Inheritance of anthracnose resistance in the common bean cultivar Widusa

Snap bean (Phaseolus vulgaris L.) cultivar, Widusa, was crossed to Michigan Dark Red Kidney (MDRK), Michelite, BAT 93, Mexico 222, Cornell 49–242, and TO cultivars to study the inheritance of resistance to anthracnose in Widusa. The segregation patterns observed in six F₂ populations supported an expected 3R:1S ratio suggesting that Widusa carries a single dominant gene conditioning resistance to races 7, 65, 73, and 453 of Colletotrichum lindemuthianum, the causal organism of bean anthracnose. Allelism tests conducted with F₂ populations derived from crosses between Widusa and Cornell 49–242 (Co-2), Mexico 222 (Co-3), TO (Co-4), TU (Co-5), AB 136 (Co-6), BAT 93 (Co-9), and Ouro Negro (Co-10), inoculated with races 7, 9, 65 and 73, showed a segregation ratio of 15R:1S. These results suggest that the anthracnose resistance gene in Widusa is independent from the Co-2, Co-3, Co-4,Co-5, Co-6, Co-9, and Co-10 genes. A lack of segregation was observed among 200 F₂ individuals from the cross Widusa/MDRK, and among 138 F₂ individuals from the cross Widusa/Kaboon inoculated with race 65, suggesting that Widusa carries an allele at the Co-1 locus. We propose that the anthracnose resistance allele in Widusa be named Co-1 ⁵ as Widusa exhibits a unique reaction to race 89 compared to other alleles at the Co-1 locus. RAPD marker A18₁₅₀₀ co-segregated in repulsion-phase linkage with the Co-1 ⁵ gene at a distance of 1.2 cM and will provide bean breeders with a ready tool to enhance the use of the Co-1 ⁵ gene in future bean cultivars.     

An allelic series at the Co-1 locus conditioning resistance to anthracnose in common bean of Andean origin

In this study, we characterized the genetic resistance of the Andean bean cultivars Kaboon and Perry Marrow and their relation to other sources of anthracnose resistance in common bean. Based on the segregation ratio (3R:1S) observed in two F₂ populations we demonstrated that Kaboon carries one major dominant gene conferring resistance to races 7 and 73 of Colletotrichum lindemuthianum. This gene in Kaboon is independent from the Co-2 gene and is an allele of the Co-1 gene present in Michigan Dark Red Kidney (MDRK) cultivar. Therefore, we propose the symbol CO-1 ² for the major dominant gene in Kaboon. The Co-1 is the only gene of Andean origin among the Co anthracnose resistance genes characterized in common bean. When inoculated with the less virulent Andean race 5, the segregation ratio in the F₂ progeny of Cardinal and Kaboon was 57R:7S (p = 0.38). These data indicate that Kaboon must possess other weaker dominant resistance genes with a complementary mode of action, since Cardinal is not known to possess genes for anthracnose resistance. Perry Marrow, a second Andean cultivar with resistance to a different group of races, was shown to possess another resistant allele at the Co-1 locus and the gene symbol Co-1 ³ was assigned. In R × R crosses between Perry Marrow and MDRK or Kaboon, no susceptible F₂ plants were found when inoculated with race 73. These findings support the presence of a multiple allelic series at the Andean Co-1 locus, and have major implications in breeding for durable anthracnose resistance in common bean. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genetic characterization of anthracnose resistance genes Co-4 3 and Co-9 in common bean cultivar tlalnepantla 64 (PI 207262)

Tlalnepantla 64 (PI 207262) is an important source of genes for resistance to common bean anthracnose, caused by Colletotrichum lindemuthianum. However, these genes have not been fully characterized. Inheritance studies using crosses involving PI 207262 show that two independent genes confer resistance to anthracnose. Allelism tests showed that the genes are located at distinct loci from the previously identified resistance genes Co-1, Co-2, Co-3, Co-5, Co-6, and Co-10. Also, no segregation was observed in relation to Co-4, Co-4 ², Co-9, and to the gene present in cultivar Widusa, indicating that PI 207262 harbors alleles of these genes. We conclude that PI 207262 harbors two anthracnose resistance genes, Co-4 and Co-9. The Co-4 allele of PI 207262 would be different from Co-4 and Co-4 ² and it is proposed Co-4 ³ as the genetic symbol for this resistance allele. As PI 207262 is the parent of BAT 93, the Co-9 symbol represents the gene of both cultivars. Also, one allele of Co-9 gene was detected in cultivar Widusa.     

Use of molecular markers to accelerate the breeding of common bean lines resistant to rust and anthracnose

The main goal of this work was to introduce resistance genes for rust, caused by Uromyces appendiculatus, and anthracnose, caused by Colletotrichum lindemuthianum, in an adapted common bean cultivar through marker-assisted backcrossing. DNA fingerprinting was used to select plants genetically closer to the recurrent parent which were also resistant to rust and to race 89 of C. lindemuthianum. DNA samples extracted from the resistant parent (cv. Ouro Negro), the recurrent parent (cv. Rudá), and from BC₁, BC₂ and BC₃ resistant plants were amplified by the RAPD technique. The relative genetic distances in relation to the recurrent parent varied between 9 and 59% for BC₁, 7 and 33% for BC₂, and 0 and 7% for BC₃ resistant plants. After only three backcrosses, five lines resistant to rust and anthracnose with, approximately, 0% genetic distance in relation to the recurrent parent were obtained. These lines underwent field yield tests in two consecutive growing seasons and three of them presented a good yield performance, surpassing in that sense their parents and most of the reference cultivars tested.     

Partial resistance to anthracnose in Brazilian land races of dry beans shows race specificity

Summary Fifty-four land races of dry beans (Phaseolus vulgaris), indigenous to areas of Brazil where anthracnose (caused by Colletotrichum lindemuthianum) is a common problem, were evaluated in field nurseries for partial resistance to race Brazilian 1 (B1) of C. lindemuthianum using symptom severity classes (SSC) from 0 to 6. Plants were selected if symptoms were present and the SSC was less than the 95% confidence interval of the mean SSC of the susceptible cultivar Carioca. S₁ progeny from selected plants were evaluated in air-conditioned chambers for partial resistance to races B1, delta, and kappa of C. lindemuthianum. Of 246 S₁ families evaluated, 145 families were partially resistant to one or two of the races [symptoms present, but S₁ family mean significantly (p<0.05) less than the mean of Carioca] and susceptible to the third. Six families were partially resistant to all three races. The remaining families were either susceptible or segregated for reaction to race B1. Partial resistance to C. lindemuthianum showed race specificity in the air-conditioned chambers and field nurseries.     

New sources of resistance to anthracnose and angular leaf spot of beans (Phaseolus vulgaris L.)

Summary over 13000 CIAT bean accessions were evaluated for their reactions to the anthracnose (Colletotrichum lindemuthianum) and angular leaf spot (Isariopsis griseola) pathogens over a 3 yr period. Among these accessions, 156 were resistant to all races of the anthracnose pathogen collected from Popayán, Colombia. Thirty were resistant to numerous races obtained from other parts of the world, including Europe. Although many of these new resistant sources originated in Mexico and Central America, they are quite diverse for geographic origin, plant type, seed color and seed size. In addition, more than 50 of the 156 lines were also resistant to isolates of I. griseola with diverse sources of origin throughout Colombia.     

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.     

Development and characterization of common black bean lines resistant to anthracnose,rust and angular leaf spot in Brazil

Anthracnose, rust and angular leaf spot caused by Colletotrichum lindemuthianum, Uromyces appendiculatus and Pseudocercospora griseola, respectively, are economically important diseases affecting the common bean production in Brazil. The BIOAGRO/UFV bean breeding program developed Rudá-R, a dry bean line with ‘carioca’ seed type, containing the following disease resistance genes: Co-4, Co-6 and Co-10 (anthracnose); Ur-ON (rust) and Phg-1 (angular leaf spot). To transfer this combination of disease resistance genes present in Rudá-R to a black-seeded bean, a backcrossing program aided by molecular markers was conducted, involving Rudá-R (donor genitor) and Diamante Negro (recurrent genitor). Forty black-seeded BC₃F_3:6 lines were obtained with combinations of at least three markers linked to the indicated disease resistance genes. The lines were evaluated for resistance to the three mentioned pathogens. Eight of the lines were homozygous and resistant to all four evaluated races of C. lindemuthianum, but susceptible to race 2047. Four of the lines were homozygous and resistant to two races of U. appendiculatus. Twenty of the lines were homozygous and resistant to the two races of P. griseola tested. Grain yield of the BC₃F_3:6 lines was evaluated during the ‘winter’ season of 2006 and the ‘dry’ season of 2007. All lines had statistically equal or higher yields than Rudá-R and Diamante Negro. Lines were identified that not only were high yielding but also resistant to the three pathogens tested. These lines are potential genotypes for further testing and for release as new black common bean varieties.     

The kappa race of Colletotrichum lindemuthianum and sources of resistance to anthracnose in Phaseolus beans

Summary The utilization of American and European bean cultivars as host differentials for distinction of races of Colletotrichum lindemuthianum has been discussed. The new race occurring at Ebnet. Germany, since 1973 is named kappa. It broke down resistance derived from the Are gene originating from Cornell 49–242. Resistance to this kappa race appeared to be present in some European and Asiatic bean cultivars as well as in some American bean accessions.     

以SSR标记对普通菜豆抗炭疽病基因定位

由菜豆炭疽菌引起的菜豆炭疽病是危害我国菜豆生产的主要病害之一, 鉴定和发掘新的抗病基因对于菜豆抗病育种具有十分重要的意义。以来自安第斯基因库的我国菜豆抗炭疽病地方品种红花芸豆与感病地方品种京豆杂交的F₂群体为试验材料, 通过人工接种菜豆炭疽菌81号小种进行抗病性鉴定, 发现该分离群体中抗病植株数与感病植株数符合3∶1的分离比例, 确定红花芸豆对菜豆炭疽菌81号小种的抗性由显性单基因控制, 将此基因命名为Co-F2533。用分离群体分组分析法(BSA)和微卫星多态性分析(SSR)技术对红花芸豆中的抗炭疽病基因进行分子标记鉴定, 用Mapmaker3.0计算标记与目的基因间的遗传距离, 发现B6连锁群上的4个SSR标记BM170、Clon1429、BMD37、Clon410与抗炭疽病基因Co-F2533连锁, 遗传距离分别为6.6、18.4、20.9和30.9 cM, 这些SSR标记与Co-F2533基因在B6连锁群上的排列顺序为Clon1429-Co-F2533- BM170-BMD37-Clon410。根据基因所在连锁群的位置、抗病基因的基因库来源可知Co-F2533是一个新的来源于安第斯基因库的抗炭疽病基因。     

A new gene conferring resistance to anthracnose in Andean common bean (Phaseolus vulgaris L.) cultivar ‘Jalo Vermelho’

‘Jalo Vermelho’ is a large seeded Andean landrace of common bean (Phaseolus vulgaris L.) that constitutes an important source of anthracnose resistance, disease caused by Colletotrichum lindemuthianum. This landrace has different resistance spectrum, when compared with cultivars of Andean origin, indicating the presence of an anthracnose‐resistant gene different from Co‐1 locus. This anthracnose resistance was characterized by inheritance and allelism tests were carried out on the following genes: Co‐1, Co‐1², Co‐1³, Co‐1⁵, Co‐2, Co‐3, Co‐4, Co‐5, Co‐6, Co‐7, Co‐9, Co‐10, Co‐11 and Co‐13. Resistance to races 23, 55, 89 and 453 in ‘Jalo Vermelho’ was conditioned by a single dominant gene. Allelism tests in F₂ populations demonstrated that ‘Jalo Vermelho’ carries a dominant gene located at a distinct locus, differing from previously characterized genes. Based on its independence from previously described loci, the authors propose that the ‘Jalo Vermelho’s gene should be named Co‐12. This new gene is a valuable source of resistance to anthracnose which can be transferred to commercial cultivars to enhance the effectiveness of resistance gene pyramiding in bean breeding programmes.     

以SSR标记对普通菜豆抗炭疽病基因定位

由菜豆炭疽菌引起的菜豆炭疽病是危害我国菜豆生产的主要病害之一, 鉴定和发掘新的抗病基因对于菜豆抗病育种具有十分重要的意义。以来自安第斯基因库的我国菜豆抗炭疽病地方品种红花芸豆与感病地方品种京豆杂交的F₂群体为试验材料, 通过人工接种菜豆炭疽菌81号小种进行抗病性鉴定, 发现该分离群体中抗病植株数与感病植株数符合3∶1的分离比例, 确定红花芸豆对菜豆炭疽菌81号小种的抗性由显性单基因控制, 将此基因命名为Co-F2533。用分离群体分组分析法(BSA)和微卫星多态性分析(SSR)技术对红花芸豆中的抗炭疽病基因进行分子标记鉴定, 用Mapmaker3.0计算标记与目的基因间的遗传距离, 发现B6连锁群上的4个SSR标记BM170、Clon1429、BMD37、Clon410与抗炭疽病基因Co-F2533连锁, 遗传距离分别为6.6、18.4、20.9和30.9 cM, 这些SSR标记与Co-F2533基因在B6连锁群上的排列顺序为Clon1429-Co-F2533- BM170-BMD37-Clon410。根据基因所在连锁群的位置、抗病基因的基因库来源可知Co-F2533是一个新的来源于安第斯基因库的抗炭疽病基因。     

Detection and inheritance of leaf rust resistance in common wheat lines Agra Local and IWP94

Genetic studies were undertaken to determine the number and identities of leaf rust resistance genes in common wheat lines Agra Local and IWP94. The infection type arrays of the two lines with eight pathotypes (pt.) of P. triticina were different from those of lines possessing known leaf rust resistance (Lr) genes. Agra Local possessed two recessive resistance genes, one conditioning resistance to pathotype 4R9-7, and the other, a temperature-sensitive factor, gave resistance to pt. 121R127 at high temperature (27°C). IWP94 was previously demonstrated to carry Lr23. From the present study IWP94 was determined to have at least four leaf rust resistance genes. The first of these was the same recessive gene conferring resistance to pathotype 4R9-7 which was found in Agra Local. A second partially dominant gene conferred resistance to pathotype 121R127 at high temperature and two additional recessive genes governed resistance to pathotype 93R15. When present together, these two recessive genes complemented each other and provided resistance to pathotype 69R13 as well. One of the two recessive genes conferring resistance to pathotypes 93R15 and 69R13 was Lr23.     

Evaluation of seedling and adult plant resistance to leaf rust in European wheat cultivars

Summary A set of 105 European wheat cultivars, comprising 68 cultivars with known seedling resistance genes and 37 cultivars that had not been tested previously, was tested for resistance to selected Australian pathotypes of P. triticina in seedling greenhouse tests and adult plant field tests. Only 4% of the cultivars were susceptible at all growth stages. Twelve cultivars lacked detectable seedling resistance to leaf rust, and among the remaining cultivars, 10 designated genes were present either singly or in combination. Lr13 was the most frequently detected gene, present in 67 cultivars, followed by the rye-derived gene Lr26, present in 19 cultivars. Other genes present were Lr1, Lr3a, Lr3ka, Lr10, Lr14a, Lr17b, Lr20 and Lr37. There was evidence for unidentified seedling resistance in addition to known resistance genes in 11 cultivars. Field tests with known pathotypes of P. triticina demonstrated that 57% of the cultivars carried adult plant resistance (APR) to P. triticina. The genetic identity of the APR is largely unknown. Genetic studies on selected cultivars with unidentified seedling resistances as well as all of those identified to carry APR are required to determine the number and inheritance of the genes involved, to determine their relationships with previously designated rust resistance genes, and to assess their potential value in breeding for resistance to leaf rust.     

Using molecular markers to pyramid genes for resistance to ascochyta blight and anthracnose in lentil (Lens culinaris Medik)

Ascochyta blight caused by the fungus Ascochyta lentis Vassilievsky and anthracnose caused by Colletotrichum truncatum [(Schwein.) Andrus & W.D. Moore] are the most destructive diseases of lentil in Canada. The diseases reduce both seed yield and seed quality. Previous studies demonstrated that two genes, ral1 and AbR1, confer resistance toA. lentis and a major gene controls the resistance to 95B36 isolate of C. truncatum. Molecular markers linked to each gene have been identified. The current study was conducted to pyramid the two genes for resistance to ascochyta blight and the gene for resistance to anthracnose into lentil breeding lines. A population (F_6:7) consisting of 156 recombinant inbred lines (RILs) was developed from across between ‘CDC Robin’ and a breeding line ‘964a-46’. The RILs were screened for reaction to two isolates (A1 and 3D2) ofA. lentis and one isolate (95B36) ofC. truncatum. χ² analysis of disease reactions demonstrated that the observed segregation ratios of resistant versus susceptible fit the two gene model for resistance to ascochyta blight and a single gene model for resistance to anthracnose. Using markers linked to ral1 (UBC 227₁₂₉₀), to AbR1(RB18₆₈₀) and to the major gene for resistance to anthracnose (OPO6₁₂₅₀),respectively, we confirmed that 11 RILs retained all the three resistance genes. More than 82% of the lines that had either or both RB18₆₈₀ and UBC227₁₂₉₀markers were resistant to 3D2 isolate and had a mean disease score lower than 2.5. By contrast, 80% of the lines that had none of the RAPD markers were susceptible and had a mean disease score of 5.8. For the case of A1 isolate of A. lentis, more than 74% of the lines that carriedUBC227₁₂₉₀ were resistant, whereas more than 79% of the lines that do not have the marker were susceptible. The analysis of the RILs usingOPO6₁₂₅₀ marker demonstrated that 11out of 72 resistant lines carried the marker, whereas 66 out of 84 susceptible lines had the marker present. Therefore, selecting materials with both markers for resistance to ascochyta blight and a marker for resistance to anthracnose can clearly make progress toward resistance in the population. This revised version was published online in July 2006 with corrections to the Cover Date.     

Molecular markers and allelic relationships of anthracnose resistance gene cluster B4 in common bean

Angular leaf spot is one of the major diseases of the common bean. The extensive genetic variability of this pathogen requires the constant development of new resistant cultivars. Different sources of resistance have been identified and characterized. For the State of Minas Gerais, Brazil, four main resistance sources were found: Mexico 54, AND 277, MAR 2 and Cornell 49-242. Independent characterization of these genotypes demonstrates that resistance in all four sources is dominant and monogenic. However, there are no studies on the relationship and independence of these genes. In the present work, allelism tests were carried out to understand the relationship among the resistance genes present in these four resistance sources. The data revealed a much higher complexity in the resistance inheritance of these genes than previously reported. It was demonstrated that Cornell 49-242 possesses a dominant gene (Phg-3); Mexico 54 possesses three genes, denominated Phg-2, Phg-5 and Phg-6. In MAR 2, two genes were found, one independent designated Phg-4 and the other, an allelic form of Phg-5, denominated of Phg-5². Allelic forms were also found in AND 277, Phg-2², Phg-3² and Phg-4². These results have special importance for breeding programs aiming to pyramid resistance genes.     

Evaluation of seedling and adult plant resistance in European wheat cultivars to Australian isolates of <Emphasis Type="Italic">Puccinia striiformis</Emphasis> f. sp. <Emphasis Type="Italic">tritici</Emphasis>

A set of 105 European wheat cultivars was assessed for seedling resistance and adult plant resistance (APR) to stripe (yellow) rust in greenhouse and field tests with selected Australian isolates of Puccinia striiformis f. sp. tritici (Pst). Twelve cultivars were susceptible to all pathotypes, and among the remainder, 11 designated seedling genes (Yr1, Yr3, Yr4, Yr6, Yr7, Yr9, Yr17, Yr27, Yr32, YrHVII and YrSP) and a range of unidentified seedling resistances were detected either singly or in combination. The identity of seedling resistance in 43 cultivars could not be determined with the available Pst pathotypes, and it is considered possible that at least some of these may carry uncharacterised seedling resistance genes. The gene Yr9 occurred with the highest frequency, present in 19 cultivars (18%), followed by Yr17, present in 10 cultivars (10%). Twenty four cultivars lacked seedling resistance that was effective against the pathotype used in field nurseries, and all but two of these displayed very high levels of APR. While the genetic identity of this APR is currently unknown, it is potentially a very useful source of resistance to Pst. Genetic studies are now needed to characterise this resistance to expedite its use in efforts to breed for resistance to stripe rust. Colin R. Wellings seconded from NSW Department of Primary Industries.     

Genes conferring low seedling reaction to Mexican pathotypes of Puccinia recondita f. sp. tritici,and adult-plant responses of recent wheat cultivars from the former USSR

Fifty-five spring bread wheat (Triticum aestivum L.) cultivars, mostly released between 1975 and 1991 in eight leaf rust-prone spring wheat growing regions of the former USSR, were tested in the seedling growth stage for reaction to 15 Mexican pathotypes of Puccinia recondita f. sp. tritici. In total, seven known and at least two unknown genes were identified, either singly or in combinations: Lr3 (7 cultivars), Lr10 (14), Lr13 (5), Lr14a (1), Lr16 (1), Lr23 (3); the unknown genes were identified in 14 cultivars. The first unknown gene could be either Lr9, Lr19, or Lr25; however, the second unknown gene in 9 cultivars was different from any named gene. Twelve of the 15 pathotypes are virulent for this gene, hence its use in breeding for resistance will be limited. The cultivars were also evaluated at two field locations in Mexico with two pathotypes in separate experiments. The area under the disease progress curve and the final disease rating of the cultivars indicated genetic diversity for genes conferring adult plant resistance. based on the symptoms of the leaf tip necrosis in adult plants, resistance gene Lr34 could be present in at least 20 cultivars. More than half of the cultivars carry high to moderate levels of adult plant resistance and were distributed in each region.     

Differential resistances to anthracnose in Capsicum baccatum as responding to two Colletotrichum pathotypes and inoculation methods

Chili anthracnose, caused by Colletotrichum spp., is one of the major diseases to chili production in the tropics and subtropics worldwide. Breeding for durable anthracnose resistance requires a good understanding of the resistance mechanisms to different pathotypes and inoculation methods. This study aimed to investigate the inheritances of differential resistances as responding to two different Colletotrichum pathotypes, PCa2 and PCa3 and as by two different inoculation methods, microinjection (MI) and high pressure spray (HP). Detached ripe fruit of Capsicum baccatum ‘PBC80’ derived F₂ and BC₁s populations was assessed for anthracnose resistance. Two dominant genes were identified responsible for the differential resistance to anthracnose. One was responsible for the resistance to PCa2 and PCa3 by MI and the other was responsible for the resistance to PCa3 by HP. The two genes were linked with 16.7 cM distance.     

Inheritance of resistance to angular leaf spot in common bean and validation of the utility of resistance linked markers for marker assisted selection out side the mapping population

Inheritance of resistance to angular leaf spot (ALS) disease caused by Phaeoisariopsis griseola (Sacc.) Ferr was investigated in two common bean cultivars, Mexico 54 and BAT 332. Both Andean and Mesoamerican backgrounds were used to determine the stability of the resistance gene in each of the two cultivars. Resistance to P. griseola was phenotypically evaluated by artificial inoculation with one of the most widely distributed pathotypes, 63–39. Evaluation of the parental genotypes, F₁, F₂ and backcross populations revealed that the resistance to angular leaf spot in the cultivars Mexico 54 and BAT 332 to pathotype 63–39 is controlled by a single dominant gene, when both the Andean and Mesoamerican backgrounds were used. Allelism test showed that ALS resistance in Mexico 54 and BAT 332 to pathotype 63–39 was conditioned by the same resistance locus. Resistant and susceptible segregating populations generated using Mexico 54 resistant parent were selected for DNA extraction and amplification to check for the presence /absence of the SCAR OPN02 and RAPD OPE04 markers linked to the Phg-2 resistance gene. The results indicated that the SCAR OPN02 was not polymorphic in the study populations and therefore of limited application in selecting resistant genotypes in such populations. On the other hand, the RAPD OPE04 marker was observed in all resistant individuals and was absent in those scored susceptible based on virulence data. Use of the RAPD OPE04 marker in marker-assisted selection is underway.