Location: Crop Genetics Research Unit
Title: Characterization of cottonseed nutrients composition in near isogenic cotton (Gossypium hirsutum L.) mutant lines for fuzzless seed trait under well-watered and water stress conditions Authors
Submitted to: Frontiers in Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 2, 2013
Publication Date: December 30, 2013
Citation: Bellaloui, N., Turley, R.B. 2013. Characterization of cottonseed nutrients composition in near isogenic cotton (Gossypium hirsutum L.) mutant lines for fuzzless seed trait under well-watered and water stress conditions. Frontiers in Plant Physiology. 4(516):1-13. Interpretive Summary: Cottonseed is used as a source of meal for livestock, oil, and minerals. Therefore, to maintain the nutritional value of cottonseed during cotton breeding program, continuous evaluation of cottonseed for these seed composition components is important. New varieties (near-isogenic mutant germplasm) of cotton were developed for a specific characteristic (trait) (fuzzless seed: seed with no fuzz). Conventional cotton produces fuzz (hair on seed coat or fuzz fiber) on its seed in addition to the longer commercially used lint fiber, but fuzzless seed is cotton that produces no fuzz on its seed. Cottonseed with this characteristic is considered an important tool for fiber/lint initiation and development research. Little is known about the nutritional value of cottonseed with and without fuzz. Results from greenhouse experiments conducted where one group of cotton was well-watered and the other group was water-stressed showed that minerals such as potassium, phosphorus, magnesium, copper were in higher concentrations in most fuzzless seed than in the same varieties with fuzzy seed. However, other minerals such as iron did not change. When cotton was grown under water stress, low level of minerals was observed in all varieties regardless of the fuzz characteristic. Cottonseed varieties contained a wide range of mineral levels, allowing cotton breeders to select for higher mineral qualities. Generally, seed protein was higher in fuzzy varieties that in fuzzless varieties; however, seed oil was higher in fuzzless varieties than in fuzzy varieties. Our research demonstrated that the fuzzless characteristic altered the composition (protein and oil) and level of minerals in seed of well-watered and water- stressed plants. Differences in protein and oil and in minerals between fuzzy and fuzzless seeds may indicate alteration in nitrogen, carbon, and mineral physiology and biochemistry. These varieties (near-isogenic mutants) can be used as a powerful tool to understand the role of mineral nutrition in fiber/lint development.
Technical Abstract: Cotton mutant near isogenic lines (NILs) for fuzzless seed trait has been used to investigate cell biology, genetic, and molecular processes of fiber initiation, development, fiber yield and quality. However, there is no information available on the effect of fuzzless seed trait on cottonseed nutrient composition (minerals, N, S, protein, and oil), especially under abiotic stresses such as drought. The objective of this research was to investigate the effect of the fuzzless seed trait on cottonseed nutrient composition using five sets of NILs. Each set consists of two lines that share the same genetic background, but differ in seed fuzziness. The near isogenic lines will enable us to compare the effect of the trait without confounding the genotypic background effects. The mutant lines and their equivalent wild type were: Sure Grow 747 (SG F and SG N); Mississippi Delta 51ne (MD F and MD N); Stoneville 7A gl (Stv7Agl F and Stv7Agl N); Delta Experiment Station 119 (DES F and DES N); and 243 [(source of the dominant allele (N1, N1) (PI 528610)]. Our hypothesis was that since the fuzzless trait involved in the development of ovular trichomes, and was reported to be involved in biochemical pathways, and molecular and genetic processes, this trait may also alter cottonseed nutrient composition. A repeated greenhouse experiment was conducted with cotton plants divided in two groups. One group was well watered and the other was water stressed. Results showed that NIL sets accumulated different levels of minerals in their seeds and leaves, and the fuzzless trait in most of the lines altered seed and leaf mineral accumulations when compared with fuzzy lines or the control line 243, but it did not change in others. For example, K, P, Mg, Cu, and Na concentrations in seeds were higher in MD N and STV N than in their equivalent MD F and STV F lines. Leaf concentrations of Ca, K, Mg, S, B, Cu, and Fe in MD N lines were higher than its equivalent MD F line. Line DES N had higher seed Ca and Cu than DES F, however, DES N had higher P, B, and Na than DES F in leaves. There were no changes in some nutrients such as Fe concentrations in DES lines. Lower levels of nutrients in seeds and leaves were observed under water stress conditions, especially Ca, Mg, N, and B in seeds. Boron concentration in seed was low in all lines in spite of the luxury higher B concentrations in leaves, and this was unexpected as cotton is a dicot species, indicating that B transport from leaves to seed was limited. Cell wall boron constituted more than 90% of total B in leaves in fuzzless lines under water stress conditions, indicating the structural role of B. Protein percentage in NILs ranged from 18.2 to 26% and oil from 24.2 to 29% under well watered conditions. Generally, except for line 56, seed protein was higher in fuzzy lines that in fuzzless lines; however, seed oil was higher in fuzzless lines than in fuzzy lines, except in line MD. Our research demonstrated that fuzzless trait altered the composition and level of nutrients in seed and leaves in well watered and water stressed plants. The lower concentrations of nutrients in seed in spite of luxury concentrations in leaves indicated a transport limitation from leaves (source) to seed (sink) due to unknown mechanisms. Differences in protein and oil between fuzzy and fuzzless seeds may indicate alteration in nitrogen and carbon metabolism. These mutant lines could be used as a powerful tool to further investigate nutrient regulation, mobility, and transport within plants, and their impact on seed quality. The differential accumulation of seed nutrients in this germplasm could be used by cotton breeders to select for higher cottonseed quality.