We mapped and characterized quantitative trait loci (QTL) affecting testcross performance of important forage maize (Zea mays L.) traits and investigated their consistency across different populations. Four independent populations comprising 380 F3 lines (A✕Bc), 113 F5 lines (A✕BV), 131 F4 lines (A✕CV), and 140 F4 lines (C✕DV) were produced from four elite flint inbreds (A, B, C, D) and genotyped at 89, 151, 104, and 122 RFLP marker loci, respectively. All lines were testcrossed to the same dent inbred tester and evaluated in field trials with two replications in five environments. Six traits were analyzed: dry matter yield (DMY), dry matter concentration (DMC), plant height (PHT), in vitro digestible organic matter (IVDOM), starch concentration (STC), and protein concentration (CPC) of forage. Genotypic variances (σ̂2g) were mostly significant for these traits in all populations and heritabilities generally exceeded 0.50. Between 2 and 14 QTL were detected in individual populations by composite interval mapping, which explained between 17.6 and 65.7% of the total phenotypic variance (σ̂2p). Few of the detected QTL displayed significant digenic epistatic or QTL ✕ environment interactions. Consistency of QTL positions across all four populations was greater for DMC, STC, and PHT than for DMY, IVDOM, and CPC. Across all traits' QTL, results were largely consistent among A✕BC and A✕Bv, but not among A✕Bc and A✕Cv or A✕Bc and C✕Dv. When QTL positions and substitution effects for DMY obtained in A✕BC, explaining 43% of σ̂2p, were employed for prediction of QTL positions and substitution effects in the other three populations they explained 24% of σ̂2p in A✕BV, 11% σ̂2p in A✕Cv, and 0% of σ̂2p in C✕DV. QTL results were poorly consistent among crosses within the flint heterotic pool, suggesting that prior to marker‐assisted selection, QTL mapping must be performed separately for each population.

Forty-one accessions of the genusBeta representing wild and cultivated species of all sections were analyzed by DNA "fingerprinting". Four sugar beet minisatellite DNA probes revealed characteristic banding patterns with Southern-hybridizedBeta DNA restricted withHindIII. A total of 111 polymorphic RFLP bands were scored across all accessions. Cluster analysis based on genetic similarity estimates for all 820 combinations of accessions revealed the following results. (1) All accessions could unambiguously be identified by a characteristic RFLP banding pattern. (2) The sugar beet cultivars examined displayed a low level of genetic diversity; they showed high similarity toB. Vulgaris ssp.maritima but low genetic similarity to the other wild species of section I. (3) In most cases, the present taxonomic classification of the genusBeta was confirmed. Species of sections II, III, and IV were clearly distinguishable from those of section I except forB. Macrocarpa, which showed high similarity to wild species of section II. In a second experiment, 108 single-copy RFLP probes from sugar beet were Southern hybridized withB. procumbens DNA. A surprisingly low degree of homology (34%) was found. The results are discussed with regard to the taxonomic classification of the genusBeta.

The objective of this study was to investigate the origin of chromosome segments of maize (Zea mays L.) inbred B86 from its parental inbreds B52 and Oh43 using RFLPs. B86 was selected to combine resistance to the first and second brood of the European corn borer with the favorable agronomic performance of Oh43. RFLP analyses of the three inbreds were performed with three restriction enzymes {EcoKl, £coRV, Hindlll) and 178 DNA probes covering all ten maize chromosomes. For two DNA probes in combination with one enzyme, B86 showed a new RFLP pattern not present in the two parents. Based on results from 119 polymorphic DNA probes, the proportion of the B86 genome contributed by B52 (51.3%) and Oh43 (48.7%) was almost equal.Maize {Zea mays L.) inbred B86 was developed from cross B52 X Oh43 by W. A. RUSSELL and W. D. GUTHRIE at Iowa State Agricultural Experiment Station. It represents a hne resulting from a typical recycling breeding program aimed at combining favorable traits from different parents into a single genotype. Parent B52 is an inbred with poor grain yield performance but intermediate and high resistance against leaf feeding (first brood = lEGB) and sheath and collar feeding (second brood = 2EGB), respectively, of the European corn borer (EGB) Gstrinia nubilalis Hiibner (RUSSELL and GUTHRIE 1979). Parent Oh43 is an inbred with good combining ability for grain yield but only moderate resistance to lEGB and high susceptibility to 2EGB (RUSSELL et al. 1974). B86 was the best inbred developed from 200 F3 lines of cross B52 X Oh43 by selfing and visual selection according to the ear-torow method from the F3 to F7 generations, using artificial infestation with EGB egg masses in each generation (RUSSELL et al. 1974). In addition to selection for both resistance traits, the main selection criterion was recovery of the Oh43 phenotype (W. A. RUSSELL, pers. comm.). B86 proved to be highly resistant to lEGB and nearly as resistant as B52 to 2EGB (RUSSELL and GUTHRIE 1979).The concept of graphical genotypes was proposed by YOUNG and TANKSLEY (1989) for graphical presentation of the parental contributions to the genome of an offspring as determined by a large number of molecular markers, e.g., restriction fragment length polymorphisms (RFLPs). As part of an extensive RFLP study with several maize inbreds, we applied this concept to determine the origin of chromosomal segments of B86 from its parental inbreds B52 and Oh43, and to show how this concept can be used to study the frequency of recombination events and to investigate the efficiency of phenotypic selection practised during a breeding process. Furthermore, we report on the occurrence of new RFLP patterns in a recombinant inbred line not present in the two parental inbreds. U.S.