Abstract:
Pathogenic fungal infections on seeds can reduce seed germination and seedling growth,
resulting in heavy economic losses. The objective of this study was to determine the effect of soil
borne plant pathogenic fungus Rhizopus microsporus on seed germination and early seedling
growth of seven crop varieties, viz. brinjal (SM-164), capsicum (CA-8), cucumber (Kalpitiya
white), okra (Haritha), snake gourd (TA-2), spinach (Yoda) and tomato (Rajitha). The effect on
each crop species was observed by inoculating 2 mL of the R. microsporus fungal spore
suspension (105CFU/mL) into 100 surface-sterilized seeds (20 µL droplet on each seed) placed
on a sterilized clear plastic box (approximately 20×10×6 cm3) filled with 1.5 cm of autoclaved
silica sand. This setup was replicated four times per each species. The same volume of sterilized
distilled water was used as the control. The seeds were incubated in a plant growth chamber at
25 C and 12/12 hour light/dark cycles for 14 days. Time to reach 50% seed germination (G50),
final germination percentage after 14 days and shoot and root lengths of seedlings were
measured. Germination percentage data were statistically analyzed using Kruskal-Wallis test,
whereas G50, root and shoot length data were analyzed using two sample t-tests. The seed
germination percentages of capsicum and brinjal treated with the R. microsporus spore
inoculation were significantly reduced by 35% and 5%, respectively. The G50 was significantly
affected in tomato and okra (P<0.05). The most prominent effect of R. microsporus was evident
in shoot and root lengths of the study species. Rotting stems and roots with watery appearance
was common in seedlings of all crop species treated with the spore inoculum. The shoot lengths
of all the study species were significantly affected by 0.78-4.69 cm (P<0.05). The root length of
all species except in okra was affected by 0.50-4.29 cm (P<0.05). Thus, all the study species were
susceptible to R. microsporus at seed germination and early seedling establishment stages.
Therefore, R. microsporus infections can affect the survival and early seedling growth of the
tested crop species.
