Intraspecific variation of genome size in Guarani´s maize landraces: cytological and phenological correlates.

REALINI, MARÍA FLORENCIA; POGGIO LIDIA; GONZÁLEZ, GRACIELA

Atibaia, San Pablo

Congreso; IV Reunión Brasilera de Citogenética; 2015

Sociedad Brasilera de Genética

The northern region of Argentina is one of the southernmost areas of maize landrace cultivation. Here, two distinct centres of diversity were distinguished: (a) the highland region, or Northwestern Argentina (NWA), which represents an expansion of the Peruvian Andes, and (b) the mesopotamic and Chaco plains or Northeastern Argentina (NEA), a lowland area for which maize landraces were considered to be more closely affiliated with landraces from Brazil and Paraguay. Maize chromosomes present heterochromatic subtelomeric blocks, called knobs, which vary in number and size across different races. Knobs have been described as highly repeated tandem arrays of 180 bp and TR-1 (350 bp) sequences, both repeated in different proportions. Variation in DNA content has been reported among maize landraces, due mainly to differences in the amount of knob-heterochromatin and the presence of B-chromosomes. In this study, we compare percentage of heterochromatin, the number, size, position and sequence composition of knobs, and genome size of eight representative maize landraces from each NWA and NEA region. DAPI banding allowed identified and locates the knobs as DAPI-positive bands on mitotic metaphase chromosomes. Simultaneous fluorescent in situ hybridization (FISH) experiments using 180-bp and TR-1 as probes showed that the knob sequences co-localized with all the DAPI-positive bands, and differential hybridization patterns among races were detected. The landraces DNA amount were estimated by flow cytometry. We performed analysis of variance (ANOVA), and significant differences (p