DETERMINATION OF HETEROSIS, GENE ACTION AND THE NATURE OF RESISTANCE TO FUSARIUM WILT DISEASE (FUSARIUM OXYSPORUM F.SP CAPSICI ) IN SWEET PEPPER HYBRIDS

Abstract

Four parental genotypes from a Center of Germplasm Netherland (CGN) i.e. 1 (PI 23235), 2 (PI 17171), 3 (PI 23096) and 4 (PI 17150) and their six F1 hybrids in a diallel cross system without reciprocals were used to estimate combining ability (general and specific) and heterosis percentage relative to both mid and better parents and potence ratios for some characters in pepper (Capsicum annuum L.).The experiment was conducted at Kaha Research Farm, Kaliobia Governorate under unheated plastic house during two successive seasons 2015-2016.Survey was conducted at Kaliobia Governorate during 2015 and 2016 and the pathological studies were carried out at the Plant Pathology Research Institute, Agricultural Research center, Giza Governorate. The studies showed that Fusarium oxysporum f.sp capsici (isolate 3) was the highest in frequency and the level of pathogenicity . The susceptibility of 10 genotypes to Fusarium oxysporum f.sp. capsici (isolate 3) indicated that two F1 crosses 2 × 4 and 3 × 4 were resistant to Fusarium oxysporum f.sp. capsici (isolate 3). The correlation analysis revealed that the disease severity on roots was significantly correlated with four traits; weight/plant (kg), number of fruits /plant, number of days to 50% flower anthesis and fruit length (cm). In contrast, vascular discoloration was significantly correlated with three traits; weight/plant (kg), number of fruits /plant, and fruit length (cm). The 10 genotypes (4 parents and 6 hybrids) were evaluated for yield ;yield components and fusarium wilt resistance to determine the combining ability and heterosis effects.The obtained results reflected that the mean squares for both general combining ability (GCA) and specific combining ability (SCA) were significant for all studied traits except SCA in fruit shape index and fruit flesh thickness, suggesting the presence of both additive and non-additive gene effects in the inheritance of the various studied characters. Estimates of SCA effects showed that the F1 crosses 2 × 4 and 2 × 3 reflect the highest value in most studied traits; i.e. total yield as weight and number, fruit length and low disease severity of roots and shoots. Hybrid vigour was documented for total yield, as well as, most fruit characters and disease severity. In some crosses, high rate of parent heterosis and potence ratio values were attained for these traits supporting the over dominance hypothesis.