Flowering Study and Effect of Various Hand Pollination Methods on Fertility of Some Iranian Native Salvia Species

Document Type : Research Article

Authors

Ferdowsi University of Mashhad

Abstract

Introduction: The genus Salvia L. (Lamiaceae) is one of the most interesting plant genera with a variety of annual, biennial, perennial and shrub forms. According to recent reports, there are 61 species of Salvia genus in Iran, among which 18 species are endemic. The use of Salvia species dates back to ancient times, and they are now being used for different purposes such as antimicrobial, anthelmintic, anti-inflammatory, tonic, carminative, digestive, Alzheimer’s disease, antispasmodic as well as for traditional medicines and food industries. Compared to crop plants, the breeding programs of medicinal plants are still in nascent stages due to high biological and biochemical variations. Since breeding programs, especially in medicinal plants, are expensive, suitable mating can help reduce the costs of breeding programs. Understanding the flowering biology, reproductive systems and pollination mechanism is essential to management and protection of ecosystems and mating programs. Despite the high diversity of Salvia genus in Iran, there is a paucity of studies on reproductive biology.

Materials and methods: seeds of seven Salvia species including S. virgata (with four accessions), S. frigida, S. nemorosa, S. atropatana, S. macrosiphon, S. sclarea, and S. syriaca were collected from different geographical regions. The seeds were treated by various methods such as washing, cold treatment (stratification), scarification (sand and sulfuric acid), Gibberellic acid (GA3) and KNO3 to enhance germination. The seedlings were produced at the greenhouse and after growing as high as 15 cm or reaching the10-leaf stage, the seedlings were transferred to the farm. Plants phenology and flowering duration were recorded in the second year. Furthermore, some flower characteristics and pollinator were monitored. The Various pollination treatments were designed to investigate the breeding system of Salvia species including open pollination, spontaneous autogamy, geitonogamy, xenogamy, apomixis, and control. The self-incompatibility index (ISI) was calculated for each species in different pollination treatment.

Results and discussion: The germination study exhibited that washing seeds for 24 h and applying 250 ppm GA3 exerted the highest effect on seed germination. The seedlings in early growth stages required medium to high porosity (high permeability to water and air) like natural habitat, but they were sensitive to dry and high EC at these stages. The phenology studies were shown Salvia virgata (all accessions) and S. nemorosa flowered three months after cultivation and other species flowered in the second year. The results showed that all species had long flowering periods ranging from 15 (S. atropatana) to 41 days (S. virgata).  Increased flowering period led to the enhancement of flower over-lapping and the sharing of the pollen among different plants or species. Two species including S. atropatana and S. syriaca had heterostyly flowers (long-styled morph). The staminal-lever-mechanism was observed in all species. The results of manual pollination indicated that open pollination provided the best treatment with the highest average of seed set (73.63%) in all species. Salvia virgata (A1) with a seed set of 90.3% was the best species, and S. syriaca with a seed set of 51.5% demonstrated the poorest performance in open pollination system. The seed set in the xenogamy treatment of different species and accessions was in the range of 10.2 (S. syriaca) to 32.5% (S. frigida). It was observed that seed set among different species in geitonogamy and spontaneous autogamy varied widely from 2.60 - 17.30% and 2.98 - 12.18%, respectively. In treatments with a wide variety of pollen sources, the fruit set was higher, indicating that the pollen limitation triggered low seed set.

Conclusion: Salvia species in the present study have a high potential for cultivation as medicinal and ornamental due to suitable adaptability and long flowering period. Salvia species were relatively self-incompatible that intention to the out-crossing and breeders can use in breeding programs as a valuable characteristic. The self-incompatible and specific structure in flower and pollination are the reasons for the diversity of this taxa.

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Articles in Press, Accepted Manuscript
Available Online from 10 March 2021
  • Receive Date: 14 May 2019
  • Revise Date: 15 February 2023
  • Accept Date: 10 March 2021
  • First Publish Date: 10 March 2021