Nutritional Improvement of Horticultural Crops Through Plant Breeding

The improvement of nutritional quality of horticultural crops presents a rewarding challenge for plant breeders in the 21st century stated Frederick Bliss in his paper Nutritional Improvement of Horticultural Crops through Plant Breeding. This paper which was published in HortScience 34(7)(1999):1163-1167 called to our attention the fact that in industrialized countries there was a realization that nutritious food can effect a healthy lifestyle. Being more conscious of this fact, we incorporated these items in our daily diet as a means of alleviating certain medical conditions such as obesity, heart disease and certain types of cancers. In third world countries, this was not the case since many of these people did not have enough food to even meet basic metabolic requirements. The author was quick to point out however, that increasing supplies would not effect these circumstances, since it was the micronutrient deficiencies that played a large role and were often widespread. An illustration which was given involved iron deficiencies. Iron deficiencies could affect normal growth, reduced appetites, increased lethargy, slow mental development, reduced attention span and lower immunity to various diseases. Diversification within the diet to include fruits, vegetables and nuts could vastly improve a predominately grain based diet, but in order to take nutritional improvement to the next level plant substances which are important to the human diet must be clearly identified and described if the intention was to breed cultivars with improved nutritional attributes. The improvement of nutritional properties of food crops could be accomplished through the alteration and hybridization of plants with selected traits. Not all attempts however, are successful in producing the desired results due to certain limiting factors. To avoid disappointments and frustrations due to finding that the improved cultivar was in fact ineffective in changing nutritional status, feasibility studies should always precede the attempts. These studies should evaluate the likely outcome and whether or not the derived cultivar would in fact change the nutritional status of the people who consume the food. In order to be effective, these studies required a multidisciplinary team comprised of nutritionists, plant breeders, scientists, and economists to be established. In a large number of cases however, plant breeders were accustomed to working by themselves, or occasionally in a collaborative situation with others of the same discipline. Recognition for accomplishments in their work was usually higher in situations where they were the primary contributor as opposed to those in collaborative situations. For these reasons they found it more difficult to adjust to group settings where others were not even of the same discipline. Another problem which faced the multidisciplinary team, but had to be overcome, was the understanding of jargon used in the various disciplines. Success in overcoming these problems would help assure the group's success in defining the objectives, setting the goals, and analysis of the results. With the members of the group in place, and the jargon issues worked out, the next step was the assessment of whether or not the breeding program would achieve the desired results. It should be understood that the nutritional requirements of varying populations of people are not always the same. The diversity often results in inequities in food acquisition, consumption, differing nutritional requirements and nutrient status. In the example of iron deficiency, the author stated that iron deficiencies are most likely to occur in people that have diets containing large quantities of plant -derived foods and small amounts of animal products. In this instance, it would not be prudent to establish a breeding program to remedy iron deficiency for a group of people whose diets are predominately animal based products. Therefore proper assessment of the diet for the population participating in the study is necessary. Once this assessment had been made, came the consideration of whether the new cultivar would achieve the desired effect on the nutritional status of that population and whether or not the benefit was greater than the cost of developing and producing such cultivar. To properly evaluate this question, the example of iron deficiency was again used. It was determined that an understanding of the cause for deficiency must be considered. It was determined that while an abundance of iron and also zinc might be present, the bioavailablilty might be as low as 10%.Reasons for this could be low levels of heme-bound iron in plants, the presence of substances such as phylates, oxylates and polyphenols which bind iron in insoluable complexes and the low intake of iron absorption enhancing products such as vitamin C. With the possible causes identified, the possible solutions were considered. These solutions included the addition of increasing the vitamin C through the addition of vitamin C enriched fruits and vegetables to a grain based diet, reducing the levels of phytic acid by adding phytase to the diet, or by creating mutant grain crops which contained lower levels of phytic acid. The option of breeding such mutants would require not only the utilization of current technology, but might also require additional new technology to be developed in addition to testing for field performance and the distribution of new cultivars. The development of new cultivars with genetic modifications might be determined to be the best and most cost effective method to solve the problem of iron deficiency in some populations but not in others, and the method determined for the iron deficiency might not be feasible for other deficiencies.

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