Polymorphism of waxy proteins in Spanish durum wheats

A collection of 547 durum wheats (103 cultivars and 444 landraces) from Spain was analysed for waxy protein composition. The electrophoretic patterns showed low polymorphism. At the Wx‐A1 locus, 99.8% of the wheats had the Wx‐Ala allele and only one had the null Wx‐Alb allele. The Wx‐Bl locus was more polymorphic and four different alleles were detected: Wx‐Bla (41.3%), Wx‐Blc (42.6%), a new allele, not detected before in bread wheat and named Wx‐Blf (16.0%), and the null Wx‐Blb allele, found for the first time in one durum wheat. Eleven durum wheats with different allelic composition at the Wx‐l loci were analysed for amylose content. Wheats with the Wx‐Bla allele had a lower amylose content than those with Wx‐Blc or Wx‐Blf. The lowest amylase content was found in the only durum wheat having the null Wx‐Blb allele.     

Polymorphism of two waxy proteins in the emmer group of tetraploid wheat, Triticum dicoccoides, T. dicoccum, and T. durum

Gel-electrophoretic analyses detected polymorphism of two waxy (Wx) proteins, Wx-Al and Wx-Bl, in 334 accessions of the emmer group of tetraploid wheat, Triticum dicoccoides, T. dicoccum and T. durum. The null allele for the Wx-Al protein (Wx-Alb) was found in one accession of T. dicoccoides and seven of T. dicoccum, but it was not present in those T. durum accessions analysed. The null allele for the Wx-Bl protein (Wx-Blb) did not occur in three emmer-wheat species. Wx-Al and Wx-Bl proteins showing alteration in mobility in SDS-PAGE gel or in isoelectric points were found in five accessions and considered to be the products of new alleles, Wx-Ald, Wx-Ale and/or Wx-Bld. Densitometric analysis of Wx protein bands revealed that Wx-Al was present in smaller amounts than Wx-B1 in almost all accessions.     

Waxy proteins in diploid, tetraploid and hexaploid wheats

Electrophoretic analyses of waxy proteins, encoded by genes present at the Wx‐1 loci, present in several cultivars and accessions of hexaploid wheat, Triticum aestivum, have permitted the detection of null alleles at the Wx‐B1 and Wx‐D1 loci. Polymorphism at the Wx‐A1 and Wx‐B1 loci was also investigated in several accessions of tetraploid wheats, Triticum durum, Triticum dicoccoides and Triticum timopheevi, and in diploid species, Triticum urartu, Triticum boeoticum and Triticum monococcum. One null allele at the Wx‐A1 locus and three polymorphic alleles at Wx‐B1 locus were detected in T. durum; a new allele at one of the two waxy loci was identified in the tetraploid wheat T. timopheevi; no polymorphism was detected in diploid species. Polymerase chain reaction techniques made possible the detection of further polymorphism existing at the Wx‐1 loci and the reason for the lack of expression of the null genotypes to be investigated. The null forms detected at each locus have been used to produce complete sets of partial and total waxy lines in durum and bread wheat.     

Polymorphism of waxy proteins in Iberian hexaploid wheats

A collection of 130 cultivars of bread wheat, 332 landraces of bread wheat and 144 spelt wheats was analysed for waxy proteins in the grain. The electrophoretic patterns showed very low polymorphism and most of the hexaploid wheats had the Wx-Ala, Wx-D1a and Wx-B1 alleles of ‘Chinese Spring’. Two alleles were detected at Wx-A1 (Wx-A1a, and Wx-A1b (null)), the latter was present in only 5.1% of the bread wheat landraces and 7.6% ofthe spelt wheats. No allelic variation was found at the Wx-D1 locus and all the hexaploid wheats had the Wx-D1a allele. Wx-B1 was the most polymorphic locus, with three alleles detected: Wx-B1a, Wx-B1b (null) and Wx-Blc coding for a Wx-B1 protein with a slightly different mobility from Wx-B1a. The null Wx-B1b allele was found in 10.8% of the bread wheat cultivars, 21.4% of the bread wheat landraces and 12.5% of the spelt wheats. Among the 604 hexaploid wheats analysed, only two bread wheat landraces (0.6%) and two spelt wheats (1.4%) had the null allele at both Wx-A1 and Wx-B1 loci.     

Assessment of genetic diversity in synthetic hexaploid wheats and their Triticum dicoccum and Aegilops tauschii parents using AFLPs and agronomic traits

Synthetic hexaploid wheats are of interest to wheat breeding programs, especially for introducing new genes that confer resistance to biotic and abiotic stresses. A group of 54 synthetic hexaploid wheats derived from crosses between emmer wheat(Triticum dicoccum, source of the A and B genomes) and goat grass (Aegilops tauschii, D genome donor) were investigated for genetic diversity. Using the AFLP technique, dendrograms revealed clear grouping according to geographical origin for the T. dicoccum parents but no clear groups for the Ae. tauschii parents. The geographical clustering of the T. dicoccum parents was also reflected in the dendrogram of their derived synthetic hexaploids. Diversity of the T. dicoccum parents and their derived synthetic hexaploids was further evaluated by measuring 18morphological and agronomic traits on the plants. Clustering based on morphological and agronomic data also reflected geographical origin. However, comparison of genetic distances obtained from AFLP and agronomic data showed no correlation between the two diversity measurements. Nevertheless, similarities among major clusters with the two systems could be identified. Based on percentage of polymorphic markers, the synthetic hexaploids had a considerably higher level of AFLP diversity (39%) than normally observed in cultivated hexaploid wheat (12–21%). This suggests that synthetic hexaploid wheats can be used to introduce new genetic diversity into the bread wheat gene pool. This revised version was published online in July 2006 with corrections to the Cover Date.     

Intraspecific differentiation and geographical distribution of Wx alleles for low amylose content in endosperm of foxtail millet, Setaria italica (L.) Beauv.

To clarify the genetic mechanism which controls the variation in amylose content among nonwaxy landraces of foxtail millet, the inheritance of different starch types in endosperm was examined by I₂-KI staining. The level of starch granule bound protein in foxtail millet endosperm was also analyzed using SDS-PAGE. The segregation for starch types in F₂ and F₃ seeds determined by I₂-KI staining showed that there are three different alleles at the waxy (wx) locus. A major protein bound to starch granules was detected in nonwaxy endosperm but it was absent in most of the waxy endosperm, suggesting that the protein is the Wx gene product which is responsible for the synthesis of amylose in endosperm. The level of Wx protein proportionally corresponded to the amylose content among nonwaxy landraces. This implies that two different Wx alleles regulate quantitative levels of Wx protein. Landraces with the allele for low amylose content are from Taiwan, the Philippines, Indonesia and Thailand. This revised version was published online in July 2006 with corrections to the Cover Date.     

Green haploid plants from unpollinated ovary culture in tetraploid wheat (Triticum durum Defs.)

In Triticum durum Defs., gynogenesis was investigated on six genotypes, Cocorit, Isly, Jori, Oued Zénati, Sarif, issued from Morocco,and Cham1 from Syria. The experiments described here were made during two seasons (spring and summer) in which batches of 1,036 and 3,750 unpollinated ovaries were used. A 4 ^°C pretreatment was applied, during 7, 11 or 15 days and the A (modified Jähne's et al.,1991) and B (modifed San N?um's, 1976) induction media were compared. The spikes were harvested when microspores were at bi- or trinucleate stage. After the 4 ^°C cold pretreatment, they were sterilized, and the excised ovaries underwent the following phases and sequence of successive media. The A or B ‘induction’ media, induced cell divisions in the female gametophytes, and after 4 to 9 weeks in dark conditions, the swelling ovaries burst. The growing calluses were excised and transferred to 16 h. light onto a differentiation medium (dif); there generated shoots were then placed on a development (dev), followed by a rooting medium (r). The comparison of the two experiments showed that summer was the best season, for in vitro unpollinated ovary culture; this period corresponds to a growth of mother-plants during spring, while those developing in winter gave rise to lower scores. In Experiment 1 the best level of regenerated plants per 100 ovaries were obtained for Isly with 14.3% and for Oued Zénati with 10.1%. In Experiment 2, the best values were those of Isly with 21.8%, after a 7 day cold pretreatment and use of induction medium B, and of Cocorit with 18.1%. Jori, exhibited good results, in three define situations, with 17.1%, 16%, and 9.3%.Only Cham1 and Sarif showed very low scores or no plants. Jori remaining aside, for each genotype, the best values rose up from a specific treatment combination, as a very strong interaction was expressed between genotype, induction medium and cold pretreatment duration. After this ‘first phase’ of regeneration by ovary culture 150 haploid plants were obtained. When combining these results with other attempts, a total number of 191 green plants was regenerated, 90 for Isly, 74 for Jori, 19 for Cocorit, 7 for Oued Zénati and 1 for Cham1. In a ‘second phase’, permanent regenerating callus lines were obtained through subculture on dif medium. Depending on genotype, 2 to 9 transfers (up to one year for Jori) were performed, giving 507 regenerated plants. From direct regeneration and subcultures, a total of 698 plants were produced, all green and mostly haploid. Fertile doubled haploid plants were obtained, either spontaneously or by colchicine treatment, for all these genotypes. These results are of interest for breeders, who need pure lines for genotypes evaluation and for the creation of improved homozygous varieties.     

Agronomic and qualitative traits of T. turgidum ssp. dicoccum genotypes cultivated in Italy

Summary The increasing popularity of organic agriculture and health food products has led to a renewed interest in hulled wheat species such as emmer (Triticum turgidum ssp. dicoccumSchubler). Knowledge on agronomic and quality traits is required for effective and efficient use of germplasm collections in breeding programs. The objective of this study was to estimate agronomic and grain quality traits of emmer wheat cultivated in Italy. A total of 20 emmer accessions consisting of landraces, breeding lines or cultivars selected from landraces and modern cultivars were examined under low input conditions. The study was conducted for three successive years (2002–2004) at one location of Southern Italy (Foggia). The entries were characterized for agronomic and qualitative traits [grain yield (t ha⁻¹), thousand grain weight (g), test weight (kg hl⁻¹), grain protein content (%), HMWG composition, dry gluten content (%), gluten index and yellow index, alveograph indices and Total Organic Matter (TOM) on cooked pasta]. The results showed a large genetic variability for most of the traits measured and, even if most of the accessions showed inferior bread- and pasta-making performance, modern cultivars exhibited improved quality traits with some potential to perform healthy and tasty food.     

Variation in landraces of durum wheat (T. turgidum L. conv. durum (Desf.) M.K.) from Turkey

Summary Durum wheat is historically an important crop in Turkey. Diverse durum wheat germplasm has been recorded many times in Turkish collections. 812 single plant genotypes from 190 durum wheat populations of 23 provinces in Turkey have been studied for number of days to germination, tillering, shooting, heading, maturity, and yield per plant. Variation in samples for traits studied was large enough and subsamples with different characteristics were identified. Grouping samples into provinces and altitudes of origin have revealed that variation in samples existed for some traits depending on province and altitude of origin. Yield per plant were not correlated with any of the developmental stages: but developmental stages were correlated with each other in varying magnitudes. Variation in yield per plant was not explained as well by developmental stages studied under a dry-cold environment. Further studies on samples needed to explore genetic variation more for other traits of economic importance.     

Evaluation of proline analysis and chlorophyll fluorescence quenching measurements as drought tolerance indicators in durum wheat (Triticum turgidum L. var. durum)

Summary The possibility of using proline accumulation and fluorescence inhibition as predictive tests for drought tolerance in durum wheat has been investigated. The drought susceptibility of 25 genotypes was evaluated by comparing yields and yield components in irrigated and non irrigated conditions in the field. A drought susceptibility index (DSI) was calculated based on yields from irrigated and dry treatments and compared with the results obtained using the two physiological criteria. Proline accumulation and chlorophyll fluorescence inhibition were found to be significantly and negatively correlated with DSI of grain yield, biological yield, and thousand kernel weight, and tiller index. The use of both criteria for breeding durum wheat in Mediterranean dryland is discussed.     

Hybrid necrosis and hybrid chlorosis in Indian varieties of Triticum dicoccum Schubl.

Summary Forty-four varieties of Triticum dicoccum ex India were crossed to two T. aestivum testers, namely, C 306 (Ne ₁ ne ₂ ch ₁ Ch ₂) and Sonalika (ne ₁ Ne ₂ ch ₁ Ch ₂), to determine their necrosis and chlorosis genes. Thirty-six (81%) varieties were found to be carriers of the Ch ₁gene; the genotype of their necrosis gene (Ne ₁or ne ₁) could not be determined for want of suitable testers with the authors. Six varieties were found to be noncarriers for necrosis and chlorosis genes and two varieties were found to be carriers of the Ne ₁gene and non-carriers for the chlorosis gene. Allelic variation at the Ch ₂locus was observed; two alleles, Ch ₂ ^s and Ch ₂ ^m, are suggested.     

Evaluation of slow rusting resistance components to leaf rust in CIMMYT durum wheats

Information about slow rusting resistance to leaf rust (Puccinia triticina) in durum wheat (Triticum turgidum var. durum) is limited. Three slow rusting components, latent period, receptivity, and uredinium size, were determined at the adult plant stage for seven durums with slow rusting resistance to leaf rust and two susceptible durums in three greenhouse experiments. Additionally, area under the disease progress curve (AUDPC) and final disease severity (FDS) were determined in three field trials under artificial epidemics with the same P. triticina race BBG/BN. Compared to the most susceptible check, the AUDPC and FDS of slow rusting resistant durums were significantly lower and ranged from 13–47 to 22–59%, respectively. The latent period was significantly longer (8.5–10.3 days) and uredinium size significantly smaller (8.1–14.8 × 10⁻² mm²) on slow rusting durums than on the susceptible checks (8.0 days and 17.3–23.8 × 10⁻² mm², respectively). Uredinium size was the most stable slow rusting component across experiments. Correlations between uredinium size versus AUDPC and uredinium size versus FDS for each environment were high (r = 0.86–0.88). Correlations between latent period and field parameters were significant (r = −0.60 to −0.80). Correlations between receptivity and the field parameters were not significant. A multiple regression analysis showed that the variation in AUDPC and FDS was significantly explained only by uredinium size (P < 0.0001). The best slow rusting resistant lines can be used for developing high-yielding durums with more durable resistance to leaf rust.     

Effects of substituted D genome chromosomes on photosynthetic rate of durum wheat (Triticum turgidum L. var. durum)

Summary A durum wheat cultivar Langdon (LDN) and fourteen disomic D genome chromosome substitution lines of Langdon, where A or B genome chromosomes were replaced with homoeologous D genome chromosomes of Chinese Spring (CS), were used to assess the compensatory effect of the D genome chromosomes on photosynthetic rates at tetraploid level. The LDN 1D(1B) and LDN 3D(3B) lines showed significantly higher photosynthetic rates than Langdon, whereas LDN 1D(1A) and LDN 3D(3A) lines were not greatly different from Langdon. It appears that chromosomes 1B and 3B decrease photosynthesis. This suggests the differentiation of the effects on the photosynthesis within the first and third homoeologous groups. Substitution with the 2D chromosomes did not compensate the effects of either 2A or 2B chromosomes as it reduced photosynthetic rate compared to plant with either chromosomes 2A or 2B. Tetra CS had a higher photosynthetic rate than CS and Penta CS. The photosynthetic rate of CS was similar to that of Penta CS, which lacked one set of D genome. The results suggest that it may be possible to increase photosynthesis, if both sets of the D genome were entirely removed from hexaploid wheat. However, it is difficult to conclude that the lower rate of photosynthesis of the hexaploids was mainly attributable to D genome chromosome effects, because we did not find a dose dependent effect of D genome. Homoeologous differentiation of chromosomes may be involved in photosynthesis.     

Levels of phenotypic variation for developmental traits in landrace genotypes of durum wheat (Triticum turgidum ssp. Turgidum L. conv. durum (Desf.) MK.) from Jordan

Summary A germplasm collection comprising 132 landrace genotypes of durum wheat (Triticum turgidum) ssp. turgidum L. conv. durum (Desf.) MK., from 10 districts in Jordan was evaluated for days to booting (DB), days to heading (DH), days to anthesis (DA), days to maturity (DM), filling period (FP) and grain yield (GY). In spite of the relatively strong genetic (Gr) and phenotypic (Pr) correlation coefficients between the developmental traits, the variation among genotypes was significant. GY was only positively and significantly correlated with DA and FP, while it was negatively correlated with DH. Genotypes with different combinations of early, medium and late developmental traits have been identified. Different combinations of DH and FP may or may not lead to differences in DM and GY. However, genotypes with long FP and medium-late DH gave the highest grain yield. Multiple linear regression of the duration of maturity (M) stage on the duration of booting (B), heading (H) and anthesis (A) stages (M = –260.87 + 2.09 B + 1.23 H + 0.9 A, R ² = 0.92) indicates that it is possible to manipulate the duration of these developmental stages and develop genotypes with high yield potential and early maturity, a highly desirable in drought-prone environments.     

Expression of 17 rye (Secale cereale L.) traits in a range of durum wheat (Triticum durum Desf.) and bread wheat (T. aestivum L.) genetic backgrounds

Summary Expression of 17 rye traits in 24 bread wheat x rye and 8 durum wheat x rye crosses was studied, using a self-compatible, homozygous, dwarf rye. Rye showed epistasis for hairiness on the peduncle in all the crosses of Triticum aestivum and T. durum wheats with rye. Dark greenness of leaves of rye was expressed in all the durum wheat x rye and in some of the bread wheat x rye crosses. Similarly, absence of auricle pubescence, a rye trait, was expressed in most of the durum wheat x rye crosses but not in the bread wheat x rye crosses, indicating the presence of inhibitors for these traits frequently on the D genome and rarely on the A and/or B genome of wheat. Most of the wide hybrids resembled rye fully or partially for intense waxy bloom on the leaf-sheath and for the absence of basal underdeveloped spikelets. Similarly, most of the amphihaploids resembled rye for the anthocyanin in the coleoptile, stem and node. The presence of some inhibitors on A and/or B genome of wheat was indicated in some of the wheat genotypes for the expression of rye traits viz. intense waxy bloom, anthocyanin in node and absence of basal underdeveloped spikelets. Enhancement in the level of expression of the intensity and length of bristles on the mid-rib of the glume of the hybrids might be due to wheat-rye interaction. Less number of florets/spikelet as in rye showed variable expression in different wheat backgrounds. Some other rye traits like absence of auricles, terminal spikelet and glume-awn were not expressed in the wheat background. The expression of some of the rye genes might have been influenced by their interaction with Triticum cytoplasm and/or the environment.     

Inheritance of amylose content in rice (Oryza sativa L.)

Summary The inheritance of low and very low amylose contents in six rice crosses and their reciprocals was studied by single grain analysis of parents F₁, F₂, B₁ and B₂ seeds. To minimize the environmental effects, the seeds of all generations of all crosses were produced in a single season. The results indicated different dosage effects in different crosses. One major gene was found to govern a difference of 6–12% in amylose content in low and intermediate amylose parents. Very low amylose content was similarly found to be governed by one major gene in crosses between very low- and low-amylose content parents. Minor genes and modifiers also seem to play some role. In the cross between two low amylose parents differing by about 2.5% in amylose content, the differences appeared to be controlled by some minor genes and modifiers. The selection program in different crosses has been suggested.     

Clonal propagation of Triticum durum Desf. from immature embryos and shoot base explants

Summary Immature embryos from five durum wheat cultivars were grown on Murashige and Skoog medium supplemented with two concentrations of kinetin or 6-benzylaminopurine (BAP). The embryos cultured on the medium containing 5 mg/l of BAP proliferated several axillary shoots. Shoot base segments subcultured on the same medium gave more shoot proliferation. The shoots developed into ear-bearing plants. This technique could be used for clonal propagation of wheat.     

Callus formation and plantlet regeneration from immature Triticum durum Desf. embryos

Summary Experiments upon in vitro culture of immature durum wheat embryos, harvested at different growth stages, were made in two consecutive years. Callus formation and plantlet regeneration were obtained. The ability to form callus and the degree of morphogenetic processes varied with the different hormonal treatments used and with the age of the embryos. In the first year the best response for callus growth was observed with 2,4-D 2 mg l^-1 plus adenine 50 mg l^-1 or 2,4-D 5 mg l^-1 alone in the more mature embryos (15 and 20 days after anthesis). On the contrary, NAA 5 mg l^-1 had a greater shoot regeneration effect. In the next year, at all 2,4-D concentrations and for the two different ages of the embryos tested, all embryos formed callus. Regeneration of plantlets was obtained in higher percentage in calli originated from the more developed embryos. The effect of changed media upon plantlet regeneration was studied after callus transplant.Investigation by cytophotometry and chromosome counts on different calli showed, practically in all cells, a diploid condition. A histological analysis demonstrated embryogenic somatic characteristics in many samples of callus. The pattern of organogenesis seemed to be via adventitious bud formation but structures resembling embryoids were also observed in the callus.     

Variations in the content of starch-granule bound protein among several Japanese cultivars of common wheat (Triticum aestivum L.)

Summary The starch-granule bound proteins of common wheat (Triticum aestivum L.) and six related species were examined by SDS-polyacrylamide gel electrophoresis. They showed almost the same molecular weight, 61 kD. The amount of the starch-granule bound protein varied among Japanese wheat cultivars although the variation was not as wide as that for rice. The amount of this protein of Kanto 107 and Kanto 79 was about 40% of that of Norin 98. In addition, wheats with lower starch-granule bound protein also possessed lower amylose content.     

Studies on the amylose content and gelatinisation temperature in certain local cultivars and induced grain shape mutants in rice

Summary Ninety local cultivars and 124 induced grain shape mutants were screened for their amylose content and gelatinisation temperature as indexed by the alkali disintegration patterns. The amylose content was high in most of the local cultivars and ranged from 19.2 to 32.0% and from 12.3 to 33.2% in the mutants. Wide variation was also observed for the alkali disintegration values and most of the varieties had low alkali values. A positive but low correlation between alkali values and amylose content and a negative correlation between alkali values and protein content was observed. The preliminary studies suggest that the amylose content at different milling levels increased with an increase in the level of milling. Some of the local cultivars and induced mutants were found to be superior with high amylose and high gelatinisation temperature and could be utilized in breeding programmes directed towards improving the cooking quality of high yielding varieties.