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By Pat Malcolm
When agricultural crops are reproduced by division after several generations, often a decline occurs in qualities such as vigor, yield, disease resistance, plant and fruit appearance and uniformity of size or shape. This condition of decline is commonly called, ‘run out.’
Strawberry plants have demonstrated this clonal decline (running out) for many years. After growing strawberry plants for five or more years, gardeners became accustomed to dividing a clump of plants that contained the mother plant (oldest plant) in the center and replanting the smaller daughter plants to be used as seed plants the following season. Certain genetic, undesirable changes (mutations) were brought to the surface, as seen in daughter plants; as more and more plants were continuously grown, generation after generation. Some of these corrupting mutations may be visually observed as the plant vigor decelerates (declines); the yield of strawberries is less, and sometimes the berries are misshapen; and finally, the plants become extremely susceptible to diseases caused by virus, bacteria, fungi, insect susceptibility, and nematode victimization. Agricultural researchers advised strawberry growers to discontinue old variety lines and clones and were told to buy new, certified plants that restore the vigor needed to increase yields of future strawberry gardens.
This phenomenon of strawberry decline has been experienced with other agricultural crops such as sweet potato vines, raspberry bushes, blackberry bushes or vines, and banana trees. The problem with banana trees has emerged as the greatest possible catastrophe facing modern agriculture today, since bananas, produced only by plant division and not seed, are the most popular fruit in the world and may face extremely serious setbacks, unless the efforts of scientists from Israel to ‘clean up’ the evolved, accumulated defects by using tissue culture that could cause the commercial banana production to rebound.
Old ‘run out’ clones of agricultural crops have in the last decade been rejuvenated to produce unprecedented yields and to restore confidence in a high quality product. Growers of agricultural, commercial, crop plants can avoid clone decline, ‘run out,’ by buying certified plants that have been grown under strict governmental watchdog supervision, under a technique called, ’tissue culture.’ To ‘clean up’ problems in weakened, flawed clones of raspberry plants, a clump of cells is taken from the growing tip of the plant called the apical meristem. These cells grow rapidly and rarely contain virus or other harmful defects and are placed within a sterile growing medium, where they grow into a clump that develops roots and a growing shoot. This micro-plant is grown into many other mother plants called ‘nuclear stock mother plants.’ These mother plants are sent out to be multiplied over and over into certified plants by nursery propagators with a regained vigor, disease-free status and desirable qualities that were once present in the original profitable varieties.
One eclectic segment of agriculture that has been negatively impacted by clonal decline, ‘run out,’ is the pick-your-own operation, where berry plants are not replaced often by operators with certified plants. Diseases and pests appear as a greater threat every year. This same phenomenon of disease and pest buildup is well known in home gardens where tomatoes, pepper plants, and many other vegetable plants are abandoned after a few years in favor of new soil locations. The decline of strawberry plants, raspberry plants, and blackberry plants in pick-your-own operations can not always be reversed by simply replanting the site with certified plants, unless the soil is first fumigated and sterilized. Very little attention has been paid to certify muscadine and scuppernong grape vines to be free of virus, bacteria and fungal infestations in pick-your-own operations. Those grapevines are normally multiplied by various methods other than seed planting.
Recent improvements in offering agricultural plants for certification will ultimately insure the survival of valuable berry crops like blackberry plants, raspberry plants, and strawberry plants. Crops such as banana trees that are grown in tissue culture in Israel for planting in Central America can offer hope that commercial interruption of banana fruit will be avoided. Recent tissue culture advancements have given commercial growers the security of continued profits and quality, sweet potato products to enjoy by growers and consumers.
The application of tissue culture propagation to the future of canna bulb, (rhizome), and commercial production could save growers who are floundering in complaints and indecision to restore a once important agricultural crop with a promise of future profits and a satisfied wholesale and retail customer. This application of tissue culture to future crops of every type that are grown by plant division will determine whether or not those crops will survive and not ‘run out.’
About the Author: Patrick A. Malcolm, owner of TyTy Nursery, has an M.S. degree in Biochemistry and has cultivated berry plants for over three decades.
Source: isnare.com
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