A study on the flowering characteristics and fruit growth models of Guiengzao longan

Abstract:【Objective】To provide theoretical basis for formulating high-yield and high-quality cultiva-tion and management measures, the flowering characteristics and fruit growth mathematical models of Guifengzao, a new line of longan were studied. Guifengzao was an excellent mutant strain with early maturity, high TSS, high edible rate and other excellent characteristics. The development patterns of re-productive organs were closely related to the yield formation. The dynamic models of fruit growth and development were established by using linear, quadratic, cubic and Logistic equations, which could be used as the evaluation and prediction method of important indicators such as fruit growth and yield.【Methods】From April 3 to 27, 2019, the number of male and female flowers was counted every day.From April 27, 2019 [0 days after flowering (DAF)] to August 17, 2019 (110 DAF), the change patterns  of fruit transverse and longitudinal diameters were traced using an electronic vernier caliper every 10 days. From July 1, 2019 (64 DAF) to August 22, 2019 (116 DAF), the single fruit weight, peel weight, peel thickness, kernel weight, flesh weight, edible rate and soluble solids (TSS) were mea-sured every 5 or 7 days. The weights of single fruit, peel and kernel were measured with an electronic scale. The peel thickness at fruit equator was obtained with an electronic vernier caliper. The fleshweight was calculated by subtracting peel and kernel weight from single fruit weight. The edible rate was the ratio of flesh weight to single fruit weight. Four equations were used to fit the above 10 growth indexes, including transverse diameter, longitudinal diameter, fruit shape index, single fruit weight, peel weight, peel thickness, kernel weight, flesh weight, edible rate and TSS. The dynamic change pattern of fruit growth and development was established with the regressed equations of growth indexes against DAF and the derivative equation displayed change pattern of the growth rate(g). Meanwhile, the linear and partial correlation analyses were carried out among the 10 fruit growth indexes. The SPSS 21.0 software was used to analyze the data.【Results】The flowering period of Guifengzao in Nanning was about 24 days. The male flowers bloomed first and the number of blooming female flowers reached a peak 12 days after initial blooming. The ratio of male to female flowers was 2∶1. The changes in longitudinal diameter (y2), single fruit weight (y4), flesh weight (y8), edible rate (y9) and TSS (y10) were fitted well with quadratic equations (y2=-0.001x2+0.285x+3.094,y4=- 0.002x2 + 0.445x- 17.962,y8=- 0.002x2 + 0.399x- 17.953,y9=- 0.02x2 + 4.182x- 151.845 andy10=-0.012x 2+2.380x-94.493, respectively). The changes in fruit transverse diameter (y1), fruit shapeindex (y3) and peel thickness(y6) could be fitted to cubic equations (y1=- 2.405 × 10- 5x3 + 0.003x2 +0.146x+2.067, y3=7.822×10-7x3-5.878×10-5x2-0.009x +1.542, and y6=6.551×10-7x3-0.019x+1.610, re-spectively). Peel weight (y5) and kernel weight (y7) fitted well with Logistic equation [y5=2.75/(1+11.80e-0.024x) and y7=1.94/(1+1.70e-0.031x), respectively]. After flower falling and fruit setting, the trans-verse diameter, longitudinal diameter, single fruit weight, peel weight, kernel weight, flesh weight and edible rate of Guifengzao showed“S”or near“S”growth pattern, while fruit shape index and peel thickness showed an inverse“S”pattern. TSS increased first and then decreased. The fruit diam-eter and peel weight increased rapidly until 41 DAF and 99 DAF, respectively. The inflection points of fruit shape index occurred at 25 DAF, after which fruit gradually changed from oval shape to near-ly round shape. The fruit longitudinal diameter, single fruit weight, kernel weight, flesh weight and edible rate grew slowly, and the single fruit weight, flesh weight and edible rate gradually increased until 111 DAF, 99 DAF and 104 DAF, respectively. The peel thickness was lowest from 85 DAF to 99 DAF, and gradually increased after 99 DAF. TSS gradually increased till 85 DAF and then gradu-ally decreased, reaching >18% from 85 DAF to 106 DAF. The highest value was at 92 DAF, and the inflection point occurred at 99 DAF. Correlation analysis showed that there was significant correla- tion between the other indexes except peel thickness.【Conclusion】In Nanning, the male and female flowers of Guifengzao bloomed in order; the pollen source for the female flowers was sufficient. In the process of fruit development and maturity, quadratic equation could accurately describe the growth of fruit longitudinal diameter, single fruit weight, flesh weight, edible rate and TSS; cubic equation could accurately describe the growth of fruit transverse diameter, fruit shape index, and peel thickness; and Logistic equation could accurately describe the growth of peel weight and kernel weight.