Green Yield as a Potential Predictor of Cured Burley Tobacco Yield in a Phytophthora nicotianae-Infested Field over Four Seasons

Phytophthora-induced plant diseases are most effectively managed using an integrated strategy that includes host resistance, best cultural practices, and fungicide applications. Black shank, caused by Phytophthora nicotianae, is the most significant soilborne disease affecting tobacco, and extensive breeding for resistance has resulted in an array of varieties with a spectrum of black shank resistance. Estimates of plant survival are the most common measurement in black shank variety and disease management trials; however, survival might not be the most accurate indicator of yield for varieties with robust resistance. Through the presented analyses, at-harvest green yield estimates are shown to be more closely associated with cured tobacco yields than survival counts, irrespective of black shank resistance status. However, under high black shank pressure, green yield is an excellent descriptor of only low-resistance varieties’ cured yield, with other factors likely contributing to moderate- and high-resistance varieties’ cured yield models. This prevents development of a unified (variety-nonspecific) cured yield model, which would be useful not only for tobacco scientists but also commercial growers in planning labor activities and the industry at large in managing cured tobacco inventory. More broadly, this suggests that research in other Phytophthora pathosystems may benefit from preliminary yield estimates in place of or in addition to survival counts in resistant variety evaluations.