CÓRDOBA NATIONAL UNIVERSITY
College of Agriculture, P.O. Box 509, 5000 Córdoba, Argentina.
R.H. Maich, Z.A. Gaido, S.P. Gil, G.A. Manera, and M.E. Dubois.
We evaluated four cycles of recurrent selection for grain yield in bread wheat and determined direct and correlated responses. The cycles compared were the C0 (initial); C1, C2, and C3 (intermediate); and C4 (more advanced).
During 3 consecutive years, 1998, 1999, and 2000, 12 S1-derived families/population were sown at the Experimental Farm of the College of Agriculture (31^o^29' S and 64^o^00' W), Córdoba, Argentina. Plot data were recorded on grain yield, aerial biomass, harvest index, fertile florets/spikelet, seed number/spikelet, seed number/spike, grain-protein content, test weight, gluten percentage, and mixograms. The information was processed using ANOVA and Duncan's Multiple Range Test. The results indicated that although there was no significant difference between C0 and C4 for grain yield and its physiological components, a positive trend was denoted. Statistically significant differences between cycles were observed for the physical components of grain yield including fertile florets/spikelet, seed number/spikelet, and seed number/spike, where the C4-derived families had higher mean values than that of the original population (C0).
Published results of the physical components of grain yield (i.e., seed number/spike) showed associated changes with respect to improvement in seed production, however, we remain cautiously optimistic about the efficiency of our plant-breeding program. Test weight and bread-making quality measured in the C4 (protein content, gluten, and mixograms) were similar to the C0 population with good quality values.
M.M. Cerana, S.P. Gil, and R.H. Maich.
We are interested in flag-leaf morphology because it changes throughout different cycles of recurrent selection and it is one of the main organs related to grain filling in bread wheat. We evaluated the effects of three cycles (C0,C1, C2, and C3) of recurrent selection for grain yield on the length, width, and flag leaf area of wheat plants.
All material was sown at the Experimental Farm of the College
of Agriculture (31^o^29' S and 64^o^00' W), Córdoba, Argentina,
during 3 consecutive years (1996, 1997, and 1998). Five flag leaves
from each experimental unit were studied. Data were processed
with ANOVA and Duncan's Multiple Range Test. Significant differences
were observed among cycles only for length, the C3 (the more advanced
cycle) plants had shorter leaves than those of the C0 (the original
population), whereas no significant changes were noted in the
width and total area of the flag leaves.
INSTITUTO DE RECURSOS BIOLÓGICOS, CNIA-INTA
CC 25 (1712), Castelar, Pcia. de Buenos Aires, Argentina.
M.M. Manifesto and E.Y. Suárez.
Two important dwarfing genes, Ppd1 and Rht8, were introduced in Argentina from the Japanese variety Akakomugi in the 1930s by Professor Nazzareno Strampelli. Studies in different European countries suggest that Rht8 reduces height by an average of 7 cm (Worland et al. 1988; Worland and Law 1986) with no observable adverse effect on plant yield. Korzun et al. (1998) identified that the microsatellite marker WMS261, tightly linked to Rht8, was located on the short arm of chromosome 2D.
Varietal characterization in European wheats shows a high association between the marker and the presence of Rht8. Worland et al. (1998) described the role of the 192-bp allele, which came from Akakomugi through the cultivar Ardito, as a reduced-height allelic variant. Similarly, the 165-bp allele would be a height promotor and would be diagnostic for CIMMYT varieties and their descendants. This allele would be present in varieties carrying Norin alleles to counteract extremely low height.
Our study includes 165 bread wheat cultivars from Argentina, released between 1920 and 1998, for microsatellite screening. Modern and key varieties in pedigrees were included. Eight allelic variants were found at the Rht8 locus with the WMS261 microsatellite. The majority of varieties fell into three major groups. The 165-bp allele was the most numerous and was found in 94 varieties; a 192-bp allele group contains 41 varieties, and the group with a 174-bp allele contains 11 varieties. Other allelic variants were scarce and represented in only one or two, but no more than seven, varieties. Six varieties had two allelic variants simultaneously and were excluded for further analyses.
However, the direct association of each allelic variant and its effect was not possible to establish in this set of varieties. The effect of the 192-bp allele on reduced height in several cases was unclear, because this allele also is present in Chinese Spring and its derivatives 38MA and Sinvalocho that were widely used, and is sometimes found together with Ardito in the pedigree of a single variety. Similarly, the 165-bp allele, diagnostic for CIMMYT varieties (Worland et al. 1998), also was present in old varieties such as Americano 25e, which was largely used in the development of local germ plasm. Apparently, the same SSR has two different alleles of identical weight but with different sequences adjacent to the microsatellite motif (Worland, personal commnication). Extensive molecular analyses of the complete pedigrees are required, and more experiments need to be designed for a complete understanding.
References.
M. Bonafede, G. Tranquilli, and E. Suárez.
Grain texture is one of the characters that determines the end-use potential of wheat. This character is inherited as a single genetic factor and is controlled mainly by the hardness (Ha) locus on the short arm of chromosome 5D in hexaploid wheat. Recent studies indicate a strong linkage among the Ha, pinaD1, and pinbD1 loci. Pina and Pinb code for puroindoline a and b proteins, respectively.
We wanted to characterize the genetic variability of Argentinian wheat varieties at the Pina-D1 and Pinb-D1 loci by using specific PCR molecular markers. One hundred twenty varieties of common wheat from the Base Gene Bank located at our institute were analyzed. We also evaluated were varieties released between 1932 and 1998.
To date, results have shown a low variability for both grain
texture-related genes. The germ plasm we evaluated owes its hard
texture to two conserved mutations. These allelic variants are
the lack of the purindoline a protein, and a glycine to serine
mutation in Pinb. These variants are represented equally among
the germ plasm. These observations are representative of frequency
of these alleles to those observed in germ plasm surveys from
Europe and the U.S.
Adrián E. Bossio, Cecilia Bender, and Alberto Acevedo (also of the Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Roque Sáenz Peña 180, B1876BXD Bernal, Buenos Aires, Argentina).
The description of the few chlorina mutants that have been reported in wheat (Pettigrew and Driscoll 1970; Sears and Sears 1968; Williams et al. 1983) share a common feature, relative terms are used to refer to the color of their leaves. To solve this ambiguity, absolute chromatic measurements were determined in a chlorina mutant that was isolated from the bread wheat cultivar Leones INTA (Acevedo et al. 2001). A temporal and spatial study on leaf color was made in plants of the mutant and a mother line that were grown in the greenhouse (Table 1). Color was determined with a Minolta Chroma Meter CR-300 in fully expanded leaves. Color as perceived has three dimensions: hue (a), chroma (b), and lightness (L). Chromaticity includes hue and chroma, specified by two chromaticity coördinates (a and b). Because these two coördinates cannot describe a color completely, a lightness factor also must be included to identify a specimen color precisely. This method is nondestructive.
| Date of measurement | Leaf number |
|---|---|
| 5 May, 2001 | 4* - 5 - 6 |
| 29 May, 2001 | 6 - 7 - 8 |
| 7 July, 2001 | 8 - 9 - 10 - 11 |
| 24 August, 2001 | 9 - 10 - 11** |
| * lower leaf; ** upper leaf. | |
In seedlings, the temporal and spatial patterns of leaf color reveal slight differences between the mutant and the mother line (Table 2). Interestingly, these slight differences cannot be detected with the naked eye, and both mutant and mother line genotypes have normal green leaves.
| Leaf number | Mother line | Chlorina mutant | ||||
|---|---|---|---|---|---|---|
| hue | chroma | lightness | hue | chroma | lightness | |
| 4 | - 15.58 | 20.75 | 40.97 | - 17.84 | 26.59 | 44.61 |
| 5 | - 15.34 | 19.48 | 39.21 | - 17.40 | 23.98 | 43.26 |
| 6 | - 15.77 | 17.90 | 38.45 | - 18.15 | 25.39 | 42.76 |
As the plants developed, the temporal and spatial patterns of leaf color in the mutant were increasingly different from those of the mother line. Accordingly, leaves in the mutant turned yellowish, whereas they remained green in the mother line. At the adult-plant stage, dramatic differences were observed between the temporal and spatial patterns of leaf color in the mutant and the mother line (Table 3).
| Leaf number | Mother line | Chlorina mutant | ||||
|---|---|---|---|---|---|---|
| hue | chroma | lightness | hue | chroma | lightness | |
| 9 | - 15.50 | 25.48 | 46.20 | - 15.95 | 34.85 | 55.43 |
| 10 | - 11.53 | 14.58 | 39.26 | - 16.05 | 37.45 | 57.89 |
| 11 | - 10.49 | 12.55 | 37.20 | - 15.87 | 35.67 | 52.65 |
Cristina A. Kamlofski, Ruben Marrero, and Antonio Diaz Paleo; Instituto de Genética 'Ewald A. Favret', CICV / INTA, B1712WAA Castelar, Buenos Aires, Argentina.
Plant productivity is influenced by environmental stress. Several reports have shown that salt, freezing, and drought stress are accompanied by the formation of reactive oxygen intermediates. These toxic molecules damage membranes, membranes-bound structures, and macromolecules resulting in oxidative stress. Plant cells contain several antioxidant enzyme systems that scavenge these reactive oxygen intermediates. One enzyme system is catalase (CAT), which catalyzes the disassociation of H2O2 into O2 and H2O (Willekens et al. 1995). The protective role of CAT has been examined under several abiotic stress conditions and in plantpathogen interactions.
One way to increase tolerance to environmental stress can be achieved by over-expressing transgenes encoding protective proteins or enzymes in a target genotype. To evaluate this strategy, we cotransformed bread wheat with the Cat1 gene from barley (Skadsen et al. 1995), the selectable hph (hygromycin resistance) gene, and the marker gene gusA. Immature embryos from two Bobwhite lines, one of them the commercial variety ProINTA Federal, were the target for the genetic transformation. The biolistic method was applied using a Particle Inflow Gun (Finer et al. 1992) as the microprojectile accelerator. Approximately 600 immature embryos were bombarded with gold particles coated with plasmid DNA. The cotransformation was performed with three plasmids: pAc-H1, which contains a truncated hph coding sequence (Bilang et al. 1991) under the control of rice actin 1 5' regulatory signals; pUbiCat, which contains the barley Cat1 gene under the control of maize ubi-1 5' promoter region; and pBPFA 9gus (Gonzalez-Cabrera et al. 1998). Calli growth and selection were made on an MS medium (Murashige and Skoog 1962) with 2 mg/l 2,4-D mg/l. PCR analysis of the nine, T0 antibiotic-resistant plants revealed that six plants had the hph gene. Among the hph-positive plants two were Cat positive only, four were gusA positive only, and one was Cat and gusA positive. The three plants that were PCR negative for hph also were negative for Cat and gusA. Taken together, these results demonstrate the all transgenic plants showed cointegration of at least two genes, and in one case, cointegration of three genes. Currently, ongoing research is devoted to confirming the number of integration sites by Southern hybridization analysis. Northern blot analysis and CAT activity will be used to study CAT over-expression on the T1 and subsequent generations.
References.