Construction of An EMS-Induced Garlic Mutant Library and Evaluation of Major Agronomic Traits

This study conducted chemical induction breeding experiments using EMS to overcome the bottleneck in germplasm improvement caused by the asexual reproduction of garlic. The results provide valuable support for the genetic mapping, functional analysis and molecular breeding of garlic bolting traits, and form the basis for selecting parents in garlic induction breeding.

In this study, two widely cultivated, early-maturing garlic varieties, ESZ and ZYZ, were selected as mutagenic materials. These materials were treated using ethyl methanesulfonate (EMS) chemical mutagenesis technology to systematically construct a library of early-bolting garlic EMS mutants. Field surveys were conducted at fixed locations for two consecutive years on the second-generation (M₂) and third-generation (M₃) clonal plants of the mutagenised population under standardised field cultivation and management conditions. 11 core agronomic traits were measured, including pseudostem height, pseudostem diameter, leaf length, leaf width, number of leaves, flower stem length, flower bud length, flower stem diameter, flower stem weight, bulb weight and bulb diameter. Statistical analysis of the coefficients of variation for each trait, population variation characteristics and inter-annual trait differences was used to systematically investigate the patterns of trait variation, genetic segregation characteristics and inter-annual genetic stability of the EMS-induced population. Combining trait variation advantages and genetic stability, directed screening was conducted to identify superior mutant materials with high yield potential, improved maturity and special breeding value.

EMS mutagenesis effectively induced extensive phenotypic variation in garlic. The coefficients of variation for yield-related traits-such as pseudostem height, single scape weight, and bulb weight-all exceeded 25%, indicating high-frequency variation. The coefficients of variation for conservative morphological traits, such as the number of leaves and bulb diameter, were below 15%, indicating greater genetic stability. The mutant library as a whole exhibited predominantly negative variation, and the population stability of traits related to M₃-generation plants, scapes, and bulbs was significantly improved compared to the M₂ generation. Regarding quality traits, 7 early-bolting and 12 late-bolting stable genetic mutants were selected, and unique mutants such as ESZ046 (yellowing due to lack of cutin on leaves) and ZYZ053 (folded cotyledons) were also obtained. Annual trait correlations indicated that ZYZ exhibited overall superior genetic stability compared to ESZ. Pseudostem height, single scape weight, and bulb weight were identified as traits with mutagenic instability, while bulb diameter was the trait with the highest stability. Key mutagenic mutants were predominantly concentrated in yield-related traits, with a higher proportion of deleterious mutations. ZYZ demonstrated greater tolerance to EMS mutagenesis, making it easier to obtain superior mutants.

This study confirms that EMS mutagenesis can induce significant variation in agronomic traits in early-maturing garlic, and that different traits respond distinctly to EMS mutagenesis. Genetically stable mutants were obtained by continuously identifying and screening M₂ and M₃ generation populations.