Reduced Iris Yellow Spot Symptoms through Selection within Onion Breeding Lines

Seyed Nourbakhsh,Christopher Cramer,Neel Kamal

doi:10.3390/horticulturae7020012

Seyed Nourbakhsh, Christopher Cramer + Show 1 more

Open Access

https://doi.org/10.3390/horticulturae7020012

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Abstract

Iris yellow spot (IYS) disease in onion (Allium cepa L.) is caused by onion thrips (Thrips tabaci L.) vectored Iris yellow spot virus (IYSV). The absence of cultivars that are resistant/tolerant to thrips and/or IYS is a challenge for onion bulb and seed production worldwide. To measure selection progress for reduced/delayed IYS symptom expression in onion breeding lines after two selection cycles, selections were performed in 2011 on previously evaluated lines that exhibited a reduced symptom expression after one selection cycle. Selected plants from each line were massed in a cage and the resulted progenies were evaluated in 2013 and 2014 along with their original populations and a susceptible check—’Rumba’. In some comparisons, the selection progress for delayed/reduced IYS symptom expression was observed for some breeding lines. Plants of most selected breeding lines exhibited less disease expression than plants of ‘Rumba’. For some selections, a low disease severity was observed even with a relatively high number of thrips per plant. These results suggest that further improvement might be achievable with additional cycles of selection.

Highlights

IntroductionHorticulturae 2021, 7, 12. https://Iris yellow spot virus (IYSV) (family Bunyaviridae, genus Tospovirus) and Iris yellow spot (IYS) disease occurrence have been reported in several onion (Allium cepa L.) growing regions of the world including several US states since first reported as the Tomato spotted wilt virus in southern Brazil [1]
Iris yellow spot virus (IYSV) and Iris yellow spot (IYS) disease occurrence have been reported in several onion (Allium cepa L.) growing regions of the world including several US states since first reported as the Tomato spotted wilt virus in southern Brazil [1]
The presence of IYSV was confirmed in these plants with ELISA

Summary

Introduction

Horticulturae 2021, 7, 12. https://Iris yellow spot virus (IYSV) (family Bunyaviridae, genus Tospovirus) and Iris yellow spot (IYS) disease occurrence have been reported in several onion (Allium cepa L.) growing regions of the world including several US states since first reported as the Tomato spotted wilt virus in southern Brazil [1]. Onion thrips acquire the virus after feeding on infected plants, the virus multiplies inside them, and while feeding on healthy leaf tissue, they can transmit the virus [4,5,6]. IYS-infected onion plants initially produce small necrotic, irregular or diamond-shaped straw-colored lesions on their leaves, which later grow and coalesce into larger lesions that can encompass an entire leaf [1]. This decrease in leaf photosynthetic area eventually affects bulb yield by decreasing the number of larger-sized bulbs that often have a higher market value than smaller bulbs [7,8,9,10,11]. Yields can be substantially reduced due to girdling and lodging of seed scapes when the number and sizes of lesions increase [8]

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