Recessive loci Pps-1 and OM differentially regulate PISTILLATA-1 and APETALA3-1 expression for sepal and petal development in Papaver somniferum.

The involvement of PISTILLATA (PI) and APETALA (AP) transcription factors in the development of floral organs has previously been elucidated but little is known about their upstream regulation. In this investigation, two novel mutants generated in Papaver somniferum were analyzed--one with partially petaloid sepals and another having sepaloid petals. Progeny from reciprocal crosses of respective mutant parent genotypes showed a good fit to the monogenic Mendelian inheritance model, indicating that the mutant traits are likely controlled by the single, recessive nuclear genes named "Pps-1" and "OM" in the partially petaloid sepal and sepaloid petal phenotypes, respectively. Both paralogs of PISTILLATA (PapsPI-1 and PapsPI-3) were obtained from the sepals and petals of P. somniferum. Ectopic expression of PapsPI-1 in tobacco resulted in a partially petaloid sepal phenotype at a low frequency. Upregulation of PapsPI-1 and PapsAP3-1 in the petal and the petal part of partially petaloid sepal mutant and down-regulation of the same in sepaloid petal mutant indicates a differential pattern of regulation for flowering-related genes in various whorls. Similarly, it was found that the recessive mutation OM in sepaloid petal mutant downregulates PapsPI-1 and PapsAP3-1 transcripts. The recessive nature of the mutations was confirmed by the segregation ratios obtained in this analysis.

AFLP studies on downy-mildew-resistant and downy-mildew-susceptible genotypes of opium poppy.

Downy mildew (DM) caused by Peronospora arborescens, is a serious disease in opium poppy (Papaver somniferum), which has a world-wide spread. The establishment of DM-resistant cultivars appears to be a sustainable way to control the In this paper, we present the results of a study aimed at the identification of amplified fragment length polymorphism (AFLP) markers for DM-resistance in opium poppy. Three opium poppy genotypes (inbred over about 10 years): Pps-1 (DM-resistant), Jawahar-16 (DM-susceptible) and H-9 (DM-susceptible) were crossed in a diallel manner and the F(1) progeny along with the parents were subjected to AFLP analysis of chloroplast (cp) and nuclear DNA with seven and nine EcoRI / MseI primer combinations, respectively. cpDNA AFLP analysis identified 24 Pps-1 (DM-resistant)-specific unique fragments that were found to be maternally inherited in both the crosses, Pps-1 x Jawahar-16 and Pps-1 x H-9. In the case of nuclear DNA AFLP analysis, it was found that 17 fragments inherited from Pps-1 were common to the reciprocal crosses of both (i) Pps-1 and Jawahar-16 as well as (ii) Pps-1 and H-9. This is the first molecular investigation on the identification of polymorphism between DM-resistant and DM-susceptible opium poppy genotypes and development of DM-resistant opium poppy genotypespecific AFLP markers. These AFLP markers could be used in future genetic studies for analysis of linkage to the downy mildew resistance trait.

Genetic variation revealed in the chloroplast-encoded RNA polymerase beta' subunit of downy mildew-resistant genotype of opium poppy.

Two accessions of opium poppy, Pps-1 (dark green leaves, highly resistant to downy mildew [DM]) and H-9 (yellowish green leaves, susceptible to DM), which originated from common progenitor SPS49 were selected, and their F(1) and F(2) progenies showed that leaf color trait was governed by single recessive nuclear gene, whereas DM resistance appeared to be the interaction between cytoplasmic and nuclear genes. Chloroplast DNA (cpDNA) analysis of these 2 accessions through arbitrarily-primed polymerase chain reaction generated a unique fragment in Pps-1. Subsequent sequence analysis upon cloning of this cpDNA fragment revealed its similarity with the plastid-encoded RNA polymerase beta' subunit (rpoCI). Full-length rpoCI DNA was therefore isolated from both the genotypes that was 2707 bp long with a 658-bp intron (436-1093) and a 2049-bp open reading frame encoding 682 amino acid long polypeptide. Comparative sequence analysis of the rpoC1 gene from both the genotypes, revealed 4 single-nucleotide substitutions at 4 positions that caused 3 amino acid changes in the protein sequence--1) A to C transversion at position 825 (Glu275Asp), 2) A to G transition at position 1203 (Ile401Met), and 3) T to C transition at position 1422 and G to A transition at position 1423 both in same codon of the reading frame (Ala475Thr). This investigation is the first report indicating base substitution changes in the plastid-encoded rpoCI gene in DM-resistant genotypes of opium poppy. This finding may lead to implication of possible role of RNA polymerase beta' subunit in resistance to DM caused by Peronospora arborescens.

Genetic parameters and correlations of collar rot resistance with important biochemical and yield traits in opium poppy (Papaver somniferum L.).

Collar rot, caused by Rhizoctonia solani Kühn, is one of the most severe fungal diseases of opium poppy. In this study, heritability, genetic advance and correlation for 10 agronomic, 1 physiological, 3 biochemical and 1 chemical traits with disease severity index (DSI) for collar rot were assessed in 35 accessions of opium poppy. Most of the economically important characters, like seed and capsule straw yield per plant, oil and protein content of seeds, peroxidase activity in leaves, morphine content of capsule straw and DSI for collar rot showed high heritability as well as genetic advance. Highly significant negative correlation between DSI and seed yield clearly shows that as the disease progresses in plants, seed yield declines, chiefly due to premature death of infected plants as well as low seed and capsule setting in the survived population of susceptible plants. Similarly, a highly significant negative correlation between peroxidase activity and DSI indicated that marker-assisted selection of disease-resistant plants based on high peroxidase activity would be effective and survived susceptible plants could be removed from the population to stop further spread.