|Overview of Breeding Strategy|
Objective - To develop rice cultivars that will benefit
Decrease Production Costs and Reduce Risks
Increase Crop Value
Maintain Industry Standards of Quality
Main and Ratoon Crop Yield- Central to all breeding programs is development of cultivars which have improved yield potential. Rice is unique in that after the main crop is harvested, the field can be re-flooded for a ratoon, or second crop. New shoots of growth develop from the stubble that is left in the field and these shoots produce grain. Highly productive cultivars can produce about half of the main crop yield as a ratoon crop. The Gulf Coast area provides a long enough growing season that ratoon cropping of rice is feasible. The ratoon crop has been called the Providence crop because relatively high yields can be produced from relatively little input by the producer. Thus, for every single grain that a farmer plants in the ground in the spring, hundreds of kernels can be harvested by the fall. Components of yield include number of tillers (stems), number of kernels/panicle-tiller, and kernel size (weight). The breeding program endeavors to develop cultivars which will have high main crop and ratoon yield potential under a diversity of environmental growing conditions.
Milling Yield- The grain that is harvested from the field in the fall is called rough rice. Each kernel consists of a straw-like covering (hull) over the rice seed that is coated by a bran layer (brown rice). Most people consume rice as white milled whole grain. During the milling process, the hull and bran layers are removed through abrasion, leaving whole and broken kernels of white milled rice. Farmers are paid for the amount of whole milled kernels that they produce per acre, not just rough rice. Thus, developing cultivars which have high whole grain milling yields directly impacts the farmers' profitability.
Although production of whole milled grain is the ultimate objective, there are many obstacles that a farmer is faced with during the growing season that may affect production. The breeding program selects for improvement in many different traits in an effort to develop cultivars which can withstand a wide range of stresses due to pathogens, insects, weeds, and inclimate weather.
Seedling Vigor- Rapid emergence of seedlings through the soil is critical for establishment of a uniform plant population. Temperatures during the planting season can vary widely and thus, strong seedling vigor is particularly important if a cold snap occurs after planting. Rapid growth during the seedling stage will allow farmers to flood their fields early. Flooding of rice fields is not necessary for plant growth but it is used as a non-chemical means of controlling weeds. Rice is unique in that it can grow under aquatic conditions whereas many weeds cannot.
Plant Height and Lodging Resistance- Since the 1980's, most rice cultivars grown in Texas have possessed the semidwarf gene which reduces plant height and strengthens the stem holding the grain. Conventional height cultivars which do not possess the semidwarf gene tend to lodge (fall down) prior to harvest. This type of cultivar is particularly vulnerable to high winds which are common during the fall hurricane season on the Gulf Coast. In addition, farmers can boost yields by using higher fertility rates with semidwarfs without significantly increasing plant height. Deployment of semidwarfing genes in cereal crops around the world has dramatically increased yields while reducing losses due to lodging. This resulted in what has been called the "Green Revolution" in crops.
Days to Harvest Maturity- Breeders have made dramatic progress in reducing the time required for the plant to reach harvest maturity. This reduces the exposure of the crop to inclimate weather that can result in yield losses. Most current cultivars mature in 110 to 130 days from planting which is a 3 week decrease in the growth cycle from cultivars that were grown during the 1940's. Farmers that are interested in ratoon cropping want very early maturing cultivars so that the second crop will be flowering while it is still warm in the fall. Cool temperatures during flowering of the second crop will result in reduced seed set and lower yields.
Resistance to Pathogens- The two most prevalent diseases of rice worldwide are blast (caused by Pyricularia grisea) and sheath blight (caused by Rhizoctonia solani). Although other diseases occur, these two fungal organisms cause reoccuring problems for rice producers in the U.S. These pathogens result in reduced yields and milling quality which affect the farmers' economic bottomline. Over the past 10 years, the USDA-ARS rice breeding program in Texas has made significant accomplishments in improving rice cultivars for disease resistance (e.g. cultivars Jefferson and Saber). This has been accomplished by deploying resistance genes in combinations that provide broad-spectrum resistance as well as identifying and incorporating new resistance genes from rice germplasm sources from other parts of the world. Enhancing the plants' natural defense mechanisms will reduce the reliance on chemical control of rice pathogens and will reduce crop losses due to disease.
Resistance to Insects- There are several insect species that attack the rice plant at different growth stages. The rice water weevil (RWW) feeds on the roots of the rice plant early during the growing season and result in reduced yields. The three species of stem borers that occur in the Texas Rice Belt feed inside the stalks causing them to weaken and lodge. The rice stinkbug attacks developing grains causing discoloration of the kernels and increased breakage during milling which reduces the crop value. The fall armyworm defoliates rice from the seedling stage to maturity with most damage occurring before heading. The chinch bug damages seedling rice by removing plant sap with piercing-sucking mouth parts. Severe damage can result in poor rice stands that compromise yield. Selecting for cultivars having improved tolerance to insect pests has been very difficult because of problems associated with rearing insects and setting up controlled screening tests. Some progress has been made in selecting for tolerance to the RWW because of access to screening locations where heavy natural infestations of the insect occur. However, most producers monitor their fields for insects throughout the growing season to determine if economic thresholds have been reached and then use chemical and cultural methods for control. Researchers have worked to teach farmers how to scout their fields for insects and have cooperated with chemical companies to register chemicals that pose low risk to non-target organisms but are effective against rice pests.
Conventional rices are long, medium, or short grains having distinct cooking properties as specified by industry end-users. Specialty rices possess unique attributes that are desired by the consumer or end-user. Although the majority of the breeding effort is directed towards development of cultivars for conventional markets, it is important to have cultivars that meet the needs of niche markets because these generally command a premium that is passed on to the farmer. Thus, we strive to have portfolio of cultivars for US producers that will help them be competitive in all of these markets.
Niche Markets- These require specialty rices that usually have unique sensory and cooking traits that are preferred by defined groups of consumers.
Aromatics- Generally a long grain rice that cooks dry and fluffy and smells like popcorn (e.g. Dellmont).
Basmati-like- Extremely slender long grain rice which cooks dry and fluffy and smells like popcorn. During cooking, the grains elongate to over twice their original size.(eg. Sierra)
Jasmine-like- A long grain rice that cooks soft and sticky and smells like popcorn (e.g. Jasmine 85).
Arborio- An extremely large medium grain with a very large chalky center that is used to make Italian dishes like risotto.
Baldo- A very bold medium grain that is desired in some Mid-Eastern markets.
Japanese Premium Quality- Unique very bland tasting short grain rice that is desired by the Japanese market (e.g. Koshihikari).
Waxy- Rice cooking quality is largely determined by the ratio of amylose/amylopectin in the grain. Waxy rice has no amylose and is all amylopectin. When cooked as whole grain, this type of rice is extremely sticky and slick. Flour and starch produced from waxy rice is being used by the ingredients industry as a thickener in sauces and gravies, as well as in fat-reduced products like low fat yogurt and salad dressing.
Parboil and Canning Stability-Some rices possess a unique gene which produces a better cooked product after parboiling or canning. Parboiled rice is essentially pre-cooked and is generally used by large food chains because of its stability of grain integrity when served from steam tables. Further processing after parboiling is needed for rice that is used by the canning industry (i.e. soups). Cultivars which possess the gene for superior processing quality have reduced starch losses during parboiling and improved grain shape integrity after canning. This gene is not commonly found in U.S. cultivars but has been introduced from the Mexican cultivar Jojutla to produce superior processing rices (e.g. Dixiebelle and Bolivar).
New Uses- Innovations in technology and an evolving consumer market allow for the development of new concepts in rice sensory and cooking quality. The breeding program interacts with the rice industry end-users to identify new market opportunities and ways to exploit the natural genetic variation in rice to fill these markets. An example of this has been the development of the cultivars Cadet and Jacinto. These cultivars were developed in partnership with the processing industry and possess atypical long grain cooking quality. This combined with new processing technology has resulted in a rice product that is particularly suited for the European export market.
Organic Market- The consumer market for organically produced foods has increased dramatically over the last two decades. These products are now commonly found in mainstream grocery stores instead of just specialty stores. From the production field to the consumer, there are stringent requirements placed on any product that is to be certified as organic. Farmers usually have much lower yields using organic cultural management and thus, the cost of production is much higher. The breeding program is evaluating genetic lines from other countries to identify ones that may be particularly suited for production under organic conditions. This would reduce the cost of production, increase the profit to farmers and allow this market to expand further.