Determination of optimal sampling time of grape embryo rescue based on near infrared spectroscopy combined with...

Grape embryo rescue technology is currently the primary method for breeding new seedless grape cultivars. The timing of berry sampling directly impacts the efficacy of this technique. Therefore, achieving efficient, accurate, and non-destructive determination of the optimal sampling time for seedless grape embryo rescue breeding has long been a challenge. This study collected near-infrared spectral data and data on 19 physiological indicators from 2940 grape berries of six grape cultivars at six sampling times to construct a baseline dataset. Remarkably, it was discovered for the first time that pericarp puncture hardness (PPH) is closely associated with the embryo development rate of seedless grape. Subsequently, the optimal sampling times for 'Flame Seedless', 'Ruby Seedless', and 'Jingzaojing' were determined when their PPH reached 720 ​± ​20 ​g, 990 ​± ​20 ​g and 633 ​± ​20 ​g, respectively. Then, a total of 840 models for PPH recognition were established and assessed based on their coefficient of determination (R ²) and root mean square error (RMSE). The optimal recognition models for three seedless grape cultivars suitable for embryo rescue-'Flame Seedless', 'Ruby Seedless', and 'Jingzaojing'-were identified as follows: D1+PLSR (R ² ​= ​0.94, RMSE ​= ​42.26), D1+MLR (R ² ​= ​0.79, RMSE ​= ​66.31) and D1+PLSR (R ² ​= ​0.93, RMSE ​= ​47.9). Utilizing the established D1+PLSR or D1+MLR models for PPH, a non-destructive and precise method for sampling seedless grapes during embryo rescue was introduced for the first time. This approach led to a notable increase in the embryo development rate by 15 ​% and enhanced the plantlet rate by 14 ​%. Overall, our proposed strategy provides new perspectives for accelerating the breeding process of new seedless grape cultivars.