INHERITANCE OF RESISTANCE TO ASCOCHYTA PISI RACE "C" IN PEAS

6 PNL Volume 16 1984

RESEARCH REPORTS

Csizmadia, L. Research Station of Vegetable Crops Research Institute

Ujmajor, Hungary

Ascochyta pisi, a component of the Ascochyta disease complex,

frequently causes severe seedling losses in Hungary. To determine the

races present in Hungary, several isolates were obtained from diseased

plants collected in five different locations throughout the country.

To test for resistance to A. pisi, seeds were germinated for 3 days

at 10C and inoculated by dipping in a spore suspension containing

4-5 x 10⁶ conidia per ml. Ten inoculated seeds were planted in a

15 cm pot filled with moist sand; then 20 ml of the inoculum were

sprayed on the surface of the sand. The pots were kept at 17°C with

16 hr diurnal illumination in a growth room. Disease ratings were made

ten days after inoculation and were based on the size and type of stem

lesions as follows:

1 - no stem reaction

2 - small (<1 mm) lesions only

3 - lesions 2-3 mm in length, no pycnidia

4 - deep necrotic lesions with pycnidia

5 - seedlings killed

Plants with ratings higher than 2 were considered susceptible.

Race identification was performed according to the methods of

Hubbeling (2). From Table 1, we can conclude that only race "C" was

present at the five locations.

Previous reports vary with respect to the proposed inheritance of

resistance of peas to A. pisi: two dominant genes (2); three dominant

genes (5); duplicate dominant genes (3); single gene with incomplete

dominance (1); single or 2-3 recessive genes (4).

Of nearly 200 varieties tested for resistance in the present study,

'Regis', 'Eldo', 'Rovar', and 'Venlona II' proved to be resistant.

Three susceptible varieties were crossed with Regis or Rovar and the F2

and BC generations were tested. In these crosses resistance to ract

"C" seems to be controlled by a single dominant gene (Table 2).

1. Cousin, R. 1974. Le pois. INRA, Versailles

2. Hubbeling, N. 1972. Proc. Eucarpia Conf. Peas 161-164.

3. Lyall, L. H. and V. R. Vallen. 1958. Canad. J. Plant Sci.

38:215-218.

4. Matthews, P. and P. Dow. 1972. 63rd Ann. Rep. John Innes Inst.

36-39.

5. Wark, D. C. 1950. Austr. J. Agric. Res. 1:382-390.