Utility of RAPD markers in identifying genetic linkages to genes of economic interest in peach

The identification of molecular markers linked to economically important traits for use in crop improvement is very important in long-lived perennial species. Three-hundred-and-sixty RAPD primers were used with bulked segregant analysis to identify markers linked to loci of specific interest in peach [(Prunus persica) L. Batch] and peach x almond [(Prunus dulcis) Batch] crosses. The traits analyzed included flesh color, adhesion, and texture; pollen fertility; plant stature; and three isozyme loci. The Mendelian behavior of the RAPD loci was established, and RAPD markers were mapped relative to the loci controlling flesh color, adhesion, and texture, and the isozyme loci Mdh-1, 6Pgd-2 and Aat-1, as well as the existing RFLP genetic linkage map constructed previously using a peach x almond F₂ population. This technique has facilitated rapid identification of RAPD and RFLP markers that are linked to the traits under study. Loci controlling these traits mapped predominantly to linkage groups 2 and 3 of the peach genetic linkage map. Linkages to genes with both dominant and co-dominant alleles were identified, but linkages to dominant genes were more difficult to find. In several crosses, RAPD marker bands proved to be allelic. One co-dominant RAPD formed a heteroduplex band in heterozygous individuals and in mixtures of alternate homozygotes. The Mendelian behavior of the RAPD loci studied was established and the results suggest that RAPD markers will be useful for plant improvement in peach.     

A genetic linkage map of cowpea (Vigna unguiculata) developed from a cross between two inbred, domesticated lines

 We have constructed a genetic linkage map within the cultivated gene pool of cowpea (2n=2x=22) from an F₈ recombinant inbred population (94 individuals) derived from a cross between the inbreds IT84S-2049 and 524B. These breeding lines, developed in Nigeria and California, show contrasting reactions against several pests and diseases and differ in several morphological traits. Parental lines were screened with 332 random RAPD decamers, 74 RFLP probes (bean, cowpea and mung bean genomic DNA clones), and 17 AFLP primer combinations. RAPD primers were twice as efficient as AFLP primers and RFLP probes in detecting polymorphisms in this cross. The map consists of 181 loci, comprising 133 RAPDs, 19 RFLPs, 25 AFLPs, three morphological/classical markers, and a biochemical marker (dehydrin). These markers identified 12 linkage groups spanning 972 cM with an average distance of 6.4 cM between markers. Linkage groups ranged from 3 to 257 cM in length and included from 2 to 41 markers, respectively. A gene for earliness was mapped on linkage group 2. Seed weight showed a significant association with a RAPD marker on linkage group 5. This map should facilitate the identification of markers that “tag” genes for pest and disease resistance and other traits in the cultivated gene pool of cowpea. Received: 16 September 1996 / Accepted: 25 April 1997     

Mapping of RFLP and qualitative trait loci in Brassica rapa and comparison to the linkage maps of B. napus,B. oleracea,and Arabidopsis thaliana

A linkage map of restriction fragment length polymorphisms (RFLPs) was constructed for oilseed, Brassica rapa, using anonymous genomic DNA and cDNA clones from Brassica and cloned genes from the crucifer Arabidopsis thaliana. We also mapped genes controlling the simply inherited traits, yellow seeds, low seed erucic acid, and pubescence. The map included 139 RFLP loci organized into ten linkage groups (LGs) and one small group covering 1785 cM. Each of the three traits mapped to a single locus on three different LGs. Many of the RFLP loci were detected with the same set of probes used to construct maps in the diploid B. oleracea and the amphidiploid B. napus. Comparisons of the linkage arrangements between the diploid species B. rapa and B. oleracea revealed six LGs with at least two loci in common. Nine of the B. rapa LGs had conserved linkage arrangements with B. napus LGs. The majority of loci in common were in the same order among the three species, although the distances between loci were largest on the B. rapa map. We also compared the genome organization between B. rapa and A. thaliana using RFLP loci detected with 12 cloned genes in the two species and found some evidence for a conservation of the linkage arrangements. This B. rapa map will be used to test for associations between segregation of RFLPs, detected by cloned genes of known function, and traits of interest.     

An extended map of the sugar beet genome containing RFLP and RAPD loci

An updated map of sugar beet (Beta vulgaris L. ssp. vulgaris var altissima Doell) is presented. In this genetic map we have combined 248 RFLP and 50 RAPD loci. Including the loci for rhizomania resistance Rr1, hypocotyl colour R and the locus controlling the monogerm character M, 301 loci have now been mapped to the nine linkage groups covering 815 cM. In addition, the karyotype of some of the Beta vulgaris chromosomes has been correlated with existing RFLP and RAPD linkage maps.     

Marker enrichment and high-resolution map of the segment of potato chromosome VII harbouring the nematode resistance gene Gro1

The dominant allele Gro1 confers on potato resistance to the root cyst nematode Globodera rostochiensis. The Gro1 locus has been mapped to chromosome VII on the genetic map of potato, using RFLP markers. This makes possible the cloning of Gro1 based on its map position. As part of this strategy we have constructed a high-resolution genetic map of the chromosome segment surrounding Gro1, based on RFLP, RAPD and AFLP markers. RAPD and RFLP markers closely linked to Gro1 were selected by bulked segregant analysis and mapped relative to the Gro1 locus in a segregating population of 1105 plants. Three RFLP and one RAPD marker were found to be inseparable from the Gro1 locus. Two AFLP markers were identified that flanked Gro1 at genetic distances of 0.6 cM and 0.8 cM, respectively. A genetic distance of 1 cM in the Gro1 region corresponds to a physical distance of ca. 100 kb as estimated by long-range restriction analysis. Marker-assisted selection for nematode resistance was accomplished in the course of constructing the high-resolution map. Plants carrying the resistance allele Gro1 could be distinguished from susceptible plants by marker assays based on the polymerase chain reaction (PCR).     

Theobroma cacao L.: a genetic linkage map and quantitative trait loci analysis

A genetic linkage map of Theobroma cacao (cocoa) has been constructed from 131 backcross trees derived from a cross between a single tree of the variety Catongo and an F1 tree from the cross of Catongo by Pound 12. The map comprises 138 markers: 104 RAPD loci, 32 RFLP loci and two morphologic loci. Ten linkage groups were found which cover 1068 centimorgans (cM). Only six (4%) molecular-marker loci show a significant deviation from the expected 11 segregation ratio.The average distance between two adjacent markers is 8.3 cM. The final genome-size estimates based on two-point linkage data ranged from 1078 to 1112 cM for the cocoa genome. This backcross progeny segregates for two apparently single gene loci controlling (1) anthocyanidin synthesis (Anth) in seeds, leaves and flowers and (2) self-compatibility (Autoc). The Anth locus was found to be 25 cM from Autoc and two molecular markers co-segregate with Anth. The genetic linkage map was used to localize QTLs for early flowering, trunk diameter, jorquette height and ovule number in the BC₁ generation using both single-point ANOVA and interval mapping. A minimum number of 2–4 QTLs (P<0.01) involved in the genetic expression of the traits studied was detected. Coincident map locations of a QTL for jorquette height and trunk diameter suggests the possibility of pleiotropic effects in cocoa for these traits. The combined estimated effects of the different mapped QTLs explained between 11.2% and 25.8% of the phenotypic variance observed in the BC₁ population.     

A genetic linkage map for Pinus radiata based on RFLP, RAPD, and microsatellite markers

A genetic linkage map for radiata pine (Pinus radiata D. Don) has been constructed using segregation data from a three-generation outbred pedigree. A total of 208 loci were analyzed including 165 restriction fragment length polymorphism (RFLP), 41 random amplified polymorphic DNA (RAPD) and 2 microsatellite markers. The markers were assembled into 22 linkage groups of 2 or more loci and covered a total distance of 1382 cM. Thirteen loci were unlinked to any other marker. Of the RFLP loci that were mapped, 93 were detected by loblolly pine (P. taeda L.) cDNA probes that had been previously mapped or evaluated in that species. The remaining 72 RFLP loci were detected by radiata pine probes from a PstI genomic DNA library. Two hundred and eighty RAPD primers were evaluated, and 41 loci which were segregating in a 11 ratio were mapped. Two microsatellite markers were also placed on the map. This map and the markers derived from it will have wide applicability to genetic studies in P. radiata and other pine species.     

Genetic analysis of RFLPs, GATA microsatellites and RAPDs in a cross between L. esculentum and L. pimpinellifolium

A population of 257 BC₁ plants was developed from a cross between an elite processing line of tomato (Lycopersicon esculentum cvM82-1-7) and the closely related wild species L. pimpinellifolium (LA1589). The population was used to construct a genetic linkage map suitable for quantitative trait locus (QTL) analysis to be conducted in different backcross generations. The map comprises 115 RFLP, 3 RAPD and 2 morphological markers that span 1279 cM of the tomato genome with an average distance between markers of 10.7 cM. This map is comparable in length to that of the highdensity RFLP map derived from a L. esculentum x L. pennellii F₂ population. The order of the markers in the two maps is also in good agreement, however there are considerable differences in the distribution of recombination along the chromosomes. The segregation of six GATA-containing loci and 47 RAPD markers was also analyzed in subsets of the population. All of the microsatellite loci and 35 (75%) of the RAPDs mapped to clusters associated with centromeric regions.     

A consensus map for <Emphasis Type="Italic">Cucurbita pepo</Emphasis>

Using random amplified polymorphic DNA (RAPD), amplified fragment length polymorphism (AFLP), simple sequence repeats (SSR), and morphological traits, the first genetic maps for Cucurbita pepo (2n=2x=40) were constructed and compared. The two mapping populations consisted of 92 F₂ individuals each. One map was developed from a cross between an oil-seed pumpkin breeding line and a zucchini accession, into which genes for resistance to Zucchini Yellow Mosaic Virus (ZYMV) from a related species, C. moschata, had been introgressed. The other map was developed from a cross between an oil-seed pumpkin and a crookneck variety. A total of 332 and 323 markers were mapped in the two populations. Markers were distributed in each map over 21 linkage groups and covered an average of 2,200 cM of the C. pepo genome. The two maps had 62 loci in common, which enabled identification of 14 homologous linkage groups. Polyacrylamide gel analyses allowed detection of a high number of markers suitable for mapping, 10% of which were co-dominant RAPD loci. In the Pumpkin-Zucchini population, bulked segregant analysis (BSA) identified seven markers less than 7 cM distant from the locus n, affecting lignification of the seed coat. One of these markers, linked to the recessive hull-less allele (AW11-420), was also found in the Pumpkin-Crookneck population, 4 cM from n. In the Pumpkin-Zucchini population, 24 RAPD markers, previously introduced into C. pepo from C. moschata, were mapped in two linkage groups (13 and 11 markers in LGpz1 and LGpz2, respectively), together with two sequence characterized amplified region (SCAR) markers linked to genes for resistance to ZYMV.     

Interval mapping of genes for quantitative resistance of maize to Setosphaeria turcica,cause of northern leaf blight,in a tropical environment

Quantitative trait loci (QTL) involved in the resistance of maize to Setosphaeria turcica, the causal agent of northern leaf blight, were located by interval mapping analysis of 121 F_2:3 lines derived from a cross between Mo17 (moderately resistant) and B52 (susceptible). A linkage map spanning 112 RFLP loci with 15 cM mean interval length was constructed, based on marker data recorded in a previous study. Field tests with artificial inoculation were conducted at three sites in tropical mid- to high-altitude regions of Kenya, East Africa. Host-plant response was measured in terms of incubation period, disease severity (five scoring dates), and the area under the disease progress curve (AUDPC). Heritability of all traits was high (around 0.75). QTL associated with the incubation period were located on chromosomes 2S and 8L. For disease severity and AUDPC, significant QTL were detected in the putative centromeric region of chromosome 1 and on 2S, 3L, 5S, 6L, 7L, 8L and 9S. On 2S the same marker interval which carried a gene enhancing latent period was also associated with reduced disease severity of juvenile plants. QTL on chromosomes 3L, 5S, 7L and 8L were significant across environments but all other QTL were affected by a large genotype x environment interaction. Partially dominant gene action for resistance as well as for susceptibility was prevailing. Single QTL explained 10 to 38% of the phenotypic variation of the traits. All but the QTL on chromosomes 1, 6 and 9 were contributed by the resistant parent Mo17. On chromosome 8L a QTL mapped to the same region as the major race-specific gene Ht2, supporting the hypothesis that some qualitative and quantitative resistance genes may be allelic.Abbreviations AUDPC area under the disease progress curve - CIMMYT International Maize and Wheat Improvement Center - KARI Kenya Agricultural Research Institute - NCLB northern corn leaf blight - QTL quantitative trait locus/loci     

RFLP and RAPD mapping of the sunflower Pl1 locus for resistance to Plasmopara halstedii race 1

The Pl1 locus in sunflower, Helianthus annuus L., conferring resistance to downy mildew, Plasmopara halstedii, race 1 has been located in linkage group 1 of the consensus RFLP map of the cultivated sunflower. Bulked segregant analyses were used on 135 plants of an F₂ progeny from a cross between a downy mildew susceptible line, GH, and RHA266, a line carrying Pl1. Two RFLP markers and one RAPD marker linked to the Pl1 locus have been identified. The RFLP markers are located at 5.6 cM and 7.1 cM on either side of Pl1. The RAPD marker is situated at 43.7 cM from Pl1. The significance and applications of these markers in sunflower breeding are discussed.     

Genetic linkage map of melon (<Emphasis Type="Italic">Cucumis melo</Emphasis> L.) and localization of a major QTL for powdery mildew resistance

Powdery mildew caused by Podosphaera xanthii has become a major problem in melon since it occurs all year round irrespective of the growing system. The TGR-1551 melon genotype was found to be resistant to several melon diseases, among them powdery mildew. However, the corresponding resistance genes have been never mapped. We constructed an integrated genetic linkage map using an F2 population derived from a cross between the multi-resistant genotype TGR-1551 and the susceptible Spanish cultivar ‘Bola de Oro’. The map spans 1,284.9 cM, with an average distance of 3.6 cM among markers, and consists of 354 loci (188 AFLP, 39 RAPD, 111 SSR, 14 SCAR/CAPS/dCAPS, and two phenotypic traits) distributed in 14 linkage groups. QTL analysis identified one major QTL (Pm-R) on LG V for resistance to races 1, 2, and 5 of powdery mildew. The PM4-CAPS marker is closely linked to the Pm-R QTL at a genetic distance of 1.9 cM, and the PM3-CAPS marker is located within the support interval of this QTL. These codominant markers, together with the map information reported here, could be used for melon breeding, and particularly for genotyping selection of resistance to powdery mildew in this vegetable crop species.     

A linkage map for sugi (Cryptomeria japonica) based on RFLP,RAPD, and isozyme loci

A linkage map for sugi was constructed on the basis of restriction fragment length polymorphism (RFLP), random amplified polymorphic DNA (RAPD), and isozyme loci using a three-generation pedigree prepared for genetic analysis of heartwood color. A total of 128 RFLP (123 cDNA and 5 genomic probes), 33 RAPD, 2 isozyme, and 1 morphological (dwarf) loci segregated in 73 progeny. Of the 164 segregating loci, 145 loci were distributed in 20 linkage groups. Of these loci, 91 with confirmed map positions were assigned to 13 linkage groups, covering a total of 887.3 cM. A clustering of markers with distorted segregation was observed in 6 linkage groups. In the four clusters, distortions with a reduction in the number of homozygotes from one parent only were found.Abbreviations MAS marker-assisted selection - PAGE polyacrylamide gel electrophoresis - QTL quantitative traits of loci - RAPD random amplified polymorphic DNA - RFLP restriction fragment length polymorphism This work was supported by a Grant-in-Aid from the Ministry of Agriculture, Forestry and Fisheries of Japan (Integrated Research Program for the Use of Biotechnological Procedures for Plant Breeding) and by a Grant-in-Aid from the Ministry of Education, Science and Culture of Japan (Cooperative Research, no. 04304017)     

Use of Random Amplified Polymorphic DNA Markers for Mapping the Chickpea Genome

Three interspecific crosses were developed using Cicer arietinum (ICC 4918) as the female parent and wild Cicer species [C. reticulatum - JM 2100, JM 2106 and C. echinospermum - ICCW 44] as the male parent. Cicer arietinum (ICC 4918) × C. reticulatum (JM 2100) cross produced the largest number of F₂ plants and was chosen for linkage mapping using Random Amplified Polymorphic DNA (RAPD) primers. A partial linkage map was constructed based upon the segregation of 36 RAPD markers obtained by amplification using 35 primers. The linkage map consists of two linkage groups with 17 linked markers covering a total of 464.9 cM. Analyses also revealed association of three morphological traits with linked RAPD markers. Out of seven morphological traits tested for association with linked markers in the segregating plants, four Quantitative trait loci (QTL) were detected for the trait leaf length and three QTLs each for the traits leaf width and erect plant habit.     

Tagging and combining bacterial blight resistance genes in rice using RAPD and RFLP markers

Four genes of rice,Oryza sativa L., conditioning resistance to the bacterial blight pathogenXanthomonas oryzae pv.oryzae (X. o. pv.oryzae), were tagged by restriction fragment length polymorphism (RFLP) and random amplified polymorphic DNA (RAPD) markers. No recombinants were observed betweenxa-5 and RFLP marker lociRZ390, RG556 orRG207 on chromosome 5.Xa-3 andXa-4 were linked to RFLP locusXNpb181 at the top of chromosome 11, at distances of 2.3 cM and 1.7 cM, respectively. The nearest marker toXa-10, also located on chromosome 11, was the RAPD locusO07 ₂₀₀₀ at a distance of 5.3 cM. From this study, the conventional map [19, 28] and two RFLP linkage maps of chromosome 11 [14, 26] were partially integrated. Using the RFLP and RAPD markers linked to the resistance genes, we selected rice lines homozygous for pairs of resistance genes,Xa-4 +xa-5 andXa-4 +Xa-10. Lines carryingXa-4 +xa-5 andXa-4 +Xa-10 were evaluated for reaction to eight strains of the bacterial blight pathogen, representing eight pathotypes and three genetic lineages. As expected, the lines carrying pairs of genes were resistant to more of the isolates than their single-gene parental lines. Lines carryingXa-4 +xa-5 were more resistant to isolates of race 4 than were either of the parental lines (quantitative complementation). No such effects were seen forXa-4 +Xa-10. Thus, combinations of resistance genes provide broader spectra of resistance through both ordinary gene action expected and quantitative complementation.     

A genetic linkage map for Eucalyptus globulus with candidate loci for wood,fibre, and floral traits

A genetic linkage map containing potential candidate loci for wood, fibre and floral traits has been constructed for Eucalyptus globulus (Labill.) based on the segregation of 249 codominant loci in an outbred F₁ population of 148 individuals. The map contains 204 RFLP loci, including 31 cambium-specific expressed sequence tags (ESTs) and 14 known function genes, and 40 microsatellite and five isozyme loci. Independent male and female maps were constructed, and the 98 loci (39%) that segregated in both parents were used to combine the parental maps into an integrated map. The 249 loci mapped to 11 major linkage groups (n=11 in eucalypts) and a 12th small linkage group containing three loci that segregated in the male parent only. Total map distance is 1375 cM with an average interval of 6 cM. Forty one of the mapped loci identify known proteins (five isozymes) or sequences with known function (14 genes and 22 ESTs). The mapped genes include enzymes involved in lignin and cell-wall polysaccharide biosynthesis, and floral-development genes. This map will be used to locate quantitative trait loci for wood, fibre, and other traits in Eucalyptus. Received: 30 August 2000 / Accepted: 23 March 2001     

QTL analysis and mapping of pi21, a recessive gene for field resistance to rice blast in Japanese upland rice

Field resistance is defined as the resistance that allows effective control of a parasite under natural field conditions and is durable when exposed to new races of that parasite. To identify the genes for field resistance to rice blast, quantitative trait loci (QTLs) conferring field resistance to rice blast in Japanese upland rice were detected and mapped using RFLP and SSR markers. QTL analysis was carried out in F₄ progeny lines from the cross between Nipponbare (moderately susceptible, lowland) and Owarihatamochi (resistant, upland). Two QTLs were detected on chromosome 4 and one QTL was detected on each of chromosomes 9 and 12. The phenotypic variation explained by each QTL ranged from 7.9 to 45.7% and the four QTLs explained 66.3% of the total phenotypic variation. Backcrossed progeny lines were developed to transfer the QTL with largest effect using the susceptible cultivar Aichiasahi as a recurrent parent. Among 82 F₃ lines derived from the backcross, resistance segregated in the expected ratio of resistant 1 : heterozygous 2 : susceptible 1. The average score for blast resistance measured in the field was 4.2 ± 0.67, 7.5 ± 0.51and 8.2 ± 0.66, for resistant, heterozygous and susceptible groups, respectively. The resistance gene, designated pi21, was mapped on chromosome 4 as a single recessive gene between RFLP marker loci G271 and G317 at a distance of 5.0 cM and 8.5 cM, respectively. The relationship to previously reported major genes and QTLs conferring resistance to blasts, and the significance of marker-assisted selection to improve field resistance, are discussed. Received: 8 June 2000 / Accepted: 24 November 2000     

Linkage map construction in allotetraploid creeping bentgrass (Agrostis stolonifera L.)

Creeping bentgrass (Agrostis stolonifera L.) is one of the most adapted bentgrass species for use on golf course fairways and putting greens because of its high tolerance to low mowing height. It is a highly outcrossing allotetraploid species (2n=4x=28, A₂ and A₃ subgenomes). The first linkage map in this species is reported herein, and it was constructed based on a population derived from a cross between two heterozygous clones using 169 RAPD, 180 AFLP, and 39 heterologous cereal and 36 homologous bentgrass cDNA RFLP markers. The linkage map consists of 424 mapped loci covering 1,110 cM in 14 linkage groups, of which seven pairs of homoeologous chromosomes were identified based on duplicated loci. The numbering of all seven linkage groups in the bentgrass map was assigned according to common markers mapped on syntenous chromosomes of ryegrass and wheat. The number of markers linked in coupling and repulsion phase was in a 1:1 ratio, indicating disomic inheritance. This supports a strict allotetraploid inheritance in creeping bentgrass, as suggested by previous work based on chromosomal pairing and isozymes. This linkage map will assist in the tagging and eventually in marker-assisted breeding of economically important quantitative traits like disease resistance to dollar spot (Sclerotinia homoeocarpa F.T. Bennett) and brown patch (Rhizoctonia solani Kuhn).     

Genome-wide analysis of maize cytoplasmic male sterility-S based on QTL mapping

Three types of sterile cytoplasm in cytoplasmic-male-sterility (CMS) maize, T, C and S, can be identified according to their fertility-restoration and mitochondrial DNA RFLP patterns. CMS-S, which is the least stable among the three types of CMS, is controlled by sterile cytoplasm interactions with certain nuclear-encoded factors. We constructed a high-resolution map of loci associated with male-restoration of CMS-S in BC1 populations of maize. The map covers 1730.29 cM, including 32 RFLP, 51 SSR 62 RAPD and 21 AFLP markers. Genome-wide QTL analysis detected 6 QTLs with significant effects on male fertility as assessed by their starch-filled pollen ratios. Four QTLs out of six were located between the SSR markers MSbnlg1633-Mrasg20, MSbnlg1662-Msume1126, MSume1230-MSumc1525, and RAPD marker MraopQ07-2-MraopK06-2 on chromosome 2. Two other minor loci were mapped between MraopK16-1-Mraopi4-1, on chromosome 9, and between Msuncbnlg1139-MraopR10-2, on chromosome 6. The Rf3 nuclear restoring gene was precisely located on the chromosome 2, 2.29 cM to the left of umc1525 and 8.9 cM to the right of umc1230. The results provide important markers for marker-assisted selection of stable CMS-S maize.     

A partial genetic linkage map of slash pine (Pinus elliottii Engelm. var. elliottii) based on random amplified polymorphic DNAs

A set of 420 random, 10-base, oligonucleotide primers was screened for random amplified polymorphic DNA (RAPD) fragments within a sample of eight megagametophyte DNAs of a single slash pine (Pinus elliottii Engelm. var. elliottii) tree. The apparently repeatable RAPD fragments were further characterized within a sample of 68 megagametophytes from the same tree. Fragments segregating in a 11, present-to-absent, ratio were classified and mapped using multi-point linkage analysis. The analysis revealed 13 linkage groups of at least three loci, ranging in size from 28 to 68 cM, and nine linked pairs of loci. The 22 groups and pairs included 73 RAPD markers and covered a genetic map distance of approximately 782 cM. Genome size estimates, based on linkage data, ranged from 2880 to 3360 cM. Using a 30-cM map scale and including the 24 unlinked markers and the ends of the 13 linkage groups and nine linked pairs, the set of RAPD markers accounts for approximately 2160 cM or 64–75% of the genome. This extent of genomic coverage should allow for the efficient mapping of genes responsible for a reaction to the causal agent of fusiform rust disease, Cronartium quercuum (Berk.) Miyabe ex Shirai f. sp. fusiforme.