Location: Vegetable Research2010 Annual Report
1a. Objectives (from AD-416)
Develop pinkeye-type southernpea (cowpea) lines that exhibit yield potential equivalent to leading blackeye-type bean cultivars. Identify host-plant resistance to emerging viral diseases (e.g., Tomato spotted wilt) in southernpea genetic resources and determine the genetic control of resistance. Develop open-pollinated advanced breeding lines of sweet peppers (Capsicum annuum) and Habanero-type peppers (C. chinense) highly resistant to root-knot nematodes. Develop Habanero-type F1 hybrid pepper cultivars which are tolerant to heat stress and highly resistant to Tomato spotted wilt virus, Pepper mottle virus, and root-knot nematodes.
1b. Approach (from AD-416)
The southernpea pinkeye-type cultivar GreenPack-DG and the high-yielding blackeye bean cultivar California Blackeye No. 46 will be used as the parental lines to initiate a plant breeding project with the major goal of breaking the apparent yield barrier in pinkeye-type southernpeas; the two cultivars will be crossed and pedigree and single-seed-descent breeding procedures will be employed to quickly advance progeny populations three generations per year (spring field cycle, fall field cycle, and a winter greenhouse cycle). Efforts to identify sources of resistance to Tomato spotted wilt virus (TSWV) in southernpea will involve the development of an efficient and effective methodology for evaluating germplasm and then the progressive evaluation of all available sources of resistance to other cowpea viruses, a collection of named southernpea and blackeye bean cultivars, and the 720 accession core of the USDA cowpea germplasm collection. If a source of TSWV resistance is identified, the methods of classical genetics will be employed to determine the genetic control of that resistance. A backcross breeding procedure will be used to incorporate a dominant root-knot nematode resistance gene into several non-bell, open-pollinated, sweet-type peppers; a similar approach will be used to incorporate a dominant resistance gene into open-pollinated Habanero-type peppers. An effort will be initiated to develop a series of candidate F1 hybrid Habanero-type cultivars that are resistant to root-knot nematodes and the major viral diseases and tolerant to heat stress. The USDA-developed, open-pollinated, Habanero-type cultivar TigerPaw-NR will be crossed with open-pollinated Habanero-type accessions from the Texas A&M University; TigerPaw-NR is a well adapted, high yielding cultivar that is homozygous for a dominant gene conditioning resistance to root-knot nematodes and the Texas accessions are homozygous for dominant genes conditioning resistance to Tomato spotted wilt and Pepper mottle viruses, compact plant habit, and the ability to set fruit during periods of high temperatures.
3. Progress Report
The program to develop pinkeye-type southernpea lines that exhibit yield potential equivalent to leading blackeye-type bean cultivars was continued; selections from a field-grown F2 population made during the summer of 2009 were advanced two generations off-season in the greenhouse using a single-seed-descent breeding scheme, and populations of F5 plants grown from the seeds harvested from the second greenhouse planting were evaluated in a 2010 field test for needed plant habit, yield, pod, and seed characteristics. Efforts to evaluate the 677-accession core of the USDA Cowpea Germplasm Collection for reaction to a tomato strain of the Tomato spotted wilt virus (TSWV) were completed; the TSWV infections were restricted to the inoculated tissues and none of the newly developed leaves on inoculated plants exhibited symptoms. Efforts were continued to develop various types of open-pollinated Habanero- and sweet-type peppers that exhibit high levels of resistance to root-knot nematodes. Truhart-NR, a root-knot nematode resistant, pimento-type pepper cultivar, was released 20 October 2009; PA-560, a root-knot nematode resistant, yellow-fruited, Habanero-type pepper breeding line, was released on 20 October 2009; and PA-566, a root-knot nematode resistant, pimento-type pepper breeding line was released on 30 April 2010. A program to develop F1 hybrids of Habanero-type peppers that are resistant to root-knot nematodes and virus diseases and tolerant to heat stress was continued; three experimental hybrids were evaluated in a second year of field tests.
1. Release of Truhart-NR, a root-knot nematode resistant, pimento-type pepper cultivar. Truhart Perfection was once a predominant pimento-type pepper cultivar for the food processing industry and it is still recommended for use by specialty crop growers in several southern states. However, Truhart Perfection is highly susceptible to root-knot nematodes, a major pest of peppers throughout the southern United States. In 2000, ARS researchers at Charleston, SC, initiated efforts to incorporate a dominant root-knot nematode resistance gene into a Truhart Perfection-type genetic background. These efforts resulted in the 20 October 2009 release of the root-knot nematode resistant, pimento-type cultivar Truhart-NR. The newly released cultivar is recommended for use by both home gardeners and commercial growers. It is recommended particularly for use by organic farmers and growers of specialty crops because these segments of the pepper industry do not have easy access to alternative production sites or nematicides and nematicide application equipment.
2. Release of PA-560, a root-knot nematode resistant, yellow-fruited, Habanero-type pepper breeding line. The increasing popularity of hot peppers in the United States has created intense interest in the Habanero, an extremely pungent type of pepper belonging to the domesticated Capsicum species C. chinense. Root-knot nematodes are major pests of Habanero-type peppers, and the ideal solution to this pest problem would be the use of resistant cultivars. In 1995, efforts were initiated by ARS researchers at Charleston, SC, to transfer a root-knot nematode resistance gene from a Scotch Bonnet-type pepper into a yellow-fruited Habanero-type pepper. These efforts resulted in the 20 October 2009 release of the yellow-fruited, root-knot nematode resistant, advanced breeding line PA-560. PA-560 is recommended for use as a parental line by pepper breeders interested in developing yellow-fruited, root-knot nematode resistant cultivars of Habanero-type peppers. The dominant nature of the gene conditioning the root-knot nematode resistance trait makes PA-560 useful as an inbred parent for development of root-knot nematode resistant F1 hybrids.
3. Release of PA-566, a root-knot nematode resistant, pimento-type pepper breeding line. The root-knot nematodes are major pests of pimento-type peppers in the United States, and the ideal solution to this pest problem is the development and use of resistant cultivars. The pimento-type cultivar Pimiento L is widely grown in the Southern states where it can produce good yields under high temperature conditions. Pimiento L, however, is quite susceptible to root-knot nematodes. In 2000, ARS researchers at Charleston, SC, initiated efforts to transfer a nematode resistance gene from the pimento-type cultivar Mississippi Nemaheart into a Pimiento L-type genetic background. These efforts resulted in the 30 April 2010 release of the root-knot nematode resistant, pimento-type breeding line PA-566. The newly released breeding line is recommended for use as a parental line by pepper breeders interested in developing root-knot nematode resistant cultivars of pimento-type peppers. PA-566 is a relatively well-adapted, pimento-type pepper, and is potentially useful in commercial production without further development. It is particularly recommended for trial for the organic, specialty crop, and home garden markets because these segments of the pepper industry do not have easy access to alternative production sites or nematicides and nematicide application equipment.
5. Significant Activities that Support Special Target Populations
A significant portion of the resources of this project is directed towards the development of southernpea and pepper cultivars needed by small farmers and limited resource producers. Several of the southernpea and pepper cultivars under development are targeted for use by market gardeners.