Validation of Molecular Markers Genetically Linked to S-Cytoplasm and Restoration-of-fertility (Rf) Loci in Hot Pepper (Capsicum annuum L.)

Existence of CGMS system in hot pepper is due to the rearrangements in the mitochondrial genome and is largely used in economized and pure F 1 hybrid seed production around the world. The orf456, a new ORF present at flanking region of the coxII gene at the 3’ end, was distinguished male sterile cytoplasm in hot peppers along with atp6-2gene. In the current study, eighteen pepper genotypes (nine each of A and corresponding B lines) of varied origin were used to validate with two male sterile cytoplasm (S-cytoplasm) specific sequence characterised amplified region (SCAR) markers viz., atp6-2 (875 bp) and orf456 (456 bp) and one restoration-of-fertility (Rf) locus specific marker, CRF (550 bp). The results clearly showed that the presence of CMS-S-cytoplasm and absence of restoration-of-fertility (Rf) gene in the pepper genotypes studied and is comparable with the phenotypic data. In view of the outcomes it has been reasoned that the accessible S and Rf markers available in the public domain are reproducible and can be promptly utilized for marker assisted selection (MAS) in hot pepper crop improvement program.

Advancement in CMS Based Hybrid Development in Cauliflower (Brassica oleracea var. Botrytis)

Among the different mechanism of male sterility operated in the Brassica group crop. Cytoplasmic male sterility mechanism is most suitable for hybrid development in cauliflower because here the curd (intermediate stage) is an edible part of the cauliflower. Further, there is no requirement of restorer line in this case as required in other seed crop. For the multiplication and maintenance of the different lines (A line and B line), sib mating and selfing is not always desirable. In fact, in such situation doubled haploid production through microspore culture is a more appropriate mechanism. Apart from this, the undesirable effect of integration of male sterile cytoplasm can be mitigated by adopting the repeated back crossing, through chloroplast substitution or somatic hybridization mechanism.

Genetic Resources for Fertility Restoration Lines and Maintainers of Capsicum annuum L.

Male fertility reactions of one hundred and forty-one accessions of chilies were classified. Three groups were found. Some accessions maintained male sterility and were determined to carry a non-sterile cytoplasm and to lack fertility restoration genes or N rfrf genotype. Some accessions segregated for the ability to restore male sterile cytoplasm and were determined to be heterozygous in restorer genes with genotype N/SRfrf. Some accessions restored fertility of CMS and had the genotype N/SRfRf. A few maintainers with good horticultural characteristics were selected. They were selfed and selected for a few generations and then their progeny were evaluated. There were differences in the genetic stability of cytoplasmic male-sterility among the selected lines. Some lines were good maintainers, but a few lines were discarded. The stable maintainers were distributed to 10 seed companies and the government of China. Some F1 hybrid chilies produced using these lines have been commercially sold both in China and Thailand. Fruit physio-chemical qualities of maintainer accessions, restorers and heterozygous accessions were also recorded. The level of capsaicin of the accessions varied from 3,250 to 8,850 Scoville units. The level of vitamin C showed a range of 4.43 to 103.16 mg./100g.fw. Horticultural characteristics of the accessions were recorded and the fruit physio-chemical qualities of the accessions were reported.

PCR identification of Petunia male sterile cytoplasm

Petunia is a very important ornamental plant with a broad range of flower colour and size, and most of the cultivars grown are propagated through seeds. Cytoplasmic male sterility (CMS) is a maternally inherited character determined by mitochondrial genes that results in impaired pollen development. The unique and well characterized male sterile cytoplasm in Petunia is a valuable resource for hybrids production because it prevents self-fertilization of mother plants and ensures the purity of F1s. Introgression of the male sterile cytoplasm in elite lines of Petunia is achieved following a backcross scheme and can be assisted using molecular markers associated to the trait of interest. The objective of this study was to develop a molecular marker to identify the male sterile cytoplasm of Petunia. A PCR-based marker amplifying a region of the mitochondrial CMS-associated urfS only in the male sterile plants was designed. Results showed differential PCR amplification of a ≈ 600 bp product in plants carrying male sterile cytoplasm in four Petunia species and their F1s and BC1 generations. A multiplex PCR reaction was subsequently set up, adding specific primers amplifying a ≈ 800 bp product from the conserved region trnT-trn-L of the chloroplast genome as a positive control in order to unambiguously identify the cytoplasm types as normal or sterile. A rapid, simple and precise molecular marker is now available for assisting breeding of F1 hybrids in Petunia.

A novel source of cytoplasmic male sterility in Calibrachoa pubescens

Calibrachoa pubescens is a species native from the south of Brazil, Uruguay and northeast Argentina. An accession identified as 7.3.1.1 was collected at San Martín Department in Corrientes Province, Argentina and is included in the calibrachoa breeding program at the Institute of Floriculture, INTA. This accession is male sterile and produces male-sterile progeny, characterized by the lack of pollen production. Male sterility may be controlled by nuclear or cytoplasmic genes with each type presenting a different mode of inheritance. The objective of this research was to present a novel source of cytoplasmic male sterility in Calibrachoa pubescens. Crosses were made in the greenhouse between the male-sterile line 7.3.1.1 as the female parent and seven male-fertile lines of diverse origin. F1s were backcrossed and self-pollinated. Individual plants of the progenies were classified as male-fertile or male-sterile according to pollen viability. Analyses of observed segregations showed that male sterility observed in 7.3.1.1 results from the interaction of a male sterile cytoplasm and nuclear restorer genes. A novel male sterile cytoplasm is now available for breeders. Main advantages of cytoplasmic male sterility in ornamentals breeding are: efficient hybrid production, increased flower longevity, avoidance of pollen allergens and control of plant invasiveness.