A study on the floral cluster pruning of the ‘Kyoho' grape

Abstract: 【Objective】Floral cluster pruning is an important technique in improving grape fruit quality, including improving berry-setting, exterior quality and so on, and it is imperative to establish and improve this technique in the grape industrialization process.‘Kyoho'grapes have one of the largest planting areas in China, but its production is facing some difficulties, and one of them is the problem of panicle shaping. Improperly pruning floral clusters can cause predictable losses in‘yoho'grape production, including panicle type heterogeneity, packing inconvenience, uneven coloring, poor resistance and so on. It is imperative to screen, evaluate and compare panicle shaping methods with the fruit quality to determine their effectiveness.【Methods】In order to identify the desired panicle mode, this paper primarily analyzed the influence on the fruit quality of the‘Kyoho'grape and its operational effectiveness with different panicle shaping methods, which included the following scenarios: leaving spikelet tips 4 cm (A) , 5 cm (B) , 6 cm (C) , 7 cm (D) , 8 cm (E) or 9 cm (F) , shorting branch (G) , retaining middle ear (H) and the remaining secondary ear of the cluster only (I) . By measuring and analyzing the growth, quality and effectiveness indexes of these modes, 9 indexes, including bunch mass, berry mass, berry number, branch density, souble solids content, total acid, tannin content, CIRG and operational efficiency were analyzed using the principal components analytic method.【Results】The results showed that the leaving spikelet tip 4 cm can satisfy the production requirements, when the panicle mass was 410.6 g. And the leaving spikelet tip 5 cm had the biggest berry mass, followed by the leaving spikelet tip 6 cm, while the remaining secondary ear of the cluster was only shown to be contrary. The berry-settingpercentage increased with the spikelet tip length and the difficulty of fruit thinning, and the leaving spikelet tips 4 cm, 5 cm, 6 cm and the remaining secondary ear of the cluster caused a considerable reduction in the berry-setting percentage. The soluble solid content of leaving spikelet tips 4 cm, 5 cm, and 6 cm was significantly increased, and the shorting branch had the lowest content recorded. The total acid content of the leaving spikelet tips 4 cm, and 5 cm was significantly higher than the other treatments. The different panicle modes in this research had no significant effects on the tannin content in the pericarp, but affected the tannin content of the sarcocarp, and the retaining middle ear had the lowest tannin content of all the sarcocarp. The effect of different inflorescence shaping methods on the color difference of the grapes was determined by using a portable colorimeter. The color brightness (L) of treatment“I”was the best, while“H”was the lowest.“H”has the highest value of a and“C”has the lowest value of a, but there was no significant difference among all the treatments. The value of h and CIRG varied slightly among the treatments, but the difference is not significant. The remaining secondary ear of the cluster only provided the maximum operating efficiency by the order of the ranking, followed by the leaving spikelet tips 6 cm, and 7 cm; leaving spikelet tips 8 cm, and 9 cm took a long time, which showed that there was no simple linear correlation between the working efficiency and panicle length of the‘Kyoho'grape. These findings suggested that a spikelet tip length of more than 7 cm required a great deal of effort and time. Nine main characters showed significant differences through using the principal components analysis and three principal components were extracted using the pathway analysis, and the contribution rate of the accumulative total of the variance of the 3 principal components in in this experiment was 76.097%. By using the remaining secondary ear of the cluster only, the leaving spikelet tip 5 cm performed relatively better, the retaining middle ear and shorting branch were exactly the opposite, and the retaining middle ear was in common use in the‘Kyoho'grape production, due to the results of principal component analysis, from the highest to the lowest in rank, they were, the remaining secondary ear of the cluster only, leaving spikelet tips 5 cm, 4 cm, 6 cm, 8 cm, 7 cm, 9 cm, retaining middle ear and shorting branch. The leaving spikelet tip 5 cm may be the best solution, though the remaining secondary ear of the cluster only was the optimal panicle mode, for one cluster may not have an ideal pair of ears in production practice.【Conclusion】The different panicle shaping methods not only affected the quality of the‘Kyoho'grapes, but also exerted a measure of influence over user effectiveness, according to the preliminary evaluation based on the results using the principal components analysis. The remaining secondary ear of the cluster only provided the maximum operating efficiency by the order of the ranking, but it had an unacceptable bunch mass and berry mass performance, which was difficult to get used to in a range of different circumstances, for it can only take place when there was an ideal pair of ears of one cluster. Beyond that, the only optimal panicle of the‘Kyoho'grape was the leaving spikelet tip 5 cm, and it was able to satisfy the actual demand, which may represent the best solution of floral cluster pruning of the‘Kyoho'grape.