**Session IV -- Physiology, Ecology and Production -- Poster IV-1**

Improving Productivity of Oats as a Priority Forage Species in Tunisia

M. Chakroun, M.B. Allagui, S. Ben Youssef S, I Hemmami, H. Sltani ans S.
Haffani

Institut National de la Recherche Agronomique de Tunisie (INRAT), Rue
Hedi Karray, 2049, Ariana, Tunisia. Email :
chakroun.mohamed@iresa.agrinet.tn

Abstract

Oats (*Avena* spp.) are the dominant fodder crops in Tunisia. They are
grown mainly for hay and silage. Crown rust (CR) caused by *Puccinia*
*coronata* f. sp. *Avenae*, is the major disease that affects oats. Its
severity varies with seasons and it often causes significant losses.
Therefore, in Tunisia, resistance to CR is an important selection
criterion to consider when improving oat productivity. Choosing a
variety is one of the most important decisions a farmer must make. Oat
growers in Tunisia often produce low yields when they grow varieties not
adapted to their region and conditions. The objectives of this study,
funded by the USDA-ARS, USA are: i) to develop superior varieties with
high forage yield potential and good level of tolerance to the
prevailing foliar diseases and ii) to contribute to the development of
improved management practices and technology transfer package for seed
multiplication and large-scale production of this species. Several
unrelated trials with different experimental protocols were carried out.

Evaluation of the prospected local oat genotypes showed that small
genetic variation has been found among the local oat material. Among
studied local genotypes, Bezina and Borj dhab presented high dry matter
yield and acceptable tolerance to CR. These genotypes may constitute the
base of crosses between *A. sativa* and *A.* *byzantina* to increase the
productivity of oats in favorable producing regions.

Over three hundred pure lines, from the Quaker International Oats
Nursery (QION), have been studied for agronomic, CR resistance and
adaptation. Promising genetic material with better forage and grain
yields and good tolerance to foliar diseases were selected from the
QION. A line originating from the 1996 QION is considered leaf rust
resistant and will be released as a new forage oat variety under the
name of "Ghzala". From each QION, the two best dry matter yielding
lines, which were considered to be moderately resistant to CR and had
very good seed production, are retained for final testing. New potential
lines (Q01-L25, Q01-L33, Q02-L29 and Q02-L35) will have at least two
more years of regional yield evaluation and data to support disease
resistance claims and yield stability. On another hand, a large number
of oat lines (QIONs) have been screened for CR resistance and, several
lines with high level of CR resistance have been identified.
Furthermore, two *Rhamnus* species (*R. lycioïdes* and *R. alatermus*)
were found in the prospected sites of northern Tunisia. Pycnia with
viable pycniospores and aecia with viable aeciospores have been found on
*R. lycioïdes*. However, no characteristic structures of CR have been
found on *R. alaternus*. Consequently, *R. lycioïdes*, a common and
endemic plant in northwest Tunisia, was considered as the new alternate
host of oat crown rust.

In a separate studies, the effect of eight seeding densities (from 100
to 450 seeds m^-2^ at an increment of 50 seeds m^-2^) on subsequent
forage and grain production of Meliane fodder oat cultivar was
investigated over two sites and two consecutive cropping seasons.
Results showed that grain yield, forage yield and plant height did not
significantly vary with seeding densities but depended significantly on
year and site by year interaction. Individual plant phytomass, stem
diameter and major grain yield components were significantly affected by
seeding density, and grain yield seemed to be compensated through
variation of grain yield components. Over all sites and years, Meliane
averaged 2234 and 14445 kg DM ha^-1^ as grain and forage yield,
respectively. From these trials, it was concluded that optimal seeding
density for oat seed production should not exceed 200 viable seeds per
m² for the new released cultivars of *Avena sativa* L.

**Key words:** *Oat, selection, variety, crown rust, seeding density,
seed production*