Effect of endophytic fungi on plant growth and blast disease incidence of two traditional rice varieties

Abstract

Traditional rice varieties, although low producers of yield, are more amenable to organic farming practices that cause less damage to the environment and human health. Improved growth and reduced disease incidence would produce higher yields, and endophytic fungi have proven to be effective in achieving these ends in wheat. With this in view, endophytic fungal assemblages of two traditional rice varieties of Sri Lanka i.e. Suwandel and Kaluheenati were evaluated for their effect on the growth and disease incidence of rice plants, because the endophytic mycoflora of these two traditional rice varieties and their effects have not been studied before. The most common and the highest occurring endophytes of both rice varieties i.e. Absidia and Cylindrocladium were tested to determine their effect on rice plant growth and the results showed that the plants inoculated with both fungal isolates showed significant increases (p ≤ 0.05) in plant height, fresh weight and dry weight. Twenty two endophytic fungal isolates common to both rice varieties were screened using dual culture assay for their ability to control the mycelial growth of Magnaporthe grisea, the causative agent of rice blast disease. All tested endophytes controlled pathogen growth by coiling the hyphae around the pathogen and forming clamps and loops. However, Absidia and Acremonium showed the highest growth inhibition of the pathogen (100 %) and showed an abundance of the above inhibitory structures. The effect of crude culture filtrates of thirteen endophytic fungi tested using the diffusion plate method indicated antagonistic activity against the rice pathogen. In planta tests were carried out to assess the effect of three endophytic fungi i.e. Acremonium, Absidia and Penicillium on infection by M. grisea. Disease symptoms were observed only on the leaves of the rice plants grown from Penicillium inoculated seedlings and on plants used as controls sprayed with a 1×10 7 spores/mL suspension of the pathogen. Pre-inoculation with Acremonium and Absidia were effective in preventing infection by the blast fungus. No disease symptoms were observed in plants pre-inoculated with endophytes and in plants used as controls sprayed with a 1×10 5 spores/mL suspension of the pathogen. Twenty one endophytic fungi common to both rice varieties were assessed by the culture plate method in this study.

An inoculum of endophytic fungi for improved growth of a traditional ricevariety in Sri Lanka

“…(Atugala & Deshappriya 2015, Ponnawila & Deshappriya 2014. Therefore, the present study was carried out to test whether fungal endophytes of the Sri Lankan traditional rice variety Kuruluthuda would show a similar capacity for growth and yield enhancement of rice plants under green house and field conditions.…”

“…Most fungal genera isolated from Sri Lankan traditional rice varieties Suwandel and Kaluheenati belonged to the class ascomycetes and they have been identified as being members of commonly observed genera of soil fungi, e.g. Fusarium, Penicillium, Rhizopus, Rhizoctonia, Absidia, Aspergillus and Paecilomyces (Atugala & Deshappriya 2015). In a comparison of endophytic assemblages between traditional and newly improved rice varieties in Sri Lanka, higher fungal colonization and species richness have been shownby the traditional rice varieties Suwandel and Herath Banda compared to the newly improved variety Bg 352.…”

“…A suitable surface sterilization regime is essential to eliminate epiphytic microbes present on the plant surface whilst maintaining the viability of the endophytes. Therefore, the most effective surface sterilizing regimes developed in a previous study (Atugala & Deshappriya 2015) were used for the effective surface sterilization of the plant parts used for isolations. Once surface sterilized,the plant parts were plated on MEA medium supplemented with tetracycline (50 mg/L) as soil and endophytic fungi are reported to grow more effectively on MEA resultingin a higher fungal yield and species richness (Bills & Polishook 1993).…”

“…Each plant part was cleaned separately by rinsing under running tap water for 10-15min and the cleaned plant parts were surface sterilized using the sterilization protocols reported previously (Atugala & Deshappriya 2015).…”

“…Fungal endophytes also have been detected in cultivated rice and they have shown to possess antagonistic or plant growth stimulating properties (Yuan et al 2009, Naik et al 2009). Previous studies in Sri Lanka have shown that some endophytes present in the traditional rice varieties Suwandel, Kaluheenati and Herath Banda have the ability to increase the growth of plants significantly (Atugala & Deshappriya 2015, Ponnawila & Deshappriya 2014. However, the endophytic fungal assemblage of the rice variety Kuruluthuda and their effect on plant growth and yield has not been reported in Sri Lankapreviously.…”