Comparative analysis of fruit appearance traits of 18 accessions in pine- apple germplasm

Abstract: 【Objective】Pineapple is one of the most important tropic fruits in China, but lack of desir-able varieties are the key factor that restricts Chinese pineapple industrial development. It is urgent to breed new pineapple varieties with good fruit quality to meet market demand. In this study, fruit appear- ance traits of pineapple accessions were compared in order to determine their variations among germ- plasm resources, and discover the relationship between these traits, which will provide scientific basis for germplasm evaluation, identification and utilization as hybridized parents in pineapple breeding program.【Methods】Eighteen accessions in the pineapple germplasm nursery at the South Subtropical Crops Research Institute, the Chinese Academy of Tropical Agricultural Sciences, were selected. The management levels during the growth period of all pineapple accessions were the same. Nine fruit ap-pearance traits were measured at the fruit ripening stage. Fruit weight, fruit diameter, fruit length, fruit eye depth, fruitlet width, and core diameter were determined by using a vernier calliper, fruitlet weight  were measured by using an electronic balance, the number of fruit eye was counted manually, and fruit shape index was calculated from the ratio of fruit length to fruit diameter. Each accession had 2 repli-cates and 5 individual fruits were set per replicate. Excel 2013 was used to calculate the mean standard deviation and variation coefficient of each trait, and the SPSS 16.0 software was used to perform vari-ance and correlation analysis.【Results】There were significant differences among these 18 pineapple accessions in the 9 fruit appearance traits. Fruit weight varied from 377.44 to 1 992.07 g, and its varia-tion coefficient was 48.62%. Core diameter varied from 11.80 to 36.01 mm, and the variation coeffi-cient was 28.50%. The number of fruit eyes varied from 56.00 to 118.40, and the variation coefficient was 19.71%. The fruit length varied from 98.46 to 193.23 and its variation coefficient was 18.83%. The variation range of fruit diameter was between 84.15 and 156.24 mm, and the variation coefficient was 17.54%. The variation range of fruitlet height was 19.99 to 31.92 mm, and the variation coefficient was 14.23%; fruitlet width varied from 16.26 to 28.72 mm, and the variation coefficient was 16.36%. Fruit eye depth varied from 7.72 to 10.68 and the variation coefficient was 9.83%. Fruit shape index varied from 1.11 to 1.40, and the variation coefficient was 7.04%. Fruit weight had the maximum variation and fruit shape index had the minimum variation in these traits among the 18 accessions. Variation coeffi- cient within accession of each trait was much less than the corresponding variation coefficient among germplasm. Correlation analysis showed that the fruit weight was positively correlated with the fruit di- ameter, fruit length, fruit eye depth, fruitlet width, and core diameter. The fruit eye depth, number of fruit eye, and fruit index were significantly correlated with each other, but not with other traits. Fruitlet height was extremely positively correlated with fruit diameter, fruit length, and core diameter. Fruitlet width was extremely significantly and positively correlated with fruit diameter and fruit length. Core di- ameter was significantly and positively correlated with fruitlet width and fruit diameter. The relation-ship was extremely significantly and positively correlated with the fruit length and fruit diameter. Fruit eye depth and fruit shape index were not correlated with fruit weight, fruit diameter, fruit length, and fruit shape index. The fruit of Black Pineapple was the heaviest, reaching 1 992.07 g, significantly higher than other accessions except Cayenne No.1 and N36. The fruit of Cayenne No.1 was heavier and its variation coefficient was minimum, which indicated its genetic stability. Josapine had the lightest fruit weight, but its core diameter and the eye depth were the minimum, significantly less than other accessions in this study. The fruit index of Malaysia Sarawak was 1.40, the largest one in the 18 accessions,and its fruit depth was of most genetic stability since its variation was the minimum.【Conclusion】Fruit weight, core diameter, number of fruit eye, fruit eye size and fruit diameter were rich in genetic di-versity among pineapple germplasm resources, which can be used in identification on pineapple in the market. Fruit eye depth, number of pineapple fruit eyes, fruit shape index, etc., which determined the utilization rate of pineapple fruit, were all significantly and positively correlated with each other. Fruit eye depth and fruit shape index that determined the processing efficiency of pineapple fruit were not correlated with traits that reflected the size of pineapple fruit, indicating that both traits should be con-sidered simultaneously in breeding program, in order to select individuals that can meet the require- ments in both aspects. That the variations of same traits of different accessions were different showed that different accessions had different genetic stability in these traits. Cayenne No.1, N36, and Malaysia Sarawak had the further development and utilization potential.