Proceedings of the XLV Italian Society of Agricultural Genetics - SIGA Annual Congress

Salsomaggiore Terme, Italy - 26/29 September, 2001

ISBN 88-900622-1-5

Poster Abstract

CHARACTERISATION OF A NEW DWARF MUTANT IN SUNFLOWER (HELIANTHUS ANUUS L.) DEFICIENT IN GIBBERELLIC ACID METABOLISM

CECCONI F.*, GAETANI M.**, LENZI C.**

* Università di Pisa, Dipartimento di Biologia delle Piante Agrarie sez. Genetica.Via Matteotti 1/b, 56124 Pisa

Fax +39-050-576750

fcecconi@agr.unipi.it

** Università di Pisa, Dipartimento di Agronomia e Gestione dell’Agroecosistema, Via S. Michele degli Scalzi 2, 56124 Pisa

Fax +39-050-540633

Sunflower, mutant, dwarf, gibberellic acid

In Sunflower the recovery of spontaneous variants is not a rare event. In our breeding work practically every year we find some strange plants that in some cases result to be real genetic mutants. In the nursery we had in 1999 there was an F3 progeny coming from a cross between two restorer lines that segregates for dwarf plants with any internode elongation. For a better control we sowed again the same F3 in pots in the green house, the result was that among the 200 plants it was possible to recover 10 plants with this type of dwarfism. Unfortunately the dwarf plants didn’t produce any seed, but it was possible to recover again the mutation in some progenies of the normal plants self-pollinated by paper bags. In this case the segregation ratio was 3:1 (0,1>p<0,5) indicating that the mutation is recessive and controlled by a single gene that we named dw1.

Considering the different segregation rate between the original F3 (20:1) ant the etherozigous F4 plants (3:1), we suppose the chimaeric nature of the F2 plant from which the mutation originated, data fits for a mutated sector of ¼ of the capitulum surface.

The principal morphological characteristics of dw1 mutant are:

- Absence of internode elongation resulting in a final height between 10 and 30 cm (normal height 120-150)

- Crenate leaves with a deep green colour.

- Abortive ovary development

- Low percentage of viable pollen that remains in the flower tube for the absence of anther elongation.

Periodic treatment with gibberellic acid (GA3) was effective to revert to the wild type phenotype.

The best result was achieved spraying the leaves with a 10 ppm solution of GA3 every week.

Internode elongation was directly related to the GA3 concentration.

The GA3 treatment permits a normal expansion of the leaf lamina that reverts from the deep green to the light green colour.

The duration of GA3 effects was lost after about 7 days permitting to have on the same plant the alternation of normal and mutated characteristics.