Distant hybridization:

• Crossing between individuals belonging to two different species of the same genus or of different genera.

a) Interspecific hybridization: Crossing between plants belonging to different species of the same genus. Eg: cultivate rice (Oryza sativa) and the wild rice (Oryza perennis).

b) Intergeneric hybridization: Crossing between plants belonging to different genera. Eg: 4x or 6x wheat (Triticum spp.) and rye (Secale cereale)

Techniques for production of distant hybrid:

• Large no. of flowers is pollinated.
• Hybridize with more than one strain of each of the parental species.
• Embryo culture technique
• Crosses under different environmental conditions
• Using bridging species. Eg: Wheat, tobacco.

Barrier to production of distant hybrid

a) Failure of zygote development:

• Lethal gene, chromosome elimination, incompatible cytoplasm, endosperm abortion.
• Eg: Triticum + Secale —> Triticale

b) Failure of seedling development:

• Complementary lethal gene
• aestivum + T. dicoccum à Hybrid chlorosis à necotic hybrid.

c) Failure of zygote formation:

• Pollen unable to reach embryo sac.
• Pollen burst on other species.
• Long style out short pollens.