Molecular characterization,vector identification and partial host range determination of phytoplasmas associated with faba bean phyllody in Iran

During surveys of phytoplasma diseases, faba bean phyllody (FBP) was observed in several locations in Fars and Bushehr provinces (southern Iran). Samples of affected plants from Borazjan (Bushehr province) and Fasa (Fars province) were used to transmit the phyllody agent to faba bean, mung bean, pea, alfalfa and periwinkle by grafting, dodder and/or vector insect. Orosius albicinctus (Distant) was identified as the vector of Borazjan (BFBP) and Fasa (FFBP) faba bean phyllody. Naturally affected faba bean plants and all inoculated plants were positive for phytoplasma by direct PCR using the P1/P7 primer pair and nested PCR using P1/P7 and R16F2n/R16R2 primer pairs. Sequencing of PCR products identified the associated phytoplasmas as members of 16SrII phytoplasma group. Phylogenetic analysis using full length 16S rRNA gene sequences also confirmed similarity of the BFBP and FFBP phytoplasmas to the 16SrII group phytoplasmas. In this analysis the FFBP phytoplasma was grouped with ’Candidatus Phytoplasma australasia’, representative of 16SrII-D subgroup, while the BFBP phytoplasma formed a discrete group close to the 16SrII-C subgroup. Restriction fragment length polymorphism (RFLP) confirmed that BFBP and FFBP phytoplasmas belong to 16SrII group. Virtual RFLP confirmed that as members of peanut witches’ broom (16SrII) phytoplasma group, BFBP and FFBP phytoplasmas belonged to 16SrII-C and16SrII-D subgroups, respectively. Phytoplasmas associated with BFBP and FFBP were shown to be serologically related to the Fars alfalfa witches’broom phytoplasma, a member of 16SrII-C subgroup. It seems that witches’broom affected alfalfa fields are natural reservoirs of the FBP phytoplasma in southern Iran.     

Identification of a phytoplasma associated with pomegranate little leaf disease in Iran

During 2012–2014 surveys for the presence of phytoplasma diseases in Fars province (Iran), pomegranate little leaf symptoms were observed in several orchards in Khafr and Neyriz areas. Samples collected from symptomatic plants positively reacted in nested PCR assays using P1/P7 followed by R16F2n/R16R2 primer pairs producing the expected 1,250 bp DNA fragments. Real and virtual RFLP analysis showed that the sequences of phytoplasma strains from Khafr and Neyriz (KPLL and NPLL strains, respectively) were identical to each other and belong to 16SrII phytoplasma group, subgroup D. Phylogenetic analysis of the R16F2n⁄R16R2 DNA region confirmed that KPLL and NPLL phytoplasmas were enclosed in the same clade as other 16SrII-D subgroup phytoplasmas. This is the first reported occurrence of a 16SrII phytoplasma infecting pomegranate trees.     

Evidence for the role of an invasive weed in widespread occurrence of phytoplasma diseases in diverse vegetable crops: Implications from lineage-specific molecular markers

During the period from 2011 to 2013, several plant diseases repeatedly occurred in vegetable crops grown in Yuanmou County, Yunnan Province, China. Affected plants included cowpea, sword bean, string bean, tomato, lettuce, and water spinach. The diseased plants exhibited symptoms of witches'-broom growth and floral deformations, linking each disease to phytoplasmal infection. Phylogenetic and virtual RFLP analyses of the phytoplasmal 16S rRNA gene sequences amplified from DNA of diseased plants revealed that all of the individual strains present in the diverse vegetable plants were affiliated with a single ‘Candidatus Phytoplasma’ species (‘Ca. Phytoplasma aurantifolia’) and a single ribosomal subgroup (16SrII-A). While presence of subgroup 16SrII-A phytoplasma in this geographic region was reported previously, such widespread infections in diverse plant hosts are unveiled for the first time in this study. In pursuing the source of the infections, we found that areas surrounding the affected vegetable fields were extensively invaded by parthenium weeds (Parthenium hysterophorus); and many of the weed plants exhibited abnormal morphologies that were suspicious of, and later diagnosed with, phytoplasmal infections. Results from genotyping of 16S rRNA and lineage-specific immunodominant membrane protein genes revealed that the vegetable-infecting phytoplasmas and the parthenium weed phytoplasma belong to the same genetic lineage. The findings indicate that parthenium weed poses a substantial risk as a reservoir of phytoplasmal infection of nearby agricultural crops in the geographic region since the ecosystems of Yuanmou are insect-rich, and parthenium weed is known to attract diverse leafhoppers. Further studies are warranted to assess the impact of farmland invasions by the noxious weed and to devise practical measures for improved weed control.     

Occurrence of ‘Candidatus Phytoplasma asteris’ in citrus showing Huanglongbing symptoms in Mexico

Huanglongbing (HLB), one of the most devastating citrus diseases in the world, was detected in Mexico in 2009. Currently, HLB is associated with the bacteria Candidatus Liberibacter spp., although several phytoplasmas have been found from trees showing HLB-like symptoms in Brazil and China. The aim of this study was thus to determine if, in addition to ‘Ca. L. asiaticus’ (CLas), phytoplasma species are also associated with HLB-like symptoms in citrus groves of Mexico. Citrus plants exhibiting symptoms such as diffuse chlorosis, blotchy mottle and vein yellowing were collected in the Mexican States of Nayarit, Colima and Sinaloa between August 2011 and September 2012. Samples were then evaluated for phytoplasmas and CLas by PCR, using primers that respectively target the genes for the 16S ribosomal RNA and 50S ribosomal protein of the β operon (rplA-rplJ). Out of 86 HLB-symptomatic citrus plants, 54 were positive for CLas, 20 were positive for phytoplasmas, 7 were found in mixed infections with both pathogens and 19 samples were negative for CLas and phytoplasmas. Actual and virtual RFLP analyses of the 16S rDNA sequences enabled us to classify two HLB phytoplasma strains as members of the aster yellows group (16SrI) ‘Candidatus Phytoplasma asteris’, which was confirmed by phylogenetic analysis. The HLB phytoplasma strain identified from Nayarit (HLBpc-Nay-IB) belongs to subgroup B (16SrI-B), and the strains identified from Colima (HLBpc-Col-IS) and Sinaloa (HLBpc-Sin-IS) belong to subgroup S (16SrI-S). The partial ‘Ca. L. asiaticus’ rplA-rplJ gene sequences were 100% identical to the ‘Ca. L. asiaticus’ strains isolated from several countries affected by HLB. These results confirm the association of ‘Candidatus Phytoplasma asteris’ with HLB-like symptoms in citrus groves in Mexico. Nonetheless, further studies are required to fully describe the ‘Ca. L. asiaticus’ and ‘Ca. P. asteris’ interactions in citrus, which will greatly assist the design of efficient management strategies.     

Identification and molecular characterization of phytoplasmas and rickettsia pathogens associated with ‘Bunchy Top Symptom’ (BTS) and ‘Papaya Bunchy Top’ (PBT) of papaya in Cuba

Two different papaya diseases have been previously reported in Cuba, Bunchy Top Symptom (BTS) associated with a phytoplasma of group 16SrII ‘Candidatus Phytoplasma aurantifolia’ and Papaya Bunchy Top (PBT), associated with a rickettsia. Regarding the regional phytosanitary impact of both diseases for the papaya crop, the present study investigated the occurrence of BTS and PBT in papaya fields in Cuba, and the possible mixed infection of phytoplasma and rickettsia pathogens associated. Papaya plants showing symptoms of BTS or PBT or both, were collected in Las Tunas and Havana provinces from January 2009 to February 2010, and evaluated for phytoplasma and rickettsia by PCR with primers targeting the 16S ribosomal RNA and the rickettsial succinate deshydrogenase (sdhA) genes, respectively. Phytoplasmas and rickettsia were individually detected in 76/86 BTS-symptomatic and 22/22 PBT-symptomatic papaya plants, and simultaneously detected in 5/86 (5.81%) of the BTS-symptomatic and 17/22 (77.27%) of the PBT-symptomatic plants. Conventional and virtual RFLP analyses of the 16S rDNA sequences revealed the presence of phytoplasmas of group 16SrI ‘Candidatus Phytoplasma asteris’ and 16SrII in papaya plants affected by BTS and PBT, and identified two new phytoplasma subgroups, 16SrI-X and 16SrII-N in papayas fields of Las Tunas, which was confirmed by phylogenetic analysis. The partial rickettsia sdhA gene sequences were 100% identical to that of the rickettsia associated with PBT in Puerto Rico. Results confirm that phytoplasmas are consistently associated with both BTS and PBT symptoms, and that mixed infections of phytoplasma and rickettsia pathogens can occur in either BTS or PBT-affected papaya fields, which implies new epidemiological constraints for the disease control.     

海南槟榔黄化植原体分子检测及其系统发育关系研究

由植原体引起的槟榔黄化病是海南特色经济作物槟榔种植上的一种毁灭性病害。本研究通过PCR扩增测序、序列多重比对和系统发育分析,对海南部分代表性地区槟榔致死性病原植原体的序列信息与系统发育关系进行检测分析。结果表明：本研究检测的保亭、屯昌、万宁等海南部分代表性地区的槟榔黄化植原体的16S rDNA序列一致;BLAST分析表明各株系16S rDNA与16SrI组植原体同源性为100%。序列多重比对分析表明,本研究各槟榔黄化植原体株系与海南苦棟丛枝、长春花绿变、马松子变叶、辣椒黄化皱缩、蛇婆子丛枝、细圆藤丛枝和日本洋葱黄化、美国翠菊黄化等植原体同源性为100%;与已报道的海南万宁、印度、海南三亚的槟榔黄化植原体16S rDNA序列同源性分别为99.9%、99.9%、99.8%。系统发育分析表明,本研究槟榔黄化植原体与海南苦棟丛枝、长春花绿变、马松子变叶、辣椒黄化皱缩、蛇婆子丛枝、细圆藤丛枝等株系聚于一个分枝,支持率为100%。此外,在发病槟榔叶片、花穗、心叶等组织部位均可检测到植原体。研究结果表明,海南槟榔黄化植原体与海南苦棟丛枝、长春花绿变、马松子变叶、辣椒黄化皱缩、蛇婆子丛枝、细圆藤丛枝等植原体株系的同源性极高,槟榔黄化病很可能会以这些寄主植物作为病原传播载体进行传播扩散。     

海南省槟榔病理性黄化发生分布情况及其植原体检测分析

槟榔是海南省重要的热带经济作物,受多种病害组成的槟榔病理性黄化的影响,尤其是槟榔黄化病,使槟榔产量造成严重损失。为明确当前海南省槟榔病理性黄化的发生分布情况及槟榔黄化病的危害情况,本研究对全省槟榔病理性黄化的发生分布进行调查,并对全省采集的槟榔黄化样品进行植原体检测分析。结果显示,当前海南省槟榔病理性黄化发生面积为38 300.04 hm²,占全省槟榔种植面积的33.27%,主要发生在海南东部、南部及中部市（县）,三亚市发生率最高,为77.48%,万宁市发生面积最大,为9734.66 hm²,西部市（县）的病理性黄化发生率均低于10%;当前海南省槟榔黄化病发生面积为32 102.38 hm²,占全省槟榔种植面积的27.89%,全省各市（县）均有槟榔黄化病发生,主要在海南中部和东部地区的发病率较高,琼海市、定安县、文昌市、屯昌县及琼中县的植原体检出率分别高达100%、100%、100%、98%、95.38%,除临高县、白沙县及东方市外,其余市（县）检出率均高于50%,万宁市槟榔黄化病发生面积最大,为7909.41 hm²,其次为琼海市;每个市（县）槟榔植原体在各树体间的含量分布差异较大,定安县植原体的平均含量最高,为1443.36 copies/μL,向周边市（县）递减,除了在海南东北部市（县）的槟榔植原体含量较高外,其他市（县）植原体含量较低。以上研究表明,当前海南槟榔病理性黄化发生严重,植原体是造成海南省槟榔病理性黄化的主要病原之一。     

Preliminary investigation and detection based on loop-mediated isothermal amplification (LAMP) of phytoplasmas associated with diseases in B. napus L.

In the last decade, some disease occurred on our experimental farms that had caused serious losses. They were not caused by fungi, bacteria or viruses. By loop-mediated isothermal amplification (LAMP) technique, the detection results pointed to the possible pathogen as phytoplasma. The investigation results implied that phytoplasmas could cause more than 13 kinds of symptoms in almost all parts of plants in B. napus L., including witches’ broom, multi-stems, aggregate main inflorescences, and flat stems. The incidences of these phytoplasma-associated diseases in our experimental farms rose from 1.61% in 2010 to 6.00% in 2021. Some phytoplasma infected plants died without any growing points. These studies would be helpful for detecting phytoplasmas diseases, selecting disease resistant germplasm and improving varieties with disease resistances in B. napus L.     

苦楝丛枝病植原体海南株系SecY基因序列分析及亚组分类

利用植原体16SrⅠ组通用引物对secYF1／secYR1,应用PCR技术从采白海南省儋州地区的表现典型丛枝症状的苦楝植株总DNA中扩增到约1．4kb的特异片段,将此片段克隆后进行序列测定,序列分析及系统关系树构建的结果表明,该片段长1358bp,苦楝丛枝病海南株系（Chinaberry witches＇-broom phytoplasma strain Hainan,CWB-Hn）与玉米丛矮（Maize bushy sttmt,MBS）植原体聚类在同一条进化枝上;AluⅠ,MseⅠ和Tsp509Ⅰ这3种酶的电子酶切图谱表明,CWB-Hn与MBS的酶切图谱一致,故初步判定苦楝丛枝病植原体海南株系属于secY-L亚组,在亚组水平上进一步明确了苦楝丛枝病植原体海南株系的分类地位。     

The incidence of stolbur disease and associated yield losses in vegetable crops in South Moravia (Czech Republic)

The study was performed at a vegetable farm from 2006 to 2008 in the intensive horticultural area of Lednice (South Moravia, Czech Republic), where a stolbur (phytoplasma) epidemic had occurred. The study showed that the incidence of stolbur disease reached 15% in both tomato (Lycopersicon esculentum) and pepper (Capsicum annuum), and up to 6.7% in celeriac (Apium graveolens). There were significant yield losses in the stolbur-affected plants; total yield losses were up to 60% in tomato, 93% in pepper, and 100% in celeriac. The mean yield was significantly decreased in stolbur-affected plants, compared to healthy plants (i.e. from 42.79 to 17.21 fruits per plant in tomatoes; from 10.11 to 0.74 fruits per plant in peppers). In the locality studied, it was mainly the weed plants Convolvulus arvensis and Cirsium arvense (which were frequently interspersed among the crops), which tested positive for the stolbur phytoplasma and might have provided a reservoir for the phytoplasma infection.     

海南长春花小叶病植原体16S rDNA基因片段的比较分析

从海南儋州地区的长春花上采集了表现小叶症状,疑似植原体感染的病样,利用植原体165 rDNA通用引物对R16mF2/R16mR1,应用PCR技术从该样品的总DNA提取物中扩增到预期大小的特异片段(约1.4kb),该片段的序列分析及系统关系树构建的结果表明,该片段与16Sr Ⅰ组中的植原体同源率均达到99%以上,而与其它组的植原体16S rDNA序列的同源率均低于96%,与16Sr Ⅰ组植原体缬草黄化、翠菊黄化、桑萎缩和玉米丛矮等在同一条进化枝上.故初步认为引起海南长春花小叶病的植原体应归属于16Sr Ⅰ组,将其暂命名为长春花小叶植原体海南株系(Periwinkle little leaf phytoplasma strain Hainan,PLL-Hn).     

Activity of benzothiadiazole on chrysanthemum yellows phytoplasma (‘Candidatus Phytoplasma asteris’) infection in daisy plants

A commercial preparation of the plant resistance elicitor benzothiadiazole (BTH) (Bion, Syngenta Crop Protection) was tested for its capacity to induce systemic resistance against chrysanthemum yellow phytoplasma (CYP) infection in the Chrysanthemum carinatum plant. Following one 2.4 mM BTH application, plants were exposed to CYP-infective Macrosteles quadripunctulatus leafhoppers. Symptom development and phytoplasma multiplication in the test plants were measured over time. BTH application delayed symptom development and phytoplasma multiplication in treated plants compared with the control ones. CYP titre and symptom severity were significantly lower for the first two weeks post-inoculation in treated plants compared with the control ones, suggesting that systemic acquired resistance (SAR) induced by BTH in C. carinatum is temporary. Higher concentrations of BTH resulted in phytotoxic effects involving the whitening of apical leaves. BTH application was ineffective in reducing the transmission efficiency of CYP by its leafhopper vector. Actually, in both single and group transmission tests, the proportion of infected plants was similar among BTH-treated and untreated plants. The survival of M. quadripunctulatus was unaffected by feeding on BTH-treated daisy plants. Moreover, when leafhoppers were allowed to choose between treated and untreated plants, they showed no preference. We conclude that SAR induced in daisy plants by BTH has no detrimental effects on the vector leafhopper. If the activity of BTH against phytoplasmas is confirmed also on other phytoplasma/host–plant associations, BTH applications might be included in new, more environmentally friendly, integrated management strategies of phytoplasmoses.     

Morphological identification of foodborne pathogens colonizing rice grains in south Asia

The aim of this study was to identify the foodborne pathogens mainly, Aspergillus sp. colonizing rice grains using cultural and microscopic methods. Four differential media (Czapek Dox Agar (CZA), Czapek Yeast Agar (CYA), Malt Extract Agar (MEA) and Czapek yeast 20% sucrose agar (CYA20S)) were used for differentiation of five Aspergillus sp., colonizing rice grains comparing with standard cultures. We studied macroscopic (colony color and diameter, conidia color, exudates, sclerotia and colony texture) and microscopic (conidiophore color, length and breadth, conidia size, shape and surface texture, vesicle diameter and phialides length and breadth) characteristics for identification of 110 isolates of Aspergillus sp. isolated from 65 rice grain samples collected from various countries in South Asia (Cambodia, India, Indonesia, Malaysia and Thailand). According to morphological characters, all these isolates were belonging to Aspergillus flavus (45), A. fumigatus (8), A. ochraceus (7), A. niger (42) and A. tamarii (8). This is the first report on identification of large number of Aspergillus strains isolated from rice grains in South Asia.     

西沙群岛维管植物资料增补（I）

2018年5、6月份对西沙群岛的永兴岛、石岛、赵述岛、西沙洲、南沙洲、中沙洲、北沙洲、北岛、中岛和南岛共10个岛屿的植物资源进行了野外考察、标本采集、鉴定以及文献查阅,共记录西沙群岛维管植物90科406种,确定西沙群岛未记录野生维管植物52种,新归化植物10种,新增栽培植物87种,隶属于59科130属,凭证标本保存于中国热带农业科学院植物标本室ATCH。西沙群岛原记录维管植物398种,在此次调查的基础上,结合相关文献资料及植物标本进行统计,西沙群岛维管植物共计101科352属543种,其中野生植物292种,栽培植物251种。此研究为西沙群岛植物资源提供了重要信息。     

国内油料作物市场整合关系研究

市场整合是衡量市场机制效率的重要指标,研究国内油料作物空间市场整合关系有利于宏观把握市场的运行情况,对优化地区分工和提高资源配置效率具有重要意义。本文以油菜籽、花生和芝麻为例,依次使用Johansen协整分析、向量误差修正模型和格兰杰因果检验,系统分析了国内油料作物的空间市场整合关系。研究表明：从长期来看,油菜籽、花生和芝麻的市场价格之间关联较为密切,国内油料作物市场存在长期整合关系;从短期来看,国内油料作物市场的短期整合程度较高,根据调整速度,从高到低依次是花生、油菜籽和芝麻;从因果关系来看,70%的油菜籽、57.14%的花生和30%的芝麻市场价格之间存在双向因果关系,说明市场价格信息并非完全对称传递。为提高国内油料作物市场整合程度,本文分别提出了改善市场环境、完善信息平台建设和加强构建现代物流体系的建议。     

Morphological and DNA Barcoding Evidence for Invasive Pest Thrips,Thrips parvispinus (Thripidae: Thysanoptera), Newly Recorded From India

South East Asia pest thrips species, Thrips parvispinus (Karny), is a serious pest on a number of agricultural and horticultural crops in a number of plant families. Based on an integrated approach of morphology and DNA barcoding, invasion of this serious pest is reported first time from India on papaya plantations. Molecular data have corroborated with the morphological identification. Haplotyping data suggested that the Indonesia may be a probable source of invasion of this pest to India.     

福建水生植物浮萍的形态学和分子系统学鉴定及遗传多样性研究

在福建53个市县(区)收集获得119份浮萍种质。通过叶片大小、根系和叶脉数等形态性状初步鉴定为4个属:少根紫萍属(Landoltia)、多根紫萍属(Spirodela)、无根萍属(Wolffia)、浮萍属(Lemna)。利用叶绿体atp F-atp H间隔序列和rp S16内含子序列进行系统发育分析。结果表明,119份浮萍种质分别属于4个种Landoltia punctata,Spirodela polyrhiza,Wolffia globosa,Lemna aequinoctialis。利用DnaSP 5.10.01软件分析结果显示,福建浮萍种质存在丰富的遗传多样性,且rpS16比atp F-atpH多样性大,两者的核苷酸多态性指数分别为0.051 23和0.031 53,每kb平均核苷酸差异数为44.675和20.374,群体突变率分别为0.051 64和0.036 40,单倍型多态性指数分别为0.617和0.577。稀脉萍、无根萍和多根紫萍基于atpF-atpH和rp S16序列的单倍型数为4、2、2。另外,闽南地区浮萍遗传多样性高于闽北地区,其核苷酸多态性指数、每kb核苷酸变异数以及群体突变率分别是闽北地区的2倍以上。     

青枯雷尔氏菌在不同作物根际定殖与轮作防病

青枯病是芝麻和花生的重要病害之一。为探索合理的轮作防控模式,运用青枯雷尔氏菌（Ralstonia sola⁃ nacearum）抗利福平标记菌株JXS02-L土壤接种,测定菌株在芝麻、花生、甘薯、大豆、玉米和小葱等6种作物根际土 壤和根部的定殖与消长动态,分析了不同轮作模式对芝麻/花生青枯病发生程度的影响。结果表明：播种后3w,6种 作物根际土壤菌量均低于初始接种菌量;播种后6 w,芝麻、花生、甘薯根际土壤菌量已上升至初始接种菌量水平 （3.20 ×106~4.93×106 CFU·g-1）,之后菌量持续上升,大豆、玉米根际土壤菌量则持续下降;播种后12 w,大豆、玉米根 际土壤菌量比芝麻、花生、甘薯根际土壤菌量低4个数量级,小葱植种后6 w~12 w,均未检测到病菌。播种后3 w~ 12 w,芝麻、花生和甘薯根部菌量持续上升,大豆和玉米根部菌量先升后降;至播种后12w,大豆和玉米根部菌量比 芝麻、花生和甘薯根部菌量低5个数量级,小葱根部则始终未检测到病菌。芝麻-大豆-小葱-芝麻、芝麻-大豆-玉 米-芝麻2种轮作模式芝麻青枯病病情指数比芝麻-花生-甘薯-芝麻轮作模式分别降低19.95%、12.87%;花生-大 豆-玉米-花生轮作模式花生青枯病病株率比花生-芝麻-甘薯-花生轮作模式降低11.63%。本研究结果对于了解 青枯雷尔氏菌的生态多样性,以及指导青枯病的科学防控具有重要意义。     

海南长春花变叶病病原物的分子鉴定

本研究分别利用植原体16S rDNA和核糖体蛋白(ribosomal protein,rp)基因的通用引物对自然表现变叶症状的海南长春花样品总DNA进行PCR扩增,获得16S rDNA基因片段长为1 432 bp,rp基因片段长为1 211 bp。BLAST程序比较、系统进化树构建及iPhyClassifier分析表明:海南长春花变叶病是由植原体引起的,该植原体株系属于16S rⅠ-B亚组,与候选种Ca.Phytoplasma asteris相关,将其暂命名为长春花变叶病植原体海南株系(Periwinkle phyllody strain Hainan,PP-Hn)。     

Soil Salinity in South India: Problems and Solutions

SUMMARY

Soil salinity is assuming menacing proportions for production of agricultural and horticultural crops in South India. South India comprises of Andhra Pradesh (AP), Tamil Nadu (TN), Karnataka, Kerala, Goa, and Islands in Bay of Bengal (Andaman and Nicobar) and Arabian Sea (Lakshadweep). It comprises central uplands, Deccan plateau (Karnataka plateau and Telangana plateau of AP), Nilgiri hills of TN, South Sahiailri, Eastern hills (Eastern Ghats, TN, upland) and Coastal Plains. The rainfall ranges from 400 to 500 mm in AP, 450 to 1300 mm in Karnataka, 500 to 1215 mm in TN, 100 to 450 mm in Kerala. Climate is mainly semi-arid in nature. Red soils (Alfisols, Inceptisols, and Entisols) make up about 60–65% and are well drained, blacksoils (Vertisols and Inceptisols) comprise about 20–25% and the rest are coastal sands. Soil salinity problems are encountered in almost all the districts in Karnataka and AP. The area extends to about 0.176 million ha in AP, 0.2 million ha in Karnataka, 0.0427 million ha in TN and about 0.03 million ha in Kerala. Introduction of canal irrigation water and use of underground saline waters accelerated the appearance of salt affected soils. Soil salinity observed in South India ranges from hydrometphic saline soils in Kerala to highly saline (EC 20–30 dS m^?1) in Karnataka and AP. Saline soils were classified in to Natrargids or Solarthrids at subgroup level depending on the occurance of nitric or salic horizon within few centimetres of the surface. Soil salinity has reduced crop yields upto 50% and consequently cropping has been abandoned in many areas. Excess soluble salts can be removed through scrapping the surface salt crust or flushing and leaching or through subsurface drainage depending on the problem. Crops also vary in their ability to tolerate salinity at different stages of growth. In most crops subjected to irrigations with saline waters, germination and early seedling stages are generally the most sensitive and their tolerance increases with age. Salt tolerant varieties and nutrient management of crops in saline soils are important solutions for crop production under saline soils.