Onions Selected for Reduced Symptom Expression of Iris Yellow Spot Have Higher Photosynthetic Rates

Bulb onion ( Allium cepa L.) is an economically valuable vegetable crop in the United States. Onion production threatened by thrips, which are vector for Iris yellow spot virus , causal agent of (IYS). New Mexico State University (NMSU) breeding lines 12-236, 12-238, 12-243, and 12-337 have exhibited fewer IYS disease symptoms field; however, little known about effects on photosynthesis rate (P n ). We hypothesized that these NMSU would a higher P than IYS-susceptible cultivars Rumba Stockton Early Yellow. To test this hypothesis, field study was conducted 3 years at NMSU, measured five times throughout each season 2-week intervals. During bulb development maturation, occurred 10 12 weeks after transplanting, all when compared with cultivar. highest end vegetative growth stage decreased as bulbs approached maturation cultivars. Additionally, high transplanting coincided weight harvest. increased resulted larger more marketable bulbs. These results indicate maintaining may be related to reduced symptom expression onion.