Variability and heritability studies in floral homeotic mutants of Papaver somniferum L.

Abstract

Papaver somniferum is an important medicinal plant, which also has culinary and ornamental significance. We have earlier reported floral homeotic mutants, Pps-1 and OM, which had partially petaloid sepals and sepaloid petals, respectively and thereby showed differential expression of the MADS box genes, PISTILLATA (Paps PI-1) and APETALA-3-1 (Paps AP3-1), in the first two whorls. Here, we report additional floral characters in the OM mutant like modified third whorl (carpeloid stamen) as well as early flowering and cleistogamy. Real-Time PCR analysis indicated that in both, OM mutant and its parent (I-268), the AGAMOUS homologs (PapsAG-1 and PapsAG-2) believed to be involved in the development and identity of the two innermost whorls had higher transcript abundance in the carpels as compared to the stamens. Interestingly, the abundance of AGAMOUS transcripts was found to be higher in the carpeloid stamens of OM vis-a-vis the normal stamens. Presence of major benzylisoquinoline alkaloids in the carpeloid stamens, unlike that in the normal stamens, indicated functional similarities between the carpeloid stamen and the capsule wall. We also report another spontaneous floral homeotic mutant, PS-1 that is early flowering and shows stamens converted into petal-like structures in the third whorl. Genetic divergence of the three homeotic mutants (Pps-1, OM, PS-1), their respective parents (I-14, I-268, I-311) and 22 other genotypes of P. somniferum was studied on the basis of 14 morpho-metric traits, which grouped them into six clusters. PS-1 exhibited maximum genetic divergence among the homeotic mutants. Additionally, it was concluded that hybrids of parents from cluster II (I-268, I-14, Pps-1) and cluster V (OM) would produce most desirable recombinants. These mutants not only serve as models for better understanding the interplay of MADS box genes in flower morphogenesis but also have the potential to be incorporated in further breeding programs for crop improvement.