A Novel ZmLG1 Allele as a Genetic Resource for Breeding Compact Plant Architecture in Maize

Background: Leaf angle is a key determinant of plant architecture and yield under high-density planting. Loss of the ligule reduces leaf angle, offering a strategy for breeding compact maize. This study aims to identify the genetic basis of the liguleless mutant jd30 and develop a functional marker for breeding. Methods: The jd30 mutant was phenotypically characterized and compared with the wild type (WT). Genetic analysis was performed using F2 populations. Map-based cloning was conducted with simple sequence repeat (SSR) and insertion/deletion (InDel) markers. Candidate genes were annotated and sequenced. Allelism tests were performed by crossing jd30 with other lg1 mutants. A Cleaved Amplified Polymorphic Sequence (CAPS) marker was developed based on the causal mutation. Results: The jd30 mutant showed complete ligule loss from the V2 stage onward and had a significantly smaller leaf angle than the wild type. The phenotype is controlled by a single recessive nuclear gene, mapped to a 123-kb interval on chromosome 2 containing four candidate genes. A single-base cytosine (C) deletion at nucleotide 522 of ZmLG1 caused a frameshift and premature stop codon. Two other lg1 mutants, 20292 and 29163, carried distinct mutations—a C insertion and multiple base substitutions, respectively. Allelism tests confirmed jd30 as a novel allele of ZmLG1. A co-dominant CAPS marker, M5, was developed to distinguish wild-type and mutant alleles. Conclusions: This study identifies a novel loss-of-function allele of ZmLG1, designated ZmLG1-1, and the M5 marker, providing valuable genetic resources for modifying leaf architecture and improving maize plant compactness.