Positional mapping - constitutive purple trait locus (pl) in guava (Psidium guajava L.) in F2 and BC1F1 populations of Purple Local × Allahabad Safeda.

Abstract

Guava (Psidium guajava L.) is a popular fruit crop in Southeast Asia. Landrace Purple Local (PL), also known as Malaysian guava, is rich in anthocyanin content in all the plant parts but has poor yield. Genetic inheritance and physical location of the allele(s) controlling the constitutive purple trait in guava have not yet been reported. The F₁ plants generated by cross hybridizing PL × green cv. Allahabad Safeda (AS) and analysed for 7 years did not exhibit purple trait. Evaluation of F₁, F₂ and BC₁F₁ populations derived from the cross between PL x AS revealed that purple color is a recessive trait in guava. Equally spaced (~10 Mb) co-dominant polymorphic markers developed by in silico analysis of AS and PL genome (mapped to AS genome assembly) into PCR-based assay mapped the purple color locus (pl) on pseudochromosome 11 (PC 11) of guava genome. Further mapping on PC 11 identified 2 InDel markers at 2.49 Mb (Pg11_INDL_2.49 M) and 4.99 Mb (Pg11_INDL_4.99 M) closely associated with pl. Also, QTLseqr for purple and non-purple bulks in F₂ provided two co-localized significant peak ΔSNP-indices at positions 2489072 and 4978573 on PC 11. The mapped genomic interval harbours 85 coding genes, including the potential candidates MYB-like ETC1, anthocyanidin reductase, MYB41-like transcription factors and F-box protein SKIP27-like. Markers flanking pl would potentiate the marker-assisted introgression of anthocyanin trait in popular cultivars of guava.