The basic concept of varietal development

1. The basic concept of varietal development Produce or identify genetically variable germplasm Carry out selection procedure Stabilize and multiply these superior genotypes

2. A successful plant breeder will require knowledge in many (if not all) of the following subjects: Evolution (Geographic area of origin) Botany Biology: mode of reproduction, types of cultivar and breeding systems Genetics Pathology: nematology, entomology, virology Weed science Food science Biometry: (A numbers game), Breeder are required to be good data manager Agronomy Molecular biology: molecular markers, genetic engineering, tissue culture Production Management (people, time and money) Communication (verbal and written communication): at least some plant breeder must be good at passing on the essential information about the subject to future plant breeders Information technology

3. Professor N.W. Simmonds defined domestication as follow: A plant population has been domesticated when it has been substantially altered from the wild state and certainly when it has been so altered to be unable to survive in the wild.

4. A cultivar (or variety) is defined as a group of one or more genotypes which have a combination of characters giving it distinctness, uniformity and stability (DUS) Modes of reproduction and types of cultivar Distinctness Morphological characters (not to be influenced by environment) Physiology Disease or virus reaction-insect resistant-chemical quality Molecular Distinctness is described as follow: The variety, whatever the origin, artificial or natural, of the initial variation from which it has resulted shall be clearly distinguishable, by one or more important characteristics, from any other plant variety

5. Stability It must remain true to its description when it is reproduced or propagated. The plant variety shall continue to exhibit its essential characteristics after successive reproductions or, where the breeder has defined a particular cycle of reproduction, at the end of each cycle of reproduction (three of four way crosses). UniformityAny variation should be predictable and capable of being described by the breeder از دیگر ویژگیهای یک کولتیوار جدید (VCU) value for cultivation and use

6. از 122 گیاه تجاری مشهور 32 گیاه خودگشن 70 گیاه دگرگشن 20 گیاه دگرگشن با درجات مختلف خودگشنی

7. در ناسازگاریها دانه گرده روی کلاله جوانه نمی زند لوله گرده نمی تواند خود را به تخمدان برساند لوله گرده نمی تواند وارد تخمدان شود درون تخمدان لقاح صورت نمی گیرد جنین لقاح یافته قادر به تشکیل بذر نیست

8. Bulb is a modified shoot consisting of a very much shortened stem enclosed by fleshy leaves (onion) Asexual reproduction A rhizome is an underground stem with buds in the axils of reduced leaves (Mint) A tuber is a swollen stem that grows beneath the soil surface bearing buds (potato) Corm is a swollen stem base bearing buds in the axils of scale-like remains of leaves from the previous years growth (garlic) Cutting A stolon is a horizontally growing stem that roots at nodes (strawberry runners)

9. Apomixis Androgenesis: sperm nucleus of a pollen grain Apospory: somatic ovary cells Diplospory: 2n megaspore mother cells Partenogenesis: egg cell without fertilization Semigamy: sperm and egg cells independently without fussion به مواردی که برای رخ دادن آپومیکسی گرده افشانی لازم باشد pseudogamy گفته می شود

10. 1- Pure line cultivars 90% or more homozygosity در مورد گیاهان خودگشن پروسه تولید لاینهای خالص با تلاقی دو والد خالص شروع می شود و انتخاب دوره ای روشی کارا است. در مورد سیب زمینی تولید مثل غیر جنسی و وجود آللهای کشنده مغلوب سبب می شود تولید چنین لاینهایی بسیار مشکل باشد. Type of cultivar 2- Open pollinated cultivars از تلاقی دو گیاه دگرگشن شروع می شود بنابراین F1 دارای تنوع می باشد 3- Hybrid cultivars هموژن و هتروزیگوت هستند

11. 4- Clonal cultivars یکنواخت از نظر ژنتیکی و هتروزیگوت هستند Type of cultivar 5- Synthetic cultivars معمولا برای گیاهانی که تا حدی ناسازگاری نشان می دهند (مثل چمنها) بکار می روند. حاصل تلاقی تعدادی لاین می باشد و نسل اول این تلاقی syn1، خودگشنی یا دگرگشنی آن Syn2 و ....را تشکیل می دهد. 6- Multiline cultivars (Near isogenic lines) هر ژنوتیپ حداقل 5 درصد را تشکیل می دهد. اغلب خودگشن هستند. برای غلبه بر بیماریها خیلی مفیدند. 7- Composite-cross cultivars از تلاقی بین دو یا تعدادی کولتیوار یا لاین اصلاحی به دست می آید که خودگشن هستند. بعد جمعیت حاصل با هم مخلوط و کشت می شود. بنابراین نسبت ژنوتیپهای سازگار افزایش و نسبت ژنوتیپهای ناسازگار کاهش خواهد یافت. Breeders seed can never be maintained as the cultivar was originally released.

12. -what political and economic factors are likely to be of greatest importance in future years? Breeding objectives -what criteria will be used to determine the yielding ability required of a new cultivar? -what end-use quality characters are likely to be of greatest importance when the new releases are at a commercial stage? -what diseases or pests are likely to be of greatest importance in future years? -what type of agricultural system will the cultivar be developed for?

13. -Increasing the yield per planted area, assuming input costs remain constant (biomass and partition) Plant breeders can increase grower’s profitability by: -Increasing the region of crop production -Reducing input costs (including herbicide, insecticide and fungicides) while maintaining high yield per unit area -Increasing the inherent quality component of the end product so that growers receive a higher unit price when the harvestable product is sold, or such that the product is more nutritious. For example boiled potatoes need to remain relatively firm and not disintegrate on boiling (lower solid content of tuber) Potato chip (high solid content with low water content and low reducing sugare)