Effects of reduced irrigation on blossom-end rot incidence and increases in soluble solids in early autumn-cropping tomato
2019
Hiei, K. | Ito, M. | Takagi, S. | Ban, Y. | Tsunekawa, Y.
Reduced irrigation causes severe blossom-end rot (BER), as well as an increase in soluble solids (Brix) in tomatoes. We attempted to model the relationships between reduced irrigation and either BER incidence or Brix increase in the early autumn-cropping season using regression analysis. Tomatoes were cultivated through fertigation in isolated beds filled with sandy loam. Experimental plots were drip irrigated to maintain several predetermined soil-water tension levels within pF 1.8-2.6 under a common fertilizer application regime. The performances of two cultivars, Rinka 409 and Ringyoku, were examined over four and two years, respectively. Data acquired were analyzed using generalized linear mixed models with the number of fruits affected by BER or the mean Brix value as response variables, relevant soil-water tension level as an explanatory variable, and trial year as a random effect. Regression models, involving a logistic function for BER or a linear function for Brix, were derived for each cultivar. BER incidence and Brix level had mutually different response characteristics to soil-water tension. The response of the BER incidence trait showed nonlinearity and larger annual fluctuations than did the Brix value. In addition, the degree of reaction differed between cultivars. In particular, BER incidence in cultivar Rinka 409 sharply increased under reduced irrigation. These models are useful for evaluating the risks of BER incidence associated with Brix increase and can inform irrigation management according to a particular business strategy.
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