Biologiczne aspekty produkcji cebuli (Allium cepa L.) ze szczególnym odniesieniem do strefy tropikalnej

Franciszek Bednarz


It is believed that Allium cepa L. was domesticated in Central Asia about 6000 years ago. Its growing area has been expanding ever since, so that now it is grown in almost all inhabited parts of the world. This was accompanied by ecological differentiation in the crop, resulting chiefly from the horizontal and vertical differentiation of climates. The spread of the onion from climatically privileged environments at intermediate latitudes, which favour both a biennal production cycle and a long growing period of the main season crop, to increasingly less suitable environments - with either lower or higher mean levels and/or seasonal variations of major climatic parameters (photoperiod, temperature, rainfall) - at these or other latitudes was associated with a gradual shift from generative to vegetative propagation. This tendency manifested itself by declining biological productivity, increasing lateral branching, shorter growing periods, smaller bulb size, higher dry matter content and better keeping ability of the bulbs, culminating eventually in the occurrence of different bulb-propagated ecotypes in geographically distant areas of marginal suitability for the crop (the coldest temperate climates, highland climates, equatorial rain climates). At the same time, though the onion remained a long-day plant with respect to bulb formation, its minimum photo-periods for bulbing were becoming shorter or contrarily longer with respectively decreasing or increasing seasonal variations of photoperiod and, to a certain extent, of other factors. The above arrangement of traits is indicative of the main correlations observed between them in the onion. In highly variable materials with respect to adaptation or when different planting dates are applied, some of the relationships assume a parabolic pattern, especially when certain traits are related to the length of growing period. The scheme of the ecological variability of the onion proposed here implies that during a long evolutionary process, the bulb-propagated ecotypes, commonly called shallots or potato onions, evolved independently in many places along the everchanging boundaries of the onion's distribution as a response to different climatic barriers, often being subsequently replaced by seed-propagated onion crops and contributing to the emergence of new bulb-propagated types as the crop spread to more distant areas. In all the environments under which they are grown, the bulbpropagated onions are generally of limited variability and distinguish themselves by a short growing period (60 to 90 days), excellent keeping quality, high dry matter content and the ability to produce clusters of small, pungent bulbs. Depending on ecotype, their bulbs can be well vernalized when stored at tempera¬tures ranging from 4 to 10°C. Less pungent types of such onions are sometimes grown within the areas of seed-propagated crops and these are usually considered to be exotic and rather early introductions of known origin, though they c local selections from seed-propagated crops. In seed-propagated onions the period from emergence to harvest usually r from 90 to 240 days, reaching its maximum length and variation in sub-trop areas and decreasing markedly in both temperate and tropical climates, equatorial areas, when bulb-propagated onions are also taken into acclaim, similar pattern in growing period length seems to result from the ye differentiation of climate. Generally for well adapted crops, planted at the time, onion yields increase with longer growing periods, but there is a nepti correlation between length of the growing period and keeping ability of the hu when different varieties, seasons or environments are compared. Nevertheless, humid environments are less suitable for onion storage than cooler and drier It should be also kept in mind that the relationship between marketable yield keeping ability and the length of growing period often assumes a parabolic pa when highly variable materials are used or different planting dates compared. observation probably also applies to dry matter content and possibly some traits as well. Onion production in the tropics has certain features that stern from the lar hot and humid climates, from small seasonal variation of photoperied temperature, and from the overlapping periods of drought, lower temperatures shorter days in the areas of high seasonal variation of rainfall. In the cooler trop regions, onions usually give good yields when grown under irrigation in the season, but their production can be much more successful if the rather high rate bolting in the local strains is reduced by selection. This problem results partly fr a negative correlation between the minimum length of day for bulbing and optimum level of temperature for vernalization that seems to be observed in seed-propagated ecotypes of the onion. In tropical areas with a sufficiently gt vertical differentiation of climate it is possible, and often desirable, to both prod seed and carry out supplementary selection against bolting at higher elevatio Care should be taken however to keep the selection pressure involved wi reasonable limits, so as not to affect adversely the crop seed productivity possibly the keeping quality of the bulbs. At low as well as at high elevations the humid tropical areas, especially equatorial ones, the bulb-propagated oil appear to be most suitable. Tice empirical information on the diversity of the onion within its worldwi growing area as well as on the variability of the environments in which the call plant is grown is not satisfactory. It is difficult therefore to fully take into accou the ecological aspect while classifying onion varieties. Also the rclationshi between traits in the onion are not known well enough and, in particular, rno research on the biological traits and generally a better understanding of the gene of A. cepa are necessary to make further progress in this respect.
Book typeMonograph
Author Franciszek Bednarz (UAK)
Franciszek Bednarz,,
- University of Agriculture in Krakow
PublisherUniwersytet Rolniczy im. Hugona Kołłątaja w Krakowie, MNiSW [80]
Publishing place (Publisher address)Kraków
Issue year1994
Book series /Journal (in case of Journal special issue)Zeszyty Naukowe Akademii Rolniczej im. H. Kołłątaja w Krakowie. Rozprawy, ISSN 1233-4189, (0 pkt)
Publication size in sheets6.6
Languagepl polski
Score (nominal)20
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