Plant breeding for organic and sustainable, low-input agriculture

Breeding for organic greenhouse production in zucchini squash
S. Manzano 1 , H. Bos 1 , M.A Suarez 1 , J. Ferre 1 , C. Payán 2 , P. Gómez 2 and M. Jamilena 1
1 Department of Applied Biology. University of Almería, Spain.
2 Department of Plant Breeding and Biotechnology, IFAPA Almería, Spain.
The production of zucchini squash under organic greenhouse conditions in the southeast of Spain
requires the development of new varieties which not only satisfy the needs of growers but also
the fruit quality that European consumers demand. In collaboration with organic growers, the
University of Almería has started a zucchini breeding program, the main goal of which is the
development of parthenocarpic varieties adapted to low-input production in greenhouses.
Parthenocarpy is an essential trait for zucchini organic greenhouse production, since the use of
synthetic hormones for fruit set is a conventional practice that is prohibited in organic agriculture
and the use of pollinating insects is insufficient for winter productions.
Landraces of zucchini squash derived from the Spanish COMAV germplasm bank, as well as a
number of hybrids from different seeds companies were evaluated in two variety trials that were
carried out under organic greenhouse conditions in the research centre of IFAPA-Almería for
Spring-Summer 2005, and in the greenhouse of an organic grower for Spring-Summer 2006.
Both essays were done in absence of pollinating insects, but following the recommendations
proposed by organic growers. In each trial, the field plan was a randomized complete block
design with three blocks, and 6-10 replicates per block, for each cultivar.
In addition to the general performance of a number of commercial varieties and landraces under
organic greenhouse conditions, it was evaluated the parthenocarpic potential of each material and
the quality of parthenocarpic fruits, including their postharvest storage potential. In the first trial,
the evaluation was carried out on a number of Spanish landraces. The most parthenocarpic
materials were then selected and compared with commercial hybrids in a second variety trial
grown in collaboration with an organic grower association in Almería. Longitudinal and
transversal fruit growth rates before and after flower anthesis allowed us to determine the level
of parthenocarpy in each variety. In most of the commercial varieties non-pollinated
parthenocarpic fruits reached a commercial size, although the quality of some of the fruits
diminished considerably. In many of the analysed landraces the fruits of non-pollinated flowers
aborted a few days after anthesis. Nevertheless some of the evaluated landraces showed a level
of parthenocarpy and fruit quality comparable to that of the commercial hybrids used as the
positive control. The most parthenocarpic landraces and hybrids under organic conditions, but
also those that developed fruit with superior quality and better postharvest conservation, are
being selected as the starting plant material for an organic breeding program in zucchini squash.
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