Reduced Iris Yellow Spot Symptoms through Selection within Onion Breeding Lines
Neel Kamal | Seyed Shahabeddin Nourbakhsh | Christopher S. Cramer
Iris yellow spot (IYS) disease in onion (<i>Allium cepa</i> L.) is caused by onion thrips (<i>Thrips tabaci</i> L.) vectored <i>Iris yellow spot virus</i> (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.
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