Screening of Okra Varieties for Resistance to Okra Yellow Vein Mosaic Disease under Field Conditions

Sabir I Khoso,Ali A Lakho,Fahad N Khoso,Aftab R Jarwar,Khalid H Dhiloo,Suman T Qazi,Khadim H Wagan,Manzoor A Abro,Syed Rizwan,Jamal-U-Ddin Hajano

doi:10.33687/phytopath.010.01.3516

Sabir I Khoso, Ali A Lakho + Show 8 more

Open Access

https://doi.org/10.33687/phytopath.010.01.3516

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Abstract

Okra (Abelmoschus esculentus L.) can contract okra yellow vein mosaic disease (OYVMD) caused by Bhendi yellow vein mosaic virus (genus: Begomovirus and family: Geminiviridae), vectored by whitefly (Bemisia tabaci). This study was carried out to screen okra varieties for resistance to OYVMD and to determine the correlation of vector population with the severity of the disease. Six varieties namely, Tulsi, Durgah, Sabz Pari, Sarahariya, Ramaan Kirshna and Pooja were grown under field conditions at localities of Shahpur, Tando Adam and Peer Kathi during rabi (winter cropping) and kharif (summer cropping) seasons during 2016 and 2017, respectively. The first incidence percent of the disease was recorded in the 8th week during rabi and the 6th week during kharif growing season. The Tulsi variety remained disease-free during both growing seasons. A significantly lower disease incidence % was recorded in Sabz Pari (29.32%) and Sarahariya (30.09%) varieties than Durgah, Ramaan Kirshna and Pooja during the rabi growing season. Both varieties were disease-free during the kharif season. There was remarkable variation in disease severity recorded in okra varieties at different trials during rabi and kharif seasons using a 0-6 rating scale (i.e., 0 = The disease-free plants, 1 = 1-10 % vein clearing, 2 = 11-25 % vein yellowing of small leaves , 3 = 26-50 % yellow network on some leaves, 4 = 51-60 % yellow network on all leaves, 5 = 60-70 % complete leaves turn yellow or cream color and 6 = 70 % plant stunted, deformed and small fruit and whole plants becomes colorless). Whitefly appeared in the 5th week during the rabi and 4th week during the kharif growing seasons. Vector population during the rabi growing season was significantly higher than in the kharif season. There was a nonsignificant relationship between disease severity and whitefly population in Ramaan Kirshna, Sarahariya, and Sabz Pari varieties. The disease severity in the Pooja variety showed a significant relationship with vector population, but only in the Tando Adam trial (R2= 0.7455, P= 0.0084), whereas the Durgah variety showed a significant relationship between disease severity and vector population in Shahpur (R2= 0.6615, P= 0.0267) and Tando Adam trials (R2= 0.8235, P= 0.0018). The same variety showed a nonsignificant relationship between disease severity and vector population in the Peer Kathi trial. It is concluded that Sabz Pari and Tulsi varieties are resistant to the disease

Highlights

Okra (Abelmoschus esculentus L.) is placed in the Malvaceae family; it originated in tropical Africa but can be cultivated in different regions of the world (Ali et al, 2012)
Incidence of okra yellow vein mosaic disease in different okra varieties during rabi and kharif growing seasons Disease incidence percent results were recorded in the 8th week after sowing during the rabi growing season
The disease incidence showed a gradual increase in all the varieties until the 11th week of assessment

Summary

Introduction

Okra (Abelmoschus esculentus L.) is placed in the Malvaceae family; it originated in tropical Africa but can be cultivated in different regions of the world (Ali et al, 2012). The virus poses a serious threat to okra cultivation worldwide including in Sindh, Pakistan owing to its long-term survival in the insect vector, highly efficient transmission through the insect vector and overlap cropping. Incorporation of resistant varieties into a disease management program is the most efficient, cost-effective, and feasible strategy to suppress plant diseases and this strategy has been used for centuries It may suppress initial disease and/or suppress the rate of epidemic development. Ali et al (2005b) used different varieties of okra, i.e., Pahuja, Safal, Subz Pari, and Surkh Bhindi, for measuring disease severity and analyzing the correlation with vector population size and environmental conditions. The present study was conducted to screen different commercial varieties of okra for resistance/susceptibility to Bhendi yellow vein mosaic viral disease under field conditions and determine its correlation, if any, with vector (i-e whitefly) population size

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