番茄串收机械臂运动规划方法与试验

番茄串的采收环境复杂,果实体积相对较大,机械臂采收运动路径规划不仅要考虑如何采摘,还需要考虑采摘后如何避开障碍,并从复杂环境中提取出番茄串。为此,该研究以温室栽培的番茄串采摘为对象,提出了基于空间分割的实时运动路径规划算法。首先通过聚类拟合环境中的枝条,简化空间障碍物;然后分割采摘空间,筛选可行采摘空间,并引入评价函数选取最优采摘空间,指导机械臂以合理有效的姿态完成采摘;最后在采摘任务的基础上加入实时避障子任务,引导机械臂躲避障碍完成任务,保证采摘番茄串任务安全无损。在以上研究的基础上,通过大量采收试验验证算法的有效性。试验结果表明:通过基于空间分割的实时运动路径规划算法,采收机器人的单串番茄采摘时间为12.51 s,且采摘成功率接近100%。与目前主流的采样算法RRT*-connect相比,单串番茄的采摘时间降低了31.23%,大幅提高了采摘效率。     

基于构型空间先验知识引导点的柑橘采摘机械臂运动规划

柑橘采摘过程中机械臂有时需要深入树冠内部进行采摘,而在树冠内众多枝干往往构成一个个封闭的多边形通道,比起单个枝条的障碍物,封闭多边形障碍物更加难以避开,需要更长的时间进行规划。针对此问题,该文通过对构型空间的离线构建,分析了封闭多边形障碍物在构型空间的拓扑结构性质,根据这一性质对双向快速扩展随机树算法(RRT-connect)进行改进,提出了一种基于构型空间先验知识引导点的RRT-connect算法(informedguidancepointRRT-connect,IGPRRT-connect),并将RRT-connect与IGPRRTconnect进行了并行规划编程,提高在不同环境下的适应性。通过仿真:所提出的并行算法在各种环境下规划时间均处于较低水平,以边长为30 cm与25 cm的正方形封闭通道为例,与RRT-connect相比规划时间分别缩短了51%、86%。同时进行室内避障试验,试验结果表明,使用提出的并行算法,对封闭障碍物和未封闭障碍物均有较好的避障效果,平均规划时间为1.263 s左右,成功率为91%,可为柑橘采摘机器人在不同环境下的运动规划问题提供参考。     

基于改进YOLOv3-LITE轻量级神经网络的柑橘识别方法

柑橘识别是实现柑橘园果实自动采摘、果树精细化管理以及实现果园产量预测的关键技术环节。为实现自然环境下柑橘果实的快速精准识别,该文提出一种基于改进YOLOv3-LITE轻量级神经网络的柑橘识别方法。在采摘机器人领域,果实识别回归框的准确率直接决定了机器手的采摘成功率,该方法通过引入GIo U边框回归损失函数来提高果实识别回归框准确率;为便于迁移到移动终端,提出一种YOLOv3-LITE轻量级网络模型,使用MobileNet-v2作为模型的骨干网络;使用混合训练与迁移学习结合的预训练方式来提高模型的泛化能力。通过与Faster-RCNN以及SSD模型对比在不同遮挡程度的测试样本下模型的识别效果,用F1值与AP值评估各模型的差异,试验结果表明:该文提出的模型识别效果提升显著,对于果实轻度遮挡的数据集,该文提出的柑橘识别模型的F1值和AP值分别为95.27%和92.75%,Average IoU为88.65%;在全部测试集上,F1值和AP值分别为93.69%和91.13%,AverageIoU为87.32%,在GPU上对柑橘目标检测速度可达246帧/s,对单张416×416的图片推断速度为16.9 ms,在CPU上检测速度可达22帧/s,推断速度为80.9 ms,模型占用内存为28 MB。因此,该文提出的柑橘识别方法具有模型占用内存低、识别准确率高及识别速度快等优点,可为柑橘采摘机器人以及柑橘产业产量预测提出新的解决方案,为柑橘产业智能化提供新的思路。     

苹果采摘路径规划最优化算法与仿真实现

采摘路径规划对苹果采摘机器人的工作效率有很大的影响,为了提高苹果采摘机器人采摘效率,研究了采摘路径规划最优化方法。将苹果采摘的路径规划问题转化为三维的旅行商问题进行求解,结合图像识别得到的苹果位置特征,提出了有限域信息素自适应更新的改进蚁群算法,避免了基本蚁群算法求解过程中的早熟和局部收敛的问题,研究了三维模型的建模和驱动方法。试验结果表明将蚁群算法用于解决苹果采摘路径规划问题,当苹果数量达到250个时,改进蚁群算法迭代次数是基本算法的25.3%,而搜索到的最优路径是其94.3%,可见改进算法在搜索次数和最优结果上都有明显的优势。本研究为苹果采摘机器人采摘路径规划的提供理论参考。     

苹果采摘机器人关键技术研究现状与发展趋势

目前国内苹果基本采用人工采摘方式,随着劳动力资源短缺以及机械自动化技术的迅速发展,利用机器人采摘替代人工作业成为必然趋势,开发苹果采摘机器人用于果园收获作业具有重要意义。由于苹果采摘作业环境复杂,严重制约了采摘自动化的发展。目标识别、定位与果实分离是苹果采摘机器人的关键技术,其性能决定了苹果采摘的效率及质量。该文概述了具有市场化前景的苹果采摘机器人发展和应用现状,综述了在复杂自然环境光照变化、枝叶遮挡、果实重叠、夜间环境下以及同色系苹果的识别方法,介绍了多种场景并存的复杂环境下基于深度学习的苹果识别算法,遮挡、重叠及振荡果实的定位方法,并对采用末端执行器实现果实与果树的分离方法进行了分析。针对现阶段苹果采摘机器人采摘速度低、成功率低、果实损伤、成本高等问题,指出今后苹果采摘机器人商业化发展亟需在农机农艺结合、优化识别算法、多传感器融合、多臂合作、人机协作、扩展设备通用性、融合5G与物联网技术等方面开拓创新。     

改进类圆随机Hough变换及其在油茶果实遮挡识别中的应用

为将目标油茶果实从树枝、树叶等外界遮挡中分离出来,以利于油茶采摘机器视觉的图像形态学识别,该文提出了一种改进的类圆随机Hough变换算法,在算法中添加了边缘预检测、快速定位圆心点等模块以提高算法的识别率。仿真结果表明,改进算法对遮挡果实的识别率较其他Hough遮挡识别算法有所提高,最高达到90.70%,识别时间为1.3s。该研究为采摘机器人的后续采摘工作打下了基础。     

机耕道自动驾驶农机局部路径规划

针对机耕道场景下自动驾驶农机行驶的安全性、平稳性与规划实时性的实际需求，该研究提出了一种基于二次规划的局部路径规划方法。首先基于有限状态机构建农机机耕道行驶模式，其次采用横纵向解耦的方法，通过改进状态栅格法分别对农机速度行为和轨迹行为进行决策，随后利用二次规划方法生成满足多目标、多约束条件的农机轨迹和速度，得到最优路径，最后在多种行驶环境中进行仿真和实车试验，行驶参考速度为2 m/s。实车试验结果表明，在绕行静态障碍物场景中，规划轨迹的平均绝对曲率为0.021 m^-1，最大绝对曲率为0.056 m^-1，平均绝对横向误差为3.23 cm，最大绝对横向误差为8.69 cm，农机与障碍物外轮廓的距离大于0.76 m；在规避相向行驶、同向行驶和横穿机耕道的动态障碍物场景中，规划速度的平均绝对速度误差为0.08～0.12 m/s，绝对速度误差小于0.38 m/s，加速度变化范围为-0.38～0.44 m/s²。在规划周期为200 ms的仿真试验中，本文算法平均耗时48 ms，最大耗时75 ms，相比采用静态状态栅格法平均耗时减少38 ms，算法效率提升44%。研究结果可为机耕道场景下的农机局部路径规划提供技术支持。     

改进随机样本一致性算法的弯曲果园道路检测

果园道路检测的目的是为农业采摘机器人鲁棒实时地规划出合适的行走路径,因果园环境的复杂性,例如光照变化、杂草和落叶遮挡等因素的影响造成视觉检测算法鲁棒性差,为此提出融合边缘提取和改进随机样本一致性的弯曲果园道路检测方法。首先,根据果园道路的颜色分布特征和几何形状特征,使用有限差分算子提取图像边缘,再使用灰度值对比度约束和霍夫直线检测去除噪声,实现道路边缘点提取。然后,提出多项式函数描述直线和弯曲道路,使用改进的随机样本一致性算法和线性最小二乘法拟合道路边缘点,以估计多项式函数的参数,实现果园道路检测。在华南农业大学果园采集240张道路图像作为试验对象。试验表明:在光照变化、阴影和遮挡背景的影响下,该方法能有效地提取果园道路边缘点,并能正确地拟合道路以实现道路检测,平均正确检测率为89.1%,平均检测时间为0.2639 s,能够满足视觉导航系统的要求。该研究为农业采摘机器人的视觉导航的鲁棒性和实时性提供指导。     

苹果四臂采摘机器人系统设计与试验

针对鲜食苹果智能化高效采收需要,该研究设计了四臂并行采摘的“采-收-运”一体式机器人系统,以代替人工采收作业。以中国矮砧密植高纺锤果树为对象,根据树冠内果实空间分布特征,提出了四臂并行采摘执行部件的作业方式;建立了基于多任务深度卷积网络的果实可见区域识别模型,实现受遮挡果实离散区域语义分割及其归属关系的端到端判别;在此基础上,根据果实表面局部点云信息对其质心进行空间定位;提出了基于时间最优的四臂协同采摘任务规划方法,以实现机械臂对树冠内不同区域的高效遍历。最后在采摘机器人关键部件集成的基础上,在矮砧密植标准果园进行生产试验。试验结果表明,机器人对树冠内可见果实的识别率为92.94%,被识别果实中定位精度满足机器人采摘操作要求的比例为90.27%;机器人平均采摘效率为7.12 s/果,其中四臂协同采摘效率约为单臂采摘效率的1.96倍;对可见果实采摘成功率为82.00%,对树冠内全部果实的采收率为74.56%,枝叶遮挡干涉是造成采摘失败的主要原因。该研究可为鲜果智能化采摘模式的探索应用提供技术支撑。     

低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响

【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。     

Pasture Vegetation Elemental Analysis by Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing.     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Macroinvertebrates in North American tallgrass prairie soils: effects of fire, mowing, and fertilization on density and biomass

The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.     

Assessing the effectiveness of conservation measures: Resolving the “wicked” problem of the Steller sea lion

“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options.     

Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage

Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate.     

Variation in quality parameters between and within 14 Nordic tree fruit and berry species

Abstract

A 3-year study was carried out to investigate quality parameters in 14 tree fruit and berry species grown in southern Norway. The species were blueberry, apple, aronia, sour cherry, sweet cherry, red raspberry, strawberry, blackcurrant, gooseberry, red currant and elderberry, harvested along with wild bilberry, cloudberry and lingonberry. Significant differences between species were identified for all quality parameters. The coefficient of variation between species was lowest for pH (12.5%), dry matter (18.9%) and soluble solids (25.3%), followed by titratable acids (59.3%), total phenolics (83.8%), antioxidant capacity FRAP (85.7%) and antiradical power by the DPPH-assay (97.8%), total monomeric anthocyanins (132%) and ascorbic acid (137%). Average coefficient of variation within species were lower and ranged from 4 (pH) to 62% (ascorbic acid). Only the FRAP values were significantly affected by harvesting year with lower levels in 2004 than in 2005 and 2006. There were significant interactions between species and harvesting year for dry matter, soluble solids, pH, ascorbic acid and FRAP. The results indicate generic ranges in composition within species independent upon growing location and climate, and the composition of the tree fruits and berries is not likely to deviate from these ranges. It is concluded that desirable composition of tree fruits and berries and their products should primarily be achieved by selection among species rather than searching fors broadened variation within individual species.     

Potassium Fixation and Release Characteristics in Rhizosphere and Nonrhizosphere Soils for a Rapeseed–Rice Cropping Sequence

Potassium (K) fixation and release in soil are important factors in the long-term sustainability of a cropping system. Changes in K concentration and characteristics of K fixation and release in rhizosphere and nonrhizosphere soils in the rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation were investigated using a rhizobox system. The concentrations of different forms of K in both rhizosphere and nonrhizosphere soils decreased with plants compared to without plants, regardless of K fertilizer application. Potassium uptake by crops mainly came from the rhizosphere soil. In the treatment without K fertilizer (–K), the main form of K supplied by the soil to the crops was 1.0 mol L^?1 nitric acid (HNO₃) nonextractable K, followed by nonexchangeable K, and then exchangeable K. In the treatment with K fertilizer (+K), the main K forms supplied by the soil to the crops were exchangeable K and nonexchangeable K. The amount and rate of K fixation after one cycle of the rapeseed–rice rotation was greater in rhizosphere soil than in nonrhizosphere soil. The amount and rate of K fixation of soil in the +K treatment were significantly less than in the –K treatment. The cumulative amounts of K released with 1.0 mol L^?1 ammonium acetate (NH₄OAc) and 1.0 mol L^?1 HNO₃ extraction increased with the increasing numbers of extractions, but the K-releasing power of soil by successive extraction decreased gradually and finally became almost constant. The release of K was less in rhizosphere soil than in nonrhizosphere soil. The release of K in the +K treatment was similar to that in the –K treatment in rhizosphere soil, but the K release in nonrhizosphere soil was greater with the +K than the –K treatment. Overall, the information obtained in this study will be helpful in formulating more precise K fertilizer recommendations for certain soils.     

Enhanced establishment and growth of giant cardon cactus in an eroded field in the Sonoran Desert using native legume trees as nurse plants aided by plant growth-promoting microorganisms and compost

To evaluate the feasibility of long-term desert reforestation technology of mixed vegetation, cardon cactus (Pachycereus pringlei) seedlings from indoor and outdoor nurseries were planted in the field adjacent to one seedling of potential legume nurse trees: mesquite amargo (Prosopis articulata), yellow palo verde (Parkinsonia microphylla), and blue palo verde (Parkinsonia florida). Some of the planting holes were also supplemented with common dairy compost. Additionally, the combinations of legume tree–cactus were inoculated with either a consortium of desert arbuscular mycorrhizal (AM) fungi, plant growth promoting bacteria (PGPB; the diazotroph Azospirillum brasilense Cd, and the phosphate solubilizer Paenibacillus sp.), or a mixture of all. The field experiments were evaluated periodically during 30 months for survival and growth. Cardons reared in an outdoor screen house survived better in the field than those reared in a controlled growth chamber and hardened later outdoors. Association with any legume nurse tree increased survival and enhanced growth of untreated cardons. For cardons growing alone, application of either compost, AM fungi, and all the treatments combined increased survival. For these plants, no treatment affected plant growth during the first 3 months after transplanting. Later, all treatments, except for AM fungi, enhanced plant growth. However, only 2 years after transplanting the enhanced growth effect of AM fungi was also significant. In the presence of the legume nurse trees, transient positive effects on cardon growth were recorded. General evaluation after 30 months of cultivation showed that the treatments positively affected cardon growth when growing alone or in combination only with mesquite amargo but not with the other two legume trees. This study proposes that young legume trees have the capacity to enhance survival and growth of cardon cactus, depending on the legume cactus combination. Additional treatments such as compost or PGPB can either amplify the effect or else attenuate it.     

Karyotypic and genome size variation in Cajanus cajan (L.) Millsp. (pigeonpea) and some wild relatives

Detailed karyotypes and 4C DNA amounts have been studied in five cultivars of Cajanus cajan and 20 species belonging to Cajanus, Rhynchosia, Dunbaria, Flemingia and Paracalyx. C. cajan shows intraspecific variability and its karyotype is most similar to that of C. cajanifolius (sect. Cajanus) in the morphology and number of satellite chromosomes and the lack of any correlation between chromosome size within the complement and asymmetry. Karyotypes of C. lineatus and C. sericeus belonging to sect. Atylia are similar with respect to maximum r-index and the ratio of longest and shortest chromosomes in their respective complements. C. acutifolius (sect. Frutocosa) is distinct in having a very low ratio (1.44) between the longest and the shortest chromosomes, while in C. albicans, C. goensis, C. scarabaeoides (sect. Cantharospermum) there is no chromosome pair with r-index >2.0. C. mollis and C. volubilis (sect. Volubilis) show similarity with regard to ratio between the longest and the shortest chromosomes and a distinct chromosome pair with an arm ratio of 2.7 and C. platycarpus is distinct (sect. Rhynchosoides) in having the smallest ratio (1.36) between the longest and the shortest chromosomes. 4C DNA amounts in Cajanus and Rhynchosia vary between 3.28 pg to 11.69 pg and 4.92 pg to 11.13 pg respectively, while in Dunbaria, Flemingia and Paracalyx these vary between 4.70 and 7:06 pg. In the genus Cajanus karyotypic features and 4C DNA amounts agree with the sectional classification and bring out a close relationship between C. cajan and C. cajanifolius. This is supported by studies based on seed protein patterns, isozyme analysis, trypsin and chymotrypsin inhibitor patterns, RFLP and RAPD data and crossability relationships. A clear relation between DNA amount and abnormalities effecting the extent of pairing and recombination in interspecific hybrids shows the importance of this study in developing future breeding programme involving C. cajan and its wild relatives that are of potential value.