Inheritance of resistance to damping-off (Rhizoctonia solani) in watermelon

Abstract

This study aimed to find sources of resistance to damping-off and to determine the inheritance of resistance in watermelon.Firstly, 72 watermelon accessions were inoculated with CMM 1053 isolate of Rhizoctonia solani. Only two accessions (BGH 29 and BGH 76) were considered moderately resistant to the disease. The inoculated plants without symptoms from accession BGH-29 identified as resistant were self-fertilized and the inbred line S 1 was used for the crosses. The reaction to R. solani after inoculation of the segregating populations of the cross and backcrosses between susceptible cultivar Crimson Sweet and the inbred line BGH-29 was evaluated. In other experiment eight S1 lines of watermelon were inoculated with six different isolates of R. solani and the reaction was evaluated by partial diallel analysis using the Griffing's method IV to obtain estimates of general resistance ability (GRA), general aggressiveness ability (GAA), and specific interaction ability (SIA). According to ratings of the susceptible and resistant parents, generations F 1 , F 2 , BC 1 (F 1 × P 1 ) and BC 2 (F 1 × P 2 ), resistance to damping-off was conferred by at least nine genes with additive effect and low heritability which indicates polygenic inheritance. The results of the diallel analysis corroborate with the analysis of segregating population, indicating inheritance of resistance was horizontal, since 46.1% of the total sum of squares of the variation observed in the crosses was due to GRA, while the SIA corresponded to only 20.39% of variation. This is the first report about inheritance of resistance to damping-off caused by R. solani in watermelon.

Identification of resistant cowpea genotypes and aggressiveness of Macrophomina phaseolina isolates by diallel analysis

“…The diallel methodology proposed by Melo and Santos (1999) was efficient in evaluating cowpea lines inoculated with isolates of the fungus M. phaseolina , as well as evaluating the aggressiveness of isolates of the pathogen. This methodology has already been used for studies in other pathosystems, proving to be efficient (Buiate et al., 2010; Cunha et al., 2022; Davide & De Souza, 2009; Paiva et al., 2018; Pereira et al., 2015; Silva et al., 2014; Valdo et al., 2016). Therefore, diallel analysis is another useful tool for breeders to select the most promising genotypes in addition to identifying the most aggressive isolates, thus being able to direct the actions of the breeding program.…”

“…This methodology was also used to study resistance in common bean genotypes inoculated with the fungus Pseudocercospora griseola (Pereira et al., 2015). In addition, the inheritance of resistance to damping‐off caused by Rizoctonia solani in watermelon was studied using segregating populations, as well diallel analysis using different genotypes and isolates, showing the complexity of the trait (Cunha et al., 2022). Thus, the aim of this study was to assess cowpea lines inoculated with different Macrophomina phaseolina isolates to determine the aggressiveness of the pathogen isolates and the predominant type of resistance in the host.…”

Evaluation of the Efficiency of some Biological Control Agents in Inducing Systemic Resistance of Potato Plants Against Black Scale Disease Caused by the fungus Rhizoctonia solani Kühn

“…Biological control has received great attention. by researchers according to its positive aspects in the environment compared to chemical pesticides used for the same purpose, The microorganisms present in the root zone are among the biological means that were used to combat plant pathogens by exploiting their activities against various pathogens by raising the efficiency of the plant to absorb nutrients [9]. As well as its role in stimulating the systemic resistance (ISR) of the plant, which leads to an increase in its resistance to many diseases [11].…”