Resistant Radish Research Articles

Inoculation of chromium-tolerant bacterium LBA108 to enhance resistance in radish (Raphanus sativus L.) and combined remediation of chromium-contaminated soil.

Cr(VI) has been a carcinogen for organisms and a hazard to human health throughout the food chain. To explore a cost-effective and efficient method for removing Cr(VI), a Cr-resistant strain named LBA108 was isolated from the soil of a molybdenum-lead mining area. It was identified as Microbacterium through biochemical tests and 16S rDNA sequence analysis. Following 48 hours of incubation in LB culture medium containing 60 mg L-1 Cr(VI), the LBA108 strain exhibited reduction and adsorption rates for Cr(VI) at 96.64% and 15.86%, respectively. The removal mechanism was subsequently confirmed through Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction analysis. In an experimental setup, radish seedlings were cultivated as test crops under varying levels of Cr stress (ranging from 0 to 7 mg L-1) in a hydroponic experiment. With the inoculation of the LBA108 strain, the fresh weight of radish seedlings increased by 2.05 times and plant length increased by 34.5% under 7 mg L-1 Cr stress. In addition, the plant produced more antioxidant enzymes/enhanced antioxidant enzyme activities such as superoxide dismutase and catalase to prevent oxidative stress. Under Cr stress (6 mg L-1), the accumulation of Cr in rhizomes of radish seedlings increased compared to the control group by 91.44%, while the absorption of Cr by leaves decreased by 52.10%. These findings suggest that the LBA108 strain possesses bioremediation capabilities as a microbial-phytoremediation option for Cr-contaminated soil.

Silicon quantum dots promote radish resistance to root herbivores without impairing rhizosphere microenvironment health

Soil-applied silicon quantum dots (Si QDs) significantly increased radish taproot resistance against white grubs and simultaneously shaped a healthy rhizosphere microenvironment.

Genome-Wide Characterization of the Aquaporin Gene Family in Radish and Functional Analysis of RsPIP2-6 Involved in Salt Stress.

Aquaporins (AQPs) constitute a highly diverse family of channel proteins that transport water and neutral solutes. AQPs play crucial roles in plant development and stress responses. However, the characterization and biological functions of RsAQPs in radish (Raphanus sativus L.) remain elusive. In this study, 61 non-redundant members of AQP-encoding genes were identified from the radish genome database and located on nine chromosomes. Radish AQPs (RsAQPs) were divided into four subfamilies, including 21 plasma membrane intrinsic proteins (PIPs), 19 tonoplast intrinsic proteins (TIPs), 16 NOD-like intrinsic proteins (NIPs), and 5 small basic intrinsic proteins (SIPs), through phylogenetic analysis. All RsAQPs contained highly conserved motifs (motifs 1 and 4) and transmembrane regions, indicating the potential transmembrane transport function of RsAQPs. Tissue- and stage-specific expression patterns of AQP gene analysis based on RNA-seq data revealed that the expression levels of PIPs were generally higher than TIPs, NIPs, and SIPs in radish. In addition, quantitative real-time polymerase chain reaction (qRT-PCR) revealed that seven selected RsPIPs, according to our previous transcriptome data (e.g., RsPIP1-3, 1-6, 2-1, 2-6, 2-10, 2-13, and 2-14), exhibited significant upregulation in roots of salt-tolerant radish genotype. In particular, the transcriptional levels of RsPIP2-6 dramatically increased after 6 h of 150 mM NaCl treatment during the taproot thickening stage. Additionally, overexpression of RsPIP2-6 could enhance salt tolerance by Agrobacterium rhizogenes-mediated transgenic radish hairy roots, which exhibited the mitigatory effects of plant growth reduction, leaf relative water content (RWC) reduction and alleviation of O2– in cells, as shown by nitro blue tetrazolium (NBT) staining, under salt stress. These findings are helpful for deeply dissecting the biological function of RsAQPs on the salt stress response, facilitating practical application and genetic improvement of abiotic stress resistance in radish.

Identification of Novel Locus RsCr6 Related to Clubroot Resistance in Radish (Raphanus sativus L.).

Clubroot is a devastating disease that causes substantial yield loss worldwide. However, the inheritance and molecular mechanisms of clubroot resistance during pathogen infection in radish remain largely unclear. In this study, we investigated the inheritance of clubroot resistance in the F2 population derived from crossing clubroot-resistant (CR) and clubroot-susceptible inbred lines “GLX” and “XNQ,” respectively. Genetic analysis revealed that a single dominant gene controlled the clubroot resistance of “GLX” with a Mendelian ratio of resistance and susceptibility of nearly 3:1. Bulked segregant analysis combined with whole-genome resequencing (BSA-seq) was performed to detect the target region of RsCr6 on chromosome Rs8. Linkage analysis revealed that the RsCr6 locus was located between two markers, HB321 and HB331, with an interval of approximately 92 kb. Based on the outcomes of transcriptome analysis, in the RsCr6 locus, the R120263140 and R120263070 genes with a possible relation to clubroot resistance were considered candidate genes. In addition, three core breeding materials containing the two reported quantitative trait loci (QTLs) and our novel locus RsCr6 targeting clubroot resistance were obtained using marker-assisted selection (MAS) technology. This study reveals a novel locus responsible for clubroot resistance in radishes. Further analysis of new genes may reveal the molecular mechanisms underlying the clubroot resistance of plants and provide a theoretical basis for radish resistance breeding.

Effects of inorganic and organic selenium intervention on resistance of radish to arsenic stress

Arsenic (As) pollution, a potential threat for human health, in vegetables is one of the primary sources of As intake by the human body. In the Pot Experiment, the As content, physiological index and antioxidant enzyme activity of radish were determined. The results demonstrated that the order of As concentration in radish tissues was roots > stems > leaves. Organic selenium (Se) can inhibit the absorption of arsenic in radish more effectively than inorganic Se. The application of organic Se and low concentration of selenite (Se(IV)) significantly enhanced the stress resistance of radish for increasing superoxide dismutase and peroxidase activity, increasing soluble protein, chlorophyll and proline content, and reducing malondialdehyde content. In contrast, the high concentration of Se(IV) and selenate (Se(VI)) treatment group demonstrated stress and toxicological effects on radish. This study provides an idea for further research on the remediation mechanism of Se to As toxicity and provides a reference for the adoption of Se fertilizer in agriculture.

Comparative transcriptome analysis reveals distinct responsive biological processes in radish genotypes contrasting for Plasmodiophora brassicae interaction

Plasmodiophora brassicae is a protozoan pathogen that causes clubroot disease, which is one of the most destructive diseases for Brassica crops, including radish. However, little is known about the molecular mechanism of clubroot resistance in radish. In this study, we performed a comparative transcriptome analysis between resistant and susceptible radish inoculated with P. brassicae. More differentially expressed genes (DEGs) were identified at 28 days after inoculation (DAI) compared to 7 DAI in both genotypes. Gene ontology (GO) and KEGG enrichment indicated that stress/defense response, secondary metabolic biosynthesis, hormone metabolic process, and cell periphery are directly involved in the defense response process. Further analysis of the transcriptome revealed that effector-triggered immunity (ETI) plays key roles in the defense response. The plant hormones jasmonic acid (JA), ethylene (ET), and abscisic acid (ABA) related genes are activated in clubroot defense in the resistant line. Auxin (AUX) hormone related genes are activated in the developing galls of susceptible radish. Our study provides a global transcriptional overview for clubroot development for insights into the P. brassicae defense mechanisms in radish.

The Use of Genitors in Biotic Stress Resistant Radish Breeding Program

Turp (Raphanus sativus L.), Brassicaceae (Lahanagiller) familyasının içinde yer alan önemli bir sebzedir. Lahanagil grubu sebze türleri içerisinde kültüre alınan en eski türdür. Turplar şekil ve irilik özellikleri yönünden çok geniş bir genetik vasyasyona sahiptir. Günümüzde turp yetiştiriciliğinde biyotik stres (hastalık ve zararlı etmenleri vb.) faktörleri nedeniyle önemli düzeylerde verim ve kalite kayıpları meydana gelmektedir. Turp yetiştiriciliğinde en yaygın olarak gözlemlenen hastalıklar; beyaz pas, Fusarium solgunluğu, mildiyö ve şalgam mozaik virüsü olarak sıralanabilir. Ayrıca turplar; kök, gövde ve yaprakları ile beslenen lahana kurdu, turp afiti, kök lezyon nematodu gibi birçok zararlının da tehlikesi ve tehdidi altındadır. Genetik kaynaklar, çeşit ıslah çalışmalarının başarıya ulaşmasında en önemli faktörlerden birisi olan fenotipik varyasyonun temelini oluşturmaktadır. Ayrıca halihazırda ticareti yapılan turp çeşitlerinde bulunmayan dayanıklılık genleri, yabani ve farklı alt varyetelerde bulunabilmektedir. Son yıllarda turp bitkisinde mevcut genetik kaynaklardan yararlanılarak hibrit çeşit ıslahı çalışmalarında hastalık ve zararlılara karşı tolerant yeni genotiplerin geliştirilmesi ve tolerantlıkta rol alan mekanizmaların belirlenmesine yönelik çalışmalara daha fazla önem verilmeye başlanmıştır. Bu derlemede turp ıslah programlarında dayanıklılık kaynağı olarak yararlanılan genitörler ve hastalık ve zararlılara karşı tolerant yeni genotiplerin geliştirilmesi konusunda yapılan ıslah çalışmaları derlenmiştir.

Genome-wide identification and characterization of NBS-encoding genes in Raphanus sativus L. and their roles related to Fusarium oxysporum resistance

BackgroundThe nucleotide-binding site–leucine-rich repeat (NBS-LRR) genes are important for plant development and disease resistance. Although genome-wide studies of NBS-encoding genes have been performed in several species, the evolution, structure, expression, and function of these genes remain unknown in radish (Raphanus sativus L.). A recently released draft R. sativus L. reference genome has facilitated the genome-wide identification and characterization of NBS-encoding genes in radish.ResultsA total of 225 NBS-encoding genes were identified in the radish genome based on the essential NB-ARC domain through HMM search and Pfam database, with 202 mapped onto nine chromosomes and the remaining 23 localized on different scaffolds. According to a gene structure analysis, we identified 99 NBS-LRR-type genes and 126 partial NBS-encoding genes. Additionally, 80 and 19 genes respectively encoded an N-terminal Toll/interleukin-like domain and a coiled-coil domain. Furthermore, 72% of the 202 NBS-encoding genes were grouped in 48 clusters distributed in 24 crucifer blocks on chromosomes. The U block on chromosomes R02, R04, and R08 had the most NBS-encoding genes (48), followed by the R (24), D (23), E (23), and F (17) blocks. These clusters were mostly homogeneous, containing NBS-encoding genes derived from a recent common ancestor. Tandem (15 events) and segmental (20 events) duplications were revealed in the NBS family. Comparative evolutionary analyses of orthologous genes among Arabidopsis thaliana, Brassica rapa, and Brassica oleracea reflected the importance of the NBS-LRR gene family during evolution. Moreover, examinations of cis-elements identified 70 major elements involved in responses to methyl jasmonate, abscisic acid, auxin, and salicylic acid. According to RNA-seq expression analyses, 75 NBS-encoding genes contributed to the resistance of radish to Fusarium wilt. A quantitative real-time PCR analysis revealed that RsTNL03 (Rs093020) and RsTNL09 (Rs042580) expression positively regulates radish resistance to Fusarium oxysporum, in contrast to the negative regulatory role for RsTNL06 (Rs053740).ConclusionsThe NBS-encoding gene structures, tandem and segmental duplications, synteny, and expression profiles in radish were elucidated for the first time and compared with those of other Brassicaceae family members (A. thaliana, B. oleracea, and B. rapa) to clarify the evolution of the NBS gene family. These results may be useful for functionally characterizing NBS-encoding genes in radish.

Target‐site resistance and cross‐resistance to ALS‐inhibiting herbicides in radish and wild radish biotypes from Brazil

AbstractRadish (Raphanus sativus L.) and wild radish (R. raphanistrum L.) are troublesome agricultural weeds in several areas worldwide, with populations resistant to acetolactate synthase (ALS) inhibitor herbicide. Information on the mechanisms of resistance is important for management and developing novel solutions to control resistant populations. The objective of this work was to determine the ALS‐resistance mechanisms in radish and wild radish biotypes resistant to ALS‐inhibiting herbicides. Resistance levels were determined by dose‐response curve using several rates of metsulfuron‐methyl herbicide in susceptible (JUC1) and resistant (JUC2, CRA3) radish, and susceptible (CAF1) and resistant (CAF2, CAF3) wild radish biotypes. The mechanism was evaluated by the in vitro activity of the ALS enzyme with imazapic herbicide and ALS gene sequencing. All resistant biotypes were insensitive to metsulfuron‐methyl and imazapic herbicides. The rate of metsulfuron‐methyl to reduce 50% growth of the plants (GR50) were 17‐ to 60‐fold (JUC2, CRA3) and 9‐ to 21‐fold (CAF2 and CAF3) higher than the susceptible biotypes of radish and wild radish, respectively. One‐point mutation in the ALS gene, Trp‐574‐Leu, was found in all resistant radish biotypes, whereas a second point mutation, Ala‐360‐Ser, was found in CAF2, CAF3, and JUC2 resistant biotypes. Changes in kinetic parameters of the ALS enzyme were found in all resistant biotypes evaluated, causing reduction of the herbicide affinity in the target‐site of action. Trp‐574‐Leu amino acid substitution resulted in resistance to sulfonylurea, imidazolinone, and triazolopyrimidine groups, with the survival greater than 75% of the plants, depending on the herbicide applied at labeled rate.

Fine-mapping of a major QTL (Fwr1) for fusarium wilt resistance in radish.

A major radish QTL (Fwr1) for fusarium wilt resistance was fine-mapped. Sequence and expression analyses suggest that a gene encoding a serine/arginine-rich protein kinase is a candidate gene for Fwr1. Fusarium wilt resistance locus 1 (Fwr1) is a major quantitative trait locus (QTL) mediating the resistance of radish inbred line 'B2' to Fusarium oxysporum, which is responsible for fusarium wilt. We previously detected Fwr1 on radish linkage group 3 (i.e., chromosome 5). In this study, a high-resolution genetic map of the Fwr1 locus was constructed by analyzing 354 recombinant F2 plants derived from a cross between 'B2' and '835', the latter of which is susceptible to fusarium wilt. The Fwr1 QTL was fine-mapped to a 139.8-kb region between markers FM82 and FM87 in the middle part of chromosome 5. Fifteen candidate genes were predicted in this region based on a sequence comparison with the 'WK10039' radish reference genome. Additionally, we examined the time-course expression patterns of these predicted genes following an infection by the fusarium wilt pathogen. The ORF4 expression level was significantly higher in the resistant 'B2' plants than in the susceptible '835' plants. The ORF4 sequence was predicted to encode a serine/arginine-rich protein kinase and includes SNPs that result in nonsynonymous mutations, which may have important functional consequences. This study reveals a novel gene responsible for fusarium wilt resistance in radish. Further analyses of this gene may elucidate the molecular mechanisms underlying the fusarium wilt resistance of plants.

Construction of a high-density genetic linkage map and identification of quantitative trait loci associated with clubroot resistance in radish (Raphanus sativus L.)

Clubroot is a devastating disease caused by Plasmodiophora brassicae, leading to substantial yield loss of cruciferous plants, especially radish (Raphanus sativus) in China. Thus, there is a need to elucidate the mechanisms underlying the pathogenicity of P. brassicae and to breed clubroot-resistant radish cultivars. In the present study, we constructed a high-density linkage map of R. sativus by restriction-site-associated DNA sequencing (RAD-Seq) using an F2 population derived from a cross between the clubroot-resistant and clubroot-susceptible inbred lines “BJJ” and “XNQ,” respectively. The genetic map spans 794.3 cM and has 1148 SNPs distributed across nine linkage groups corresponding to the nine chromosomes of R. sativus. The average distance between the adjacent markers is 0.7 cM. A set of five QTLs (viz., RsCr1, RsCr2, RsCr3, RsCr4, and RsCr5) associated with resistance to clubroot was detected on chromosomes 8 and 9. The limit of detection values of quantitative trait loci (QTLs) ranged from 5.23 to 7.65, accounting for 7.26–31.38% of the observed phenotypic variance. Synteny analysis showed that RsCr1 is homologous to the clubroot resistance gene Crr1 in Brassica rapa. This high-density genetic map of R. sativus provides valuable information for clubroot resistance gene selection and resistant variety breeding, while the QTL mapping results provide a reference dataset for effective gene exploration and marker-assisted breeding programs.

Transcriptome profiles underlying the spermidine-elevated resistance to high temperature in the radish Raphanus sativus

Radish is a common crop and vulnerable to high temperature. Pretreatment with spermidine could effectively elevate the resistance of radish to high temperature. Up to date, the underlying mechanisms remain unknown. In the present study, radish seedlings were pretreated with spermidine and then exposed to high temperature. The leaves were collected for transcriptome sequencing and the results were compared with samples only exposed to high temperature and samples consistently cultured at normal temperature. The differentially expressed genes were identified and validated using real-time quantitative PCR. Finally, the results revealed that pretreatment with spermidine significantly up-regulated the transcription level of anti-oxidation enzymes, heat-shock proteins, and proteins involved in the photosynthetic process, in comparison with treatments with high temperature and room temperature, suggesting that pretreatment with spermidine increased heat tolerance in radish probably through minimizing the harms caused by peroxidation, accelerating the corrections or degradation of misfolded proteins, and promoting photosynthesis. These findings preliminarily uncovered the molecular mechanisms underlying the spermidine-promoted heat resistance in radish.

무 시들음병에 대한 간편한 대량 저항성 검정법 개발

Root-dipping inoculation method has been used to investigate resistance of radish plants to Fusarium wilt. However, the method requires a lot of labor and time because of complicate procedure. This study was conducted to establish a simple and effective mass-screening method for resistant radish to Fusarium wilt. Radish seedlings of susceptible and resistant cultivars were used to investigate wounding method by scalpel, inoculum concentration, and pathogen-inoculated growth stage of seedlings. We established an efficient mass-screening method based on our results as following: Roots of 14-day-old seedlings of radish are cut with a scalpel at a 90° angle to a 2 cm-depth at a 1 cm-distance from main stem and then inoculated by pouring with a 10 ml-aliquot of a fungal spore suspension (1.0×107 conidia/ml) on soil. The inoculated plants are cultivated in a growth room at 25°C for about 4 weeks with 12-hour light a day. The proposed screening method enables to effectively select resistant from mass radish plants cultivars to Fusarium wilt.

Clomazone safenering with dietholate, bentazon protection against ALS inhibitors, and seed quality cost due to weed resistance

In a current research, SCHMITZ et al. (2018) elucidated the possibility of using the herbicide clomazone associated to the safener dietolate to control ryegrass and wild radish resistance to herbicides inhibitors of EPSPs, ACCase, and ALS in wheat crops. Basically, authors tested doses of dietholate ranged from 120 to 480 g (for each 100 kg of wheat seeds cv. Itaipu) and three doses of clomazone (198, 396, and 594 g ha-1. Authors found treatment of wheat seeds with dietholate did not interfere in ryegrass control and wild radish by clomazone applied in pre-emergence. Moreover, even applying at low doses, clomazone controlled ryegrass and it can be used to control resistant biotypes to EPSPs, ALS, and ACCase inhibitors. MARCHIORETTO & DAL MAGRO (2018) found the addition of bentazon to the herbicides cloransulam or imazethapyr decreased the phytotoxicity caused to the bean crop, and did not alter the weed control, with no antagonism of the herbicide mixture. In addition, the crop response was dependent on the cultivar, in spite of both cultivars Agronorte (Anfc9) and IPR Uirapuru tolerated the herbicides. To reach this conclusion, authors performed a field study where the herbicides cloransulam and imazethapyr were tested alone and in combination with bentazon for comparison with a weed and infested control in two bean cultivars. COSTA et al. (2018) hypothesized the resistance to glyphosate could provide a penalty on seed quality of glyphosate-resistant Conyza bonariensis. Authors performing tests for seed viability and seed vigor under controlled conditions. Biotypes susceptible and resistant to glyphosate were tested but no difference occurred between them regarding on seed germination and embryo viability. However, the percentage of seed germination of the R biotype was reduced under experimental conditions using the cold test, the accelerated aging test, and the high-temperature stress test. In conclusion, authors indicated they found evidences that glyphosate-resistance is responsible for a penalty on seed quality of C. bonariensis.

Identification and Molecular Mapping of the RsDmR Locus Conferring Resistance to Downy Mildew at Seedling Stage in Radish (Raphanus sativus L.)

Downy mildew (DM), caused by the fungus Peronospora parasitica, is a destructive disease of radish (Raphanus sativus L.) worldwide. Host resistance has been considered as an attractive and environmentally friendly approach to control the disease. However, the genetic mechanisms of resistance in radish to the pathogen remain unknown. To determine the inheritance of resistance to DM, F1, F2 and BC1F1 populations derived from reciprocal crosses between a resistant line NAU-dhp08 and a susceptible line NAU-qtbjq-06 were evaluated for their responses to DM at seedling stage. All F1 hybrid plants showed high resistance to DM and maternal effect was not detected. The segregation for resistant to susceptible individuals statistically fitted a 3:1 ratio in two F2 populations (F2(SR) and F2(RS)), and 1:1 ratio in two BC1F1 populations, indicating that resistance to DM at seedling stage in radish was controlled by a single dominant locus designated as RsDmR. A total of 1972 primer pairs (1036 SRAP, 628 RAPD, 126 RGA, 110 EST-SSR and 72 ISSR) were screened, and 36 were polymorphic between the resistant and susceptible bulks, and consequently used for genotyping individuals in the F2 population. Three markers (Em9/ga24370, NAUISSR826700 and Me7/em10400) linked to the RsDmR locus within a 10.0 cM distance were identified using bulked segregant analysis (BSA). The SRAP marker Em9/ga24370 was the most tightly linked one with a distance of 2.3 cM to RsDmR. These markers tightly linked to the RsDmR locus would facilitate marker-assisted selection and resistance gene pyramiding in radish breeding programs.

Resistance gene analogue isolation and RGA-based marker development for identifying downy mildew resistance in radish (Raphanus sativus L.)

Resistance Gene Analogs (RGAs)-based molecular markers can significantly enhance the breeding efficiency for disease resistance in various crops. However, RGAs isolation and RGA-based marker development have not been conducted in radish. In this study, two prevalent approaches, PCR amplification with degenerate primers and data-mining of radish EST databases, were used to isolate radish resistance gene candidate sequences. A total of 26 RsRGAs with high homology to known R-genes or RGAs were obtained by PCR amplification. Meanwhile, 257 R-gene-like unigenes/ESTs were identified using data-mining method. In total, 115 out of 124 designed RGA-specific primer pairs can successfully amplified the target bands. To explore the RGA genetic variability, 32 radish accessions were genotyped and 269 RGA loci were successfully identified. It was found that 44 RGA primers only generated monomorphic band and the remaining 71 RGA primers generated 225 RGA polymorphic bands among the 32 radish accessions. Based on RGA marker analysis, 32 radish accessions were clustered into four main groups at the similarity index of 0.68, which was in a high accordance with disease index from a downy mildew evaluation. This study might be the first report on candidate R-genes identification and RGA-based markers development in radish. These findings will facilitate the disease resistance identification and speed up the genetic improvement of DM resistances in radish breeding programs.

Chromosomal assignment of oil radish resistance to Meloidogyne incognita and M. javanica using a set of disomic rapeseed-radish chromosome addition lines

Root-knot nematodes cause severe damage to a great number of crops worldwide. The use of nematicides is restricted due to environmental and toxicological risks and control of the pest by crop rotation is difficult because root-knot nematodes have a very wide range of host plants. To verify the strategy of converting rapeseed from a tolerant host for Meloidogyne incognita and M. javanica to a resistant catch crop, a complete set of nine disomic rapeseed-radish chromosome addition lines (lines A to I) was tested for resistance against these Meloidogyne species. Thirty plants of each addition line and the rapeseed and radish parents as control were infected with 2500 second-stage juveniles per plant. The presence of the alien radish chromosome was confirmed by chromosome-specific microsatellite markers. After cultivation of the inoculated plants for 10 weeks in a climatic chamber the root systems were washed. The egg masses were stained with Cochenille Red and counted. The radish parent A24 was found to be resistant to M. incognita (2.4 egg masses (g root)−1) and M. javanica (0.4 egg masses (g root)−1) compared to 53.3 and 33.1 egg masses (g root)−1 for the susceptible rapeseed parent cv. Madora. The radish chromosome e was shown to be the carrier of radish root-knot nematode resistance with an average number of <1 egg mass (g root)−1 for M. incognita and M. javanica. The disomic addition lines B, C, D, G, H and I and the parental radish line A107 were classified as highly susceptible, whereas the addition lines A and F showed significantly reduced susceptibility for M. incognita but not for M. javanica. To our knowledge this is the first study on resistance effects of individual radish chromosomes in a rapeseed background against these root-knot nematodes.

Structure of syncytia induced by Heterodera schachtii Schmidt in roots of susceptible and resistant radish (Raphanus sativus L., var. oleiformis)

The structure of syncytia induced by <i>Heterodera schachtii</i> Schmidt in roots of susceptible <i>Raphanus sativus</i> L. cv. "Siletina" and resistant radish cv. "Pegletta" was investigated. In the radish cultivar "Siletina" the syncytia most often appeared in the elongation zone of lateral roots. They were initiated in the procambium and pericycle but also included the parenchyma cells of vascular cylinder. In the susceptible cultivar "Siletina" the cells forming the female's syncytia were subject to hypertrophy. Their cytoplasmic density increased. The cytoplasm contained numerous organella. The proliferation of the smooth endoplasmic reticulum took place. Branched cell wall ingrowths were formed next to the vessels. In the male's syncytia the cells were only slightly increased. Their protoplasts contained few organelles. The cell wall ingrowths were poorly developed. In the syncytia of the resistant cultivar "Pegletta" there was only a slight increase of the cell volume. A well developed system of rough endoplasmic reticulum was observed in the protoplast. Distended ER cisterns contained fine fibrillar material. Material of similar structure also appeared in numerous small vacuoles. In resistant plants only some, not numerous, syncytia spreading in procambium fully developed and functioned long enough for the parasite females to mature. At an advanced stage of infection a well developed system of a rough ER was observed also in those syncytia and numerous vacuoles appeared.

무 시들음병균이 생산하는 Phytotoxin의 병원성 및 저항성에서 역할

무 시들음병에 대한 저항성 검정 체계를 확립하기 위하여 실험하는 과정에서 병원균인 Fusarium oxysporum f. sp. raphani가 무 유묘에 독성(phytotoxicity)을 일으키는 독소(phytotoxin)를 생산한다는 것을 발견했다. F. oxysporum f. sp. raphani KR1 균주는 여러 배지 중 malt extract broth 배지에서 배양하였을 때 그리고 <TEX>$25^{\circ}C$</TEX>에서 14일 동안 150rpm으로 진탕배양하였을 때 가장 많은 독소를 생산하였다. 무에 대한 독성 반응을 이용하여 F. oxysporum f. sp. raphani의 배양액으로부터 phytotoxin을 분리하였다. 그리고 Mass와 NMR Spectroscopy 분석을 통하여 이 화합물은 fusaric acid로 동정되었다. 독소의 역할을 규명하기 위하여 fusaric acid를 무, 양배추, 브로콜리 등 F. oxysporum f. sp. raphani의 기주 및 비기주 배추과 작물에 대한 독소 활성을 조사하였다. Fusaric aicd는 무 유묘에 대하여 농도 의존적으로 활성을 보였으며, F. oxysporum f. sp. raphani에 대한 감수성 품종뿐만 아니라 저항성 품종에 대해서도 유사한 정도의 독성을 나타냈다. 그리고 F. oxysporum f. sp. raphani가 생산하는 fusaric acid는 병원균의 비기주 배추과 작물인 양배추와 브로콜리에 대해서도 강한 활성을 보였다. 따라서 이들 결과는 이 독소가 병원성 관련 독소이나 비기주 특이적 독소이며, 무 시들음병 저항성 검정에서 이 독소가 제거된 포자현탁액을 접종원으로 사용해야 한다는 것을 나타낸다. In the course of a developing screening method for resistant radish to Fusarium oxysporum f. sp. raphani, we found that the fungus produces phytotoxic compound against Raphanus sativus. The culture filtrate of F. oxysporum f. sp. raphani KR1 represented the strongest phytotoxicity when the fungus was incubated in the malt extract broth with 150 rpm at <TEX>$25^{\circ}C$</TEX> for 14 days. Under bioassay-guided purification, we isolated a substance from liquid culture of F. oxysporum f. sp. raphani KR1, with phytotoxic effect against R. sativus. The compound was identified as fusaric acid by mass and nuclear magnetic resonance spectral analyses. Phytotoxicity of the compound against cruciferous vegetable crops, including radish, cabbage, and broccoli, was investigated. Fusaric acid represented phytotoxicity on radish seedlings by concentration dependant manner. And the phytotoxin demonstrated strong phytotoxicity on the resistant cultivars as well as susceptible cultivars of radish to F. oxysporum f. sp. raphani. In addition, fusaric acid isolated from the fungus also showed a potent phytotoxic efficacy against non-host Brassicaceae crops of the fungus such as cabbage and broccoli. The results demonstrate that fusaric acid produced by F. oxysporum f. sp. raphani is non-host-specific toxin and for screening of resistant radish to the fungal pathogen, spore suspension of the fungus without the phytotoxin has to be used.

Limited occurrence of resistant radish (Raphanus sativus) to AHAS-inhibiting herbicides in Argentina

Radish has developed feral and weedy biotypes, which is a concern for agriculture around the world. In Argentina, it is one of the most widespread and troublesome crop weeds. In Brazil, this species has developed herbicide-resistance to acetohydroxyacid synthase (AHAS) inhibiting herbicides. The objective of this study was to record the presence of herbicide-resistant weedy radish plants in Argentina. In spring 2008, we found a small population of radish at the end of the flowering stage in an imidazolinone-tolerant canola field treated with imazethapyr. Screening and dose-response tests were conducted to two successive generations. They proved the biotype resistant status, and showed extensive survival (between 50 and 80% of control) to the application of a double dose of four AHAS‑inhibiting herbicides from two different chemical families (imidazolinones and sulfonylureas). Dose-response assays exhibited very high resistance for imazethapyr (LD50 = 2452.5 g a.i. ha-1, GR50 = 2926.9 g a.i. ha-1) and intermediate for metsulfuron (LD50 = 3.0 g a.i. ha-1, GR50 = 43.2 g a.i. ha-1). The acquisition of cross-resistance to different herbicide families would confer an adaptive and invasive advantage in agricultural environments to this biotype. Due to the herbicide rotation conducted in the field, the dispersion of this biotype was restricted. This is the first report of resistance in weedy radish in Argentina.