A biotic interaction between fungi from soil within and outside the rhizosphere of potato and fungi responsible for black scurf – Rhizoctonia solani Kühn and silver scurf – Helminthosporium solani (Dur., Mont.). It was found that fungi population connected with crop environment under investigation promoted the growth of Rhizoctonia solani, thus indicating no resistance of this environment to this pathogen. These fungi, however, inhibited the growth of Helminthosporium solani.
The investigation was conducted in 2004 and 2005 to test 28 sesame genotypes for resistance and susceptablity to Rhizoctonia solani under artificial infection conditions at the Plant Breeding Experimental Farm of the Faculty of Agriculture, Suez Canal University, Ismailia, Egypt. All screened sesame genotypes showed varied significant degrees of infestation with the root rot pathogen. It is worth to mention that some of sesame genotypes kept their resistance characterestic classes as moderately resistant (MR) or resistant (R) during the two successive seasons. Such genotypes might be useful for breeding programs due to stability of their resistant character as well as their seed yield. Phenotypic coefficients of variation (P.C.V.) and genotypic coefficients of variation (G.C.V.) were of high value regarding resistance characters during both seasons and comparable to seed yield character. The heritability estimates indicate that selection is a suitable way for picking up sesame genotypes that have high chance for resistance character to root rot disease (R. solani) with high seed yield potential. The genetic advance and heritability estimates in all cases supported the selection of some sesame genotypes to be used in next breeding programs for root rot resistance, they also showed a high seed yield potential.
Serious losses caused by root rot of sugar beet were observed in Poland in 2001 and 2002. The disease occurred in most of regions of sugar beet cropping from June to the end of growing season. Very high losses of yield were observed on many fields especially on cultivar Lolita in 2001. The aim of this work was to detect the casual agent of root rot (2001) and to compare susceptibility of sugar beet cultivars to this disease (2002–2003). The laboratory tests (2001) showed that most of destroyed roots were infected by Aphanomyces cochlioides Drechsler. This species is very well known as a pathogen of sugar beet seedling damping-off in Poland. The fungus Rhizoctonia solani Kühn was found only in 12% of rotten roots collected in south-eastern part of Poland. In field trails the highest number of infected roots and the highest infection inde xwere found for cultivar Arthur (2002–2003). That cultivar was significantly more susceptible to root rot than the rest of tested cultivars.
Essential oils from four plants , i.e. geranium, rosa, lemon and mint were tested for their activity in vitro and in vivo against Rhizoctonia solani and Fusarium oxysporum f. sp. phaseoli, the cause of root rot and wilt of beans. In vitro, they were found to have an inhibitory effect against the mycelial growth of R. solani and F. oxysporum f. sp. phaseoli. Complete inhibition in fungal growth was observed at a concentration of 4% of each essential oil and Topsin M at 400 ppm as well. In greenhouse the four essential oils were tested as seed coating and/or foliar spray. Results of seed coating at a concentration of 1% clearly demonstrate a good protection of emerged bean seeds against invasion of R. solani and F. oxysporum f. sp. phaseoli compared with the fungicide treatment. A similar trend was observed in a lower extent when the essential oils were applied as bean seeds coating followed by seedlings foliar spray under field conditions. Obvious yield increase as bean green pods, in all treatments, was significantly higher than in the control.