In the present investigation, F1 hybrids were developed in guava (Psidium guajava L.) by crossing high leaf-anthocyanin reflective-index (ARI1) content cultivars purple guava (local) ‘PG’, ‘CISH G-1’ and low leaf-ARI1 content cultivar Seedless ‘SL’ with Allahabad Safeda ‘AS’. On the basis of phenotypic observations, high ARI1 content was observed in the cross ‘AS’ × ‘PG’ (0.214). Further, an SSR-markers-based genetic linkage map was developed from a mapping population of 238 F1 individuals derived from cross ‘AS’ × ‘PG’. The linkage map comprised 11 linkage groups (LGs), spanning 1601.7 cM with an average marker interval distance of 29.61 cM between adjacent markers. Five anthocyanin-content related gene-specific markers from apple were tested for parental polymorphism in the genotypes ‘AS’ and ‘PG’. Subsequently, a marker, viz., ‘MdMYB10F1′, revealed a strong association with leaf anthocyanin content in the guava mapping population. QTL (qARI-6-1) on LG6 explains much of the variation (PVE = 11.51% with LOD = 4.67) in levels of leaf anthocyanin colouration. This is the first report of amplification/utilization of apple anthocyanin-related genes in guava. The genotypic data generated from the genetic map can be further exploited in future for the enrichment of linkage maps and for identification of complex quantitative trait loci (QTLs) governing economically important fruit quality traits in guava.

In the present investigation, seeds of guava cv. ‘Lalit' and ‘Shweta' were irradiated with different dosages of gamma rays ranging from 25 to 150 Gy using the ⁶⁰Co source to examine its effects on morphological and physiological traits. The LD₅₀ value calculated on the basis of germination percentage of irradiated seedlings using probit curve analysis, was 57.81 Gy and 57.42 Gy for ‘Lalit' and ‘Shweta', respectively. Seed germination and growth parameters viz., plant height, internode number, internodal length and leaf dimensions had negative correlation with gamma irradiation., while the parameters, number of leaves and branches experienced the hormetics radiostimulant effect at lower dosage (up to 50 Gy), but a marginal reduction was observed at higher dosages (125–150 Gy). Reduction in stomatal number with increased stomatal size were observed in the mutant populations. With ascending irradiation doses, a marginal signifcant reduction was observed in leaf chlorophyll content. The results of this study will allow implementation of mutagenesis-based genetic improvement programmes in guava and, serve as a morphological and physiological marker to identify some desirable mutants at early stage.