Investigation on Seed Borne Nature of Pepper mild mottle virus and Assessment of Yield Losses in Capsicum
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Date
2019-06-04
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CSKHPKV, Palampur
Abstract
Capsicum (Capsicum annuum L. var grossum Sendt), a member of family Solanaceae commonly known as bell pepper or sweet pepper, is highly popular and economic crop grown throughout India under both open and polyhouse conditions since the 15th century. The crop is being attacked by numbers of fungal, bacterial and viral pathogens. Among viral pathogens Pepper mild mottle virus (PMMoV), a member of family Virgaviridae and genus Tobamovirus is extremely destructive due to its highly contagious and seed borne nature. The present investigations on PMMoV were undertaken to study the transmission of PMMoV through seeds, detect PMMoV from seeds through ELISA and RT-PCR and assess yield losses in capsicum due to PMMoV. The typical virus symptoms produced on infected plants were upward cupping of the leaves, mild mosaic, reduction in leaf lamina, mild mottling on the newly emerging leaves and leaf deformation. The infected plants remained stunted and had less number of fruits which showed mottling, deformation, and reduction in their size as compared to healthy plants. DAS-ELISA and coat protein gene amplification confirmed the identity of the virus as PMMoV. For seed transmission study of PMMoV, Grow Out Test (GOT) and RT-PCR using coat protein gene-specific primers were performed in three capsicum cultivars viz., Capsicum annuum (California Wonder), Capsicum annuum (Yolo Wonder) and Capsicum annuum (Doux des Landes) under greenhouse conditions. Seed transmission was highest in cultivar California Wonder (63.04 %) followed by Yolo Wonder (33.80 %) and Doux des Landes (33.30 %) on the basis of visual symptom observation in Grow Out Test, however, indexing of randomly selected symptomatic plants from Grow Out Test through DAS-ELISA and RT-PCR confirmed the seed transmission behavior of the three test varieties, though the percentage transmission was lower than the GOT. The RT-PCR based assay of seed transmission showed 60.32, 36.94 and 33.13 percent transmission of the PMMoV in cv. California Wonder, Yolo Wonder, and Doux des Landes, respectively. This suggests that RT-PCR and DAS-ELISA as more reliable techniques over GOT. 20 mg (~3-4 seeds) and ~8-10 mg (1 seed) infected seeds of cv. California Wonder is sufficient to detect PMMoV by DAS-ELISA and RT-PCR assay, respectively. The DAS ELISA values and band intensity in RT-PCR suggested uneven distribution and concentration of the virus in a given sample. The yield loss assessment in capsicum hybrid Indra under polyhouse and greenhouse conditions revealed a significant reduction in fresh fruit yield and market quality trait. The yield attributing factors affected by virus infection included average plant height, average leaf size, number of leaves per plant and number of branches per plant, number of marketable fruits, average fruit weight, PMMoV infection at early growth stages causes severe infection and pronounced yield losses than later stages infection. However, seed-borne infection of PMMoV causes even higher yield losses than artificially inoculated plants.
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