Effect of xenia on fruit quality and sucrose metabolism enzyme activity in red bayberry

Abstract:【Objective】Xenia is a phenomenon that pollen source influences fruit traits, including color,size, soluble solids, seed size and so on. In this study, we evaluated different pollination combinations inimproving fruit quality.【Methods】Pollens from different parent cultivars were collected from Huangyanand Zhoushan counties in Zhejiang province before the male flowers opened and stored under -20 ℃. Female flowers were selected from 15-year-old trees of Myrica rubra‘Biqizhong’and‘Dongkui’in Hain⁃ing county, Zhejiang province. The pollination combinations included natural pollination of‘Biqizhong’(CK1),‘Biqizhong’× Huangyan(BH),‘Biqizhong’× Zhoushan (BZ), natural pollination of‘Dongkui’(CK2),‘Dongkui’× Huangyan (DH),‘Dongkui’× Zhoushan (DZ). The fruit weight, size, color, hardness,TSS, total sugars, titratable acids, and vitamin C were tested. Fruit weight was measured using a balance,size with a caliper, color parameters detected with a spectral photometer (HITACHI307), hardness using atexture analyzer and TSS with a saccharimeter. The contents of total sugars, titratable acids, and vitamin Cwere determined with alkaline acid solution method, sodium hydroxide solution method, and 2, 6-dichlo⁃rine indophenol solution, respectively. Sucrose phosphate synthase (SPS) and sucrose synthase (SS) cata⁃lyze the synthesis of sucrose in plants. The activities of both enzymes on May 19 and Jun 19 were deter⁃mined to understand sucrose synthesis in bayberry trees. Data collected were analyzed with SPSS 17.0 todo analysis of variation and multiple comparison for significance of difference.【Results】The fruit weight,size, appearance, hardness and color had significant differences among different pollination combinations.The fruit weight in BH and BZ was lower than in CK1 by 6.5% and 18.6%, respectively. BZ had the heavi⁃est fruit mass (7.9 g) among the artificial pollination combinations. The fruit transverse and longitudinal di⁃ameters in BH were 4.3% and 7.6% smaller than those in CK1, respectively, and those in BZ were shorterby 4.62% and 9.16%, respectively. However, fruit weight, and transverse and longitudinal diameters inpollination combinations with‘Dongkui’had no significant difference compared with CK2. The flesh re⁃covery had no significant difference among all the pollination combinations with both female parent culti⁃vars. The hardness of BZ and BH fruit was significantly higher than that of CK1 by 7.81% and 18.47%, re⁃spectively. The fruit hardness in DH and DZ was also higher than that in CK2. The fruit brightness in BHand BZ was significantly lower than that in CK1 by 5.1% and 16.4%, respectively, and the yellow index inBH and BZ was 6.43% and 20.30% lower, respectively. The red index of BZ fruit was the highest amongthe six combinations, being 4.8% higher than CK1. The fruit brightness in DH was significantly and5.75% lower than that in CK2, but that in DZ significantly and 5.87% higher. However, the yellow indexof‘Dongkui’fruit produced from different pollen sources was significantly different with that of CK2fruit, but red index had no difference. The content of soluble solids was different in different pollinationcombinations. Soluble solids in BH and DZ fruits were 0.17% and 3.24% lower than the controls, respec⁃tively, but those of BZ and DH fruits were significantly higher than that of the control by 7.14% and31.95%, respectively. The total soluble sugars in all the cross pollination combinations were lower than inthe controls, but the content titratable acids was higher. The vitamin C in the fruits generated from crosspollination combinations with‘Biqizhong’as the female parent was lower than that in CK1, but that inthe fruits from the pollination combinations with‘Dongkui’was higher than that in CK2. The contents ofsoluble sugars in BH and BZ were 14.17% and 16.67% lower than that in CK1, but DH had a significant⁃ly (3.06% ) higher content of soluble sugars than CK2. The titratable acids in BH and BZ fruit were20.30% and 16.99% higher than that in CK1, respectively. In addition, the titratable acids in DH dramati⁃cally increased by 25.39% compared with CK2, but those in DZ decreased by 2.73%. The contents of vitamin C in BH and BZ were 10.3% and 6.73% lower than those in CK1, respectively. However, the contentof vitamin C in DH and DZ was higher than that in CK2, with that in DZ being 8.63% higher than that inCK2. The SPS activity in the six pollination combinations on May 19 and June 19 were measured. The re⁃sults indicated that SPS activities in all pollination combinations on June 19 were higher than those onMay 19. The enzyme activity in BZ and DZ increased greatly. SPS activity in BH and BZ on May 19 in⁃creased by 82.55% and 87.06% compared with CK1, respectively, and that on June 19 increased by28.8% and 37.08%, respectively. SPS activity in BZ was 47.7 mg·g-1 (expressd by the sucrose content) onMay 19 and 57.75 mg·g^-1 on June 19. In DH and DZ, the enzyme activity was increased by 28.20% and35.33% respectively on May 19, and by 31.62% and 44.77% respectively on June 19, compared withCK2. SPS activity in DZ was 41.75 mg·g^-1 and 58.24 mg·g^-1 on May 19 and June 19, respectively, whichwas higher than that in DH. The SS activity in BH and BZ was higher than in CK1, being 99.81% and115.89% higher on May 19 and 76.49% and 105.98% higher on June 19, respectively. The enzyme activi⁃ty in BH was 77.71 mg·g-1 on May 19 and 66.86 mg·g^-1 on June 19, which was the highest among all thepollination combinations. The SS activity in DH was 52.14 mg·g^-1 and 66.64 mg·g^-1 on May 19 and June19, respectively, which was higher than that in CK2. However, the enzyme activity in DZ on May19 waslower than that in CK2.【Conclusion】‘Biqizhong’and‘Dongkui’displayed a high pollination compatibility with the cultivars in Huangyan county and Zhoushan county. The fruit weight, transverse and longi⁃tudinal diameters and SS activity in DH were the highest among the six pollination combinations. However, the fruit hardness, TSS and SPS activity in BZ were higher compared with those of the other treatments.It was clear that the quality of DH and BZ fruit had improved greatly and that pollen source significantlyinfluenced the quality of fruit. The results provided information for pollination combination selection to im⁃prove fruit quality via artificial pollination. The results showed that the male plants in Zhoushan had a bet⁃ter effect in improving quality of‘Biqizhong’, while those in Huangyan seemed better for‘Dongkui’.