Abstract:

Effects of nitrogen（N）rate on the growth of autumn field-grown potato plants and the expression of nitrate reductase gene（StNR）and ammonium transporter gene（StAT）were studied. SPAD reading increased as fertilizer N rate increased from 0 to 360 kg · hm-2 at the tuber initiation and the tuber bulking periods；Interestingly，the expression of StNR and StAT in leaf tissue decreased as fertilizer N rate increased，exhibiting a significant（P < 0.01）negative correlation with nitrate application rate and SPAD reading at the tuber initiation and the tuber bulking periods. Plant height and stem diameter increased with increasing fertilizer N rate. For the total tuber number per plant， the mean tuber weight and the total yield，they increased to the maximum values，then decreased while fertilizer N rate increased. Forstarch content，it decreased with increasing fertilizer N rate. Taken together，fertilizer N rate at 90–135 kg · hm-2 can be recommended for the autumn potato crop. Additional analysis demonstrated that as fertilizer N application increased，soil and tuber ammonium-N concentration increased. In soil of 0–20 cm depth in the potato root zone，ammonium-N level was between 1.55 to 9.34 mg · kg-1；And no significant increase was observed when N fertilizer N rate was below 360 kg · hm-2. In tubers，ammonium-N concentration was between 20.58 to 49.81 mg · kg-1；And as fertilizer N rate increased，a significant increase（P < 0.01）of tuber ammonium-N was observed. The results would provide theoretical basis for establishment of the molecular detection method for nitrogen sufficiency in field-grown potato plants and field nitrogen fertilizer managements.

Key words: Solanum tuberosum, nitrate reductase, ammonium transporter, nitrogen rate, photosynthesis