Assessment of genetic diversity in Egyptian barley (<Emphasis Type="Italic">Hordeum vulgare</Emphasis> L.) genotypes using SSR and SNP markers

A barley core collection can be studied extensively and the derived information can be used to identify loci/genes for the genetic improvement of quantitative and qualitative traits. To assess genetic diversity, allelic variation and population structure of Egyptian barley, 134 barley genotypes collected from a different region along with 19 cultivated genotypes obtained from of the Egyptian Agricultural Research Center. All genotypes were analyzed with 261 polymorphic SSR and SNP alleles. The mean number of alleles per locus was 4 and PIC was 0.49, while the level of genetic diversity was 0.55 ranging from 0.03 to 0.82. The genotypes were assigned to three subpopulations that were consistent with their origins. The genetic variation within population was higher (51%) than among population at the molecular levels (F_ST =?0.491 when P?<?0.10). The level of polymorphic variation was highest in subpopulations-II, due to collected from different regions with different ear-types thus, expected to contain more diversity than local genotypes in subpopulations-I and subpopulations-III. The structured study found that the 153 barley genotypes are in harmony with clustering approaches using the SSR and SNP genotypic data in a neighbor-joining tree and principal components analysis, which identified three subpopulations. These results demonstrated genetic diversity among the Egyptian barley genotypes can be applied to suggest approaches, such as association analysis, classical mapping population development, and parental line selection in breeding programs. Therefore, it is necessary to use the exotic genotypes as the genetic resources for developing new barley cultivars in Egypt.     

Diversity and geographic distribution of adaptive traits in Triticum turgidum L. (durum group) wheat landraces from Turkey

Summary A collection of 2,420 accessions derived from single-spike population samples of durum wheat landraces collected in 1984 from 172 sites in 28 provinces in Turkey was evaluated for nine adaptive traits at the ICARDA research station at Tel Hadya, near Aleppo, Syria. Differentiation of these accessions among provinces was found for number of days to heading, maturity, grain-filling days, as well as for plant height, peduncle length, number of spikelets per spike, spike length, awn length, and kernel weight. The first three canonical variables accounted for 90% of the total variance. Canonical analysis also revealed significant correlations to province mean temperatures, altitude, latitude, and length of the growing season, but not with total seasonal rainfall. Eight distinct groups of provinces were identified by cluster analysis. These clusters had both geographical orientation to eastern and western Turkey and to agroecological zonation for clusters having both eastern and western provinces. Accessions were found with high kernel weight, early heading and maturity, and awnless spikes which could be utilized in crop improvement programs targeted at either favorable or stressed environments.     

Genes for resistance to stripe rust in four spring wheat varieties

Summary Four spring wheat (Triticum aestivum L.) varieties differing in origin and reaction in the seedling stage to pathotype CDL-6 (extant in California) were intercrossed and examined in greenhouse conditions in F₁, F₂, and F₃ generations. Digenic and transgressive segregation was found in all crosses. The four varieties each had infection types (1 immune, 9 susceptible) and putative resistance genes as follows: Anza, IT 7, YrA; Glennson 81, IT 2, Yr9; Yecora Rojo, IT 6, YrC; and Ollanta, IT 4–6, YrL. Anza was classified as susceptible, Yecora Rojo and Ollanta as intermediate in seedling resistance, and Glennson 81 as resistant in the seedling stage.     

A New Source of Resistance to Pseudocercosporella herpotrichoides, Cause of Eyespot Disease of Wheat, Located on Chromosome 4V of Dasypyrum villosum

Resistance to Pseudocercosporella herpotrichoides in five wheat cultivars, accession W6 7283 of Dasypyrum villosum, and ‘Chinese Spring’ disomic addition lines of the D. villosum chromosomes IV, 2V, 4V, 5V, 6V and 7V, was evaluated in seedlings by measuring disease progress 6 weeks after inoculation with a β—glucuronidase—transformed strain of the pathogen and by visual estimates of disease severity. D. villosum and the disomic addition line of chromosome 4V were as resistant as wheat cultivars ‘VPM—1’ and ‘Cappelle Desprez’, but less resistant than ‘Rendezvous’. Resistance of the chromosome 4V disomic addition line was equivalent to that of D. villosum.‘Chinese Spring’ and disomic addition lines of IV, 2V, 5V, 6V and 7V were all susceptible. These results confirm Sparaguee's (1936) report of resistance in D. villosum to P. herpotrichoides and establish the chromosomal location for the genes controlling resistance. The presence of chromosome 4V in the addition line and its homocology to chromosome 4 in wheat were confirmed by Southern analysis of genomic DNA using chromosome group 4-specific clones. This genetic locus is not homoeologous with other known genes for resistance to P. herpotrichoides located on chromosome group 7, and thus represents a new source of resistance to this pathogen.     

Introgression of Dasypyrum villosum chromatin into common wheat improves grain protein quality

Dasypyrum villosum (L.) Candargy (DV) is adiploid (2n = 14, VV genomes), allogamous grass of theMediterranean region. It may be hybridized with wheatand is thus a gene resource for wheat improvement. Westudied grain protein concentration andSDS-sedimentation (SED) as indicators of end-usequality. The latter is a good predictor of glutenstrength. A-PAGE and SDS-PAGE were used to identifymonomeric and polymeric seed storage proteins,respectively, to relate proteins of DV to those foundin Chinese Spring (CS), Triticum aestivum L.,wheat. Two full-sib lines of DV had high grain protein(19.3 and 20.3%), but one had very low mean SED (69mm) and one had very high (118 mm) based on onegreenhouse and one field test. CS had very low grainprotein (12.0%) and weak gluten (33 mm). Single-DVchromosome addition and substitution lines and twoDV-wheat recombinant lines all had higher grainprotein than CS (range 13.9 to 16.7%). SED valuesshowed a different pattern. CS=4V and CS=6V hadlow SED, 63 and 44 mm, similar to CS, whereas CS=1Vand full sib DV 200 had very strong gluten, 118 mm, asdid substitution lines CS1V (1A) and CS1V (1B), 125and 131 mm, respectively. One hybrid-derived line withDV-wheat 1V recombinant chromosome had SED of 99 mmand one line with a 6V added chromosome had SED of 64mm. The large positive effects of quality in the wheathaving DV chromosome 1V are believed to be due to DValleles at the Glu-V1 and Gli-V1/Glu-V3loci. DV chromosomes 4V and 6V did not contribute toimproved quality probably due to Gli-V2 and Gli-V3 which, as the orthologous loci in wheat, donot enhance wheat quality. Based on the positiveeffects of alleles on DV chromosome 1V in a breadwheat background, we conclude that D. villosumis a source of allelic diversity that can beconsidered for improving end-use quality in breadwheat.     

Complementary competition in cultivated barley (Hordeum vulgare L.)

Summary Grain yield and its endpoint components were studied for three barley varieties, Dayton, Hudson, and Tenn 60-34, as pure stands and two-way and three-way mixtures at three widely separated sites for two years. The populations, including the pure stands, produced similar grain yields. Complementary competition was observed in all mixed populations in which Tenn 60-34 occurred. Its yield was suppressed in mixtures about 20% while Dayton and Hudson increased a like amount so that total mixed population yield was equal to that expected from pure stand performance. Tenn 60-34 occurred at 33, 50, and 80% frequencies in mixed populations with no difference in competition, indicating a lack of frequency dependency for the effect.Yield component data indicated that the reduced yield of Tenn 60-34 in mixed stands was due entirely to a decreased number of spikes produced per unit area. It was inferred that this was due to competition at time of tillering although this could not be determined since the varieties were indistinguishable during vegetative growth.An examination of population-environment interaction provided some evidence for the idea that heterogeneous populations in which there is intense competition show greater micro-environment (within-site) instability. Heterogeneous populations generally showed lower than expected contribution to the population-environment variance although the differences were quite small.These results have important implications for the utilization of heterogeneous populations in agricultural production and for the management of genetically diverse populations in plant breeding practice since genotypic frequencies are expected to change rapidly with complementary competition.     

Evaluation of three sources of pollen fertility restoration genes and natural outcrossing of cytoplasmic male-sterile wheat

Summary Fertility restoration genes in Triticum aestivum L. in Texas Restorer Composite (TRC), D6301, and four CIMMYT restorer lines were studied, and selection was made for higher fertility in TRC. Mean-while, outcrossing percentages of seed set for 27 spring habit cytoplasmic male sterile (cms) varieties were evaluated for 3 to 5 years at Davis. The winter-habit TRC material did not restore reasonably good fertility, and the response to selection for higher fertility seemed to be slow. This poor fertility could be partly due to its late winter growth habit causing flowering at a period of high temperature and low humidity at Davis. The highest F₁ fertility was 46.6% in the cross cms Ramona x TRC-6, and its F₂ segregated into the ratio of 15 fertile to 1 sterile, with fertility ranging from 3.2 to 100%. Suggested for its improvement was intensive selection in the original TRC material and in the segre-gating F₂ population, followed by intercrossing. D6301 has 2 fertility restoration genes with different strengths which restore fertility up to 45.2% when both genes are heterozygous. D6301 is quite likely heterogeneous for these genes. Four CIMMYT restorer lines, D7464, D7465, D7466, and D7467, had satisfactory F₁ fertility restoration after crossing with cms Ramona 50. In 1975, the fertilities of the F₁'s ranged from 71 to 85% and were over 90% in 1976. The F₂ population of the cross cms Ramona 50 × D7464 segregated into a ratio of 3 fertile to 1 sterile, indicating that D7464 has a single dominant gene for fertility restoration. The F₂'s of crosses cms Ramona 50 × D7465, cms Ramona 50 × D7466, and cms Ramona 50 × D7467 gave a ratio of 15 fertile to 1 sterile, indicating that two gene pairs in these three lines were responsible for the fertility restoration. The best of this group was D7467 which restored fertility fully after being crossed with cms Ramona 50 (T. timopheevi cytoplasm).The early-flowering cms male-sterile varieties had higher outcrossing rates (16 to 38%) than late varieties (6 to 30%) over a 5-year period. This was due to hot and dry weather during the late growing season as well as to the rarity of windborne pollen. In 1970, 1971, 1972, and 1976, the variation among varieties was rather great. Some of them such as Roque 66 and Bajio 67, had consistently high outcrossing rates. This outcrossing ability seemed to be inherited and probably associated with the open-flowering characteristics of each variety.     

Quantitative trait locus analysis of wheat quality traits

Milling and baking quality traits in wheat (Triticum aestivum L.) were studied by QTL analysis in the ITMI population, a set of 114 recombinant inbred lines (RILs) generated from a synthetic-hexaploid (W7985) × bread-wheat (Opata 85) cross. Grain from RILs grown in U.S., French, and Mexican wheat-growing regions was assayed for kernel-texture traits, protein concentration and quality, and dough strength and mixing traits. Only kernel-texture traits showed similar genetic control in all environments, with Opata ha alleles at the hardness locus Ha on chromosome arm 5DS increasing grain hardness, alkaline water retention capacity, and flour yield. Dough strength was most strongly influenced by Opata alleles at 5DS loci near or identical to Ha. Grain protein concentration was associated not with high-molecular-weight glutenin loci but most consistently with the Gli-D2 gliadin locus on chromosome arm 6DS. In Mexican-grown material, a 2DS locus near photoperiod-sensitivity gene Ppd1 accounted for 25% of variation in protein, with the ppd1-coupled allele associated with higher (1.1%) protein concentration. Mixogram traits showed most influence from chromosomal regions containing gliadin or low-molecular-weight glutenin loci on chromosome arms 1AS, 1BS, and 6DS, with the synthetic hexaploid contributing favorable alleles.Some RI lines showed quality values consistently superior to those of the parental material, suggesting the potential of further evaluating new combinations of alleles from diploid and tetraploid relatives, especially alleles of known storage proteins, for improvement of quality traits in wheat cultivars.Contribution number 06-77J from the Kansas Agricultural Experimental Station.