PNL Volume 16 1984

RESEARCH REPORTS

COMPETITIVE EFFECTS AMONG ISOGENIC LINES OF PEAS

Leone, A.

Centro di Studio per il Miglioramento

Genetico degli Ortaggi

Consiglio Nazionale delle Richerche

Portici, Italy

In order to study the effect of single genes or of the interaction

of few genes on the competitive ability, eight isogenic lines of peas,

provided by G. A. Marx, were utilized. They were a complete set of all

combinations of the three genes, af (afila), st (reduced stipules) and

tl (acacia), affecting the foliage morphology.

In 1980 a seed mixture of an equal number of seed from each

genotype was sown at two different planting densities (100 plants/m² and

25 plants/m² ); in the two following years a sample of the bulk harvested

seed was sown. Data concerning 1981, 1982, and 1983 are reported here.

The proportion of both the conventional (+++) and the "acacia"

(+ + tl) types increased each year, reaching about 60% in the last year,

whereas the other six genotypes contributed very little to the total

yield of the mixtures (Fig. 1). The conventional and acacia plants had

the highest seed yield per plant (Table 1) and consequently they were

the majority of the plants in the mixture, as shown by Glover (1). In

1982 the eight lines were also grown in pure stand and the conventional

and the acacia types showed the highest yield per plot (2); a positive

relationship between agronomic value and competitive ability is sug-

gested, as found by other authors in different species.

The eight genotypes were gathered on the basis of the presence or

absence of one, two, or three genes, in order to study their effects on

competitive ability.

The af genotypes and the st genotypes showed lower productivity

than their corresponding dominant genotypes. In contrast, the acacia

types had the same productivity as their corresponding dominant

genotypes (Fig. 2). Therefore, the alleles af and st disappeared

quickly in the mixture in comparison with their corresponding dominant

alleles, whereas the tl allele was in equilibrium with its dominant

allele (Fig. 3). This behavior presumably is related to the increased

foliage area of the acacia types.

This experiment is being continued; in 1981, 1982 and 1983 three

new similar experiments were begun.

1. Glover, T. J. 1980. PNL 12:12-14.

1. Gritton, E. T. 1972. PNL 4:11-12.

Contribution No. 5 from Centrol di Studio per il Miglioramento

Genetico degli Ortaggi, CNR - Portici (Napoli).



	36 PNL Volume 16 1984	RESEARCH REPORTS





	Fig. 1. Contribution of each genotype to the total seed yield of the mixture at two planting densities.