--Victor R. Corcuera*, Luis B. Mazoti and Carlos A. Naranjo
*Assistant Technician of C.I.C.
The maize plant is essentially neutral to photoperiod, though short days speed up its induction to flowering.
With the sole purpose of obtaining waxy endosperm commercial hybrids qualified for industrialization proceedings (such as WET MILLING and others), different types of waxy endosperm maizes were studied: three inbred lines, three populations and one hybrid.
The inbred lines analyzed were:
a. "c-tester" (c sh wx), introduced to Santa Catalina during 1937 from Cornell University, and kept under inbreeding since then.
b."CEL WAXY SMC2" and "CEL WAXY SMC3", introduced to Santa Catalina during 1990 from CIMMYT (Mexico).
The populations studied were: SCV1, SCV2 and WEM of the Instituto Fitotécnico de Santa Catalina.
Finally, the hybrid measured was FUNKS WAXY, sent to Santa Catalina from CIMMYT (Mexico) during 1990.
Three different evolutive cycle traits were measured and analyzed in all these materials: T, days to tassel (number of days computed from the date of emergence); S, days to silking; Po, days to pollen. All of these traits were measured as is recommended in the General Catalog of Maize Descriptors by IBPGR (International Board for Plant Genetic Resources).
In addition, to make the results obtained comparative amongst themselves and with others coming out from our next studies, the value of the Heat Units necessary to flower has also been calculated according to a residual method (method of the degrees/day), taking as a baseline temperature 12.8 C (approximately 55 F).
All of the measurements were practiced on the basis of individual plants (nearly 300).
As is well known, the evolutive cycle traits are closely related amongst themselves, therefore the analysis of the results can be done without discriminating each trait.
Table 1 shows the commonest statistical measurements (means, standard
deviation, variability %, variance and range) for all the traits studied
in each of the materials. The variability % obtained for most of the traits
considered was low. This tendency is also observed in the ranges. It must
be pointed out that the materials sent by CIMMYT showed a long evolutive
cycle in our country. They were protoginous as well. This fact may be due
to the latitude in which these maizes were grown, and consequently to the
photoperiod. It is known that when maizes adapted or grown in low latitudes
are moved to high latitudes, the evolutive cycle becomes longer.
Table 1. Statistical measures for evolutive cycle traits in all the
|CEL WAXY SMC2||S||70.37||2.11||3.00||4.45||66-74|
|CEL WAXY SMC3||S||70.47||1.61||2.29||2.59||68-73|
Table 2 shows the existence of statistically significant differences among the maizes evaluated when their evolutive cycle traits are considered.
Table 2. Differences between means for evolutive cycle traits.
|CEL WAXY SMC2||66.42d||70.37c||74.49d|
|CEL WAXY SMC3||66.24d||70.47c||74.30d|
Table 3 shows the Heat Units, the average number of days to silking, and a classification of each of the materials studied according to these data.
Table 3. Evolutive cycle traits, general data and classification for
each material studied.
|Material||S||Heat Units ( C)||Cycle|
|CEL WAXY SMC2||70||628.40||long|
|CEL WAXY SMC3||70||628.40||long|
The single fact that the waxy endosperm maizes show a short evolutive
cycle of precocity makes them doubly interesting: 1. On the one hand commercial
hybrids of waxy endosperm and short evolutive cycle could be obtained.
2. On the other hand, their precocity could be incorporated into the most
cultivated maizes of our country.
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