Genetic nature and heritability of Orobanche crenata resistance in faba bean, Vicia faba L.

The present study aimed to understand the genetic nature and heritability of orobanche crenata resistance in faba bean, using a diallel analysis of F 1 generation. Five genotypes were used; Misr 1, x- 1714, x-1722 (tolerant), Nubaria 1 and Giza 40 (susceptible). Seed yield and its attributes (days to 90% maturity, plant height (cm.), no. of branches/plant, no. of pods/plant, no. of seeds/plant, seed yield/plant (g) and 100-seed weight (g) were recorded under both free and infested field. The orobanche resistance related criteria (Date of Orobanche emergence, no. of Orobanche spikes/ m. and Orobanche dry weight (g/m. ) were recorded under infested field. The results indicated that additive effect is very important for genetic control of 90% maturity, while dominance effect plays an important role in genetic control of 100-seed weight under infested condition. Both additive and dominance effects play an important role in the genetic control of three Orobanche criteria, which related to Orobanche resistance. Mean degree of dominance (H1/D). /2 indicated the presence of over dotninance for no. of pods/plant, 100-seed weight(g) and Orobanche dry weight (g/m. )under infested field. Regarding, no. of Orobanche spikes/ m. possessed complete dominance. While, other characters had partial dominance under both free and infested conditions. Unequal frequencies of positive and negative genes were found among parents under study as well as unequal distribution occurred between dominant and recessive genes with more dominant than recessive genes in the parents for three Orobanche related resistant criteria and plant height (cm.) under infested condition. The direction of dominance was towards of late of maturity, increasing no. of branches/plant and no. of seeds/plant under free field while, under infested field the direction of dominance was towards of long of plant height (cm) and increasing 100-seed weight (g). Important and remarkable findings were noticed whereas , three Orobanche related resistance criteria possessed a positive correlation coefficient (r), the direction of dominance towards low values of three criteria were dominant over high values. Therefore, the Orobanche resistant gene was dominant over susceptible recessive genes.High heritability estimates in the borad-sense (h. bS) were recorded for all the studied characters. High heritability estimates in narrow-sense were obtained for almost criteria except 100- seed weight and Orobanche dry weight, under infested field. The F1 graphic analysis confirmed the above results on the mean degree of dominance. In addition, additive gene effects play an important role in the genetic control of 90% maturity under free condition. Misr I variety possessed most resistance genes for Orobanche. The correlation coefficient confirmed the highly negative correlation between seed yield and its attributes i,e date of Orobanche emergence and no. of Orobanche spikes/m.