There is longstanding concern that modern plant breeding reduces crop genetic diversity. Such reduction may have consequences both for the vulnerability of crops to changes in their pests and diseases and for their ability to respond to changes in climate and agricultural practices. This concern, however, has not been well validated in recent molecular studies of genetic diversity of several crop species. The objective of this study was to assess allelic diversity changes in 96 Canadian oat (Avena sativa L.) cultivars released from 1886 to 2001 by means of 30 simple sequence repeats (SSRs). A total of 62 alleles were found from 11 informative SSR loci. Thirty‐nine alleles were detected infrequently (frequency ≤ 0.15) among the cultivars and only two alleles were observed frequently (frequency ≥ 0.95). Analyses of the dynamics of SSR alleles over time in these oat cultivars revealed random patterns of allelic change at three loci, shifting patterns of change at one locus, increasing patterns of change at two loci, and decreasing patterns of change at five loci. Significant decrease of alleles was detected in cultivars released after 1970 and also in some specific breeding programs. Three different band‐sharing analyses of the genetic diversity of the grouped cultivars, however, failed to detect significant diversity changes among cultivars released from different breeding periods or programs. These findings indicate that allelic diversity at particular loci, rather than average genetic diversity, is sensitive to oat breeding practices. They also indicate the need for attention to be paid to oat germplasm conservation.
Sulfuric acid hydrolysis of steroidal glycosides of Amber fenugreek was studied by capillary gas chromatographic analysis of diosgenin [(25R)-spirost-5-en-3-ol] and isomeric spirostadiene artifacts from 100 mg samples of seed material. Following extraction with 80% ethanol, highest recoveries of diosgenin occurred when hydrolyses were conducted in sulfuric acid, prepared at 1 molar (M) concentration in water containing 60-80% 2-propanol. Compared to a previous method with aqueous hydrochloric acid, the selected conditions of hydrolysis at 100 degrees C for 2 h with sulfuric acid in 70% 2-propanol reduced diene formation but did not completely eliminate these artifacts. Extraction of steroidal saponins with various alcohol/water mixtures prior to sulfuric acid hydrolysis gave similar recoveries of diosgenin. Application of the quantitative method to experimental samples of Amber, Quatro, and ZT-5 fenugreek, using 10 mg subsamples of crushed seed that had been defatted with petroleum ether and dried at 60 degrees C, gave diosgenin levels of 0.55, 0.42, and 0.75%, respectively. Levels of smilagenin and sarsasapogenin were very low in hydrolyzed seed extracts from ZT-5, a Canadian breeder line of fenugreek.
Analysis of genetic diversity changes in existing gene pools of cultivated crops is important for understanding the impact of plant breeding on crop genetic diversity and developing effective indicators for genetic diversity of cultivated plants. The objective of this study was to assess genetic diversity changes in 75 Canadian hard red wheat (Triticum aestivum L.) cultivars released from 1845 to 2004 using 31 simple sequence repeats (SSRs) markers. A total of 267 SSR alleles were detected, and their allelic frequencies ranged from 0.01 to 0.97, with an average of 0.14. Significant allelic reduction was observed at only four SSR loci for the cultivars released from 1970 onwards. However, 51 alleles (about 19%) present in pre-1910 cultivars were undetected in cultivars released after 1990 and were spread over 27 SSR loci. The proportion of SSR variation accounted for by six breeding periods was 12.5%, by four ancestral families, 16.5%, and by eight breeding programs, 8.4%. The average genetic diversity measured by three different band-sharing methods did not change significantly among cultivars released from different breeding periods, breeding programs, and ancestral families. However, genetic shift was obvious in the cultivars released over the six breeding periods, reflecting well the various breeding efforts over years. These results clearly show the allelic reduction and genetic shift in the Canadian hard red spring wheat germplasm released over time. Consequently, more effort needs to be made to broaden the wheat breeding base and conserve wheat germplasm.
KENw-RICHARDS potatoes, cassavas, bananas, and coconuts (Thurston, 1969). These crops are either wind-pollinated or self-pollinated. Superficially, it appears that insect pollination has little effect on the world's food supply-possibly no more than 1% (McGregor, 1976).However, when total animal and plant products are considered, it appears that perhaps one-third of our total diet is dependent, directly or indirectly, on insect-pollinated plants.The importance of insect pollinators can be put in perspective by examining the total Canadian food production scene as an example. In 1991, about 68 million ha of land were cultivated. About 45 million ha were devoted to wind-or self-pollinated crops such as grains or rangeland. About 3 million ha were devoted to self-pollinated crops such as rapeseed, flax, beans, peas, soybeans, and peanuts that may receive some benefit from insect pollination. A small improvement in yield or grade can have a large positive impact on profit. The remaining 9 million ha were devoted to fruits, vegetables, and legume crops and are completely dependent on, or produced from, insect-pollinated seed. About 1 1 million ha were summerfallowed. Animal food products such as beef, pork, poultry, lamb, milk, and cheese contribute about half of the North American diet. These products are derived in part from insect-pollinated legumes such as alfalfa, clover, or trefoil. Insects also have a major impact on oilseed crops. More than half of the world's diet of vegetable fats and oils comes from rapeseed, sunflower, peanuts, cotton, and coconuts. Many of these plants depend on or benefit from insect pollination.The agronomic and economic value of bee-effected pollination has been an internationally contentious issue since at least the turn of the century. Attempts to value the pollination activity of bees have ranged from "guesstimates" of no empirical substance, to informed estimates (largely by apiculturists) to a few concerted efforts by economists (see Gill, 1991
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