Caracterização fenotípica da cor da epiderme de maçãs e expressão de genes relacionados à formação da coloração vermelha

Abstract

Apples are fruit of high economic importance, being the third most produced fruit in the world. Although there are apples with different shades on the skin ranging from red, yellow and green. In general, the redder the apple, the greater the commercial appeal and the more attractive it is to the consumer. Thus, one of the main focuses of apple breeding is the development of cultivars that produce apples with the greatest possible red coverage. In addition to this phenotypic characteristic, other characteristics sought by the apple breeders are genotype stability, disease resistance and fruit quality. The general objectives of the present work were to evaluate the colorimetric parameters related to red color, the total anthocyanins content and the expression of the anthocyanin’s pathway genes in the apple's skin during different stages of fruit development of the cultivars Fuji Mishima, Fuji Suprema and Galaxy, under different growing conditions. Apples of the Fuji Mishima and Fuji Suprema cultivars, grown in the municipalities of Caçador-SC and São Joaquim-SC, were evaluated during seven stages of fruit development (starting with fruits of approximately 21 mm until the ideal ripening point for harvesting). Galaxy apples were evaluated during two production cycles (2017/2018 and 2018/2019) over five harvest points (same as 'Fuji' apples), and the effect of cultivation under yellow, pearl and black hail nets was compared, in addition to cultivation without nets. The colorimetric parameters related to the red color (L*, a* and ºh), the total anthocyanins content and the expression of the genes MdCHS, MdCHI, MdDFR and MdLDOX in the apple skin, were evaluated separately from the sun-exposed side of the fruit and on the shaded side. Considering the Fuji sports, Fuji Suprema produced redder apples than Fuji Mishima in both regions, also presenting a higher anthocyanins content. Throughout the harvest points, there was a progressive accumulation of color and anthocyanins in Fuji Mishima apples, and in Fuji Suprema apples there were no changes from the second harvest. As for gene expression, there were no substantial differences in expression between cultivars or between regions. In this way, the cultivation of 'Fuji Suprema' is the most suitable for both regions, aiming at the production of fruits with greater red color and, consequently, reflecting in the greater commercial value of the product. In the evaluation of Galaxy apples produced under yellow, pearl and black anti-hail nets and apples produced in full sun, there was no difference in color, anthocyanin content and gene expression in the skin of fruits produced in different types of coverage, so the best cost/lifespan ratio can be prioritized when choosing the hail net color, since the protection of the orchards is extremely important to avoid damage from hail events. The studies carried out generated useful information for further work aimed at improving the color of apples.