CÓRDOBA NATIONAL UNIVERSITY
College of Agriculture, P.O. Box 509, 5000 Córdoba, Argentina.
Z. Gaido and M.E. Dubois.
For the second year, we have evaluated the effects in wheat lines
of six cycles (C0 to C6) of recurrent selection on bread-making
quality of 12 commercial bread wheat cultivars. No significant
differences were observed in the bread-making quality between
derivatives of C0 and C6 lines (Table 1). The contrast among the
value means of the C6 cycle and that of the commercial cultivars
was significant in three of the four analyzed variables, the C6
values being superior in all cases (Table 1).
| Cycles of recurrent selection |
Grain protein (%) |
Gluten (%) |
High mixograph (unid) |
Mixograph dough development time (min) |
|---|---|---|---|---|
| C0 | 12.30 bc | 28.72 bc | 6.55 b | 5.26 bc |
| C1 | 12.55 b | 28.51 bc | 6.51 b | 5.63 c |
| C2 | 12.27 bc | 29.37 bc | 6.76 b | 4.80 bc |
| C3 | 11.75 c | 26.76 c | 6.43 b | 5.16 bc |
| C4 | 12.39 bc | 31.33 ab | 7.39 b | 3.60 a |
| C5 | 12.10 bc | 28.38 bc | 6.83 b | 5.20 bc |
| C6 | 12.19 bc | 27.70 c | 6.60 b | 5.12 bc |
| Commercial cultivars | 13.51 a | 33.21 a | 7.68 a | 4.,05 ab |
| a-c: Different letters denote means statistically different at P < 0.05 according Duncan's Test. | ||||
Mixograph dough development time (MDDT) of the 96 analyzed genotypes (12 for each cycle) are presented in the Table 2. For the best interval MDDT (3.5-5.5), a proportion of the 75 % is observed in the C6, proportion only overcome by the wheat commercial cultivars (83 %).
| Cycles of recurrent selection |
MDDT < 3.5 | 3.5 > MDDT < 5.5 | MDDT > 5.5 |
|---|---|---|---|
| C0 | 2 | 5 | 5 |
| C1 | 1 | 7 | 4 |
| C2 | 2 | 7 | 3 |
| C3 | 0 | 8 | 4 |
| C4 | 5 | 7 | 0 |
| C5 | 1 | 7 | 4 |
| C6 | 0 | 9 | 3 |
| Commercial cultivars | 2 | 10 | 0 |
Of the results corresponding to baking-quality parameters,
we observed that after six cycles of recurrent selection, quality
did not suffer significant changes. Coincident results were obtained
after two cycles (Dubois et al. 1998) and three cycles (Gaido
et al. 2000) of recurrent selection. We are planning, however,
to recycle agronomic and qualitatively superior genotypes, such
as improving the qualitative profile of the germ plasm subject
to improvement genetics.
Publications.
R. Maich, I.M. Lorello, L.E. Torres, R. Rolando, and L. Torres.
Compost contains organic matter in an intermediate state of decomposition with respect to the humus and, likewise, it improves the biological, chemical, and physical properties of amended soils. The objective of this study was to measure the effects of several extracts obtained from compost suspensions on the development of wheat seedlings. The compost was obtained from the leaves of deciduous trees (Populus spp.) collected in the city of Córdoba. Seeds of the wheat cultivar Baguette 10 were imbibed in a compost suspension extract with and without a heat treatment. Seedlings derived from treated seeds possessed a longer first leaf. The seminal root number was higher in those seedlings derived from seeds imbibed in a 1:5 compost:water extract without a heat treatment. The length of the first leaf of the seedlings and of the main seminal root derived from artificially aged seeds increased when the seeds were immersed in a compost extract. These results will help to establish the real relationship between early vigor and grain yield related characters.
Publication.
S.P. Gil, R.H. Maich, and M.M. Cerana.
Currently, we are working with six cycles (C0 to C6,) of recurrent selection in order to evaluate the effects of plant breeding on the number of floret primordia and fertile florets and three morphological characteristics of flag leaves, i.e., length, width, and area. The plants were grown at the Experimental Farm of the College of Agriculture (31°29' S and 64°00' W), Córdoba, Argentina, during 2002.
We compared the following cycles: C0 (initial); C1, C2, C3, C4, and C5 (intermediate); and C6 (more evolved). Five spikes of the main shoot were divided into thirds (lower third, spikelets 4 and 5; middle third, spikelets 9 and 10; and upper third, subterminal spikelet), and five flag leaves from each of 12 S-derived families/populations were studied. Data were evaluated with ANOVA and Duncan's Multiple Range Test.
The results indicated that the C4 mean values were higher than the other cycles except for the floret primordia and fertile florets in the lower third, regardless of the degree of significance. Plants from the more evolved cycle (C6) did not perform better than those from other cycles.
R. Maich, D. Ortega, G. Astolfi, R. Argenti, and G. Manera.
We investigated the existence of trait variability between genotypes and estimated to what extent the new genotypes are better than standard cultivars. The different traits that influence yield were investigated using nine wheat breeding lines and cultivars (genotypes). The experiment was set in a randomized, complete-block design with four replications on a basic plot of 5 m2 in 2003. Grain yield and its components were measured for each experimental unit. The results showed considerable variation for all measured traits and are very promising if we compare the new genotype C3-00-42 and four Argentinean cultivars. For example, a significant increase of 16 % was achieved for grain yield, and a similar tendency was observed for biological yield and grain number/m. These results are for the first year of a 3-year study. Simultaneously, we will evaluate the new genotype C3-00-42 under conditions in the farmers' field.
Publications.
G. Chaves, M.C. Coraglio, B. Costero, L.E. Torres, and R. Maich.
The objective of this research was to evaluate the actual grain yield advances in bread wheat and hexaploid triticale using two selection indices.
18-character selection index. For each trait measured at the plot or sample level and taking into account the direction of selection, the progeny mean value was compared to the corresponding 131 C2S0 (hexaploid triticale) or 121 C5S0 (bread wheat) sample mean values with respect to the controls. One (morphological) or two (physiological and physical) points were assigned when the performance of the progeny was agronomically superior to that for the reference mean value. An additional point was assigned if the frequency of superior progenies with respect to the reference mean value was less than 25 %. The score/S0 progeny was estimated and disruptive selection intensities of 7.6 % (triticale) and 8.3 % (bread wheat) were applied in each sense for the selection index variable.
11-character selection index. For each trait measured at plot level, the progeny mean value was compared to the corresponding 142 C3S0 (hexaploid triticale) or 89 C6S0 (bread wheat) sample mean values (=100). The score/S0 progeny was obtained as the sum of the 11 percentages (positives and negatives). A disruptive selection intensity of 7.0 % (triticale) and 11.2 % (bread wheat) was applied in each sense for the selection index variable.
For both indicies, 20 S1 triticale families (10/group) and 20 S1 bread wheat families (10/group) were evaluated under rainfed conditions at the Experimental Farm of the College of Agriculture. Complete, randomized designs with two replications were used. The characters measured on a plot basis were grain and above-ground biological yield (g/m2), spike number/m2, 1,000-kernel weight (g), harvest index (%), and grain number/m2. For each trait, the differential (ds) and the response to selection (RS) were estimated from the S0 progenies and S1-derived families, respectively, as the mean difference (in percent) between higher and lower (=100) selection index groups. Two over six (triticale) and four over six (bread wheat) RS and ds coincidences were observed for the 18-character selection index; whereas, six over six RS and ds coincidences were observed in both species for the 11-character selection index.
Taking into account the results of multiple trait selection in triticale and bread wheat, we propose to reduce the number of traits included in the selection index in order to obtain more equilibrate multiple trait response.
L. Dubini, R. Maich, and A. Abril.
Many microorganisms are capable of N2 fixation. Some are free-living organisms such as bacteria and cyanobacteria. One of the nonsymbiotic associations involves grasses and nitrogen-fixing bacteria of the genus Azospirillum. Azospirillum spp. are interesting plant growth promoting rhizobacteria. We determined the effect of an A. brasilense inoculant on grain yield and its principal component grain number/m2. Nine genotypes of bread wheat with different biological cycles (early and late heading) were inoculated. Preliminary results show a significant, negative relationship between the seedingheading interval in days and a difference between inoculated and uninoculated (= 100) material. Rainfed conditions and the occurrence of a terminal drought stress probably are responsible for the specific and positive association between A. brasilense and earlier heading wheat genotypes.