Asparagus officinalis L. cultivars were evaluated for resistance to asparagus stem blight caused by Phomopsis asparagi (Sacc.) Bubák under controlled environmental conditions. The plants were inoculated with the vinyl tube and cotton inoculation method. Disease severity assessments, based on the percentage of diseased plants and the disease index, were made 4 weeks after inoculation. Estimates of the percentage of diseased plants ranged from 33% to 80%, and the disease index ranged from 28 to 79. None of the cultivars and lines showed high resistance, but there were significant differences in disease susceptibility among the cultivars and lines.
To control asparagus harvest timing, we investigated the effects of short-term low (5%) oxygen (O2) treatment in the cultivation area on asparagus growth and yield using a closed cultivation system. During 120 days of cultivation, low O2 treatments were initiated at 0 to 4, 20 to 24, and 40 to 44 days after planting (DAP). The sprouting spears and control crown yield gradually decreased with increasing DAP. However, low O2 treatment at 0 to 4 DAP significantly delayed the decrease until 80 DAP, although the total yield did not change during cultivation. In contrast, low O2 treatments at 20 to 24 and 40 to 44 DAP did not affect yield performance. Taken together, short-term low O2 treatment immediately after planting can change the harvest timing of white asparagus and can be used for effective asparagus culturing in a closed system, such as a plant factory.