| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
a Dep. of Botany and Plant Sciences, Univ. of California, Riverside, CA 92521-0124
b Univ. of California Cooperative Extension, Kern County, CA
c Univ. of California Cooperative Extension, Tulare County, CA
d Dep. of Nematology, Univ. of California, Riverside, CA 92521-0415. This work was funded in part by the Bean/Cowpea Collaborative Research Support Program (USAID Grant no. GDG-G-00-02-00012-00), the California Dry Bean Advisory Board, and the Univ. of California Agricultural Experiment Station. The opinions and recommendations herein are those of the authors and not necessarily those of USAID
* Corresponding author (Jeff.ehlers{at}ucr.edu).
ABSTRACT
‘California Blackeye 50’, a blackeye-type cowpea [Vigna unguiculata (L.) Walp.] (Reg. No. CV-290, PI 655235) cultivar, was developed by the University of California, Riverside, and released by the California Agricultural Experiment Station in 2008. California Blackeye 50 distinguishes itself from the industry standard California Blackeye 46 (CB46) by its greater individual seed weight and grain quality features that are desired in the dry package trade and export markets of this crop. California Blackeye 50 was bred using traditional pedigree breeding methods. It has resistance to the two predominate races (races 3 and 4) of Fusarium wilt (caused by Fusarium oxysporum f. sp. tracheiphilum) found in the irrigated production systems of the southwestern United States, while other currently grown blackeye-type cowpea cultivars adapted to the region either have resistance only to race 3 of this disease or are susceptible to both races. Selection for resistance to Fusarium wilt was conducted using a "clip-dip" procedure in the greenhouse. California Blackeye 50 is also resistant to the two most important root-knot nematodes of the region, Meloidogyne incognita (Kofoid and White) Chitwood and M. javanica (Treub) Chitwood. Selection for resistance to root-knot nematodes was conducted at specially managed infested field sites and in "pouch tests" in growth chambers. California Blackeye 50 has given grain yields equivalent to CB46 in 13 field tests conducted over 4 yr at multiple environments in the Central Valley of California while producing highly attractive grain that is larger and more than 15% heavier.
Abbreviations: CB5, California Blackeye 5 • CB46, California Blackeye 46 • CB50, California Blackeye 50 • FSP, California Foundation Seed Program • GI, galling index • KREC, University of California Kearney Research and Extension Center • SREC, University of California Shafter Research and Extension Center • UCR, University of California, Riverside
‘California Blackeye 50’, a blackeye-type cowpea [Vigna unguiculata (L.) Walp.] (Reg. No. CV-290, PI 655235) cultivar, was developed by the University of California, Riverside, and released by the California Agricultural Experiment Station in 2008. Blackeye-type cowpea has been an important part of the cropping system in the southwestern United States for more than 100 yr (Mackie, 1946; Hall and Frate, 1996; Ehlers and Hall, 1997), providing a valuable element of crop diversity for the cotton-based cropping systems of many parts of the region. California blackeye 50 (CB50) distinguishes itself from ‘California Blackeye 46’ (CB46), the predominate blackeye-type cowpea cultivar grown in the southwestern United States, by its greater individual seed weight, grain quality features that are desired in the dry package trade and export markets of this crop, and broader based resistance to the soilborne disease Fusarium wilt caused by Fusarium oxysporum Schlechtend. f. sp. tracheiphilum (E.F. Sm.) W.C. Snyder & H.N. Hans. and to root-knot caused by the root-knot nematodes Meloidogyne incognita (Kofoid and White) Chitwood and M. javanica (Treub) Chitwood.
Fusarium wilt is a major production problem facing blackeye cowpea growers in the southwestern United States. Race 3 of this disease is present in many fields throughout the Central Valley of California, and any new blackeye cowpea variety needs to have resistance to this race to be acceptable for commercial production. The cultivar CB46 was released in 1989 (Helms et al., 1991b) in response to an urgent request by the blackeye industry for a variety with resistance to Fusarium wilt race 3, to which the formerly predominate variety ‘California Blackeye 5’ (CB5) was susceptible. Up to that time, since the late 1940s following its release in 1946 (Mackie, 1946), CB5 had been grown widely in the southwestern United States, and its grain quality set the worldwide standard for blackeye cowpea. Although its grain quality is not as good as CB5, CB46 largely displaced CB5 because of its resistance to Fusarium wilt (race 3) and high yield potential (Hall and Frate, 1996). Fusarium wilt race 4 is also present in the Central Valley of California but is less widespread than race 3. However, race 4 has been identified in blackeye production fields at several San Joaquin Valley locations that are more than 100 km apart, and the potential is present for spread of this race due to strong selection pressure from the widespread cultivation of the race 3 resistant cultivar CB46 and because of field-to-field soil movement on farm machinery, especially by custom harvesting operations that serve growers over fairly wide areas. Since it is difficult for a grower to know which race is present in any given field (except when CB46 has been planted previously and sick plants have appeared during the growing season), it is preferable from a practical standpoint to have a cultivar that is resistant to both races, so that such a determination is not necessary.
The root-knot nematodes M. incognita and M. javanica are important pests of cowpea in the southwestern United States, particularly on sandy soils (Ehlers and Hall, 1997). The currently grown cultivars of blackeye cowpea in the region, CB46 and CB5, carry the root-knot nematode resistance gene Rk that confers strong resistance to most populations of M. incognita, but they are susceptible to M. javanica. We report here that reproduction and root-galling on CB50 caused by M. javanica were considerably lower compared to CB46 in growth chamber "seedling growth-pouch" tests and in two trials conducted in field plots infested with M. javanica. Similar to the situation in which different races of Fusarium wilt may be present, it will be difficult for a grower to know which nematode is present in any given field, and it is preferable from a practical standpoint to have a variety that is resistant to both nematodes, so that such a determination is not necessary.
Methods
California Blackeye 50 was developed using a pedigree breeding approach beginning in 1999 with a biparental cross of California Blackeye 46 (CB46) x University of California, Riverside (UCR) breeding line 98-8-622-2. The pedigree of 99-8-622-2 is UCR-P-58/N294, where N294 is a UCR breeding line with pedigree of IT84S-2049/524B//524B. Breeding line 524B was developed from a cross of ‘California Blackeye 3’ and CB5, both of which are previous standard California cultivars. IT84S-2049 is a small-seeded African cowpea breeding line developed at the International Institute of Tropical Agriculture and that carries gene Rk2, which provides strong resistance against Rk-virulent forms of M. incognita and M. javanica root-knot nematodes (Roberts et al., 1996). UCR-P-58 is a blackeye-type breeding line developed from a cross of blackeye breeding line UCD 8517 (Gwathmey et al., 1992) and ‘California Blackeye No. 88’ (Helms et al., 1991a). The F1 CB46 x 98-8-622-2 was grown in the greenhouse during fall 1999, and the F2 was grown in the field at the UCR Citrus Experiment Station during summer 2000. Single plant selection was conducted from the F3 to F6 generations in nurseries grown during spring 2001 (F3) and 2002 (F5) at the UCR Coachella Valley Agricultural Research Station, summers of 2001 (F4) and 2002 at the UCR Citrus Experiment Station (F5), and at the University of California Shafter Research and Extension Center (SREC) during summer 2003 (F6). 03Sh-50 was developed from bulking a single F6 family of row 50 of the +2003 UCR Blackeye Breeding Nursery at SREC. The F6 bulked seed was used to plant replicated yield trials in 2004.
From 2004 to 2007, 13 yield trials were conducted at multiple locations in the San Joaquin Valley, CA (Table 1 ). These trials were conducted on raised beds with furrow irrigation using inter- and intrarow spacing and management systems typical of commercial fields in the San Joaquin Valley. The test fields were free from race 4 Fusarium wilt and Rk-virulent root-knot nematodes. Machine-harvested grain yields and seed size data were measured for CB50 (03Sh-50) and CB46 in each trial. All trials were conducted with four-row plots replicated four to six times in a randomized complete block design. Individual plot sizes were 9 m long, except for the three strip trials (Table 1) where plots consisted of 12 rows that were 100 m long. Each plot was buffered at the end by a 6-m strip of crop or a fallow break. Yield and grain size data were collected from whole plot for the strip trials and from the center two rows of each plot for the smaller-scale trials. All data from replicated field trails and greenhouse Fusarium wilt trials were analyzed by ANOVA using Statistix 8.0 (Analytical Software, Tallahassee FL).
|
Remnant seed of 03Sh-50-17-9 from the summer greenhouse subline grow-out was planted in the greenhouse at UCR in September 2006 and February 2007 for multiplication of Breeder seed. About 9 kg of Breeder seed was produced and handed to the California Foundation Seed Program (FSP) based at the University of California, Davis, in early June 2007 for production of Foundation seed. The initial Foundation seed was planted on about 0.2 ha by FSP in 2007 at the University of California, Davis, campus farm. Certified seed was produced from this Foundation seed by a commercial grower under the supervision of California Crop Improvement Association in 2008.
Characteristics
California Blackeye 50 has botanical and morphological characteristics similar to CB5 and CB46 with respect to flower color (white), leaf size (4.5 by 4 cm) and shape (ovate), foliage color and texture (shiny, deep green with slight blistering), and small bands of red pigmentation at the stem and branch nodes. Individual grains of CB50 are kidney shaped and less spherical than grains of CB46. Grains of CB50 have a small-sized "eye" or pigmented portion around the hilar region that was rated 5 on the USDA Objective Description rating of eye size, similar to the eye size found on grains of CB46 and CB5. This eye on the seed coat does not leak dark pigments during boiling or from canning. Canning tests conducted by the Department of Food Science at Purdue University of grain grown in two locations (Kearney and Shafter, CA) in 2006 indicated that CB50 has excellent canning quality, on the basis of an informal assessment of the canned product by experienced blackeye industry personnel.
California Blackeye 50 has an erect growth habit and is less compact than CB46, but pods are held predominately above the crop canopy (Fig. 1 ). The exceptional vegetative vigor of this cultivar provides buffering during periods of high temperature and moisture stress that often occur in its area of adaptation. With a May sowing date and typical growing conditions in the San Joaquin Valley, CA, CB50 begins flowering about 54 d after sowing and matures its first flush of pods in about 95 d from sowing, which is similar to CB5. Under the same growing conditions, CB46 flowers in about 50 d and matures its first flush of pods in 90 d. California Blackeye 50 was evaluated in performance trials conducted in California from 2004 to 2008 under the designation 03Sh-50-17.
|
California Blackeye 50 has consistently produced significantly larger and whiter grain than CB46 (Fig. 2 ). Side-by-side visual evaluations of grain samples of CB50 and CB46 produced in the same environment conducted by growers and industry personnel over several years have consistently judged CB50 to have a brighter white and more attractive appearance than CB46. Production-scale test lots of CB50 from strip plots that have been marketed have commanded premium prices, according to Cal Bean and Grain (Pixley, CA), a major cooperative (and marketer) of blackeye cowpea growers in California. On the Munsell Color Chart (Munsell Co., 1958), the white background color ("noneye" portion) of the seed coat of CB50 grains rate as a Hue 5Y, Croma 1, Value 9, while the white background color of the seed coat of CB46 grains is Hue 5Y, Croma 2, Value 8.
|
Two years of data from a commercial warehouse cleaning facility that processed large lots of grain produced in on-farm strip trials indicated that CB50 will provide performance as good as or better than CB46 in terms of USDA Grade and clean-out, the percentage of yield lost during the grain cleaning operation. Cal Bean & Grain Cooperative cleaned large-scale grower and SREC strip trials that were conducted in 2006 and 2007 and provided clean-out information for the bulked (over replication) grain produced by each variety. Clean-out percentages and USDA Grade for a strip trial conducted in a farmer's field near Visalia, CA, in 2006 were as follows: 17.2% for CB46, US Grade #2 and 12.2% for CB50, US Grade #1. Final commercial clean-outs for the 2007 SREC strip trial were 11.5% for CB46, and 11.6% for CB50. Clean-outs for a large-scale 2007 grower trial conducted near Wasco, CA, were 7.3% for CB46 and 9.7% for CB50, with the best yield and best grade being made by CB50 (US Grade #1, 1.0% damage, 0.1% splits) compared with CB46 (US Grade #2, 1.4% damage, 0.1% splits).
California Blackeye 50 has shown strong resistance to both races of Fusarium wilt present in California in greenhouse root clip–dip tests in terms of both plant appearance and degree of stem discoloration (Table 2 ). The resistance has not been tested in the field, but these clip–dip tests have always predicted field reactions to Fusarium wilt.
|
|
Foundation seed is being maintained by the Foundation Seed Program at the University of California, Davis. Certified seed is maintained by the California Crop Improvement Association, Davis, CA, and is currently available through an online ordering system at http://ccia.ucdavis.edu/. Plant Variety Protection has been applied for by UCR and is currently pending, and royalties will be assessed on the sale of Certified Seed. Small amounts of Breeders seed for research purposes may be obtained from Jeff Ehlers at the University of California, Riverside. A single nucleotide polymorphism genetic fingerprint of CB50 has been established using the Illumina GoldenGate molecular marker assay for 1344 loci (Ehlers et al., 2009).
Footnotes
All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher.
Received for publication January 26, 2009.
References
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
and internal stem discoloration (Stem) scores
of ‘California Blackeye 5’ (CB5), ‘California Blackeye 46’ (CB46), and ‘California Blackeye 50’ (CB50) to race 3 and race 4 of Fusarium wilt in greenhouse "root clip-dip" tests conducted in 2006 and 2007.