Morphological responses of potato varieties (lines) to enhanced UV-B radiation

UV-B radiation has a profound effect on plant morphogenesis, inevitably affecting potato cultivation, especially with enhanced UV-B radiation on the earth’s surface. Compared with rice, wheat, corn and other crops, the total effect of UV-B radiation on potato is still not conclusive, especially the morphological response of potato to UV-B radiation. In this study, the effect of enhanced UV-B radiation on plant height, internode length, leaf area, root to shoot ratio (R/T) and other morphological indices of 7 potato varieties (lines) were analyzed and compared. The determination of the inter-variety variations in response was critical for the evaluation of the effect of UV-B radiation on potato. It was also important for providing further understanding on the tolerance and sensitivity of different varieties of potato to enhanced UV-B radiation. An outdoor pot culture experiment was conducted to evaluate the sensitivity of 7 potato varieties (lines), 3 colored-tuber and 4 achromatic-tuber, to a range of UV-B radiation levels. Three biologically effective UV-B radiation treatments — 0 (control), 2.5 kJm^-2d^-1 (T1) and 5.0 kJm^-2d^-1 (T2) — were imposed on the potato varieties for 50 d when seedlings were over 20 cm high. Aboveground morphological indices were measured after 15 d, 30 d and 45 d of treatment, respectively. Response index (RI) and cumulative stress response index (CSRI) were eventually used to evaluate the sensitivity of the different varieties (lines) of potato to the UV-B radiations. The results showed that plant height, internode and leaf area of most of the treated varieties (lines) decreased consistently under enhanced UV-B radiation. The inhibitory effect of UV-B radiation on potato was more obvious under higher UV-B dose with longer duration. While a significant variability of morphological response was observed, the degree of sensitivity to UV-B radiation also varied among the potato varieties. Compared with colored-tuber varieties (lines), achromatic-tuber varieties (lines) were inhibited more severe under elevated UV-B radiation, with more evident reduction in aboveground biomass. For example, the shoot fresh weight response index of ‘Hezuo 88’ was 60.28 and 70.44 (negative), respectively, while that of colored-tuber ‘Zhuanxinwu’ was 107.75 and 21.4 (positive) under T1 and T2, respectively. Due to the negative effect of enhanced UV-B radiation on aboveground biomass, root biomass also dropped significantly for most of the potato varieties (lines). Compared with belowground root and tuber, the inhibition of aboveground biomass increased with increasing exposure to enhanced UV-B radiation. Thus, R/T of all the potato varieties (lines) obviously increased, especially at high UV-B radiation (T2). Based on the calculated CSRI, achromatic-tube varieties (lines) (‘Hezuo 88’ and ‘Lishu 6’) were sensitive to UV-B radiation, while colored-tube varieties (‘Zhuanxinwu’ and ‘21-1’) more tolerant to UV-B radiation. The results suggested that the biomass of both shoot and root and tuber color were important indicators in selecting or developing UV-B radiation tolerant potato varieties.