--Victor R. Corcuera*, Luis B. Mazoti and Carlos A. Naranjo
*Assistant Technician of C.I.C.
During the growing season 1990/91 two bulks were created at the Instituto Fitotécnico de Santa Catalina. Each one of these bulks was composed of a mixture of seeds of different flint and dent commercial hybrids. The purpose of creating these bulks was: 1. To keep a pool of genes useful for the later development of a breeding plan, through which it is expected to obtain commercial hybrids qualified for industrialization proceedings. 2. To focus on individual plants, genes, and on their diverse combinations.
This system definitely let us keep genes and increase the genetic variability through multiple recombinations. The last is possible, as pollination is not controlled within each bulk.
The bulks were grown in two different locations of the province of Buenos Aires: 9 de Julio and Chás. The first one has soils with a medium fertility degree, whilst the second has high fertility soils. Both bulks were grown during November, using a higher density of plants in Chás (50,000 plants/Ha) than in 9 de Julio (45,000 plants/Ha). At maturation the plants were harvested by hand, and samples were taken at random from each bulk. These samples belonged to flint and dent type in each case.
Thereafter, the samples were measured and analyzed at the laboratory through different descriptors recommended by IBPGR (International Bureau for Plant Genetic Resources). The traits/descriptors measured and evaluated in each ear were: 1. EL, ear length in cm; 2. ED, ear diameter in cm; 3. KR, number of kernel rows per ear; 4. NK, number of kernels per row; 5. EW, ear weight in g; 6. KW, kernel weight (g) per ear; and 7. %C, percentage of cob per ear.
In addition, the colour of the cob was considered for each ear measured. Then for each bulk, four groups of ears were evaluated as follows: flint type and white cob (FWC), flint type and red cob (FRC), dent type and white cob (DWC), and dent type and red cob (DRC).
Finally, the results obtained through the measurements practiced in nearly 600 ears were statistically analyzed.
Tables 1 and 2 show the commonest statistical measurements for each trait in both bulks (means, standard deviation, variability %, variance and range).
Table 1. Statistical measures for ear traits considering the coloration
of the cob. (Chás bulk).
Table 2: Statistical measures for each trait considering the coloration
of the cob. (9 de Julio bulk).
Tables 3 and 4 show the existence of some statistically significant differences amongst the average values for each trait in each bulk.
Table 3: Differences between means for ear traits of the "Chás"
Table 4: Differences between means for ear traits of the "9 de Julio"
From the detailed observation of the data given in the tables, it may be pointed out that:
1. In high fertility soils, dent maizes yielded more than the flints, though when one considers the low fertility situation (9 de Julio) there are not significant differences in yield between these two types (unless considering individual ears).
2. In high fertility soils, the DRC maizes were the highest yielding, and the FRC showed the lowest yields. The opposite occurs in low fertility soils.
Undoubtedly, the data and the general tendencies shown in this issue constitute an interesting fact, which will be deeply studied during the next growing seasons from this time on.
Furthermore, the multiple recombinations occurred in the field during the last growing season (90/91), and according to the results obtained, it can be pointed out that the coloration of the cob influences, although partially, the final yields.
The colour of the cob, as well as pericarp colour, is genetically determined
by allelomorphs of the gene P. Thus, it would be convenient to study
if there is some kind of association between this gene and the ones determining
yield, though this is very complicated as it is a phenomenon of quantitative
inheritance. If this fact could be effectively proved, the colour of the
cob related to the endosperm texture might be considered in breeding plans
to obtain commercial hybrids specifically developed for different areas
with a different fertility degree of their soils as well.
to the MNL 66 On-Line Index
Return to the Maize Newsletter Index
Return to the Maize Genome Database Page