reaction. Manganese chloride had no effect on the Km for UDP-glucose, the S_0.5 for fructose-6-P and the n value of the enzyme from potato tuber tissues.     

Molecular cloning and characterization of a granulin-containing cysteine protease SPCP3 from sweet potato (Ipomoea batatas) senescent leaves

Granulins are a family of evolutionarily ancient proteins that are involved in regulating cell growth and division in animals. In this report a full-length cDNA, SPCP3, was isolated from senescent leaves of sweet potato (Ipomoea batatas). SPCP3 contains 1389 nucleotides (462 amino acids) in its open reading frame, and exhibits high amino acid sequence homologies (ca. 64-73.6%) with several plant granulin-containing cysteine proteases, including potato, tomato, soybean, kidney bean, pea, maize, rice, cabbage, and Arabidopsis. Gene structural analysis shows that SPCP3 encodes a putative precursor protein. Via cleavage of the N-terminal propeptide, it generates a protein with 324 amino acids (from the 139th to the 462nd amino acid residues), which contains two main domains: the conserved catalytic domain with the putative catalytic residues (the 163rd Cys, 299th His and 319th Asn) and the C-terminal granulin domain (from the 375th to the 462nd amino acid residues). Semi-quantitative RT-PCR and protein gel blot hybridization showed that SPCP3 gene expression was enhanced significantly in natural senescent leaves and in dark- and ethephon-induced senescent leaves, but was almost undetectable in mature green leaves, veins, and roots. Phylogenic analysis showed that SPCP3 displayed close association with a group of plant granulin-containing cysteine proteases which have been implied to be involved in programmed cell death. In conclusion, sweet potato SPCP3 is a functional, senescence-associated gene. Its mRNA and protein levels were significantly enhanced in natural and induced senescing leaves. The physiological role and/or function of SPCP3 associated with programmed cell death during leaf senescence were also discussed.     

Cryotherapy of shoot tips: a technique for pathogen eradication to produce healthy planting materials and prepare healthy plant genetic resources for cryopreservation

Cryotherapy of shoot tips is a new method for pathogen eradication based on cryopreservation techniques. Cryopreservation refers to the storage of biological samples at ultra-low temperature, usually that of liquid nitrogen (−196°C), and is considered as an ideal means for long-term storage of plant germplasm. In cryotherapy, plant pathogens such as viruses, phytoplasmas and bacteria are eradicated from shoot tips by exposing them briefly to liquid nitrogen. Uneven distribution of viruses and obligate vasculature-limited microbes in shoot tips allows elimination of the infected cells by injuring them with the cryo-treatment and regeneration of healthy shoots from the surviving pathogen-free meristematic cells. Thermotherapy followed by cryotherapy of shoot tips can be used to enhance virus eradication. Cryotherapy of shoot tips is easy to implement. It allows treatment of large numbers of samples and results in a high frequency of pathogen-free regenerants. Difficulties related to excision and regeneration of small meristems are largely circumvented. To date, severe pathogens in banana ( Musa spp.), Citrus spp., grapevine ( Vitis vinifera ), Prunus spp., raspberry ( Rubus idaeus ), potato ( Solanum tuberosum ) and sweet potato ( Ipomoea batatas ) have been eradicated using cryotherapy. These pathogens include nine viruses (banana streak virus, cucumber mosaic virus, grapevine virus A, plum pox virus, potato leaf roll virus, potato virus Y, raspberry bushy dwarf virus, sweet potato feathery mottle virus and sweet potato chlorotic stunt virus), sweet potato little leaf phytoplasma and Huanglongbing bacterium causing 'citrus greening'. Cryopreservation protocols have been developed for a wide variety of plant species, including agricultural and horticultural crops and ornamental plants, and can be used as such or adjusted for the purpose of cryotherapy.     

湖南甘薯种质资源曲叶病毒检测分析初报

本研究依托"第三次全国农作物种质资源普查与收集行动",利用巢式PCR(Nested PCR)检测技术,对从湖南各地区采集的甘薯种质资源进行甘薯曲叶病毒的调查、检测、统计与分析,获得该地区甘薯种质资源曲叶病毒的感染和分布情况。对收集的246份甘薯种质资源进行了甘薯曲叶病毒病症状的调查,记录了每份种质资源的田间生长特性;建立了一种甘薯曲叶病毒巢式PCR检测技术,该技术相对其他技术具有特异性强、灵敏度高、检测通量大、检测成本低的特点。利用建立的巢式PCR检测技术对选取的样品进行甘薯曲叶病毒检测,分析检测结果发现:(1)巢氏PCR共检测出14份甘薯种质资源感染甘薯曲叶病毒,根据病毒基因测序结果分析湖南省至少存在2种曲叶病毒株系。(2)田间调查共发现8份甘薯种质资源的叶片具有甘薯曲叶病毒病典型的卷曲症状,但是其中仅有4份资源与曲叶病毒巢氏PCR检测结果一致;另外4份资源虽然具有明显的卷叶现象但是未检测出曲叶病毒。(3)曲叶病毒检测呈阳性的14份甘薯种质资源分别来源于邵阳市、长沙市、永州市和株洲市4个地区,占种质资源总数的5.7%;4个地区甘薯种质资源的病毒感染率分别为17.6%、14.5%、7.1%和6.7%;全省范围内的种质资源染病情况具有较大的地域差异性;综合甘薯种植情况和地理环境分析,商品薯的跨区域流通和农民自留种的种植习惯是影响甘薯病毒传播的主要因素。本研究首次利用巢式PCR技术对湖南地区甘薯曲叶病毒进行检测和调查,为甘薯种质资源的保存、繁殖、鉴定与利用提供了重要的技术支撑,也为湖南地区甘薯曲叶病毒侵染情况及相关的分子生物学研究提供了数据参考。     

Overexpression of <i>IbSINA5</i> Increases Cold Tolerance through a CBF SINA-COR Mediated Module in Sweet Potato

Seven in absentia (SINA) family proteins play a central role in plant growth, development and resistance to abiotic stress. However, their biological function in plant response to cold stress is still largely unknown. In this work, a seven in absentia gene IbSINA5 was isolated from sweet potato. Quantitative real-time polymerase chain reaction (qRT-PCR) analyses demonstrated that IbSINA5 was ubiquitously expressed in various tissues and organs of sweet potato, with a predominant expression in fibrous roots, and was remarkably induced by cold, drought and salt stresses. Subcellular localization assays revealed that IbSINA5-GFP fusion protein was mainly localized in cytoplasm and nucleus. Overexpression of IbSINA5 in sweet potato led to dramatically improved resistance to cold stress in transgenic plants, which was associated with the up-regulated expression of IbCOR (cold-regulated) genes, increased proline production, and decreased malondialdehyde (MDA) and H₂O₂ accumulation in the leaves of transgenic plants. Furthermore, transient expression of IbCBF3, a C-repeat binding factor (CBF) gene, in the leaf protoplasts of wild type sweet potato plants up-regulated the expression of both IbSINA5 and IbCOR genes. Our results suggest that IbSINA5 could function as a positive regulator in the cold signaling pathway through a CBF-SINA-COR mediated module in sweet potato, and have a great potential to be used as a candidate gene for the future breeding of new plant species with improved cold resistance.     

Leaf Spot on Sweet Potato (Ipomoea batatas) Caused by Stemphylium solani,a New Disease in China

During 2010–2011, a severe leaf spot disease of sweet potato (Ipomoea batatas) was found in Haikou City, Hainan province of China. The disease is characterized with large, irregular, brown, necrotic lesions on the margin or in the centre of leaves. A species of Stemphylium was consistently recovered from pieces of symptomatic tissues on PDA. Based on morphological characteristics and molecular identification by rDNA‐ITS gene analysis, the fungal species was identified as Stemphylium solani Weber, and its pathogenicity was confirmed by Koch's postulates. This is the first report of leaf spot on sweet potato caused by S. solani in China.     

Growth of the Tops of Sweet Potato and the Translocation of the Nutrients from Leaves

1. Experiments were carried out in Hangchow on the increase of dry matter in the tops of sweet potato plants. The increase can be divided into three periods: (1) slow accumulation of dry matter; (2) rapid increase of accumulation of dry matter, reaching a maximum; (3) decline of accumulation of dry matter, later on account of senility and the dropping of leaves, there was a marked reduction in the dry matter of the tops. The increase in dry matter is in proportion to the leaf area. The amount of fertilizer used is closely related to the increase of dry matter and leaf area. 2. The yield of sweet potato is related to the increase in dry matter of the tops of the plant. To a certain extent, the greater the amount of dry matter, the more rapidly will the tubers enlarge, finally results in a higher yield. Excessive use of fertilizer leads to an abnormal elongation of the plant. During this period an increase in dry matter of the tops not only fails to induce the enlargement of the tubers, but also leads to the consumption of the dry matter, and consequently causes a reduction in yield of sweet potato. From the curve of T/R ratio, the sooner the downward translocation of the tops nutrients occurs, the faster the tubers will form and enlarge. 3. Experiments with p32 show that the various growth conditions of the tops are closely correlated with the translocation of the tubers. With well growing and high yielding plants the nutrients move from the tops to the tubers as soon as the root enlarges. This translocation is even accelerated during the later stage. During the earlier stage of development, much of the plant nutrition is translocated to the stems and leaves, particularly to the latter; then gradually it is diverted to the leaves and the root system, and finally concentrates in the roots. The increase of the area of green leaves and the number of branches during the period of early growth, and the promoting of favourable conditions for the formation and enlargement of the roots, as well as the facilitating of the translocation of nutrients to the roots during the later stage are the determinative factors necessary for obtaining high yield of sweet potato.