JIA-2018-09

2019 HU Guo-jun et al. Journal of Integrative Agriculture 2018, 17(9): 2015–2023 the growth of the two cultivars (Table 3). For Pink Lady, the survival rate of P-1d plants was lower than that of P-4d, P-7d, P-10d, and P-13d plants when thermotherapy lasted 10, 25 and 30 d. Only five plants survived after 30 d of thermotherapy (Table 3). The effect of high temperature on plants among the five pre-culture periods was not obvious during 20 and 25 d of thermotherapy. At the end of thermotherapy, the leaves of P-1d, P-4d and P-7d plants turned yellow, brown or black and dessicated; the tips of most plants became brown or black. Moreover, growth of plants in these three treatments was nearly similar to that of the control plants, and the growth speed of P-10d and P-13d plants was higher than that of the former three treatments (Fig. 4-A). For Huafu, the survival rate of P-13d plants was higher than that of P-4d, P-7d and P-10d plants during the longest thermotherapy treatment (30 d), and there was no significant difference among different durations of the thermotherapy. The percentage of surviving plants was up to 82.2% at the end of thermotherapy (30 d) (Table 3). When the treatment lasted 30 d, the leaves of P-1d and P-4d plants turned yellow and brown and became desiccated. No growth was observed in these two treatments when compared with the control plants and the growth of P-7d and P-10d plants was higher than that of the former two treatments. The P-13d plants showed almost the same amount of growth with that of control (Fig. 4-B). Shoot proliferation was also strongly inhibited by higher temperatures. Almost no axillary shoots Fig. 3 Quantitative reverse transcription PCR (RT-PCR) was performed to quantify the relative expression levels of Apple chlorotic leaf spot virus (ACLSV) and Apple stem grooving virus (ASGV) in in vitro Pink Lady (A) and Huafu (B) plants after pre-cultured for 1, 4, 7, 10 and 13 d (P-1d, P-4d, P-7d, P-10d, and P-13d), respectively. Error bars represent the standard deviations among triplicate experimental reactions. Table 3 Survival rate of apple plants during thermotherapy Varietiy Duration of pre-culture 1) Survival rate (%) 5 d 10 d 15 d 20 d 25 d 30 d Pink Lady P-1d 100±0.0 Aa 75.6±10.2 Bb 66.6±11.5 Ab 44.5±3.9 Ac 28.9±3.8 Bd 11.1±10.2 Be P-4d 100±0.0 Aa 84.5±3.9 Bb 71.1±7.7 Ac 59.4±5.3 Ac 46.6±11.5 Ad 37.8±7.7 Ad P-7d 100±0.0 Aa 86.7±6.7 ABb 63.0±10.0 Ac 44.5±3.9 Ad 40.0±6.7 ABde 28.9±7.7 Ae P-10d 100±0.0 Aa 95.5±3.9 ABa 75.6±7.7 Ab 56.4±14.4 Ac 42.2±10.2 ABcd 35.6±10.2 Ad P-13d 100±0.0 Aa 95.6±7.7 Aa 71.9±8.8 Ab 55.6±10.2 Ac 46.6±11.5 Ac 42.2±10.2 Ac Huafu P-1d 100±0.0 Aa 80.0±6.7 Cb 73.3±6.7 Bb 54.2±7.9 Bc 40.0±6.7 Cd 37.8±7.7 Cd P-4d 100±0.0 Aa 84.5±3.9 CBb 73.3±0.0 Bc 65.3±2.4 Bd 56.4±5.3 BCe 48.9±3.8 BCf P-7d 100±0.0 Aa 91.1±7.7 BCa 75.6±7.7 Bb 65.3±2.4 Bbc 60.8±6.9 Bc 60.8±6.9 Bc P-10d 100±0.0 Aa 97.8±3.9 Aa 75.5±3.9 Bb 66.7±0.0 Bc 60.8±6.9 Bc 60.8±6.8 Bc P-13d 100±0.0 Aa 97.8±3.9 Aa 91.1±10.2 Aa 86.7±13.4 Aa 84.5±16.8 Aa 84.5±16.8 Aa 1) P-1d, P-4d, P-7d, P-10d, and P-13d, pre-cultured for 1, 4, 7, 10, and 13 d, respectively. Data were analyzed according to a general linear model-general factorial using SPSS for Windows (Release 7.5.1). To estimate homogenous subsets for various treatments, post hoc Tukey’s HSD (Honestly Significant Difference) test at α=0.05 level of significance was applied. Within each column, different letters indicate significant differences ( P <0.05). Vertical differences among treatments were denoted by capital letters, and the horizontal differences among duration were denoted by lowercase letters. B 2.0 1.5 1.0 0.5 0 Relative expression A 2.0 ACLSV ASGV ACLSV ASGV 1.5 1.0 0.5 0 Relative expression 2.0 2.5 3.0 1.5 1.0 0.5 0 Relative expression 1.5 1.0 0.5 0 Relative expression P-1d P-4d P-7d P-10d P-13d P-1d P-4d P-7d P-10d P-13d P-1d P-4d P-7d P-10d P-13d P-1d P-4d P-7d P-10d P-13d