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Classification of Crops ABT-320. Dr. Rabia Amir Lecture 3. Classification of crops. CLASSIFICATION BASED ON LENGTH OF PHOTOPERIOD REQUIRED FOR FLORAL INITIATION ( Photoperiodism ) Short-day plants:
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Classification of Crops ABT-320 Dr. Rabia Amir Lecture 3
Classification of crops • CLASSIFICATION BASED ON LENGTH OF PHOTOPERIOD REQUIRED FOR FLORAL INITIATION (Photoperiodism) • Short-day plants: • Flower initiation takes place when days are short less then ten hours. E.g. rice, green gram, black gram etc. • 2. Long-day plants: • Require long days. More than ten hours for floral initiation. E.g. Wheat, Barley. • 3. Day neutral plants: • Photoperiod does not have much influence for phase change for these plants. E.g. Cotton, sunflower.
BASED ON NO. OF COTYLEDONS • Monocots or monocotyledons: Having one cotyledon in the seed. E.g. all cereals & Millet. 2. Dicots or dicotyledonous: Crops having two cotyledons in the seed. E.g. all legumes & pulses.
BASED ON ECONOMIC IMPORTANCE • Cash crop: Grown for earning money. E.g. Sugarcane, cotton. • Food crops: Grown for raising food grain for the population & fodder for cattle. E.g. wheat, rice etc.
BASED ON CULTURAL METHOD/WATER • Rain fed: crops grow only on rain water. E.g. Bajra, Moong etc. • Irrigated crops: Crops grow with the help of irrigation water. E.g. Chili, sugarcane, Banana, papaya etc.
BASED ON LIFE/DURATION OF CROPS • Seasonal crops: A crop completes its life cycle in one season. Summer. E.g. rice, wheat etc. • Two seasonal crops: crops complete its life in two seasons. E.g. Cotton, turmeric, ginger. • Annual crops: Crops require one full year to complete its life cycle. E.g. sugarcane. • Biennial crops: which grows in one year and flowers, fructifies & perishes the next year. E.g. Banana, Papaya. • Perennial crops: crops live for several years. E.g. Fruit crops, mango, guava etc.
BASED ON GROWING SEASON • Kharif/Rainy/Monsoon crops: The crops grown in monsoon months from June to Oct-Nov, Require warm, wet weather at major period of crop growth, also require short day length for flowering. E.g. Cotton, Rice. • Rabi/winter/cold seasons crops: Require winter season to grow well from Oct to March month. Crops grow well in cold and dry weather. Require longer day length for flowering. E.g. Wheat, gram, sunflower etc. • Summer/Zaid crops: Crops grown in summer month from March to June. Require warm day weather for major growth period and longer day length for flowering. E.g. Groundnuts, Watermelon, Pumpkins, Gourds.
BASED ON CLIMATE • Tropical: Crops grow well in warm & hot climate. E.g. Rice, sugarcane. • Temperate: Crops grow well in cool climate. E.g. Wheat, Oats, Gram, Potato etc.
Major crops of Pakistan • Cotton • Wheat • Rice • Sugarcane • Maize • Groundnut • Sesame • Sunflower • Soybean • Millet • Gram
Major Fruits of Pakistan • Citrus • Dates • Bananas • Mangoes • Guava • Apple • Apricot • Grapes • Almond • Peach • Plum • Pomegranate.
Major Vegetables of Pakistan • Cabbage • Carrot • Chilies • Garlic • Okra • Onion • Tomato • Potato • Coriander • Turmeric.
Major flower crops of Pakistan Balsam, Daffodil, Dahlia, Daisy, Geranium, Gerbera, Hollyhock, Hibiscus, Lily, Lilac, Lotus, Lavender, Marigold, Mulberry, Maple, Nightshade, Orchid, Olive, Passion-flower, Petunia, Pansy, Rose, Rosemary, sunflower, Tulip, Zinnia.
Conventional methods of plant breeding • Plant breeding is an art and science that evolved in the hands of farming communities around the world. • In the twentieth century, the science of plant breeding developed in the hands of plant breeders specialized in different crop plants. • The conventional techniques of plant breeding that are being practiced by plant breeders will be discussed hereafter:
DOMESTICATION • Most of the crop plants were domesticated by pre-historic man. After domestication, the crop plants got changed considerably as compared to their wild forms. • Domestication of wild plants is still being continued and it is likely to continue in future also, since new requirements may necessitate the domestication of new plant species. • Even beverage crops like tea and coffee were domesticated only a few centuries ago. • Many latex producing plants are being domesticated recently for their potential ability to yield products like petroleum.
Patterns of changes under domestication • Domesticated populations of plants undergo continuous evolution depending upon the pressure exerted by the farmers, plant breeding and the environment. • Variability arises in these populations through mutations, recombination, transposition etc. Both natural and artificial selections take place in such populations. • Besides, natural and artificial hybridizations also occur in domesticated populations. • As a result of these processes, continuous speciation takes place in domesticated populations.
Origin of variability in domesticated populations A plant population is considerably variable at the time of domestication itself. New variability arises within domesticated populations by mutations, recombination, hybridization etc.
NATURAL SELECTION Natural selection is the process of favorable selection or elimination of variations that exist in a population so as either to maintain the population without change, or to give rise to one or more new populations, which in due course get evolved into new species.
Types of Natural Selection Stabilizing Selection: the type of natural selection in which aberrants are eliminated and the population equilibrium is maintained without change. Directional Selection: The type of selection in which evolutionary modification gradually progresses in one direction, as a result of which a new species originate from the existing one, replacing it. Diversifying Selection: The type of selection in which selection acts in more than one direction, so that more than one species originate from the existing population.
PLANT INTRODUCTION Plant introduction is the process of bringing a plant species or variety to a new country or geographical area where it was not previously grown. Thus, the introduced plant may be a new crop species or variety. Often, such plants are introduced from other countries, continents or geographical areas.
TYPES OF PLANT INTRODUCTION • Primary Introduction: This is the type of introduction in which the introduced species or variety is directly released for cultivation. This type of introduction is rare now. • Secondary Introduction: In this case, the introduced variety or species is subjected to further screening experiments via selection or they are used as parents in hybridization programs.
PROCEDURE OF PLANT INTRODUCTION The procedure of plant introduction consists of: • Procurement • Quarantine • Cataloguing • Evaluation • Multiplication • Distribution
PROCUREMENT • The material that is required to be introduced from other countries is nowadays procured through National Departments of Agriculture, National Crop Research Institutes or National Bureaus of Plant Genetic Resources. In most of the cases, free and mutual exchange of genetic resources is possible between countries. • Plant propagules like seeds, clonal propagules or cultured tissues can be exchanged. Proper packaging of the material being exchanged is very important. Nowadays, in vitro exchange of germplasm is becoming popular.
QUARANTINE • Quarantine is the screening of the living organisms introduced from foreign sources for the presence of pathogens, pests, weeds etc. • All plant materials being introduced should carry an authentic phytosanitary certificate. • Quarantine control is usually exercised by the agencies authorized for introduction, at prescribed ports of entry.
CATALOGUING • When a material is introduced, it is given an entry number and information regarding the name of the variety, species, place of origin and major characteristics are recorded.
EVALUATION • The newly introduced materials are usually assessed and evaluated by the respective Crop Research Institutes. Resistance to pests and diseases is evaluated under appropriate conditions. • The acclimatization of an introduced variety or species to the environmental conditions of the new geographical area is a serious problem. However, since the introduced lot may contain genetically different plant types, some of them may show higher levels of adaptability to the new environment. Such genotypes are multiplied and distributed widely.
MULTIPLICATION & DISTRIBUTION • Superior genotypes are selected, multiplied and made available on commercial scale. • They are subjected to field trials and released for cultivation. • Some of them are used as parents in hybridization programs so as to produce improved hybrids.
