Abstract:
Rice (On'-fl sativa L.) is the staple diet amongst almost all ethnic groups in Sri Lanka. The use
of endophytic microorganisms inhabiting the rice plant is a promising strategy for improving paddy
yields. However, little is known about the diversity and the evolutionary relationships among the
species of endophytic fungal assemblages associated with different rice varieties in Sri Lanka.
Therefore, this study was aimed at the assessment of colonization, diversity, identification, and the
phylogenetic relationships of endophytic fungi present in newly improved rice varieties At 362. Bg
352, Bw 367, and a traditional variety, Suwandel. Healthy plant samples of each rice variety were
collected during the two main rice-growing seasons, Maha and Yala (2019), from Anuradhapura,
Kurunegala, Gampaha, and Kalutara districts in Sri Lanka. Endophytic fungi were isolated from the
leaves, stems, and roots of each rice variety using previously developed protocols. All strains were
categorized into thirty-nine (39) morphological groups based on colony characteristics and micromorphological features. The Internal Transcribed Spacer (ITS) region of a representative strain of
each morphological group was amplified and sequenced. They were identified by phylogenetic
analysis based on sequences of ex-types. Thirty-one (31) isolates identified to species level belonged
to twenty-two (22) genera within nine (9) orders. Apart from that, four (04) and three (03) isolates
were identified up to generic and order levels respectively. One isolate was identified up to the family
level. Out of the fungal species, seventeen (17) were novel records for Sri Lanka. Evaluation of the
colonization percentages of endophytic fungal assemblages showed that the variety Suwandel
collected from Kurunegala during the Maha and Yala seasons respectively had the highest
colonization rate (52% and 35%). The study also showed that Aspergillus tereus, Curvularia lunata,
Dendryphiella sp.. Fusarium falciforme, Microdochium fisheri, and Penicillium oxalicum were the
most dominant species in all rice varieties. Endophytic fungal diversity evaluated by Shannon’s and
Simpsons diversity indices showed the highest species diversity in variety Bg 352 collected from
Kalutara district during the Yala season.
