National Academy of Agricultural Sciences (NAAS)
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PRINT ISSN : 2319-7692
Online ISSN : 2319-7706 Issues : 12 per year Publisher : Excellent Publishers Email : editorijcmas@gmail.com / submit@ijcmas.com Editor-in-chief: Dr.M.Prakash Index Copernicus ICV 2018: 95.39 NAAS RATING 2020: 5.38 |
Sigatoka leaf spot disease of banana is spreading at a faster rate causing a serious threat to banana cultivation in Kerala, the southern most state of Indian peninsula which enjoys a humid tropical climate. A survey was conducted under different agro-climatic zones prevailing in the state to study and document the symptomatology and etiology of the pathogen inciting Sigatoka leaf spot disease of banana occurring in the state of Kerala. The disease was noticed in most of the commercially grown varieties of banana viz., Nendran (AAB), Grandnaine (AAA), Njalipoovan (AB) and Robusta (AAA) throughout the year, but become more severe with the onset of rains. The symptoms initially appeared as small light green to yellow dashes on the lower surface of the leaf which was visible only when the leaves was held against sunlight. This later changed into faint brown visible streaks. During the next stage, these streaks turned rusty brown on the adaxial surface of the leaves, which then developed into oval or elliptical brown spots with greyish centre surrounded by definite dark brown border with black pin head like fruiting bodies embedded in it. Upon heavy infection, the spots coalesced leading to complete necrosis of the leaves thereby destroying the functional green tissues of the leaves. This resulted in drastic reduction in the photosynthetic area causing an impact in yield reduction. The disease also resulted in premature ripening of the fruits affecting the fruit quality. The microscopic observations of these necrotic lesions revealed the presence of flask shaped telomorphic fruiting bodies called perithecia bearing asci and ascospores. The presence of the pathogen wasfurther confirmed by amplification of the ITS- rDNA region of the fungus using ITS 1 and ITS 4 primers which yielded amplicons of size ranging from 540- 580 bp. The amplicons were further sequenced and blasted in NCBI which showed 97 - 100% sequence homology to Mycosphaerella emusae. Hence, the pathogen inciting Sigatoka leaf spot diseases on banana in Kerala was identified and confirmed as Mycosphaerella emusae.
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