Irfan khan

Allium sativum L. (garlic) and A. cepa L.(onion) are important Allium species cultivated in Indian Punjab. Onion is planted both in kharif and rabi seasons by bulb set or by seed, whereas, garlic in rabi by cloves. Among viruses attacking allium, Onion yellow dwarf virus (OYDV), Leek yellow stripe virus (LYSV), Garlic common latent virus, Shallot latent virus and allexiviruses are common viruses reported from other parts of India. Present study was focused on serological and molecular detection of viruses associated with both Allium species in north­western India. Allium growing regions of the state were surveyed and symptoms resembling to be caused by virus (es) were recorded. Major symptoms in onion plants were yellowing, striping and flattening of leaves. Severely infected plants showed curving, twisting, reduction of leaf size, bulb size and stunting of plants. Infected garlic plants were showing stunting, striping and curly wavy leaf margins. To confirm the association of viruses the young leaves samples were collected and subjected to ELISA against Potato virus Y (PVYo/c,PVYn), Potato virus X (PVX), OYDV, Zucchini yellow mosaic virus (ZYMV), Cucumber mosaic virus (CMV subgroup I & II) antisera (Agdia, USA) as per manufacturers protocol. ELISA confirmed the presence of PVYo/c, PVYn and OYDV in the samples, whereas, no other virus could be detected. Total RNA was isolated from ELISA positive samples and reverse transcription PCR assay was used for further confirmation using universal primers specific to Potyviridae, OYDV, allexivirus and LYSV. First strand of complementary DNA was synthesized using oligodeoxythymidine for Potyvirus and gene specific RT primers for OYDV, allexivirus, LYSV. A set of primers viz., Nib2F/Nib3R for Potyvirus (Zheng et al 2010), OYDVVKB F/OYDVVKB R for OYDV (Arya et al 2006), AllexCP/Allex­NABP for Allexivirus (Chen et al 2004), LYSV1/2 for LYSV (Dovas et al 2001) were used for PCR. An expected size of amplicon of ~350bp, 1.1 kb, 750 bp and 304 bp of potyvirus, OYDV, Allexivirus and LYSV respectively, were cloned and sequenced from infected samples. Nucleotide sequence analysis confirms the association of OYVD in onion and garlic, allexivirus in garlic and LYSV in onion causing degeneration either singly or in combination recorded first time from Indian Punjab.

Allium sativum L. (garlic) and A. cepa L.(onion) are important Allium species cultivated in Indian Punjab. Onion is planted both in kharif and rabi seasons by bulb set or by seed, whereas, garlic in rabi by cloves. Among viruses attacking allium, Onion yellow dwarf virus (OYDV), Leek yellow stripe virus (LYSV), Garlic common latent virus, Shallot latent virus and allexiviruses are common viruses reported from other parts of India. Present study was focused on serological and molecular detection of viruses associated with both Allium species in north­western India. Allium growing regions of the state were surveyed and symptoms resembling to be caused by virus (es) were recorded. Major symptoms in onion plants were yellowing, striping and flattening of leaves. Severely infected plants showed curving, twisting, reduction of leaf size, bulb size and stunting of plants. Infected garlic plants were showing stunting, striping and curly wavy leaf margins. To confirm the association of viruses the young leaves samples were collected and subjected to ELISA against Potato virus Y (PVYo/c,PVYn), Potato virus X (PVX), OYDV, Zucchini yellow mosaic virus (ZYMV), Cucumber mosaic virus (CMV subgroup I & II) antisera (Agdia, USA) as per manufacturers protocol. ELISA confirmed the presence of PVYo/c, PVYn and OYDV in the samples, whereas, no other virus could be detected. Total RNA was isolated from ELISA positive samples and reverse transcription PCR assay was used for further confirmation using universal primers specific to Potyviridae, OYDV, allexivirus and LYSV. First strand of complementary DNA was synthesized using oligodeoxythymidine for Potyvirus and gene specific RT primers for OYDV, allexivirus, LYSV. A set of primers viz., Nib2F/Nib3R for Potyvirus (Zheng et al 2010), OYDVVKB F/OYDVVKB R for OYDV (Arya et al 2006), AllexCP/Allex­NABP for Allexivirus (Chen et al 2004), LYSV1/2 for LYSV (Dovas et al 2001) were used for PCR. An expected size of amplicon of ~350bp, 1.1 kb, 750 bp and 304 bp of potyvirus, OYDV, Allexivirus and LYSV respectively, were cloned and sequenced from infected samples. Nucleotide sequence analysis confirms the association of OYVD in onion and garlic, allexivirus in garlic and LYSV in onion causing degeneration either singly or in combination recorded first time from Indian Punjab.

Onion (Allium cepa L.), an important edible species of genus Allium cultivated both in rabi and kharif season in Indian Punjab. It is planted directly by seeds or by bulb sets for table purpose and seed production. Onion is reported to be attacked by many viruses among these, Onion yellow dwarf virus (OYDV), Leek yellow stripe virus(LYSV),Garlic common latent virus, Shallot latent virus and Garlic virus X have been reported from India. These virus(es) attack onion either singly or in combination and causes severe losses. Present study was carried out to study the effect of virus (es) on symptoms and yield parameter. Serological and molecular detection from infected samples confirmed the association of OYDV and LYSV in onion. The virus symptoms associated with onion were categorized in three category (i) Symptomless plant with flattened older leaves (ii) Yellow stripping on leaves, flattening and stunting of plant        (iii )Severe twisting, thinning, partial and complete yellowing of leaves, stunting of plant and such plant did not bolt. The first category symptoms are more prominent in crops raised by seeds, whereas, the other two categories are prominent in crop raised by bulb sets. Growth parameter such as plant height, leaf diameter, number of leaves were recorded both in infected and healthy control. Severe reduction in growth parameter i.e. 16.89, 12.24, 1.50 per cent reduction in height of plant, no of leaves per plant and diameter of leaves, respectively, were recorded over healthy control. Yield parameter viz. bulb weight, seed weights were also recorded. Reduction in bulb weight by 56.16% and seed weight by 7.50% over healthy control was observed. This data revealed that virus complex of onion is responsible for drastic reduction in bulb and seed production in north-western part of India.