Evaluation of grape genotypes for seedlessness and other agronomic traits as expressed under subtropical conditions for their potential role as donor parents

Abstract

Abstract The present investigation was conducted from 2021 to 2022 in subtropical north India under New Delhi conditions by evaluating 12 grape accessions to assess the phenotypic and genetic variability across various horticultural traits. Notably, the genotypes exhibited significant variations in bunch weight, size, density, and berry traits, such as weight, shape, and seed presence. Seedless grapes, in particular, demonstrated superior bunch weight and size, with bunch weight ranging from 94.10 g (genotype Pearl of Csaba) to 325.67 g (genotype Perlette) and substantial variations in bunch size, too. For berry characteristics, the range extended from 1.37 g (genotype Beauty Seedles) to 3.57 g (genotype Pusa Aditi), with seeded genotypes displaying the largest berries. Physio-chemical analysis indicated that seedless grapes typically had higher total soluble solids (TSS) and acidity, although exceptions existed among the individual genotypes. The new hybrid genotype Pusa Purple Seedless exhibited the highest TSS (19.96 0B), while Beauty seedless had the lowest TSS (16.08 0B), with significant variations in pulp acidity and juice percentage across the genotypes. Based on seed or seed trace fresh weight anaysis, progenies were classified into four classes: completely seedless, semi-seedless, semi-seeded, and completely seeded. These categories were defined by the number of seed remnants per berry (ranging from 0.03 to 2.25), dry matter percentage (ranging from 30.82 to 60.53%), and average fresh seed trace weights (13.10, to 45.40 mg). Additionally, phenotypic and genetic correlations demonstrated positive associations between berry and seed traits with correlation coefficients ranging from r = 0.67 to 0.93 for specific traits. However, some negative correlations (r = -0.21 to -0.90) between berry and bunch size, TSS, Titratable acidity, and juice content were observed with certain traits. Principal Component Analysis identified key traits contributing to genetic diversity, which can be a valuable for seedless breeding programs in sub-tropical regions of India.