Two-row Malting Barley Research Articles

Influence of Foliar Application of Microelements on Yield and Yield Components of Spring Malting Barley

Barley is an economically important plant cultivated primarily for animal feed and in the brewing industry for the production of barley malt. Climate changes and an increase in grain demand result in a constant need to improve the volume and stability of cereal species yields and better use the potential of cultivars. In cereal production, an important aspect is the use of microelements, especially by foliar spraying. Microelements, as components or enzyme activators, play a significant role in plant growth and metabolic processes occurring in the cell. As a consequence, their availability is a factor determining plant development. The aim of this study was to determine the effect of foliar fertilization with selected microelements on the yield of two-row malting barley cultivars. In 2019–2021, a two-factor field experiment with barley was conducted in south-eastern Poland. The experimental factors were three spring barley cultivars (Baryłka, KWS Irina, and RGT Planet) of the brewing type and four single-component micronutrient fertilizers containing copper (Cu), manganese (Mn), molybdenum (Mo), and zinc (Zn). The foliar application of microelements resulted in improvements in selected elements of the yield structure and an increase in grain yield, and the effect depended on the fertilization applied. The highest grain yield was obtained from plots where fertilizer with Mo or Zn was used. Barley plants sprayed with Mo fertilizer developed the longest spikes and were characterized by the highest number of productive tillers per plant. The foliar application of Zn resulted in the formation of the highest number of spikes per unit area and grain uniformity. The RGT Planet cultivar was characterized by higher values of the measured parameters compared to Baryłka and KWS Irina.

QTL x environment modeling of malting barley preharvest sprouting.

HvMKK3 alleles are temperature sensitive and are major contributors to environmental stability of preharvest sprouting in barley. Preharvest sprouting (PHS) can severely damage barley (Hordeum vulgare L.) malting quality, but PHS resistance is often negatively correlated with malting quality. Seed dormancy is closely related to PHS. Increased temperature during grain fill can decrease seed dormancy in barley, but genetic components of seed dormancy temperature sensitivity are poorly understood. Six years of PHS data were used to fit quantitative trait locus (QTL) x environment mixed models incorporating marker data from seed dormancy genes HvAlaAT1, HvGA20ox1, and HvMKK3 and weather covariates in spring and winter two-row malting barley. Variation in winter barley PHS was best modeled by average temperature range during grain fill and spring barley PHS by total precipitation during grain fill. Average high temperature during grain fill also accurately modeled PHS for both datasets. A highly non-dormant HvMKK3 allele determined baseline PHS susceptibility and HvAlaAT1 interactions with multiple HvMKK3 alleles conferred environmental sensitivity. Polygenic variation for PHS within haplotype was detected. Residual genotype and QTL by environment interaction variance indicated additional environmental and genetic factors involved in PHS. These models provide insight into genotype and environmental regulation of barley seed dormancy, a method for PHS forecasting, and a tool for breeders to improve PHS resistance.

Transcriptome Alterations of an in vitro-Selected, Moderately Resistant, Two-Row Malting Barley in Response to 3ADON, 15ADON, and NIV Chemotypes of Fusarium graminearum.

Fusarium head blight caused by Fusarium graminearum is a devastating disease of malting barley. Mycotoxins associated with contaminated grain can be transferred from malt to beer and pose a health risk to consumers. In western Canada, F. graminearum has undergone an adaptive shift from 15ADON constituency to dominance by virulent 3ADON-producers; likewise, NIV-producers have established in regions of southern United States. Lack of adapted resistance sources with adequate malting quality has promoted the use of alternative breeding methodologies, such as in vitro selection. We studied the low-deoxynivalenol characteristic of in vitro selected, two-row malting barley variety “Norman” by RNAseq in contrast to its parental line “CDC Kendall,” when infected by 15ADON-, 3ADON-, and NIV-producing isolates of F. graminearum. The current study documents higher mycotoxin accumulation by 3ADON isolates, thereby representing increased threat to barley production. At 72–96-h post infection, significant alterations in transcription patterns were observed in both varieties with pronounced upregulation of the phenylpropanoid pathway and detoxification gene categories (UGT, GST, CyP450, and ABC), particularly in 3ADON treatment. Defense response was multitiered, where differential expression in “Norman” associated with antimicrobial peptides (thionin 2.1, defensing, non-specific lipid-transfer protein) and stress-related proteins, such as late embryogenesis abundant proteins, heat-shock, desiccation related, and a peroxidase (HvPrx5). Several gene targets identified in “Norman” would be useful for application of breeding varieties with reduced deoxynivalenol content.

Genome Assembly of the Canadian two-row Malting Barley cultivar AAC Synergy

Barley (Hordeum vulgare L.) is one of the most important global crops. The six-row barley cultivar Morex reference genome has been used by the barley research community worldwide. However, this reference genome can have limitations when used for genomic and genetic diversity analysis studies, gene discovery, and marker development when working in two-row germplasm that is more common to Canadian barley. Here we assembled, for the first time, the genome sequence of a Canadian two-row malting barley, cultivar AAC Synergy. We applied deep Illumina paired-end reads, long mate-pair reads, PacBio sequences, 10X chromium linked read libraries, and chromosome conformation capture sequencing (Hi-C) to generate a contiguous assembly. The genome assembled from super-scaffolds had a size of 4.85 Gb, N50 of 2.32 Mb, and an estimated 93.9% of complete genes from a plant database (BUSCO, benchmarking universal single-copy orthologous genes). After removal of small scaffolds (< 300 Kb), the assembly was arranged into pseudomolecules of 4.14 Gb in size with seven chromosomes plus unanchored scaffolds. The completeness and annotation of the assembly were assessed by comparing it with the updated version of six-row Morex and recently released two-row Golden Promise genome assemblies.

Breeding and brewing quality of the Canadian malting barley variety 'CDC Goldstar' lacking lipoxygenase-1.

Various types of malt quality profiles have been investigated to benefit the North American brewing industry. Herein, we report the development and brewing quality of the hulled, two-row malting barley (Hordeum vulgare L.) variety ‘CDC Goldstar’ lacking lipoxygenase-1 (LOX-1-less). This new variety offers a novel malt type for the improvement of beer flavor stability. The agronomic performance of ‘CDC Goldstar’ was tested in the Western Cooperative Two Row Barley Registration Trials during 2013–2014. In addition to high lodging tolerance, the new variety showed 6% higher yield than the current leading variety ‘CDC Copeland’. The malt quality of ‘CDC Goldstar’ showed higher diastatic power and lower wort β-glucan content than ‘CDC Copeland’ and controllable proteolytic modification (soluble nitrogen and Kolbach Index). Pilot- (100 L) and commercial-scale (5,000 L) brewing trials were conducted using ‘CDC PlatinumStar’, another LOX-1-less variety with a low enzymatic profile, as the control variety. Absence of the LOX-1 trait from ‘CDC Goldstar’ maintained trans-2-nonenal levels in aged beers as low as those in other LOX-1-less varieties without affecting major beer parameters, such as ester and aldehyde content or foam stability. The newly developed ‘CDC Goldstar’ malting barley provides added value for the beer industry and consumers.

Effect of seed size on soil cover, yield, yield components and nitrogen uptake of two-row malting barley

Summary Seed size can influence germination, growth and yield formation of crops. A two-year field experiment was conducted in eastern Austria in 2012 and 2013 with two cultivars (Paula and Tatum) and four seeds size (&lt; 2.5, 2.5–2.75, 2.75–3.25 and &gt; 3.25 mm) to assess the effect of seed size on soil coverage, yield, yield components, nitrogen concentrations and nitrogen yield of spring malting barley. Soil coverage during the vegetation period was higher with a larger seed size in one year. Above-ground biomass and grain yield were not affected by seed size but differed between varieties and years. Seed size, however, affected the yield components. Both varieties had a higher ear density with the largest seed size compared to the smallest seed size. Higher ear density resulted in a lower thousand kernel weight. Grains ear-1 did not differ between seed sizes. Harvested grain fractions, nitrogen concentrations and nitrogen yields were also not affected by seed size.

Mapping malting quality and yield characteristics in a north American two-rowed malting barley × wild barley advanced backcross population

Due to the stringent quality requirements imposed by the US malting barley industry, barley breeders have been reluctant to introduce exotic germplasm into cultivar development programs. To determine whether wild barley (Hordeum vulgare ssp. spontaneum) contains favorable alleles for yield and malting quality characteristics, we mapped quantitative trait loci (QTL) for heading date, height, lodging, yield, and nine malting parameters important to the malting and brewing industry. Traits were mapped in a wild x cultivated barley BC2-derived advanced backcross mapping population. Harrington, the recurrent parent, is a North American two-rowed malting barley cultivar, and OUH602, the donor parent, is a wild barley accession that exhibits resistance to multiple barley diseases. The 98 derived lines were grown in replicated field trials at St. Paul and Crookston, MN in 2009–2011. One to four QTL were identified for each trait, for a total of 36 QTL. Trangressive segregants for increased yield were identified and four lines had higher yield than Harrington across all environments; however, for yield QTL the OUH602 alleles decreased the trait value. Wild barley alleles had both positive and negative effects on the malting traits of diastatic power, free amino nitrogen, and soluble protein. Combined with the previously identified QTL associated with resistance to fungal diseases, this population represents a rich resource for barley breeding. To facilitate future breeding and genetics studies with this population, a set of pre-introgression lines composed of 28 BC2-derived and 6 BC3-derived lines were identified that collectively contain introgressions across the entire OUH602 genome.

Managing Fusarium Head Blight in Winter Barley With Cultivar Resistance and Fungicide.

Although there has been research on managing Fusarium head blight (FHB) in spring barley, little has been published on cultivar resistance and optimal fungicide timing for FHB management in winter barley. A 3-year (2015 to 2017) field experiment was conducted to measure FHB resistance of winter barley varieties, gauge the potential benefit from a fungicide, and help determine the optimal timing for fungicide application. The split-plot experiment took place in a misted, inoculated nursery in Raleigh, North Carolina using main plots of four winter barley cultivars (Atlantic, Endeavor, Nomini, and Thoroughbred). Three fungicide treatments were applied to subplots: prothioconazole + tebuconazole at full spike emergence, the same fungicide 6 days later, or no fungicide. The late applications significantly reduced FHB index in each of 3 years and significantly reduced deoxynivalenol (DON) in harvested grain in 2 of the 3 years. Applications at full spike emergence also yielded significant benefit in 1 of the 3 years for each parameter. Neither disease symptoms nor DON gave reason to prefer one of the fungicide timings over the other. Across the 3 years, DON ranked the cultivars Endeavor < Nomini = Thoroughbred < Atlantic. Combining the moderate resistance of Endeavor with a fungicide application and averaging the two timings resulted in a 75% DON reduction compared with unsprayed Atlantic. Taken together, our results indicate that barley growers concerned about minimizing DON should both plant moderately resistant varieties and apply fungicide if there is scab risk. During the same period, 16 commercial winter barley cultivars were tested in from three to seven Virginia and North Carolina environments each, and the DON results were compared after standardization across environments. The winter two-row malting barley cultivars Endeavor and Calypso displayed superior and robust DON resistance across environments.

Breeding of lipoxygenase-1-less malting barley variety ‘SouthernStar’ and evaluation of malting and brewing quality

The lipoxygenase-1-null (LOX-less) trait has positive effects on beer quality, and in particular, improvement of flavor stability by reduction of beer deteriorating substances such as trans-2-nonenal (T2N). ’SouthernStar’ was successfully developed as the first LOX-less malting barley variety in Australia by introducing LOX-less trait into ‘Flagship’ by successive backcross and molecular marker assisted selection (MMAS). ‘Flagship’ is a two-rowed malting barley variety in Australia and it was used as the recurrent parent for the successive backcrossing. The yield potential, agronomic performance, disease resistance and the general malting quality were almost identical between ‘SouthernStar’ and ‘Flagship’. To evaluate effects of LOX-less trait on beer quality, the brewing trials were conducted using a pilot-scale brewing apparatus. The wort and beer quality were similar between ‘SouthernStar’ and ‘Flagship’. The effect of the LOX-less trait on the reduction of beer deteriorating substances such as T2N and trihydroxyoctadecenoic acid (THOD) contents was clearly verified in this study. The scores for total staleness of the test beers were significantly lower than those of the control beers under several storage conditions in one trial.

Grain number and grain filling of two-row malting barley in response to variation in post-anthesis radiation: Analysis by grain position on the ear and its implications for yield improvement and quality

Grain weight is reported to be a relatively well conserved characteristic across spring barley (Hordeum vulgare L.) crops that vary in grain number m−2. Understanding the mechanisms that promote stability in grain weight is important to ensure that efforts to increase grain number beyond current high levels successfully increase yield without compromising grain quality. The aims of this study were to establish 1) whether post-anthesis grain abortion contributes to the stability of grain weight by helping match grain numbers to post-anthesis assimilate supply and 2) whether variations in post-anthesis assimilation per unit grain number affect the heterogeneity of grain weight. Field experiments were conducted in a high-yield potential environment for spring barley in 2011 and 2012. Crops were either shaded post anthesis (a 59% reduction in radiation incident on the crop) to reduce net carbon assimilation or grown unshaded. Grain growth was measured at different spikelet locations on the ear and on different shoots (main shoot and tillers) of the same plant. Shading crops from 14 days after anthesis until harvest maturity reduced yield by 19–20%, mean grain weight (MGW) by 12–16% and harvest index by 5–6%, but did not significantly affect grain number in either year. The magnitudes of these effects were considerably lower than the reduction in radiation imposed by shading suggesting some compensatory adjustment in radiation use efficiency or dry matter partitioning to grain after shading. The rate of grain filling was higher for grains in central spikelets than grains at distal or basal locations on the ear. Shading reduced the rate of grain filling to a similar extent (23–27%) at most locations evaluated on the ear, but had no effect on the duration of grain filling. In spite of the comparable effects of shading on grain growth across different spikelet positions and hierarchy of shoots, crops harvested after shading tended to have a more variable individual grain weight (larger interquartile range and coefficient of variation) than crops that were unshaded. The results show that post-anthesis grain abortion does not contribute to the stability of MGW in spring barley. Moreover, low levels of post-anthesis radiation in crops of large grain number m−2 (sink capacity) can increase heterogeneity of grain weight, which may have negative consequences for grain quality.

The two-row malting barley cultivar 'New Sachiho Golden' with null lipoxygenase-1 improves flavor stability in beer and was developed by marker-assisted selection.

Lipoxygenase-1 (LOX-1) null ‘New Sachiho Golden’ is a two-row malting barley (Hordeum vulgare L.) cultivar released in 2015 that was developed at the Tochigi Prefectural Agricultural Experimental Station by backcross breeding using the high-yield leading cultivar ‘Sachiho Golden’ as a recurrent parent and the LOX-1 null mutant ‘Daikei LM1’ as a non-recurrent parent. To develop ‘New Sachiho Golden’ we used a simple LOX activity assay and marker-assisted selection. This is the first LOX-1 null malting barley cultivar in Japan that is resistant to barley yellow mosaic virus (types I–III). Agronomic characteristics and malting qualities of ‘New Sachiho Golden’ were similar to those of ‘Sachiho Golden’, except that ‘New Sachiho Golden’ had no LOX activity in ungerminated grains and had clearly lower LOX activity during malting than ‘Sachiho Golden’. The concentrations of a trans-2-nonenal (T2N) precursor in wort and beer made from ‘New Sachiho Golden’ were significantly lower than in those made from ‘Sachiho Golden’, both before and after storage.

Post-anthesis warm nights reduce grain weight in field-grown wheat and barley

Wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) crops are exposed to warm nights during their growing seasons and this trend is unlikely to change. The aim of this work was to evaluate the effect of higher post-anthesis night temperatures on field-grown crop yield, focusing on final grain weight determination. Experiments combined: (i) two well-adapted crops with similar phenology: bread wheat and two-row malting barley, under (ii) two temperature regimes: ambient and high night temperatures from 10days after anthesis to physiological maturity during (iii) two contrasting growing seasons in terms of radiation and temperature: late sowing in 2011 and early sowing in 2013. The night temperature increase (ca. 4.1°C) was achieved using purpose-built heating chambers placed on the crop at 7pm and removed at 7am every day during the heating period. Across growing seasons and crops, the average minimum temperature during that period ranged from 14.3°C to 21.9°C. Thousand grain weight was reduced by ca. 3% per °C of night temperature increase, similarly for wheat and barley, causing a grain yield reduction of ca. 4% per °C. An accelerated development under high night temperatures led to a shorter effective grain filling period, reducing the final grain weight. The lack of consistent impact on source availability between crops and seasons, measured as senescence and stem water soluble carbohydrates, as well as a similar impact in magnitude and direction on individual grain weight for different grain positions along wheat or barley spikes, suggest that the negative effects of warm nights on grain weight were directly related to processes within the grain itself.

High night temperatures during grain number determination reduce wheat and barley grain yield: a field study.

Warm nights are a widespread predicted feature of climate change. This study investigated the impact of high night temperatures during the critical period for grain yield determination in wheat and barley crops under field conditions, assessing the effects on development, growth and partitioning crop-level processes driving grain number per unit area (GN). Experiments combined: (i) two contrasting radiation and temperature environments: late sowing in 2011 and early sowing in 2013, (ii) two well-adapted crops with similar phenology: bread wheat and two-row malting barley and (iii) two temperature regimes: ambient and high night temperatures. The night temperature increase (ca. 3.9 °C in both crops and growing seasons) was achieved using purpose-built heating chambers placed on the crop at 19:000 hours and removed at 7:00 hours every day from the third detectable stem node to 10 days post-flowering. Across growing seasons and crops, the average minimum temperature during the critical period ranged from 11.2 to 17.2 °C. Wheat and barley grain yield were similarly reduced under warm nights (ca. 7% °C(-1) ), due to GN reductions (ca. 6% °C(-1) ) linked to a lower number of spikes per m(2) . An accelerated development under high night temperatures led to a shorter critical period duration, reducing solar radiation capture with negative consequences for biomass production, GN and therefore, grain yield. The information generated could be used as a starting point to design management and/or breeding strategies to improve crop adaptation facing climate change.

BRS Sampa: malting barley cultivar for irrigated production

Barley BRS Sampa is a late heading, dwarf two-rowed malting barley cultivar released for irrigated production in Brazil. It combines high yield and kernel plumpness, disease and lodging resistance with malting quality. It is adapted to all major irrigated production regions of Brazil.

Comprehensive Sequence Analysis of 24,783 Barley Full-Length cDNAs Derived from 12 Clone Libraries

Full-length cDNA (FLcDNA) libraries consisting of 172,000 clones were constructed from a two-row malting barley cultivar (Hordeum vulgare 'Haruna Nijo') under normal and stressed conditions. After sequencing the clones from both ends and clustering the sequences, a total of 24,783 complete sequences were produced. By removing duplicates between these and publicly available sequences, 22,651 representative sequences were obtained: 17,773 were novel barley FLcDNAs, and 1,699 were barley specific. Highly conserved genes were found in the barley FLcDNA sequences for 721 of 881 rice (Oryza sativa) trait genes with 50% or greater identity. These FLcDNA resources from our Haruna Nijo cDNA libraries and the full-length sequences of representative clones will improve our understanding of the biological functions of genes in barley, which is the cereal crop with the fourth highest production in the world, and will provide a powerful tool for annotating the barley genome sequences that will become available in the near future.

Response of two-row malting spring barley to water cutoff under sprinkler irrigation

Agricultural production in irrigated areas is becoming more water-constrained. Scheduling the timing of the last irrigation on cereals is one effective method of reducing seasonal water use while maintaining crop yield and quality. The last irrigation application time and its impact on two-row malting barley ( Hordeum distichum cv. Moravian 37) yield, quality, and economic benefits were studied in the 2000, 2001, and 2002 cropping seasons. Irrigation was stopped for the season at Milk, pre-Soft Dough, Soft Dough, and post-Soft Dough grain formation stages. The Soft Dough water cutoff treatment produced the highest grain yield of two-row spring malting barley. Water cutoff before or after Soft Dough stage reduced the grain yield significantly at P < 0.05, but the quality of grain for malt production was not significantly different when water was cut off at pre-Soft Dough or post-Soft Dough stages. Irrigation cutoff at Milk stage produced the lowest grain yield with the lowest quality. Decreases in grain yield and quality with the last irrigation at post-Soft Dough reduced grain value by $174 ha −1 relative to Soft Dough, while irrigation costs were higher (Fig. 6). The economic benefit due to labor and power cost reduction from earlier irrigation cutoff does not offset the resulting loss of grain value/ha for any treatment except post-SD under current southern Idaho energy and labor cost conditions.

Co-bombardment, integration and expression of rice chitinase and thaumatin-like protein genes in barley (Hordeum vulgare cv. Conlon)

Pathogenesis-related (PR) proteins associated with degradation of structural components of pathogenic filamentous fungi were overexpressed in the two-rowed malting barley (Hordeum vulgare L.) cultivar Conlon. Transgenes were introduced by co-bombardment with two plasmids, one carrying a rice (Oryza sativa L.) chitinase gene (chi11) and another carrying a rice thaumatin-like protein gene (tlp). Each gene was under the control of the maize ubiquitin (Ubi1) promoter. Fifty-eight primary transformants from three independent transformation events were regenerated. T(1) plants with high rice chi11 and tlp protein expression levels were advanced to identify T(2) homozygotes by herbicide spray and subjected to further molecular analyses. T(3) progeny from one event (E2) had stable integration and expression of the rice chi11 and tlp while those from the other events (E1 and E3) showed stable integration only of tlp. The successful production of these lines overexpressing the antifungal chi and tlp proteins provides materials to test the effects of these genes on a variety of fungal diseases that attack barley and to serve as potential additional sources of disease resistance.

Occurrence of Deoxynivalenol in Korean Barley and Barley Products

Fifty-two samples of two-rowed malting barley, six-rowed husked barley, and six-rowed hulless barley were collected from fields in Korea and screened for Fusarium graminearum and deoxynivalenol (DON). Processed barley products such as commercial barley malt, pearled barley, pearled transversally cut barley, barley cookies, and barley tea were collected from various retail stores for this study. The average mold infection rates were 57% in two-rowed malting barley, 89% in six-rowed husked barley, and 38% in six-rowed hulless barley. HPLC and an enzyme-linked immunosorbent assay (ELISA) kit were used to determine the level of DON contamination in barley samples. The average level of DON was 1.19 μg/g for six-rowed husked barley, 0.44 μg/g for two-rowed malting barley, and 0.59 μg/g for six-rowed hulless barley. The average DON concentration of commercial barley products was 0.39 μg/g for barley malt, 0.35 μg/g for pearled transversally cut barley, 0.34 μg/g for pearled barley, and 0.11 μg/g for pearled and pressed barley. DON was not detected in barley tea and cookies among the processed barley products.

Genetic improvement of yield responsiveness to nitrogen fertilization and its physiological determinants in barley

Traditionally, barley in Argentina has been cultivated in low-yielding environments. A study was conducted to test whether breeding for improved performance under these conditions would have also improved the responsiveness to nitrogen availability. Four cultivars of two-rowed malting barley (released in 1944, 1960,1982 and 1998) were grown under 4 rates of nitrogen fertilizer at sowing (20, 50, 110and 160 kgN ha-1). All cultivars increased their yield with the increase in soil nitrogen. But yield of modern cultivars responded more strongly than yield of old ones. For modern cultivars, increase in grain yield was of 12 ± 0.6 kgha-1 for each 10 kg ha-1 of increase in the mean yield (environmental index). Absolute values of genetic gain were related to nitrogen availability: 1.59, 2.58, 4.52 and 4.29 g m-2 year-1 for the N20, N50, N110 and N160 treatments, respectively. Grain yield was associated with grain number m-2, which was dependent on spikes m-2 and grains spike-1. Total biomass at maturity also explained the changes in yield. It is concluded that selection under stress conditions was, in this case, beneficial to identify cultivars with high yields under a wide range of nitrogen availabilities.

A Barley Linkage Map Using an F2 Population Compared with a Map Based on Female Recombination-derived Doubled Haploid Lines.

Most of the barley RFLP linkage maps have been constructed using doubled haploid(DH) lines as mapping materials and little information is available on barley RFLP linkage map using an F2 population. In the present study, we constructed an RFLP linkage map using 120 F2 plants derived from a cross between a Japanese two-rowed malting barley cultivar Ko A and a Chinese six-rowed barley landrace Mokusekko 3. A total of 222 loci were mapped using 177 RFLP probes, one isozyme marker and one morphological marker. The total map length was 1, 389 cM and the average marker-to-marker distance was 6.5cM. We compared the Ko A × Mokusekko 3 map with the Steptoe × Morex map, one of the most representative barley RFLP linkage maps, which is based on Hordeum bulbosum(Hb)-derived DH lines that represent a recombination in female gametes. The linear orders of 60 common RFLP markers were identical and no major chromosomal rearrangements were observed between both RFLP linkage maps. A significant difference in recombination frequency was detected at six intervals flanked by the adjacent common RFLP markers. A reduced map length was detected at four intervals in the F2 map and at two intervals in the Hb-derived DH map. Three out of the six intervals were located around the centromeric regions of chromosomes 5H and 6H. On the other hand, the ratio of total length between the F2 map and Hb-derived DH map within common markers was 0.98. Remarkable similarities were present at the whole-genome level between both RFLP linkage maps. The implication of these findings for the analysis of recombination frequency was also discussed.