Sprouting Resistance in Hard White Winter Wheat

Principal Investigator (s):
* P.V.V. Prasad, Department of Agronomy, Kansas State University, Manhattan, KS 66506 (Tel: 785-532-3746; E-mail: vara@ksu.edu).
* A. K. Fritz, Department of Agronomy, Kansas State University, Manhattan, KS 66506 (Tel: 785-532-7245; E-mail: akf@ksu.edu)
* T.J. Martin,Agricultural Research Center – Hays, KS 67601 (Tel: 785-625-3425 ext 213; E-mail: jmartin@ksu.edu).

Objectives:

1. To understand the genetic and physiological basis of sprout resistance/tolerance in hard white wheat.

2. To gather phenotypic data and combine with mapping data to identify chromosomal regions associated with PHS tolerance.

3. To understand the influence of growing environment (heat and/or water stress) during grain filling on pre-harvest sprouting and quality traits of hard white wheat.

Hard White Wheat – Improved yield potential, sprout resistance and adaptability.

Procedure:

Experiments will be conducted in both field conditions and controlled environment conditions to improve understanding of genetic and physiological basis of sprout tolerance in KS01HW163-4.

Field Experiments

The 200 double haploid population of the cross between KS01HW163-4 (sprout tolerant cultivar) and Heyne (sprouting susceptible cultivar) will be grown in fall 2007 at experimental field sites in Manhattan, Hutchinson and Hays. These populations will be grown in replicated plots. Standard crop management will be adopted at each location.

As a part of phenotyping the population, data on phenology (days to ear emergence, flowering and maturity), yield components (ear length, grain numbers, and test weight), sprouting tests [germination or sprouting index (Wu and Carver, 1999), length of dormancy (Strand, 1980), falling numbers (AACC, 1983) and α-amylase enzyme activity (Hagberg, 1961)] will be measured from each of the lines across all locations using standard procedures.

Controlled Environment Experiments

The seed of 200 haploid lines was multiplied in 2006. These lines are being grown in controlled environment greenhouses at Manhattan in fall 2006 to minimize random environmental effects and their impact on sprouting. Variable growth conditions particularly rainfall and temperature during grain growth can influence development of dormancy in maturing kernels and also subsequent sprouting (Nielson et al., 1984; Mares, 1993). These variations in dormancy due to growth conditions may cause difficulty in characterizing the phenotypes of population. Therefore it is important to have an experiment in controlled environments. In second year, in fall 2007 a subset of 20 representative lines will be selected based on the results of current experiments. These lines will be grown under water stress and/or heat stress in a controlled environment to evaluate the influence of growth environment on sprouting tolerance.

Anticipated Outputs:

1. Detailed understanding of physiological basis of sprouting tolerance.

2. Accurate characterization of phenotype and comparison with field studies.

3. Contribute to understanding the influence of growth environment (water stress and/or heat stress) during grain filling on tolerance of pre-harvest sprouting.

4. Contingency in case of failure of field experiments due to weather.

Justification:

Kansas is the largest wheat producing state contributing about one fifth of the total wheat produced in United States (US). About 95% of the wheat currently grown in Kansas is hard red winter wheat (Kansas Wheat Commission). About half of the wheat produced in Kansas in consumed in US while the other half is exported. Kansas is consistently the top wheat exporting state. The wheat industry is particularly interested in increasing production of hard white winter wheat due to its preference over hard red wheat. There is an increasing demand for hard white wheat in international markets, especially growing markets in Asia, Africa and South America. The exports of hard white wheat in 2004 were 192,000 metric tons, an increase of 10 fold compared to 2003 (KACC, 2005). At a recent International Grain Program Conference it was suggested that if US does not expand hard white wheat production, others will and US strength in the international market will be diminished (KSRE News, 2005). It is important for Kansas to grow more hard white wheat to be competitive in the wheat export market.

Hard white wheat has tremendous potential in Kansas and would play a strategic role in future wheat exports due to its end-use characteristics. By producing more hard white wheat Kansas farmers will be more competitive in the international market. Kansas wheat industry is committed to develop hard white wheat because of many advantages and the possibility of higher economic return to producers (Paulsen, 1998). Many in the wheat industry believe that in the next two decades most of red wheat in Kansas will be replaced by white wheat. Hard white wheat has significant advantages over red winter wheat due to superior milling and bread making characteristics. Hard white wheat has higher milling extraction rates (i.e. more flour per bushels of grain milled) and also low phenolic compounds thus making it less bitter. Hard white wheat can be used for production of healthy whole wheat products without supplementation with additional sugars during processing. In addition hard white wheat preferred by Asian noodle makers (Nagao, 1995). Hard white wheat is the preferred choice of wheat industry in both domestic and international markets (Kansas Wheat Commission).

The need and importance for transition to hard white wheat has been recognized by Kansas State University (KSU) which now has one of the best breeding programs for hard white wheats in US. The cultivar Trego, developed by Dr. Joe Martin of KSU, is one of the most widely grown hard white wheats in the country. The yield performance data on hard white winter wheat shows that hard white wheat is highly adaptable to Kansas with yields and test weights similar to those of currently grown hard red wheat (Roozeboom, 1999). The production practices for hard white wheat are similar to those for red wheat (Paulsen, 1998). Therefore transition to white wheat will not involve changes in production practices or cost of production.

The major production problem associated with growing hard white wheat is the susceptibility of the grain to pre-harvest sprouting (Paulsen, 1998). Pre-harvest sprouting (PHS) is a condition where germination of grain occurs before harvest when the grain is still on the spike. This is caused by prolonged periods of rainfall and high humidity after physiological maturity. These conditions occur in wheat producing regions of Kansas with some degree of regularity, especially in the central part of the state. PHS results in lower grain yield due to harvest losses and, perhaps more importantly, losses in end-product quality. Flour obtained from sprouted grains loses its thickening ability due to starch degradation. This results in baked products with smaller volume and sticky compact crumb structure (Kruger, 1989). The main cause of loss of grain quality is the greater activity of the enzyme α-amylase. Most of the currently available hard white winter wheat cultivars are susceptible to pre-harvest sprouting (Roozeboom, 1999). The probability of occurrences of rainfall during ripening and pre-harvest sprouting increases from western to eastern Kansas. The frequency of pre-harvest sprouting is likely to increase with increasing acreage of hard white wheat. One of the best ways to reduce the problem associated with pre-harvest sprouting is developing sprouting resistant varieties.

In the recent years concrete efforts were made by the wheat breeders at KSU to develop sprout resistant cultivars suitable for Kansas. Genetic variability for PHS has been evaluated and identified (Morris and Paulsen, 1987). The breeders at KSU now have identified potential sources of tolerance and are incorporating the sprout resistant genes into the high yield cultivars. One experimental line with excellent tolerance to PHS is KS01HW163-4, which was selected from the cross between Trego and a sister of Betty. KS01HW163-4 was crossed to Heyne, a sprout susceptible cultivar released by K-State in 1998. About 200 double haploid populations from this cross will be available in the Spring of 2006. Genotyping (internal genetic code, heritability and molecular markers) of this population will be carried out in the laboratory of Dr. Allan Fritz (funded from other sources). In this proposal we are requesting funds to phenotype (observed outward physical, structural and functional traits) this population to better understanding the genetic and physiological basis of traits associated with sprouting tolerance. Combining phenotypic and genotypic data will allow us to identify chromosomal regions associated with trait and provide DNA markers that can be used for marker assisted selection. We will also develop plant materials than can be used to better understand the basis of tolerance to PHS.

Project Location(s):

1. Agronomy Department, Manhattan, Kansas (field and controlled environment studies).

2. South Central Kansas Experiment Site, Hutchinson, Kansas (field studies).

3. Hays Research Center, Hays, Kansas (field studies).

Duration of the Project: The proposed research was for 2 years. This proposal represents the year 2 of the proposed 2 years.

Progress Report
Summary and Details of Work (15 October 2007 – 15 January 2008)

The falling number test for the 208 double haploid lines was completed and the data is currently summarized and analyzed. The data on germination index and falling numbers were also collected the second experiment, which was aimed at understanding the impact of drought and heat stress during grain filling period on pre-harvest sprouting (PHS) of wheat (the two parents i.e. PHS tolerant and PHS susceptible). The results of the second experiment clearly indicated that environmental factors (high growth temperature and drought) had significant influence on PHS. The PHS tolerant parent lost it tolerance when grown under high temperature and drought conditions. This is very important keeping in view the variable environmental conditions (particularly high temperature and drought conditions) during grain filling periods of wheat production.

A third experiment was initiated during the last quarter with an objective of understanding in the influence exogenous application of growth hormones, particularly gibberellic acid (germination promoter), abscisic acid (ABA) and gibberellic acid inhibitor (e.g. paclobutrazol) on the impact PHS under stress conditions. The plants have completed vernalization and are currently being grown in growth chambers. They are at booting stage. The plants will be treated with various chemicals and exposed to different environmental conditions in the next two weeks and carried through harvest to quantify the impact of various hormones and environmental conditions of PHS of the two parents (one tolerant and one susceptible to PHS). The results from this experiment will be presented in the next quarterly report.