Evaluating landrace oats (Avena sp.) collected in Tunisia for crown rust resistance under natural infection

Crown rust caused by Puccinia coronata Cda. f. sp. avenae Eriks., is a major fungal disease of cultivated oats (Avena sativa L.) in Tunisia. Six landrace oats (MtK2, JT(5), BJ(35), GT(1), ZN(3) and JT(0)) locally collected and previously screened for their relative oat crown rust resistance were used in this experiment. These accessions were evaluated during a two cropping season in field plots under heavy natural oat crown rust infection. Assessment criteria to crown rust reactions were AUDPC, latent period, uredinia size and number of uredinia per cm(2) of infected leaf area. Principal components analysis showed that the variables were grouped in two components. These two principal components explained 83.56% of the total variance. The projection of the point-cloud representing the populations on the plan formed by the principal components 'Fact 1' (63.83%), in abscissa, and 'Fact 2' (19.73%) in ordinate, permitted to distribute the accessions in several groups. Three landrace oats (MtK2, JT(5), and JT(0)) showed the lowest value of all the components used. These landrace oats might be good sources of effective and durable resistance to crown rust.