ITEMS FROM ARGENTINA

CÓRDOBA NATIONAL UNIVERSITY

College of Agriculture, P.O. Box 509, 5000 Córdoba, Argentina.

Flower number in wheat spikelets related to a recurrent selection scheme for grain yield.

M.M. Cerana, S.P. Gil, and R. Maich.

Today, the bread wheat spike is one of the more relevant aspects in the development of new cultivars, because its number of kernels is related positively to grain yield. The spikelets are initiated early in the crop cycle, so the number of grains/spikelet depends on the number of floret primordia initiated, the primordia surviving as fertile florets, and the proportion of these florets setting grains after anthesis.

In this study, experiments assessed the effect of three cycles of recurrent selection for grain yield on the number of floret primordia and fertile florets/spikelet and the relationship with the grain number.

Twelve S1-derived families from each one of the three cycles of recurrent selection analyzed (C0: initial, C1, and C2: intermediate, and C3: more evolved) were evaluated in 1998 using a completely randomized block design with two replications at the Ferreyra Experimental Farm (31° 29'S and 64° 00'W). The families were derived from S1 plants selected in 1994.

The attributes measured on a plot basis were the number of primordia and fertile florets per spikelet in anthesis phase and the kernel number and the 1,000-kernel weight at maturity. From each experimental unit, five fertile culms were divided in thirds (lower third: spikelets 4 and 5, middle third: spikelets 10 and 11, and upper third: subterminal ones). Analysis of variance and Duncan's Multiple Range Test were carried out.

The more evolved cycle was significantly superior to C0 in the lower third for the number of floret primordia/spikelet. With respect to the fertile florets, significant differences were found in the lower and middle spikelet thirds.

Wheat bread-making quality after three cycles recurrent selection for grain yield.

M.E. Dubois, Z.A. Gaido, G.A. Manera, and R.H. Maich.

We evaluated three cycles of recurrent selection for grain yield in bread wheat and its effects on several quality parameters. Twelve S1-derived families from each of the analyzed cycles (C0, C1,C2, and C3) were evaluated for grain yield during 2 consecutive years (Maich RH, Ann Wheat Newslet 44:34). For bread-making quality, any measured trait did not show significant differences between cycles. A similar result was observed in a 3-year trial, where two cycles of recurrent selection were evaluated (Gaido et al., Ann Wheat Newslet 44:34). Protein and gluten percentages during 1997 were lower than those of 1996. Moreover, those flour samples with low protein percentages failed during the agglutination process. These mean protein differences between years are due to constrasting environmental conditions. A similar tendency was observed for the check varieties. Though nonsignificant differences between cycles were observed for rate of dough development time, in general, they were excessively long, probably because of the low percentage of flour protein in 1997. The mixograph analysis showed that the 73 % of the families were included in classes 6 and 7. However, some C3 families were of classes 9 and 10. We concluded that after three cycles of recurrent selection for grain yield, significant direct genetic progress was made without any significant effects on the bread-making quality traits measured.

The more evolved cycle (C3) always showed the highest mean values independently of the significant degree. Simultaneously we found higher number of grains per spikelet, but the 1,000-kernel weight decreased. These results are similar to those of a previous study comparing modern and older cultivars.

Spikelet analysis comparing four cycles of recurrent selection.

S.P. Gil, M.M. Cerana, and R. Maich.

In this study, four cycles of recurrent selection for grain yield in bread wheat and its effects on the number of floret primordia and fertile florets were studied. The families evaluated in this analysis were sown in an experimental field placed in Ferreyra (Córdoba, Argentina) at 31° 29'S and 64° 00'W during 1998. These families were derived from S1 or S2 plants selected in 1996.

The cycles compared were: C0: initial, C1, C2, and C3: intermediate, C4: more evolved. Five main shoot spikes from each family per cycle and per year divided in thirds (lower third: spikelets 4 and 5, middle third: spikelets 10 and 11, and upper third: subterminal ones) were used in order to determine the number of primordia and fertile florets. Data were evaluated with ANOVA and Duncan's Multiple Range Test.

Our results showed significant differences only in the number of fertile florets in the upper third, and the C4 cycle had more of them. Nevertheless, the observed means were greater for both variables.

Three cycles of recurrent selection for grain yield.

M.E. Dubois, R.H. Maich, G.A. Manera, and Z.A. Gaido.

The experimental lines were originated from a plant-breeding program supported on a recurrent selection scheme directed at increasing grain yield in bread wheat. The results concerning 1 year of evaluation were published previously (Maich R, Ann Wheat Newslet 43:46). In this study, a 3-year (1996-98) evaluation was performed. After three cycles of recurrent selection, significant genetic progress was achieved; the mean values of the families pertaining to C2 and C3 were statistically superior respect to that of C0. A grain yield increase of 11.4 % was observed. A similar tendency was observed with regard to aerial biomass (12.5 %), but not for the harvest index. Grain yield components showed different results; the numerical ones (grain number per spike and spikelet) increased, decreasing grain weight. In accordance with the biennial analysis (Dubois et al. Ann Wheat Newslet 45:31), no differences between cycles were observed for any one of the quality parameters measured. In summary, the cyclical process of selection and recombination was effective, generating material with higher grain and aerial biomass production, while maintaining its bread-making quality.

INSTITUTO DE RECURSOS BIOLÓGICOS, CNIA-INTA

CC 25 (1712), Castelar, Pcia. de Buenos Aires, Argentina.

Introgression of a leaf rust resistance gene (Lr47) into Argentinian wheat cultivars.

S. Lewis, L. Bullrich, and E.Y. Suárez.

Rust diseases of wheat are among the major factors that adversely affect wheat yield and quality worldwide. At present, one of our objectives is to transfer new resistance rust genes into wheat cultivars using molecular markers, which facilitate the introgression of more than one resistance gene into a particular cultivar (gene pyramiding).

Ten Argentinian commercial wheat cultivars (ProInta Puntal, ProInta Imperial, ProInta Oasis, ProInta Isla Verde, ProInta Granar, Buck Poncho, Buck Fogón, Klein Estrella, Klein Cacique, and ProInta Federal) were chosen to be crossed with a line called Pavon 7A.7S-S3 (Dubcovsky et al. 1998) carrying the Lr47 gene from Ae. speltoides, which has been shown to confer resistance to a wide spectrum of leaf rust strains. The first selections for Lr47 were done using an RFLP marker (Dubcovsky et al. 1998). Last year, PCR markers (Helguera et al. 2000) were employed to select the plants carrying the resistance gene.

Although Lr47 still is in a heterozygous condition, preliminary results were obtained about the behavior of this gene in our cultivars. During 1999, a severe rust attack occurred in our experimental field located in Castelar, Buenos Aires, Argentina. We observed that all the selected BCs carrying Lr47 were highly resistant to leaf rust compared to the original cultivars without the gene. In addition, Pavon 7A.7S-S3 was resistant compared to Pavon, which was quite susceptible. These results suggest that Lr47 is effective against leaf rust races present in this area.

In 2000, we expect to obtain BC6 for three commercial Argentinian cultivars and the final lines carrying Lr47 in homozygous condition. We plan to carry out field trials in different Experimental Stations of INTA to evaluate different agronomic characters and to test the possibility of yield penalty associated to the resistance gene coming from Ae. speltoides.

References.

• Dubcovsky J, Lukaszewski AJ, Echaide M, Antonelli EF, and Porter DR. 1998. Molecular characterization of two Triticum speltoides intersticial translocations carrying leaf rust and greenbug resistance genes. Crop Sci 38(6):1655-1660.
• Helguera M, Khan IA, and Dubcovsky J. 2000. Development of PCR marker for wheat leaf rust resistance gene Lr47. (In press).

Quantitative assessment of genetic erosion among bread wheat cultivars using SSRs.

M.M. Manifesto, A.R. Schlatter, H.E. Hopp, E.Y. Súarez, and J. Dubcovsky.

Characterization of wheat germ plasm using DNA fingerprinting techniques can provide the information required for a rational utilization of genetic diversity both in basic research aspects and practical ones like breeding.

The potential of SSR markers was evaluated in this work for studies of genetic variability. This study included 105 bread wheat cultivars from Argentina registered in the National Seed Property Register of Argentina (INASE) and released from 1932 to 1995, which represent a wide sample of the variability present in the Argentina bread wheat germ plasm.

Thirty-three pairs of primers were used to screen a subset of 15 cultivars. A subset of 10 loci with high variability and a clear banding pattern was selected.

The number of SSR alleles ranged from 5 to 13 with an average of 9.4 alleles/locus. The PIC values ranged from 0.40 to 0.84 with an average value of 0.72 ± 0.14 standard deviation.

To evaluate genetic erosion in the Argentine germ plasm, varieties were grouped by decade of release. Varieties released before 1969 were grouped in a single class to compensate for the low number of cultivars available from this period. Because the selected SSR loci showed large differences in PIC values, loci were used as blocks to increase the sensitivity of the statistic analysis.

Average diversity values for the four periods considered here were almost identical (Table 1), and no significant differences (P = 0.95) were found among the decades. An interesting result from this study that contradicts the general vision of a significant genetic erosion in modern cultivars was that genetic diversity values were very similar during the last half century. A detailed analysis of the pedigree of modern Argentine germ introgression of new materials from programs from other countries, particularly the material from CIMMYT. Alleles from old cultivars like Ciano, 38MA, Sinvalocho, Sonora 64, Nianari 59, Frontana Mentana, Buck Quequen, Buck Atlantico, Lin Calel MA, Roca MAG, and others varieties, which were the basis from which the wheat Argentinian germ plasm was developed, are still present in modern Argentine germ plasm.

Publications.

• Bullrich L, Tranquilli G, Pflüger L, Suárez E, and Barneix A. 1998. Bread making quality and yield performance of 1BL/1RS wheat isogenic lines. Plant Breed 117:119-122.
• Bullrich L, Lewis S, Schlatter AR, Manifesto MM, and Suárez E. 1998. Caracterización e identificación de cultivares de trigo pasta (Triticum durum) mediante proteínas de reserva y microsatélites. In: IV Congr Nacl de Trigo, Mar del Plata, 11-13 November, 1998.
• Bullrich L, Lewis S, Schlatter AR, Manifesto MM, and Suárez E. 1998. Determinación de la composición de proteínas de reserva asociadas a la calidad en Triticum durum e identificación de cultivares por marcadores moleculares. In: Congr Panamericano de Semillas, Buenos Aires, 19-21 de October, 1998.
• Dubcovsky J, Lijavetzky D, Appendino L, and Tranquilli G. 1998. Comparative RFLP mapping of Triticum monococcum genes controlling vernalization requirement. Theor Appl Genet 97:968-975.
• Helguera M, Echaide M, Lewis S, Schlatter AR, Suarez EY, Hopp HE, and Dubcovsky J. 1998. Desarrollo en trigo (Triticum aestivum L.) de un marcador molecular PCR-específico asociado a una translocación de Triticum speltoides portadora de genes de resistencia a roya de la hoja. In: IV Congr Nacl de Trigo, Mar del Plata, 11-13 November, 1998.
• Helguera M, Echaide M, Lewis S, Schlatter AR, Suarez EY, Hopp HE, and Dubcovsky J. 1999. Development of a PCR marker associated with wheat leaf rust resistance gene Lr47. PAG VII, 17-21 January, 1999, San Diego CA, USA.
• Manifesto MM, Feingold S, Hopp HE, Schlatter AR, and Dubcovsky J. 1998. Molecular marker s associated with differences in bread-making quality in a cross between bread wheat cultivars with the same high Mr glutenins. J Cereal Sci 27:217-227.
• Manifesto MM, Schlatter AR, Echaide M, Hopp HE, Suarez EY, and. Dubcovsky J. 1998. Microsatelites en Trigo (Triticum aestivum). Nueva herramienta para la identificacion de cultivares. In: XVI Seminario Panamericano de Semillas-Rueda de Negocios, Bs As, 19-21 October, 1998.
• Manifesto MM, Schlatter AR, Hopp HE, .Suarez EY, and Dubcovsky J. 1999. Bread wheat (Triticum aestivum) fingerprinting using microsatellites. PAG VII, 17-21 January, 1999, San Diego CA, USA.
• Schlatter AR, Manifesto MM, Helguera M, Bullrich L, Tranquilli GE, Lewis S, Marcucci Poltri S, Hopp HE, Suarez EY, and Dubcovsky J. Marcadores Moleculares en el Desarrollo de Germoplasma Premejorado de Trigo. In: XXIX Congr Argentino de Genética, Rosario, Argentina, September, 1999.
• Tranquilli G, Cuniberti M, Gianibelli C, Bullrich L, Larroque O, MacRitchie F, and Dubcovsky J. 1998. Effect of Triticum monococcum glutenin loci on bread making quality. In: Proc 9th Internat Wheat Genet Symp (Slinkard AE ed). University Extension Press, Saskatoon, Saskatchewan, Canada. 4:282 -284.
• Tranquilli G, Marcucci Poltri S, Helguera M, Schlatter AR, Suarez EY, and Dubcovsky J. 1998. Desarrollo de marcadores moleculares asociados a un gen de alto contenido de proteina en grano de Triticum dicoccoides. In: IV Congr Nacl de Trigo, Mar del Plata, 11-13 November, 1998.
• Tranquilli G, Lijavetzky D, Muzzi G, and Dubcovsky J. 1999. Genetic and physical characterization of grain texture-related loci in diploid wheat. Mol Gen Genet 262:846-850.

Barley leaf sheath and glum spot by Fusarium poae in Argentina.

D. Barreto*, M. Carmona*, M. Ferrazzini*, and B. Pérez.
*Facultad de Agronomía, University of Buenos Aires, Avda San Martín 4453, Buenos Aires, Argentina.

During field disease surveys (1992-97) and routine seed health testing of barley, a fungus-like symptom was observed as an elliptical to round spot surrounded by a dark border in leaf sheaths and grain. Fusarium poae was associated consistently with the described symptoms. Pathogenicity tests were made under greenhouse and field conditions using the cultivar Quilmes Pampa. Barley plants were inoculated at the boot stage with a conidial suspension and kept under high humidity for 24 hours at 20±3°C. In both tests, leaf sheaths showed necrotic spots within 9 days after inoculation, and glume spots developed around 12 days. The total of spotted grains from the greenhouse and 436 grains from field tests produced F. poae. The symptoms developed were similar to those observed during the field surveys. Although this fungus has been associated with symptomless infection in barley, this study showed that it is the primary cause of this disease.

Publication.

• Barreto D, Carmona M. Ferrazzini M, and Pérez B. 1999. Barley leaf sheath and glume spot by Fusarium poae en Argentina. In: Proc 3rd Symp Seed Health, 16-19 August, 1999, Ames, Iowa, USA.