Breeding and Seed Production of Ornamental Crops (2+1)

Hybrid Seed production

Methods of making a Cross Hybrid seed production can be achieved by:

1. Hand emasculation and hand pollination.
2. Hand emasculation and natural pollination.
3. Hand elimination of male plants.
4. Genetic male sterility as in marigold and zinnia, ageratum and calceolaria.
5. Cytoplasmic male sterility as in petunia.
6. Self incompatibility as in petunia, pansy, stocks and ornamental kale.
7. Chemical emasculation- selective elimination of pollen production, that is, use of gameticides.
8. Use of marker genes to identify the selfs so that they can be eliminated as seedlings.

 

Need for hybrids Seed Production in Ornamental Crops

• The shapes, forms and colours of present day ornamentals differ from those of their ancestors on account of man’s intervention.
• Progress in producing ornamentals of new types and forms has accelerated largely due to need for higher yields, novelty and disease resistance.
• Every year about 10,000 new varieties of ornamental crops are being released.
• Novelty and the quest for new varieties has remained the aim of flower breeding since years.
• All the present day cultivars and the novelties are the result of extensive hybridization, spontaneous and induced mutation, selection and molecular breeding. Since in flowers a specimen cannot maintain interest for a long time, people have desire to develop new forms through various methods of breeding.
• Presently, many peculiar shades and forms like dwarf hollyhocks, dwarf delphiniums; red and white marigolds, etc. are available in seasonal flowers.
• The possibilities for creating different forms and improving ornamentals are infinite.

Mode of reproduction:

• Based on the mode of reproduction, the ornamentals are broadly divided into two groups, viz. sexually propagated and asexually propagated.
• Sexual cycle utilizes seed propagation as a means of producing offspring plants whose characters reflect the genetic contributions of the two parents.
• Reproduction by seeds results in certain amount of variation among the progeny. Improvement of sexual forms takes a number of generations. During this period, the best types are selected from segregating material.
• Among ornamentals, seasonal flowers are propagated by seeds whenever genetic improvement of a particular plant is done through hybridization.

Breeding System:

• In seasonal flowers, breeding system fall into two groups, viz. self-pollinated (inbreeding types) and cross-pollinated (outbreeding types).
• Many species have an intermediate type of breeding system with varying proportions of crossing and selfing. They are grouped in the following breeding systems.

Inbreeders:

• Obligate inbreeders are rarely cross-pollinated.
• Highly self-pollinated. Seed propagated herbaceous annual flowers include China aster, balsam, sweet pea, lupin, clianthus, gypsophilla, bells of Ireland, salvia, saponaria, sweet William and dianthus. In these flowers, there is negligible cross-pollination in nature.

Outbreeders:

• Obligate outbreeders are cross-pollinated because of the presence of a built in system preventing self-pollination.
• The group of outbreeding seed propagated herbaceous annuals and biennial flowers include ageratum, hollyhock, arctotis, cornflower, antirrhinum, delphinium, verbena, calendula, cosmos, gazania, poppy, marigold, zinnia, primula, pansy and viola.
• Self incompatibility occurs in ageratum, gerbera, daisy, petunia and antirrhinum.
• In primula, self sterility is due to heterostyly i.e. pin and thrum type of flowers
• Cytoplasmic male sterility has been reported in petunia, ageratum and sunflower.
• Monogenic recessive factor for male-sterilty exists in marigold, zinnia, calceolaria and salvia.

Breeding Objectives in annual flower Crops:

• In ornamentals, floral quality is the major consideration for evaluation of a particular genotype.
• In commercial seasonal flowers, besides quality, total flower yield is also an important criterion for genetic improvement as is in china aster, marigold and antirrhinum,
• All the varieties do not behave in a similar manner in all the agroclimatic conditions, therefore, breeding suitable varieties for various climatic zones is necessary.
• In India, F₁ hybrid varieties in view of their superiority over open pollinated varieties have a great potential.
• Since ornamentals are affected by a number of diseases and pests, breeders should consider this aspect also while breeding for different parameters.
• Varieties resistant to abiotic stresses need to be bred in commercially viable crops.
• Transgenics can be utilized for production of transgenics in flowering plants, viz. for blue colour in rose, yellow colour in sweet peas, disease resistance in various flower crops, etc.
• Genetic improvement in ornamentals has been done through introduction of important germplasm from other countries.
• The germplasm is evaluated and some introductions are directly recommended for cultivation, which are called primary introductions, whereas others, utilized in breeding programmes, are called secondary introductions.
• Besides introduction, other methods of improvement are hybridization, mutation breeding, polyploidy breeding, heterosis breeding and biotechnology.

Institutes involved in development of varieties in India:

• The management of genetic resources of ornamental plants with an emphasis on their genetic improvement was started at Indian Agriculture Institute (IARI), New Delhi, during 1950s under the leadership of Late Dr. B. P. Pal.
• Other institutes like National Botanical Research Institute (NBRI), Lucknow; Indian Institute of Horticultural Research (IIHR), Bangalore and Bhabha Atomic Research Centre (BARC), Mumbai also contributed significantly in the genetic improvement of seasonal flowers.
• The work was greatly strengthened and streamlined with the establishment of All India Co-ordinated Floriculture Improvement Project in 1972 onwards throughout the country.