Effects of Short-cut Flowering Branches on Harvest Time, Yield and Quality of Guire No.82 Mango

Shudan WEI, Qianfu CHEN, Yong ZHONG*, Qiang JIANG, Jie HUANG, Yerong WANG, Huili HUANG, Jinying YANG, Yuanxin CAO

1. Modern Agricultural Technology Research and Extension Center of Baise, Baise 533612, China; 2. Tianyang District Institute of Science and Technology Information, Baise 5336001, China; 3. Baise Institute of Agricultural Sciences, Baise 533612, China; 4. Baise University, Baise 533000, China; 5. Administration Committee of Baise National Agricultural Sci-Tech Zone, Baise 533612, China

Abstract [Objectives] To further study the technology of short-cut flowering branches for Guire No.82 Mango, adjust its harvest time, increase yield and improve fruit quality, and increase the economic benefits of mango production. [Methods] The experiment of short-cut flowering branches was carried out for Guire No.82 Mango. [Results] At the initial flowering stage and full flowering stage of the primary inflorescence, with short-cut flowering branches and corresponding cultivation techniques, Guire No.82 Mango was easy to extract regenerated inflorescences. Compared with the control group, the flowering period of the regenerated inflorescences was delayed by 30-35 d and 40-50 d, respectively; the harvest time was delayed by 30 and 40 d, respectively; the yield significantly increased by 1.63 times and 2.25 times, respectively; compared with the control group, the number of fruits with embryo increased significantly, which were 1.39 and 2.25 times of the control, respectively; there was no significant difference in the fruit quality at the harvest time. [Conclusions] Short-cut flowering branches at the initial flowering stage and full flowering stage of the primary inflorescence is an effective measure to delay the marketing time of Guire No.82 Mango.

Key words Short-cut flowering branches, Guire No.82 Mango, Harvest time, Yield, Fruit quality

1 Introduction

Guire No.82 Mango, also known as "Gui No.7 Mango", is an excellent mid-late-ripening mango variety selected by the Guangxi Subtropical Crops Research Institute in 1994 from the seedlings of Indian Mango No.901. It is a main and dominant variety of mango cultivation areas in Guangxi, with a planting area of more than 14 000 ha in Guangxi. The unique aroma and sweet taste, about 20% soluble solid content of ripe fruit, and up to 17% total soluble sugar[1]make it popular among consumers. In recent years, its market recognition has been increasing year by year, and it is a good product for consumers to eat and give as gifts. As one of the local star varieties of mango in Guangxi, Guire No.82 Mango has good development prospects and considerable economic benefits.

With the increasing market recognition of Guire No.82 Mango and the vigorous promotion of agricultural advantages and special varieties by local governments, the planting area of Guire No.82 Mango in Guangxi will continue to increase in the next few years. However, the marketing time of Guangxi mangoes is too concentrated. The flowering period of the primary inflorescence (usually in February-March) is easily affected by bad weather, the flowering period adjustment technology is not mature enough, and the fresh-keeping storage and transportation technology is lagging behind. All these problems are development bottleneck of Guire No.82 Mango[2-3]. In order to solve the problems encountered in mango production, many scholars have carried out related experimental research. According to findings of Ou Shijinetal.[4], Guire No.82 Mango has a strong ability to extract axillary inflorescences again, and technical measures can be used to promote the extraction of regenerated inflorescences to achieve the purpose of delaying the harvest time. Based on the strong ability of extracting the regenerated inflorescences of Guire No.82 Mango, Huang Taimingetal.[5]carried out an experimental study on short-cut of primary inflorescence to promote the extraction of the regenerated inflorescences. At the end of the primary inflorescence elongation, they cut off the dense buds about 2 cm at the top of the base branch of the primary inflorescences together with the inflorescences, so as to promote the axillary buds below the cut to regenerate the inflorescence. The results showed that this technology could delay the harvest time of mangoes by about 28 d. Similar experiment carried out by Zhong Yongetal.[6]also showed that short-cut flowering branches at the end of primary inflorescence elongation can delay the harvest time to the end of August. At this time, the market benefits of mango could be greatly improved. Similar studies have been carried out on postponing the harvesting period of other mango varieties, which provided a reference for the systematic study of the technology of delaying the harvest time of Guire No.82 Mango. Chen Houbinetal.[7]studied the technique of pruning and delaying the flowering period of ‘Zihua’ mango (MangiferaindicaL.), and found that the initial flowering period of the regenerated inflorescences was delayed by 20 d after pruning, and the full flowering period was delayed by 8 d, but the yield and commercial fruit rate decreased, which is believed to be caused by the late accumulation of carbohydrates in the tree due to re-pruning. Therefore, branch cutting should be combined with time, degree and method in production to obtain the optimal effect. Peng Leietal.[8]studied the delayed flowering period technology of autumn mango and 3-year mango retraction pruning, and found that pruning flowering branches in different periods had different effects on the flowering period of regenerated inflorescences, and finally determined the optimal retraction pruning time.

From previous studies, it can be seen that the technology of postponing harvest time of mango has achieved certain results. However, there is no report on the effect of short-cut flowering branches at different flowering stages (initial flowering stage, full flowering stage, and withering stage) of Guire No.82 Mango on its harvest time, yield and fruit quality. Whether short-cut flowering branches at different flowering periods have a great effect on re-extraction of regenerated inflorescences, harvest time, yield and fruit quality needs to be further studied in a systematic manner.

In order to further study the technology of short-cut flowering branches for Guire No.82 Mango and explore better short-cut flowering branch period and method, adjust its harvest time, increase yield and improve fruit quality, and increase the economic benefits of mango production, we carried out an experiment on the effects of short-cut flowering branches on harvest time, yield, and fruit quality of Guire No.82 Mango at different (initial flowering, full flowering, and withering) stages. It is expected to provide a reference for formulating the technical regulations and guiding the adjustment of harvest time of Guire No.82 Mango.

2 Materials and methods

2.1 Time and place of experimentThe experiment was conducted in the mango experimental base of Baise National Agricultural Sci-Tech Zone in Tianyang District of Baise City, Guangxi in January to August, 2020. The tree age of Guire No.82 Mango was 15 years, and the spacing in the rows and spacing between rows were 4 m×4 m.

2.2 Experiment treatmentThree treatments were arranged in the experiment. Treatment 1: short-cut flowering branches at the initial flowering stage of the primary inflorescence. At the initial flowering stage of the primary inflorescence (on February 13, 2020, 5% of the whole tree blossomed), cut off the flower branches with branch scissors about 2 cm below the inflorescence. Treatment 2: short-cut flowering branches at the full blooming stage of the primary inflorescence. At the full blooming stage of the primary inflorescence (on March 5, 2020, 50% of the whole tree blossomed), cut off the flower branches with branch scissors about 2 cm below the inflorescence. Treatment 3: short-cut flowering branches at the withering stage of the primary inflorescence. At the withering stage of the primary inflorescence, (On March 13, 2020, 90% of the whole tree blossomed), cut off the flower branches with branch scissors about 2 cm below the inflorescence. Control group: kept the primary inflorescence. Each experimental treatment had 3 replicates, each replicate 1 tree. Each tree was randomly marked with 10 fruiting branches with comparable growth, and the time of regenerated inflorescences, inflorescence quality, fruit setting rate and other indicators were surveyed at fixed points.

Field operations during the experiment: in order to promote the flower bud differentiation of each treatment, treatment 1-3 were sprayed with 2% potassium nitrate+0.3% potassium dihydrogen phosphate+3 000 times sodium nitrofen at 5 d before conducting short-cut flowering branches. After cutting the flower branches, sprayed fungicide (1 500 times 25% Cabrio)+2% potassium nitrate+0.3% potassium dihydrogen phosphate+3 000 times sodium nitrofen, and other field management levels were the same as the control group.

2.3 Survey itemsWe tracked and surveyed the marked branch regenerated inflorescence sprouting time, full flowering time, number of inflorescences, inflorescence length and width, number of fruits, branch flowering rate,etc.At the ripening stage of the fruit, made a record of the harvest time of each treatment (the sign of reaching the harvest: the fruit shoulder is full and round; the peel color becomes darker, and the wax powder layer appears; the pulp changes from milky white to light yellow[9-10]); measured the number of fruit and yield per plant; each replicate randomly selected 5 fruits with embryo with the same maturity to measure the fruit shape index (Fruit shape index=Fruit longitudinal diameter/Transverse diameter); after fruit ripening, we determined the soluble solid content (refractometer method[11]), total sugar content (3,5-dinitrosalicylic acid colorimetry[12]), and total acid content (the determination of percentage of total acid in food[13]), vitamin C content (NationalFoodSafetyStandardforDeterminationofAscorbicAcidinFood[14]), carotenoid content (high performance liquid chromatography HPLC[15]) and other quality indicators.

2.4 Data analysisWith the aid of SPSS 19.0 software, we analyzed the number of fruits with embryo, yield and fruit quality indicators by Duncan’s new multiple range method (one-way ANOVA) for multiple comparison significant difference analysis.

3 Results and analysis

3.1 Effects of short-cut primary inflorescences at different flowering stages on the regenerated inflorescences of Guire No.82 MangoAs shown in Table 1, there were differences in the quality of the flowers between different treatments. The average number of inflorescences of the primary inflorescence was 5.87 at the initial flowering stage, the langest inflorescence length was 23.35 cm, and the branch flowering rate was 100%; the average number of inflorescences of the regenerated inflorescences treated with short-cut flowering branches at the full flowering stage of the primary inflorescence was 2.90, the longest inflorescence length was 19.16 cm, and the branch flowering rate was 70%; no regenerated inflorescences were found in the short-cut flowering branches at the withering stage of the primary inflorescence. Compared with the control, the regenerated inflorescences treated with the short-cut flowering of the primary inflorescences at the initial flowering stage were delayed by 30-35 d, and the regenerated inflorescences of the primary inflorescence treated with the short-cut flowering at the full flowering stage were delayed by 40-50 d.

Table 1 Regenerated inflorescences of Guire No.82 Mango under different treatments

3.2 Effects of short-cut primary inflorescences at different flowering stages on the yield and harvest time of Guire No.82 MangoAs shown in Table 2, the average number of fruit on branches, the number of fruits with embryo, and the yield per plant of the primary inflorescence short-cut treated at the initial flowering stage and full flowering stage were significantly better than those of the control and that short-cut treated at the withering stage. Specifically, the short-cut treatment at the full flowering stage of the primary inflorescences was the best. The average number of fruits per plant was 187.66, the number of fruits with embryo was 183.33, the number of fruits with embryo was 1.9 times that of the control, the number of fruits with embryo was 3.53 times that of the control, and the converted yield reached 28 026.3 kg/ha, which was 2.25 times that of the control, and the harvest time was 40 d later than the control. For the short-cut treatment at the initial flowering stage of the primary inflorescences, the average number of fruit per plant was 136.67, which was 1.39 times that of the control, and the number of fruits with embryo was 129, which was 2.48 times that of the control, and the converted yield was 20 347.8 kg/ha, which was 1.63 times that of the control, and the harvest time was 30 d later than the control. The fruit shape index of short-cut treatment of the primary inflorescence at initial flowering stage and the full flowering stage was 1.91 and 1.95 and the control was 2.01, the difference was not significant.

Table 2 Yield of Guire No.82 Mango under different treatments

3.3 Effects of short-cut primary inflorescences at different flowering stages on the fruit quality of Guire No.82 Mango

The fruit quality indicators of each treatment were measured by sampling at different harvest times. The results are shown in Table 3. Results of sampling on July 15: the content of soluble solids and total sugar in the control was the highest, up to 20.53% and 16.29%, respectively, reaching the maturity index of this variety; the content of soluble solids and total sugar of the short-cut flowering treated primary inflorescences at the initial flowering stage were 17.10% and 12.75%, respectively; the content of soluble solids and total sugar of the short-cut flowering treated primary inflorescences at the full flowering stage were 15.65% and 12.28%, respectively. Both results were lower than the control, reaching a significant level of difference, indicating that the fruits of the two treatments have not reached the maturity of the control. The content of soluble solids and total sugar of the short-cut flowering treated primary inflorescences at the initial flowering stage sampled on August 15 were 19.50% and 15.81%, respectively; the content of soluble solids and total sugar of the short-cut flowering treated primary inflorescences at the full flowering stage sampled on August 25 were 19.80% and 15.57%, respectively. Both were slightly lower than the results of the control sampled on July 15, but the difference was not significant, indicating that the fruit reached the maturity at this time. The total acid, vitamin C, α-carotene, β-carotene and other indicators were not significantly different between different treatments and sampling measurement results in different time.

Table 3 Fruit quality of Guire No.82 Mango under different treatments

4 Conclusions and discussion

The experimental results indicate that at the initial flowering stage and full flowering stage of the primary inflorescence, with short-cut flowering branches and corresponding cultivation techniques, Guire No.82 Mango was easy to extract regenerated inflorescences, and the yield was significantly increased compared with the control. Specifically, the short-cut flowering treatment at the full flowering stage of the primary inflorescence had the highest yield, and the converted yield reached 22 421.04 kg/ha, which was 2.25 times of the yield of the control; the converted yield of short-cut flowering treatment at the initial flowering stage of the primary inflorescence was 16 278.24 kg/ha, which was 1.63 times of the control. In addition, the short-cut flowering treatment postponed the flowering period and harvest time. The short-cut flowering treatment at the initial flowering stage of the primary inflorescence delayed the full flowering period of regenerated inflorescences by 30-35 d, and delayed the harvest time by 30 d; while the short-cut flowering treatment at the full flowering stage of the primary inflorescence delayed the flowering period of regenerated inflorescences by 40-50 d, and delayed the harvest time by 40 d. There was no significant difference in the fruit quality of Guire No.82 Mango between the control and other treatments.

In this experiment, after short-cut flowering branch treatment of the primary inflorescence at the initial flowering stage and full flowering stage, the full flowering period of regenerated inflorescence appeared in April to May, which can avoid the common low temperature and rainy February and March[2-3], increasing the probability of the inflorescence being stable and fruiting, which is similar to the experimental results of Peng Leietal.in Yuanjiang County. The regenerated inflorescence of mango avoids the hazard of unusual cold spell in an otherwise warm early spring during the full flowering period, thereby improving the flowering rate, the proportion of bisexual flowers and the fruit setting rate[8]. In addition, it extended the harvest period of mangoes, realized the staggered marketing of mangoes, and lengthened the sales period, which is of great significance for increasing the industrial benefits. In the experiment, we observed that the number of pollinating insects and flies in the orchard was significantly larger than that in February to March due to the warm weather in April to May, and the activity of insects and flies was higher, which was very beneficial to mango pollination and fertilization[9], so that the number of fruits with embryos and yield can be increased.

In this experiment, Guire No.82 Mango had poor quality of re-flowering after short-cut flowering branches at the withering stage. There are two possible reasons. (i) After short-cut flowering branches at the withering stage, higher temperature is not conducive to flower bud differentiation, but is conducive to shooting[16]. In the experiment area, the average daily temperature is high, and the differentiation of mango flower buds is restricted when the temperature is high, while the development of leaf buds is promoted, and new shoots are finally generated, which is similar to the findings of Peng Leietal.that in the event of high temperature weather after retracting the pruning branches, the inflorescence cannot be regenerated by retracting the pruning branches[8]. (ii) The mango tree at the withering stage has passed the entire flowering period, consuming a lot of nutrients in the tree body. When Peng Leietal.[17]studied the changes of fructose content in the fruiting parent branches of short-cut flowering branches of mangoes, they found that the tissues near the short cut delivered fructose to the cutting buds to meet the nutrients and energy substances required for flower bud differentiation. If the tree nutrient has been consumed too much, the nutrients needed for flower bud redifferentiation cannot be sufficiently supplied in time, it will inevitably influence the effect of flower formation.