Agronomic treatments combined with embryo rescue for rapid generation advancement in tomato speed breeding

Abstract

Unlike other major crops, little research has been performed on tomato for reducing generation time for speed breeding. We evaluated several agronomic treatments for reducing the generation time of tomato in the M82 (determinate) and Moneymaker (indeterminate) varieties and evaluated the best combination in conjunction with embryo rescue. In a first experiment under the autumn cycle, five container sizes, from 0.2 1 (XS) to 6 1 (XL), were evaluated. We found that plants from the XL containers exhibited better development and required less time from sowing to anthesis (DSA) and for anthesis to fruit ripening (DAR). In a second experiment, using XL containers in the autumn-winter cycle, we evaluated cold priming at the cotyledonary stage, water stress, P supplementation, and K supplementation on generation time. We found that, compared to the control, cold priming significantly reduced the number of leaves and plant height to first inflorescence as well as DSA (2.7 d), while K supplementation reduced DAR (8.8 d). No effects of these treatments were observed for other growth of physiological traits. In a third experiment with XL containers in the spring-summer cycle, the combination of cold priming plus K supplementation was tested, confirming the significant effect of the combination on generation time (2.9 d for DSA and 3.9 d for DAR). Embryo rescue during the cell expansion cycle (average of 22.0 d and 23.3 d after anthesis for M82 and Moneymaker, respectively) allowed shortening the generation time by 8.7 d in M82 and 11.6 d in Moneymaker compared to the in planta fruit ripening. The combination of agronomic treatments with embryo rescue can make an effective contribution to increase the number of generations per year for speed breeding in tomato from the current three to four.