Abstract: MiniMax, an early maturing, dwarf and small-seed line introduced from the US, has a potential becoming a research model in soybean. Systemic studies covering the morphological, growth and developmental characteristics of MiniMax were carried out as follows: (1) Botanical characteristics of MiniMax were recorded according to DUS standard for soybean. (2) Two photoperiodic treatments of 12 h (short day or SD) and 16 h (long day or LD) integrated with high temperature (HT) (summer sowing in Beijing) and low temperature (LT) (spring sowing) were designed to explore the photothermal effects on growth period, plant height and seed size of MiniMax. (3) QTL analysis associated with growth period, plant height and seed size was conducted. Under the summer-sowing condition of Beijing, the growth period, plant height and 100-seed weight of MiniMax were 63.1 d, 39.0 cm, and 4.6 g, respectively. Different photoperiod and temperature treatments had small effects on the seed size, but significant impact on growth period and plant height. Photoperiod sensitivity and photothermal comprehensive sensitivity of MiniMax were close to those of northern spring-sowing soybean in China, while temperature sensitivity of MiniMax was similar to that of summer-sowing varieties from Yellow-Huai-Hai River Valleys. Under SD and HT conditions, the vegetative growth stage and the whole growth period of MiniMax were short, with short plant height and small seed size; under LD and HT conditions, MiniMax had high plant height, late flowering dates and long whole growth period, and occupied large space. Five QTLs for growth period (FT 2-1, Pod mat 13-3, R7 2-2, R3 1-3 and R7 1-3), five QTLs for plant height (Pl ht 13-3, Pl ht 17-2, Pl ht 13-2, Pl ht 7-2, and Pl ht 11-3) and five QTLs for seed size (Sd wt 6-4, Sd wt 7-3, Sd wt 10-1, Sd wt 12-3, and Sd wt 13-8) were detected by SSR analysis. Based on the results mentioned above, we proposed that MiniMax with rapid life cycle, short stature and small seed under suitable photothermal conditions, can be used as a research model in soybean.

Key words: Soybean, MiniMax, Botanical characteristic, Photoperiod response, Research Model