Maize Genetics Cooperation Newsletter vol 87
2013
Buenos Aires, Argentina.
IEGEBA-CONICET and LACyE (Departamento
de Ecolog�a,
Gen�tica y Evoluci�n, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires).
Knobs number variability in Argentine Andean
maize populations (races
Amarillo Grande y Garrapata)
Fourasti� MF*, MF Realini, L Poggio and GE Gonz�lez
In this work we studied
six populations belonging
to two races of maize native of northwestern Argentina (NOA) in order to analyze
the variation respect to the number of heterochromatic blocks
(knobs), using fluorescent banding techniques (DAPI banding).
C�mara Hern�ndez et al., 2011 (Razas de ma�z nativas de la Argentina. Ed. Facultad de Agronom�a, 168pp.) identified and
described 28 native maize races from NOA. Two of these races,
Amarillo Grande and Garrapata, differ by their morphological
maize ears and grains, and grow at different altitudes in
the provinces of Jujuy and
Salta (Argentina).
Zea taxa with 2n = 20 chromosomes are
variable in number, size and position of the knobs, which can be found in 34
different chromosomal positions in corn and teosinte (Kato, Mass. Agr. St. Re. Exp. B. 635:1-185,
1976; McClintock, Maize Breeding and
Genetics 59-184, 1978). This variability was used for the characterization
of maize races of Latin America (Grobman et
al., 1961. NAS-NRC, 375
pp.; Longley, J.
Agron. Res 56:177-195, 1938; Ram�rez et al., 1960. NAS-NRC, 159pp;
Wellhausen et
al., 1957. NAS-NRC, 138 pp.). Number and size variations of the knobs are
related to intra and interspecific differences in DNA content found in the
genus Zea (Tito et al., Theor. Appl. Genet.
83:58-64, 1991; Rosato et al., Am J. Bot. 85:168 -174, 1998, Poggio et al., Ann. Bot. 82:115-117, 1998, Laurie & Bennett, Heredity 55:307-313, 1985).
In this work, we studied the number of knobs,
using DAPI chromosome banding (Summer, 1990. Chromosome banding. Ed. Unwin
Hyman, 434 pp.) on interphase nuclei and mitotic metaphases. The studied
materials were collected in the province of Jujuy, Argentina. These materials has been provided by the Vavilov Lab. of Universidad de Buenos Aires (UBA), and
cultivated in the greenhouse of the Facultad de Agronom�a, UBA.
We analyzed the number of knobs on populations
cultivated at three different altitudes above sea level of Amarillo Grande race
(populations: VAV 6669: 2000 m., VAV 6644: 2020 m. and VAV 6636: 2755 m.) and
Garrapata race (populations: VAV 6661: 2192 m., VAV 6662: 2780 m. and VAV 6626:
2795 m.). In each population 25 individuals were studied (5 individuals per maize
ear) and the results were averaged from at least 20 cells per individual.
The
results were analyzed by analysis of variance (ANOVA) with full nesting for
general linear mixed models. Factors considered were race (fixed factor), population
growing at different altitudes (random factor) nested on race, and maize ear (random
factor) nested in the population growing at different altitudes. Additionally,
we calculated the variance components to population, maize ear and error
factors (variability in the number of knobs between individuals and measurement
errors), p <0.05 values were considered significant. All statistical
analyzes were performed using the statistical program Infostat, FCA, National
University of C�rdoba (Di Rienzo et. al.,
InfoStat version 2012) with the R program interface (R Core Team, R Foundation
for Statistical Computing, 2012) for this unbalanced nested design.
No significant differences
between races Amarillo Grande and Garrapata in relation to the number of knobs
were detected (F1;2=0.47;
p=0.53). However, we found a
significant contribution to the variability between populations of the same
race cultivated at different altitudes above sea level (CI: 0.462; 4.892). We also found a significant contribution
to the variability among maize ears of the same
population (CI: 0.552;
1.672). Notwithstanding, differences among populations belonging to each race cultivated at different altitudes were
detected. Of the total variability, 45% is due to the variability among
populations and 36% is attributed to variability between the maize ears (Table
1).
Figure 1 shows a significant
decrease in the knobs number in populations cultivated at higher altitudes, in
concordance with the results found in other NOA populations (Rosato et al., Am. J. Bot. 85: 168-174, 1998).
Figure 1. Knobs number of populations of
Amarillo Grande (black) and Garrapata
(gray). Mean and standard deviation.
Ref.: m.a.s.l.: meters above sea level.
Variability
Factors Estimated variance CI
for variance relative
to the total
(%)
Population σ2ALT=1.502=2.25 (0.462;
4,892) 45.0
Maize ear σ2Esp=1.352=1.82 (0.682;
2,712) 36.5
Error (individuals) σ2Esp=0.962=0.92 (0.552;
1.672) 18.5
Table 1. Estimated variance components. CI: Confidence intervals.
Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of authors.