Fusarium solani (Teleomorph: Haematonectriahaematococca) is a widely distributed fungal plant pathogen that infects many different genera of plants 12. In nature, Fusarium solani exist as different strains that exhibit variation in their morphological and cultural characters, pathogenicity and virulence. Due to F. solanidistribution across the environments is varied, it is essential to know which isolate is most virulent within a given species. F. solani is pathogenic to at least 111 plant species spanning 87 genera 3. Recently El Haddadi Errifi et al. reported that Fusarium solani had significantly affected preemergence, post emergence mortality rate and growth parameters in Tetraclinis articulate 4. Present investigation was under taken to study the variability in growth requirement and morphological characters of F. Solani.

F. solani and R. solani are the most important saprophytic pathogens, which develop in both cultured and non-cultured soils, causing the symptoms of damping off and root rot diseases to wide range of vegetable and crop plants including tomato 5. It causes wilt and rot diseases on a wide variety of crops including Cucurbita spp.,Pisum sativum and Phaseolus vulgaris 678. Environmental factors such as temperature, and pH have a large influence on fungal growth 9. Study of effect of hydrogen ion concentration on phytopathogen is important to understand their metabolism and probable correlation with soil pH. If the soil pH is favourable for the growth of phytopathogen, the severity of disease can be high. Similarly variation in carbon and nitrogen sources provided may also influence the growth of fungal phytopathogen. Despite the immense agronomic importance of this fungus, change in pH and the pattern of utilization of the substrate have not been worked upon. In present study, we analysed effect of different pH, carbon and nitrogen substrates in PDA and CDA medium on the growth of F.solani NVS671.

Fusarium solani NVS671 was identified as a pathogen causing stem rot in sugarcane. In our previous study we have reported that F.solani NVS671 is a new pathogen found to causing stem rot in sugarcane 10. Seven-day-old active culture of F.solani NVS671was used for this study.

A total of seven different pH values were evaluated for studying the growth of Fusarium solaniNVS671. Mycelia can grow only within a definite pH range and metabolism is often affected by pH 11. Under acidic condition F. solani growth was very slow and could reach up to 5 cm after 7 days of incubation. It is observed that the optimum pH for the growth of F. solani was 7 to 8 (Figure 1). Further increase in pH had shown reduced growth of phytopathogen. Our data are in accordance with Arunakumara et al., (2017) who reported significant differences in the growth of Fusarium solani at different pH levels 12. Khan et al., (2011) reported that maximum growth of Fusarium oxysporumf. sp. ciceri mycelial mat was observed at pH 7.0 13.

It is well known that supplementation of different nitrogen sources in media affect the micro-organism growth. In present study, ten different nitrogenous sources were tested on CDA medium to know their effect on the mycelial growth rate and characteristics of the fungus. All the nitrogen sources had support good mycelial growth at 1.5gm/L concentration except Ammonium Metavanadate and cobalt nitrate. By measuring the radial mycelial growth on CDA, ammonium chloride (7.96±0.11 cm) was found to be most efficient for growth promotion followed by ammonium nitrate (7.7±0.1 cm) and ammonium sulphate (7.3±0.1 cm). Table 1. There was no significant difference among potassium nitrate sodium nitrate and calcium nitrate in efficiency to promote the mycelial growth. Although there was good mycelial growth on ammonium and nitrate, their ability to use different forms of nitrogen are varies. Kamble (2011) reported the best nitrogen source for the growth of Fusarium solani causing rhizome rot of Ginger was Calcium nitrate 14. Ammonium Metavanadate was less efficient as compare to other nitrogen sources and there was negligible growth on CDA media supplemented with it. There was no growth on cobalt nitrate, which indicates that fungus could not able to utilize it. It is possible that cobalt might have toxic effect on F. Solani.

Carbon is one of the most important nutrients required by living organisms for its growth. In present study, total nine different carbon sources were tested on CDA medium to observe their effect on the mycelial growth rate and characteristics of the fungus. All the nine kinds of carbon sources tested were found suitable for fungus growth. The efficiency of individual carbon sources could be divided into three categories. The first category which recorded to promote best radial mycelial growth included was starch (7.96±0.05 cm) and sucrose (7.93±0.05 cm). The capability of the fungus to utilized sucrose and starch was due to the possession of relevant enzymes to hydrolyze them into their component sugars 15. The second category included maltose lactose dextrose and mannitol which showed to efficiently supported growth between 6.9 cm and 7.7 cm on the 7^th day. Cellulose was in the third category which was the least satisfactory. The growth of the pathogen in different carbon sources exhibited significant differences among the treatments. Several researchers reported Dextrose as best carbon source for growth of F. oxysporum1617. (Table 2)

This study is essential to recognize the physiology and metabolite preference of Fusarium solani. Capabilities of using different N and C sources and ability to grow at different pH levels may allow species to adapt to specific soil conditions. Future research should be directed toward the study of the enzymatic activity of Fusarium solani. In this way, it will be possible to obtain a more complete picture of the characteristics of Fusarium solani.