The inhibitory effect of major seed-borne fungus,
Alternaria sesami was observed on seed germination, seedling length and seedling vigour index of sesame seed samples collected from different locations (Table 1).
Germination (%)
Significant variation in germination was observed between the inoculated and uninoculated sesame seed samples collected from different areas of Andhra Pradesh and Telangana (Table 1). The uninoculated seed samples exhibited 92.00% to 98.25% germination, while the inoculated seed samples showed germination ranging from 49.06% to 83.38% irrespective of locations and sources. The germination was inhibited by
Alternaria sesami in all the seed samples.
Maximum reduction (49.68%) in germination of inoculated seed over uninoculated sample was observed in the farmers’ saved seed sample no. 14 followed by farmers’ sample no. 15 (47.12%) of YLM-17, whereas the least reduction (15.13%) was observed in foundation seed sample of YLM-66 collected from ARS, Yellamanchili (Fig 1). Sesame seed samples collected from different locations showed that maximum per cent reduction in germination of inoculated seed over uninoculated seed was observed with samples collected from farmers’ of Darsi and Maruturu mandals of Prakasam district with the range of 30.31% to 49.68% followed by seed samples from RARS, Lam, Guntur (15.90% to 23.81%). The samples collected from ARS, Yellamanchili showed the least per cent reduction of germination ranging from 15.13% to 21.40%, while samples from RARS, Jagitial recorded 17.51% to 21.53% reduction in germination.
Seedling Length (cm)
Seedling length was found to vary significantly between the inoculated and uninoculated sesame seed samples collected from different locations of Andhra Pradesh and Telangana (Table 1). The seedling length varied from 9.12 cm to 14.96 cm in uninoculated and 5.30 cm to 11.70 cm in inoculated seed samples across different locations and sources of sample collection.
The seedling length decreased after artificial inoculation in all the seed samples. Among the 28 samples, maximum reduction in seedling length (46.14%) was observed in the farmers’ sample no. 14 of YLM-17, whereas the least reduction (12.77%) was observed in foundation seed sample of Swetha (sample no. 27) collected from RARS, Jagitial (Fig 1). maximum per cent reduction was observed with samples collected from farmers’ of Darsi and Maruturu mandals of Prakasam district with a range of 21.77% to 46.14% followed by seed samples from RARS, Lam, Guntur (18.31% to 29.59%). The samples collected from RARS, Jagitial and ARS, Yellamanchili exhibited reduction in seedling length to the tune of 12.77% to 19.75%.
Seedling Vigour Index
Inoculated and uninoculated sesame seed samples collected from different areas of Andhra Pradesh and Telangana showed significant variation in seedling vigour index. The range of seedling vigour index of uninoculated and inoculated seed samples of sesame was 839 to 1456 and 323 to 964, respectively (Table 1).
Reduction in seedling vigour index, after inoculation with
Alternaria sesami, was observed in all the seed samples of sesame. Maximum reduction in seedling vigour index of inoculated sample over uninoculated sample (72.87%) was observed in the farmers’ sample no. 14 followed by farmers’ sample no. 15 (68.42%) of YLM-17, whereas the least reduction (28.28%) was observed in foundation seed sample of Swetha (sample no. 27) collected from RARS, Jagitial (Fig 1). In sesame seed samples, maximum per cent reduction was observed with samples collected from farmers’ of Darsi and Maruturu mandals of Prakasam district with the range of 45.57% to 72.87% followed by seed samples from RARS, Lam, Guntur (31.30% to 46.33%). The samples collected from RARS, Jagitial showed the least per cent reduction of seedling vigour index ranging from 28.28% to 35.83%, while samples from ARS, Yellamanchili recorded 29.38% to 38.41% reduction in seedling vigour index of uninoculated sample over inoculated sample.
Decreased germination, seedling length and seedling vigour index were observed in seed samples of Prakasam district with an increased total number of fungal colonies. Sesame seed samples with the highest fungal flora also recorded less germination, seedling length and seedling vigour. The reduction in germination may be due to the usage of energy rich compounds by these fungi that are otherwise required for proper germination
(Irshad et al., 2017). This effect may be due to seed-borne fungi like
Alternaria, which is known to produce some toxins that are detrimental to seed germination
(Ramegowda and Naik, 2008).
Alternaria species produce non-host specific toxins [e.g., tenuazonic acid (TeA), alternariol (AOH), alternariol monomethyl ether (AME), brefeldin A, tentoxin and zinniol]
(Saha et al., 2012) as well as host-specific toxins
(Thomma, 2003) which contaminate the seed.
Rao and Vijayalakshmi (2000) reported tenuazonic acid (TA) toxin production by
Alternaria sesami in sesame resulting in reduced germination and seedling vigour.
Similar variation in reduction of germination (%), seedling length (cm) and seedling vigour index of uninoculated seed over inoculated seed was earlier reported by
Bavaji et al., (2000); Naik et al., (2017) and
Nayyar et al., (2017) in sesame.
Ahammed et al., (2006) in soybean,
Anand et al., (2008) in groundnut,
Kumar (2010) in finger millet,
Bhajbhuje (2015) in wheat and
Chaudhari et al., (2017) in redgram reported that seed borne fungi reduced the germination, seedling vigour and other seed quality parameters.
Hence, from the results it is concluded that seed borne fungus,
Alternaria sesami inhibits the seed germination, seedling length and vigour of sesame seedlings to a great extent. Hence, farmers’ are advised to take preventive measures including selection of sesame seed from healthy fields followed by treating the seeds with recommended fungicides to achieve good germination, initial vigour and optimum plant population in the field for realizing higher yields.