Phenological growth phases of dwarf apple trees: coding and description based on the BBCH scale.

Abstract

Background The BBCH scale (Biologische Bundesanstalt, Bundessortenamt und Chemieindustrie) is a fundamental tool for standardizing plant phenological observations. As apple production shifts towards high-density dwarf orchard systems to enhance yield and facilitate mechanization, a significant gap exists in a unified phenological description framework for dwarfing rootstock apple trees, particularly under desert climate conditions. This study aims to systematically characterize the phenological growth stages of dwarf-rootstock apple using an extended BBCH scale to support precision orchard management. Result In our study, phenological monitoring was carried out systematically through the utilization of optical observation equipment and manual observations throughout the entire growth cycles. The extended BBCH scale with a three-digit coding system was applied, where the first digit indicates the principal growth stage (0-9), the second digit represents a mesostage (1 for spring, 2 for autumn growth), and the third digit describes secondary stages (0-9). We described and illustrated eight main growth stages: bud development (stage 0), leaf development (stage 1), shoot development (stage 3), inflorescence emergence (stage 5), flowering (stage 6), fruit development (stage 7), fruit ripening period (stage 8), and senescence and beginning of dormancy (stage 9). A total of 43 secondary stages were defined. Crucially, mesostages were introduced to differentiate the distinct spring and autumn vegetative growth flushes characteristic of the bimodal growth pattern observed under desert conditions. Conclusions The developed three-digit BBCH scale offers a standardized and refined framework for monitoring apple phenology in high-density dwarf orchards. It serves as a vital tool for optimizing the timing of key agronomic practices like irrigation, fertilization, pruning, and pest control, thereby supporting the intelligent implementation of precision agriculture. This framework effectively standardizes phenological observations across diverse environments, laying a foundation for improved yield, fruit quality, and sustainable orchard management.

Plant phenotyping relevance

リンゴの生育段階を標準化・細分類するBBCHスケールを開発し、光学観察と手動観察によるフェノロジー取得を中心的に扱っているため、植物フェノタイピング手法として含める。

Code and data availability

The paper describes phenological monitoring of dwarf apple trees using optical observation equipment, photographs, and caliper measurements, but no public repository deposit, code release, or dataset URL is provided. The only availability statement is an on-request clause, so any underlying phenotype data, images, or视频

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