Development and application of Key Allele-Specific PCR (KASP) molecular markers for assessing apple fruit crispness

Crispness stands as a pivotal criterion in assessing apple texture, widely cherished by consumers. Yet, owing to its multifaceted nature, crispness remains a formidable challenge in artificial enhancement efforts. To expedite the early and precise evaluation of apple crispness, this study centered on a hybrid population derived from 'Fuji' and 'Pink Lady' cultivars, showcasing segregating crispness traits. We conducted measurements of flesh water content, cellular anatomical morphology, and employed a texture analyzer to assess mechanical properties of the offspring flesh. Integrating these three dimensions, we conducted a comprehensive analysis of quantitative characteristics of apple crispness, juxtaposed with sensory evaluation. Utilizing BSA-seq technology, we scrutinized extreme phenotypic individuals, revealing QTL loci intricately linked to the aforementioned dimensions, and subsequently developed Key Allele-Specific PCR (KASP) markers. These markers underwent validation in hybrid populations of 'Hanfu' x 'Pink Lady' and 'Hanfu' x 'Honey Crisp'. Our findings underscored significant correlations between mechanical properties, water content, and cell size with crispness. Higher mechanical properties and water content, alongside smaller cell size, correlated with firmer flesh texture; moderate mechanical properties, and elevated water content and cell size, with crisper texture; whereas lower mechanical properties, water content, and cell size implied softer flesh.The study yielded KASP markers effectively reflecting flesh mechanical properties (SNP_24399345), water content (SNP_8667563), and cell size (SNP_15566229). Comprehensive analysis of these markers identified CC-CC-TT as an effective identifier of soft flesh individuals; while GG-TC-TT and GG-CC-TT combinations better represented individuals with harder flesh. The Crunchy subclass could be discerned by combinations of GG-TC-TC, GG-TC-CC, GG-TT-TC, and GG-TT-CC. These findings furnish effective molecular markers for the genetic enhancement of apple crispness, bearing significant implications for the cultivation of novel apple varieties.

The online version contains supplementary material available at 10.1007/s11032-024-01509-1.