Genetic analysis of antixenosis resistance to the common cutworm (Spodoptera litura Fabricius) and its relationship with pubescence characteristics in soybean (Glycine max (L.) Merr.)

The common cutworm (CCW, Spodoptera litura Fabricius) is one of the most serious pests of soybean (Glycine max (L.) Merr.). Previously, two quantitative trait loci (QTLs) for antibiosis resistance to CCW, CCW-1 and CCW-2, were detected in the resistant cultivar Himeshirazu. In this study, we conducted an anti-xenosis bioassay using a recombinant inbred population derived from a cross between a susceptible cultivar Fukuyutaka and Himeshirazu to perform QTL analysis. Two QTLs for antixenosis resistance, qRslx1 and qRslx2, were identified on Chrs 7 and 12, and the resistant alleles of qRslx1 and qRslx2 were derived from Himeshirazu and Fukuyutaka, respectively. The position of qRslx1 is similar to that of CCW-1. We also analyzed pubescence characteristics because they have been reported to be associated with soybean insect resistance. Two QTLs for pubescence length (on Chrs 7 and 12) and two QTLs for pubescence density (on Chrs 1 and 12) were identified. The pubescence QTLs on Chrs 7 and 12 were located near qRslx1 and qRslx2, respectively. These results suggest that the antixenosis resistance could be controlled genetically by the identified QTLs and that the pubescence characteristics might contribute to the soybean antixenosis resistance to CCW.     

Resistance to a new biotype of the lettuce aphid Nasonovia ribisnigri in Lactuca virosa accession IVT280

Host plant resistance is an effective protection strategy to control aphids in many crops. However, the evolution of insensitive aphid biotypes necessitates the search for new resistance sources. Wild relatives of crop plants can be important sources for resistance genes to be introgressed into new cultivars. Nasonovia ribisnigri (Mosely) (Homoptera: Aphididae) is an important pest of cultivated lettuce, Lactuca sativa. Since 1982, resistance introduced into lettuce cultivars has relied on the Nr-gene, originating from a wild relative, Lactuca virosa. In 2007 first reports appeared that Nr-based resistance had become ineffective against certain populations of N. ribisnigri. The objective of this study was to establish if the original donor of the Nr-gene L. virosa accession, IVT 280, is resistant against recently emerged virulent (Nr:1) N. ribisnigri biotypes. To this end we investigated feeding and penetration behaviour of virulent and avirulent (Nr:0) aphids on the resistant L. virosa, IVT 280, and two susceptible L. virosa accessions, using the electrical penetration graph method. Additionally, aphid performance was analysed in terms of survival, development time and reproduction on these accessions. L. virosa accession IVT 280 was resistant against all populations of N. ribisnigri tested. The ingestion of phloem was strongly reduced on the resistant accession compared to the susceptible L. virosa accessions. Additionally, none of the aphids survived on the resistant accession that, therefore, constitutes a good source of resistance in lettuce against both biotypes of N. ribisnigri.     

Genetic and histological characterization of downy mildew resistance at the cotyledon stage in <Emphasis Type="Italic">Raphanus sativus</Emphasis> L.

Downy mildew (DM; Hyaloperonospora brassicae) is one of the most serious diseases in radish and responsible for high production losses. The objectives of this study were (1) to identify new sources of DM resistance at the cotyledon stage; (2) to determine the inheritance of the resistance; and (3) to clarify the histological and cellular response involved in DM infection. We screened 200 radish accessions for DM resistance at the cotyledon stage. Radish accessions Rd001, Rd004, Rd048 and Rd150 showed a complete resistance response (hypersensitive reaction), and accession Rd193 exhibited a partial resistance with confined sporulation. The highly susceptible accession Rd197 was then crossed with all resistant genotypes for a genetic analysis. F₂ segregation analysis suggested that cotyledon resistance in Rd001, Rd004, Rd048 and Rd150 is conferred by a single dominant gene while resistance in Rd193 is polygenic. Genetic data suggests Rd193 resistance might be conferred by two dominant genes with complementary action, althought further experiments are needed to confirm this hypothesis. To conduct a histological study using light and fluorescence microscopy, we collected cotyledons from three genotypes with either differing levels of resistance (Rd004 and Rd193) and high susceptibility (Rd197) at ten different time points, from 3 h to 7 days post inoculation. Tissue necrosis was responsible for the inhibition and reduction of H. brassicae growth in Rd004 and Rd193 within 24 h of inoculation. For susceptible accession Rd197, the first evidence of necrotic cells appeared 48 h post inoculation. Callose deposition associated with intercellular H. brassicae growth occurred 3 h post inoculation for all genotypes and was the lowest in resistant accession Rd004. Cotyledon resistance to DM identified in radish is of high commercial interest and has the potential to be used in breeding programs.     

Screening for resistance to clover rot (Sclerotinia spp.) among a diverse collection of red clover populations (Trifolium pratense L.)

Red clover (Trifolium pratense) is an important perennial forage crop that is widely cultivated in Europe. Clover rot remains a major disease in red clover, but resistance breeding is hampered by the lack of available sources of resistance. Moreover, little is known about the factors that influence clover rot resistance. In this paper we evaluated the variation in clover rot susceptibility among a diverse collection of 113 red clover accessions, with the aim of identifying more resistant accessions. Clover rot susceptibility was assessed with a high throughput bio-test on young plants. We found significant variation in clover rot susceptibility, within and among accessions. ‘Tedi’, ‘Maro’ and ‘No 292’ were the most resistant accessions. Fifteen diploid accessions were more susceptible than the average accession with the cultivar ‘Nemaro’ being the most susceptible. Clover rot susceptibility was not correlated with isoflavone levels from Mullaney et al. (Agronomy abstract. ASA, Madison, p 195, 2000). Cultivars were more resistant than landraces and wild accessions and tetraploid cultivars were more resistant than diploid cultivars. Besides the in-depth analysis for clover rot susceptibility, possible correlations with plant architecture and other diseases were investigated. Growth habit, branching, plant yield, flowering date and susceptibility to mildew, virus and rust diseases were investigated in a 3-year field trial. Unlike previously suggested, clover rot susceptibility was not correlated with branching or with plant yield over three years. On the other hand, late flowering accessions and accessions with erect growth habit were less susceptible to clover rot. Clover rot susceptibility was not correlated with susceptibility to rust disease (Uromyces trifolii) or viral diseases, but negatively with susceptibility to mildew (Erysiphe polygoni). Because no completely resistant accessions were found, the best way to improve clover rot resistance would be to select recurrently for resistant genotypes among diverse cultivars and landraces with lower susceptibility. Tetraploidisation of diploid populations with a higher resistance level can provide an additional level of protection.     

Genetic analysis of late blight resistance in Solanum pimpinellifolium accession PI 270441: Heritability and response to selection

Late blight (LB), caused by Phytophthora infestans, is a destructive disease of tomato (Solanum lycopersicum) worldwide. Currently, there are few commercial cultivars of tomato with resistance to LB, and the disease is mainly controlled by heavy use of fungicides. Due to the emergence of fungicide‐resistant pathogen isolates, there is a concerted effort to identify new genetic sources of resistance and breed new resistant cultivars. A recent screening identified several new tomato accessions with strong resistance to LB. Here, we report on the genetic basis of LB resistance in S. pimpinellifolium accession PI 270441, as determined by generation means analysis and analysis of response to selection, using populations derived from crosses with LB‐susceptible breeding line Fla. 8059. Heritability of LB resistance ranged from 0.76 to 0.78, and the minimum number of genes was estimated 1—few. These results suggest that transfer of LB resistance from PI 270441 to the cultivated tomato should be feasible via a traditional backcross breeding approach. Genetic mapping studies are underway to identify molecular markers associated with resistance in this accession.     

Identification of sources and inheritance of resistance of Chinese Brassica vegetables to white blister

There is no information in the literature about the variability of resistance of Chinese Brassica vegetables, pak choi and Chinese cabbage, to the white blister disease caused by Albugo candida (Pers.) Kuntze. A collection of 43 accessions of pak choi and 19 accessions of Chinese cabbage was screened for resistance to the Portuguese A. candida isolate Ac 506 at the cotyledon stage. Different levels of resistance were found among the germplasm tested, ranging from complete resistance to full susceptibility. Most of the accessions were highly susceptible with less than 10% of resistant seedlings, and only four accessions of pak choi, presenting more than 50% resistant seedlings, were considered as new sources or resistance to white blister. Inheritance of resistance at the cotyledon stage was studied in two crosses between the most resistant pak choi accession, BRA 117, and the highly susceptible rapid cycling Brassica rapa line CrGC 1.19. It was proposed that resistance to white blister in pak choi BRA 117 is controlled by two nuclear genes with dominant recessive epistatic gene action.     

大豆丙二烯氧化物合酶基因(GmAOS)及其启动子的克隆与分析

利用RT-PCR、RACE和LA PCR相结合的方法,从大豆中克隆了GmAOS基因及其启动子序列(登录号：EU366252),GmAOS基因共1 789 bp碱基,等电点8.97,分子量58.3 kD,在3种不同抗性大豆材料中均有2个拷贝。生物信息学分析表明,GmAOS酶的N末端有典型叶绿体定位信号肽,基因序列上有多个丝氨酸、苏氨酸、酪氨酸的磷酸化位点。该研究克隆到ATG上游472个碱基的GmAOS基因启动子部分序列,其含有赤霉素的响应元件(TAACAA),可诱导性抗性基因响应元件(W box),细菌和盐诱导的响应元件(GAAAAA),茉莉酸诱导的响应元件(G box)。GmAOS能强烈响应茉莉酸的诱导,且在黄皮小青豆(高抗斜纹夜蛾)中表达量高于徐疃大豆,两种材料抗虫性的差异可能是由GmAOS基因受诱导后的表达量差异引起的,即GmAOS基因与作物抗虫性相关,可做为培育高诱导抗性材料的候选基因。     

Molecular screening for identification of blast resistance genes in North East and Eastern Indian rice germplasm (Oryza sativa L.) with PCR based makers

Molecular screening and genetic diversity of major rice blast resistance (R) genes were determined in 32 accessions of rice germplasm from North East and Eastern India with ten gene based single nucleotide polymorphisms and sequence tagged sites (STS) markers, namely z56592, zt56591, k39512, k3957, candidate gene marker, Pita3, YL155/YL87, YL183/YL87, Pb28, 195R-1 which showed close-set linkage to nine major rice blast resistance (R) genes, Piz, Piz-t, Pik, Pik-p, Pik-h, Pita/Pita-2, Pib and Pi9 and one susceptible pita gene. Among the 32 accessions, 13 were positive for Piz gene and six for Piz-t gene. Six accessions were positive for Pik gene, seven for Pik-p and 16 for Pik-h gene. One accession, Atte thima, was positive for three of Pik multiple genes. Out of 32, only two germplasm, Dudhraj and Nepali dhan, were detected with both Pita3 and YL155/YL87 marker for Pita/Pita-2 gene. The Pib gene appeared to be omnipresent and was detected in 31 of 32 germplasm with marker Pb28. The gene specific STS marker, 195R-1, for Pi9 gene produced positive bands in only two germplasm, Kalchatti and Bachi thima. The Uniform Blast Nursery (UBN) analysis showed that out of 32, six germplasm was resistant, ten moderately resistant and 16 germplasm were susceptible. Presence of Piz-t, Pita/Pita-2 and Pi9 gene ensured a resistant reaction in outdoor blast nursery whereas germplasm carrying Pib was susceptible when present alone. Presence of multiple genes, however, contributed to slow blasting resistance in the field. These results are useful in identification and incorporation of resistant genes from the germplasm into elite cultivars through marker assisted selection in rice breeding programs.     

Inheritance of resistance in soybean PI 567516C to LY1 nematode population infecting cv. Hartwig

Worldwide, cyst nematode (SCN) Heterodera glycines is the most destructive pathogen on cultivated soybean (Glycine max (L.) Merr.). In the USA yield losses in 2001 were estimated to be nearly 60 million dollars. Crop losses are primarily reduced by the use of resistant cultivars. Nematode populations are variable and have adapted to reproduce on resistant cultivars overtime because resistance primarily traces to two soybean accessions. Recently cv. Hartwig was released which has comprehensive resistance to most SCN populations. A virulent nematode population LY1 was recently selected for its reproduction on Hartwig. LY1 population originated from a mass mating of Race 2 (HG Type 1.2.5-) females with Race 5 (HG Type 1.2-) males. LY1 nematode population infects currently known sources of resistance except PI 567516C. The female indices obtained on PI 567516C and Hartwig were 7% (resistant) and 155% (susceptible), respectively. However, the genetic basis of LY1 resistance in soybean PI 567516C is not known. Resistant PI line 567516C was crossed to susceptible cultivar Hartwig to generate 105 F_2:5 families. These families together with parents, seven indicator lines and a susceptible control cv. Lee-74 were evaluated for response to LY1 nematode population in the greenhouse. Chi-square analysis showed resistance in PI567516C to LY1 was conditioned by one dominant and two recessive genes (Rhg, rhg, rhg). Chi-square value was 0.15 and P = 0.70. This information will be useful to soybean researchers for developing resistant cultivars to nematode population that infects Hartwig.     

Constitution of resistance to common cutworm in terms of antibiosis and antixenosis in soybean RIL populations

Common cutworm (CCW; Spodoptera litura Fabricius) is a major leaf-feeding pest in Asia. The focus of this study was to explore the genetic mechanism for resistance to CCW in terms of antibiosis and antixenosis through mapping QTL (Quantitative trait locus/loci) in soybean using two recombinant inbred line populations. Larva weight (LW) and pupa weight (PW) were evaluated as indicators for antibiosis and damaged leaf percentage as the indicator for antixenosis to CCW. The obvious transgressive segregation indicated a complementary genetic status between the parents. The genetic structure for antibiosis and antixenosis was similar, about 51.1–75.7 % of the phenotypic variation (PV) accounted for by genetic variation, where 42.2–60.3 %, or the majority, was explained by the collective unmapped minor QTL. And, 0–6 additive QTL each explained 0.0–11.8 % in a total of 0.0–27.4 % of PV, and 0–3 epistatic QTL pairs each explained 0.0–7.6 % in a total of 0.0–14.0 % of PV. However, the detected QTL compositions for antibiosis and antixenosis were quite different with only one QTL qCCW10_1 shared by both antibiosis and antixenosis with 8.9–11.8 and 4.7 % contribution to PV, respectively. Within antibiosis between LW and PW, the detected QTL overlapped (r = 0.53–0.78). Among the detected QTL, qCCW6_1, qCCW10_1 and qCCW12_2 were the major contributors to antibiosis, and qCCW10_1, qCCW10_2 and qCCW12_1 the major contributors to antixenosis. Since only some major QTL could be used for marker-assisted breeding, the main concern is how to use the large amount of undetected minor QTL.     

Prehaustorial resistance to the wheat leaf rust fungus, Puccinia triticina, in Triticum monococcum (s.s.)

Diploid wheat, Triticum monococcum s.l., is a host for the wheat leaf rust fungus, Puccinia triticina. Some accessions have been reported to show a high degree of prehaustorial resistance. This is non-hypersensitivity resistance, which acts before the formation of haustoria by the pathogen. To assess the frequency of prehaustorial resistance 598 accessions of diploid wheat were inoculated with the wheat leaf rust isolate Felix. Most T. monococcum s.s. accessions (84%) were resistant whereas all T. urartu and all but three T. boeoticumaccessions were susceptible. Histological components analysis revealed that a high percentage of prehaustorial resistance to P. triticina was found in only three T. monococcum accessions. No haustoria were observed in such infection units confirming the prehaustorial nature of the resistance. Prehaustorial abortion of certain infection units in an accession always coincided with posthaustorial abortion of the other infection units. This revised version was published online in July 2006 with corrections to the Cover Date.     

Molecular mapping of two recessive genes controlling resistance to bacterial leaf pustule disease in soybean (Glycine max)

Bacterial leaf pustule (BLP) caused by Xanthomonas axonopodis pv. glycines (Xag) is a serious soybean disease. A BLP resistant genotype ‘TS-3’ was crossed with a BLP susceptible genotype ‘PK472’, and a segregating F₂ mapping population was developed for genetic analysis and mapping. The F₂ population segregation pattern in 15:1 susceptible/resistance ratio against Xag inoculum indicated that the resistance to BLP in ‘TS-3’ was governed by two recessive genes. A total of 12 SSR markers, five SSR markers located on chromosome 2 and seven SSR markers located on chromosome 6 were identified as linked to BLP resistance. One of the resistance loci (r1) was mapped with flanking SSR markers Sat_183 and BARCSOYSSR_02_1613 at a distance of 0.9 and 2.1 cM, respectively. Similarly, SSR markers BARCSOYSSR_06_0024 and BARCSOYSSR_06_0013 flanked the second locus (r2) at distances of 1.5 and 2.1 cM, respectively. The identified two recessive genes imparting resistance to BLP disease and the SSR markers tightly linked to these loci would serve as important genetic and molecular resources to develop BLP resistant genotypes in soybean.     

Single-gene resistance to powdery mildew in zucchini squash (Cucurbita pepo)

Cucurbita pepo (pumpkin, squash,gourd) is an economically important species that is susceptible to the cucurbit powdery mildew fungus, Podosphaera xanthii(syn. Sphaerotheca fuliginea). ‘True French’, an open-pollinated cultivar of the Zucchini Group of C. pepo, was crossed with an unnamed powdery-mildew resistant straight neck-type accession, the resistance of which was apparently derived from an interspecific cross with a resistant wild species of Cucurbita,and resistant plants were selected in the F₂ generation. This was followed by six cycles of backcross-pedigree selection for resistance, and resulted in the development of an accession true-breeding for resistance to powdery mildew and nearly isogenic to ‘True French’. The resistant and susceptible near-isogenics were crossed and seeds of the filial and backcross generations were produced. Plants of the parental accessions and their progenies were grown together in a controlled-environment chamber, exposed to the pathogenic fungus, and scored as resistant, partially resistant, or susceptible 27–33 days after sowing. The results indicated that resistance is conferred by a single incompletely dominant gene, designated Pm-0. This revised version was published online in August 2006 with corrections to the Cover Date.     

Evaluation of resistance sources and inheritance of resistance in kidney bean to Indian virulences of Colletotrichum lindemuthianum

Summary Forty nine common bean lines comprising of exotic accessions and locally grown cultivars evaluated against Colletotrichum lindemuthianum exhibited differential resistance to its races in Himachal Pradesh, a north-western Himalayan state of India. Some exotic accessions like G 2333, Cornell 49242, PI 207262, Mexique 222, TO, Perry Marrow, Kaboon and Widusa were resistant to more than five Indian races, whereas two Indian accessions KRC-5 and Hans showed resistance to six and four races, respectively. However, nine accessions KRC-8, KR-40, KR-43, KR-81, KR-62-2, KR-90, KR-142, KR-148, and KR-216 were resistant to three races. Race specific resistance has been observed in different bean cultivars. Studies on inheritance of resistance in exotic accession G 2333 and Indian accession, KRC-5 showed that two independent dominant genes conferred resistance in G 2333 to race 3 and 515 and a single dominant gene controlled resistance in KRC-5 to race 775, indicating resistance from these sources is easily transferable to the locally adapted susceptible cultivars.     

Assessment of Gossypium sturtianum and G. australe as potential sources of Fusarium wilt resistance to cotton

When challenged with Fusarium oxysporum f. sp. vasinfectum (Fov) from vegetative compatibility groups (VCGs) 01111 and 01112 in glasshouse tests, Gossypium australe Mueller and Gossypium sturtianum Willis accessions showed a variety of disease responses ranging from highly resistant to highly susceptible. Under high disease pressure G. sturtianum accession Gos-5275 was significantly more resistant than the commercial G. hirsutum cultivars that are designated standards for Fusarium resistance by Australian cotton breeders. Under low disease pressure G. sturtianum accession Gos-5250 was more susceptible than a highly susceptible commercial cultivar. A series of glasshouse tests was performed at two locations (Indooroopilly, QLD. and Canberra, ACT), and under low and high disease pressure. In these tests, a hexaploid cross (Gos-5271) generated from a Fusarium-resistant G. sturtianum (Gos-5275) and a Fusarium-susceptible G. hirsutum L. (CPI-138969) was significantly more resistant to Fusarium wilt than its G. hirsutum parent. Thus G. sturtianum, with a diploid genome and a range of responses to Fov challenge, has the potential to provide the basis for the elucidation of the genetic basis of resistance to Fusarium wilt in cotton species. In addition, resistant accessions of G. sturtianum are identified as a potential source of Fusarium wilt resistance genes for cotton breeding. In the glasshouse tests used to assess the resistance of various Gossypium accessions to Fusarium wilt disease, the scoring of vascular browning was found to give a more reliable indication of disease severity than the scoring of foliar symptoms. This revised version was published online in August 2006 with corrections to the Cover Date.     

QTLs associated with resistance in soybean PI567516C to synthetic nematode population infecting cv. Hartwig

Worldwide, soybean cyst nematode (SCN, Heterodera glycines Ichinohe) is the most destructive pathogen of soybean [Glycine max (L.) Merr.]. Crop losses are primarily mitigated by the use of resistant cultivars. Nematode populations are variable and have adapted to reproduce on resistant cultivars over time because resistance primarily traces to two soybean accessions, Plant Introduction (PI) 88788 and Peking. Soybean cultivar Hartwig, derived primarily from PI437654, was released for its comprehensive resistance to most SCN populations. A synthetic nematode population (LY1) was recently selected for its reproduction on Hartwig. The LY1 nematode population currently infects known sources of resistance except soybean PI567516C; however, the resistance to LY1 has not been characterized. The objective of this study was to identify quantitative trait loci (QTLs) underlying resistance to the LY1 SCN population in PI567516C, identify diagnostic DNA markers for the LY1 resistance, and confirm their utility for marker-assisted selection (MAS). Resistant soybean line PI567516C was crossed to susceptible cultivar Hartwig to generate 105 recombinant inbred lines (F₂-derived F₅ families). QTLs were mapped using simple sequence repeats (SSRs) covering 20 Linkage Groups (LGs) and three diagnostic markers, Satt592, Satt331, and Sat_274, were identified on LG O. These markers have a combined efficacy of 90% in identifying resistant lines in a second cross that has been generated by crossing a susceptible cultivar 5601T with resistant PI567516C. F₂-derived F₄ segregating population was used in MAS to identify resistant lines.     

Inheritance of Russian wheat aphid resistance from tetraploid wheat accessions during transfer to hexaploid wheat

Identification of new sources of resistance to Russian wheat aphid (RWA) (Diuraphis noxia (Kurdjumov) in wheat (Triticum aestivum L.) has become very important with the identification of several new biotypes since 2003. Our objective was to characterize inheritance and expression of resistance to RWA biotype 2 from three tetraploid wheat landraces (Triticum turgidum L. subsp. dicoccon) during transfer to hexaploid wheat. Resistant tetraploid accessions PI 624903, PI 624904, and PI 624908 were crossed to the susceptible hexaploid cultivars ‘Len’ and ‘Coteau’. Resistant F1 progeny were advanced to the F2:3 by self-pollination and to the BC1F2 and BC2F1 by backcrossing. Leaf rolling and chlorosis were recorded in standard seedling screening tests on F1 and F2:3 individuals while the F2, BC1F1, BC1F2, and BC2F1 were scored as resistant or susceptible. Segregation in the BC1F1 and BC2F1 fit a 1:1 resistant:susceptible ratio, indicative of control by a single dominant gene. Segregation for resistance in the F2 did not fit 3:1, 13:3, or 15:1 ratios for any of the resistant accessions. Expression of resistance in homogeneous resistant F2:3 lines was greater than susceptible checks, similar to the resistant tetraploid accessions, and less than a line carrying the Dn7 resistance gene. Resistance derived from these tetraploid accessions will be useful to broaden the base of RWA resistance available for use in wheat breeding.     

Inheritance of partial resistance to Myzus persicae in lettuce

Summary The genetics of partial resistance of lettuce to Myzus persicae was studied using F₁ and F₂ generations of two crosses between a susceptible and partially resistant accession (Norden x Batacer and Liba x Norden) and three crosses in which both parents were partially resistant (Batavia la Brillante x Batacer, Batacer x Liba and CGN4741 x Batacer). Partial resistance to M. persicae inherited quantitatively, without important dominance effects. Only in the cross Batacer x Liba were significant departures of the F₁ and F₂ from the midparent found, which were probably caused by epistatic effects. Reciprocal F₁s had similar resistance levels, indicating the absence of cytoplasmic or other maternal effects. Estimates of broad-sense heritability ranged from 0.34 to 0.61. The results indicated that lines with an improved resistance level can be obtained from crosses between partially resistant accessions, preferably by line selection or the application of indirect marker aided selection.Abbreviations PR partial resistance, partially resistant - S susceptibility, susceptible     

Selection of wild Cicer accessions for the generation of mapping populations segregating for resistance to ascochyta blight

In order to determine genetically diverse parents for the generation of mapping populations segregating for resistance to ascochyta blight in wild Cicer species, the genetic diversity between a selection of resistant and susceptible accessions was assessed using molecular markers. Twenty Cicer accessions — comprising eight C. reticulatum accessions, six C. echinospermum accessions, five C. bijugum accessions, and one C. arietinum accession — were compared using a combination of seven RAPD primers and seven ISSR primers. A total of 231 polymorphic bands were scored and used to determine the genetic distances between accessions using Jaccard similarity coefficients. The most genetically diverse parents for the generation of intraspecific and interspecific populations segregating for resistance to ascochyta blight are reported. This revised version was published online in July 2006 with corrections to the Cover Date.