Screening for low phosphorus tolerance in 99 spring wheat genotypes adapted to Montana ecosystems

Principal Investigator: Gadi V.P. Reddy

Investigators: Kenedy Etone Epie, Maral Etesami, and John H. Miller

Project Personnel: Phillip Hammermeister and Alyshia Miller

Western Triangle Agricultural Research Center,

Montana State University, 9546 Old Shelby Rd.,

P.O. Box 656, Conrad, MT 59425, USA.

Background

Phosphorus (P) is one of the non-renewable essential macronutrients of plants that plays a critical role in improving wheat productivity but remains generally unavailable. Considering the important role of P in growth and yield of grain crops, identifying genetic variability for low P tolerance will be critical for increasing crop productivity. Defficiency of P retards growth, reduced numbers of tillers and reproductive structures in plants. It may be abundant in some soils but less readily available due to low solubility and mobility of its phosphate forms. In the Northern Great Plains including Montana, P availability is heavily influenced by soil pH and even when applied as inorganic fertilizer, only about 20% is used by crops and the rest is converted into insoluble forms in acid and alkaline soils (Rodriguez and Fraga, 1990). Excessive amounts of expensive artificial soluble P fertilizers are therefore used in crop production which reduce profit margins and also accumulate in water bodies, causing water pollution and eutrophication.

To look for answers to the P crisis, the development of P efficient spring wheat genotypes, which are adapted to low P soils, would be a promising solution. Wheat genotypes exhibit considerable genetic diversity in response to P and screening of spring wheat genotypes for P deficiency tolerance could help to identify contrasting genotypes for low P tolerance that can be included in spring wheat improvement programs. An understanding of the relationship of growth traits and grain yield will further help to improve productivity. More so, most research attention is focused on the responsiveness of wheat genotypes to increasing P fertilization, and information is therefore lacking on responsiveness of genotypes to low or deficient P conditions.

Objectives

The objectives of this research were to characterize genetic variability and screen for P deficiency tolerance in ninety nine spring wheat genotypes that can be adapted to Montana ecosystems.

Materials and Methods

The spring wheat genotypes classified by source were AM which included elite spring wheat lines from several regional breeding programs (Table 1), 2016 off-stations and NAM (nested association mapping) originating from 30 countries, developed by crossing landraces to a common parent (Table 2). The genotypes were obtained from the Department of Plant Science and Plant Pathology, Montana State University.

Table 1. Spring wheat genotypes from AM source screened for phosphorus deficiency tolerance.

TID=Trial ID number

Table 2. Spring wheat genotypes from off-station and NAM parent source screened for phosphorus deficiency tolerance.

TID=Trial ID number

This research was conducted in a high tunnel facility (greenhouse) of the Western Triangle Agricultural Research Center, Montana State University, Conrad, MT. Plants were grown in cylindrical plastic pots in potting mix of peat, vermiculite and sand in the ratio of 1:1:1. During mixing, sufficient P treatment received 25 ppm of MAP and low P with a residual P of 5 ppm received no P fertilizer. Therefore, the two levels of P maintained in the trial were 5 ppm P (designated as P5) and 30 ppm P (designated as P30). Other required nutrients were sufficiently supplied. All nutrients were mixed thoroughly with growing media before potting with 10 kg of the mixture per pot. The treatments were performed in triplicate and arranged in a completely randomized design. Twelve seeds of each genotype were sown at 4-cm depth in each pot in April 2017. Plants were irrigated every other day to maintain a soil moisture level per pot of 60% of the field capacity during growth of the plants by weighing and adding water to make up loses.

After emergence, plants were thinned to eight plants per pot at the 2-leaf stage. The greenhouse was monitored daily by a temperature recording device, Onset Hobo Data Loggers, (Onset Computer Corporation, MA). Mean temperatures ranged from 10°C at night to 25°C during the day. Plants were harvested at 106 DAS. Height, tiller number, and head number of all 99 varieties were recorded shortly before harvest. Plant height was determined as the distance between potting mix surface level and the tip of the last head. Harvested shoots in each pot were collected and oven dried at 70 °C until a constant dry weight (g/pot). Grain yield and 1000 seed weights were determined. Grains from a subset of 20 genotypes selected based on grain yield after ranking the yields of P5 plants from highest to lowest were selected, milled and the ground samples were sent to Agvise Laboratory to analyze for grain P and N concentrations. Grain protein content was determined, and grain P uptake (mg/pot) was calculated.

Results

Table 3. Grain yields and protein content of 20 genotypes selected based on grain yield after ranking the yields of low P plants from highest to lowest. Values are means ± standard deviations.

TID Trial ID number.

Significance of results and recommendations

This study confirms the possibility of departing from rectifying P deficiencies in soils by commercial chemical fertilizers. It highlights an approach whereby the inherent genetic differences with respect to P deficiency tolerance can be exploited to partially, at least, tackle the intractable problem of P deficiency as a factor in crop production. In this study, Unity, Peace, Vida, Reeder and CLTR 15134 spring wheat genotypes showed substantial tolerance in their growth response, grain yield and protein content under a P-deficient conditions. The genetic variability identified in this research for grain yields offers useful information for spring wheat improvement programs for choosing genotypes with low P tolerance characteristics. These results could also be used to select interesting genotypes for organic spring wheat production in Montana.

This study should be repeated in the greenhouse only for the selected genotypes and field evaluations are recommended to confirm their P tolerance abilities. Detailed findings of this research project is being prepared into a manuscript for possible submission to an international peer reviewed journal.

Project Challenges

This project was well implemented except that the top of the hoop house (greenhouse) was ripped apart by strong winds in the middle of the trial. Minimal bird and rodent damage was also recorded.

Acknowledgements

This work was supported by Montana Wheat and Barley Committee. The support of the MSU- Western Triangle Agricultural Research Center staff was highly appreciated.

References

Rodriguez, D. and Fraga, R. 1999. Phosphate solubilizing bacteria and their role in plant growth promotion. Biotechnol. Adv. 17: 319339.