|CHITTOORI, RATNAPRABHA - Texas A&M University|
|SALT, DAVID - University Of Aberdeen|
|TARPLEY, LEE - Texas Agrilife Research|
Submitted to: Texas Experiment Station Field Day Handout
Publication Type: Experiment Station
Publication Acceptance Date: 6/4/2013
Publication Date: 6/25/2013
Publication URL: http://beaumont.tamu.edu/eLibrary/Newsletter/2013_Highlights_in_Research.pdf
Citation: Chittoori, R., Pinson, S.R., Salt, D.E., Tarpley, L. 2013. Patterns of element concentrations help explain varietal differences in rice seedling vigor. Texas Experiment Station Field Day Handout. Highlights in Research Special Ediction, pg. VII-VIII.
Interpretive Summary: Seedling vigor is an important factor in rice production because it minimizes exposure of emerging seedlings to soil-borne diseases and promotes the early development of a uniform stand. Seedling vigor is influenced by both genetics and environment. In this study where plants of varying levels of seedling vigor were analyzed for root and shoot concentrations of 20 elements, we found similar associations between seedling health and concentrations of specific elements regardless of whether the root-growth differences were genetically induced (e.g., variety differences) or chemically induced with application of auxin, a plant growth hormone. While fertilizers have long been used to affect plant chemistry by affecting mineral availability, this study shows that genes also play a very important role in controlling plant chemistry, likely by affecting mineral uptake and/or transport rates. This in turn means that breeders can develop varieties that will be healthy under variable soil fertility conditions by selecting for genes that improve mineral uptake and internal chemical balances.
Technical Abstract: Seedling vigor is an important factor in rice production because it minimizes exposure of emerging seedlings to soil-borne diseases and promotes the early development of a uniform stand. Seedling vigor is influenced by both genetics and environment. In this study where plants of varying levels of seedling vigor were analyzed for root and shoot concentrations of 20 elements, we found similar associations between seedling health and concentrations of specific elements regardless of whether the vigor differences were genetically induced (e.g., variety differences) or chemically induced with application of auxin, a plant growth hormone. This study explored the interrelationship between mineral element concentrations and seedling vigor by studying element concentrations in roots and leaves of seedlings of 24 diverse rice varieties. In order to generate extreme differences in root size within the study, half the seedlings per genotype (24) were treated with auxin, a plant growth hormone known to affect root development. Plants were grown in sand rather than clay so that entire root systems could be harvested for final measurement. Shoot growth (height and number of leaves developed per plant), leaf photosynthetic activity, and leaf color were measured to reflect seedling shoot health. Soil pH and redox were also tracked throughout the study. After the harvest of 3 week old seedlings, several aspects of root size (length, weight, volume, branching) and rates of cell respiration were measured to evaluate root health. Dried root and shoot tissues were analyzed for concentration of a total of 19 elements, 15 of which are generally considered beneficial to plant health (boron, calcium, cobalt, copper, iron, magnesium, manganese, molybdenum, nickel, phosphorus, potassium, sulfur, rubidium, strontium, and zinc) and four detrimental elements (arsenic, cadmium, selenium, and sodium). Although the auxin treatment did not cause measurable differences in root cell respiration (a measure of vigor at the cellular level), it did alter overall root growth, causing an increase in root growth for some varieties, but a decrease in root growth in other varieties. In spite of the varietal differences in root response to auxin treatment, increased root size was nearly always associated with increased shoot size. Furthermore, regardless of whether the observed seedling vigor differences were due to varietal or auxin-treatment differences, increased seedling vigor was significantly associated with increased root and shoot concentrations of potassium and zinc, and decreased shoot concentrations of the undesirable elements arsenic, cadmium, selenium, and sodium. The study indicated seedling health to be based on complex ratios and interactions between multiple elements within the seedlings. This is not surprising in that fertilizers have long been used to improve plant health through altered soil and plant chemistry. The new knowledge gained from this study pertains to how significant a role the genes also play in orchestrating the root growth and mineral balances that contribute to seedling vigor. This in turn indicates that breeders can develop varieties adapted to non-optimum soil fertility conditions by selecting for genes that alter mineral uptake and internal chemical balances.