Blackeye cowpea mosaic potyvirus is the most easily observable seed-borne virus in cowpeas, but is typically seed-transmitted at lower rates (i.e., 0.1 to 2%) than the less conspicuous cowpea severe mosaic comovirus or cucumber mosaic cucumovirus. All three viruses are readily vector transmissible after seed-borne inoculum reaches the field, perpetuating and spreading the viruses. Individually and particularly in mixtures, these viruses are capable of decreasing both seed quality and yield. Disease-tolerant cultivars are available, but fail to control viral diseases. Development of superior new cowpea cultivars with multiple viral-disease resistance is clearly within reach and has become essential to long-term, sustainable, profitable cowpea production. This breeding objective requires public-research supported efforts by the combined cowpea seed and processing industries. Southern bean mosaic sobemovirus is also recognized as an important cowpea pathogen, but was encountered at a much lower frequency than the above three viruses in both plant and seed samples, in 1992 and 1993.
Kathryn R. Kleiner, John J. Frett, and James Nienhuis
Lima beans are an important vegetable crop to the processing industry in Delaware, but yields in Delaware are below other areas due to heat. The objective was to correlate RAPD markers from heat-tolerant and intolerant cultivars with phenotypic data. Twenty-five primers were used, 10 of which generated 25 polymorphic bands among 11 cultivars. MDS analysis of genetic distance among the cultivars shows segregation into two major clusters, with Kingston as a distant outlier. Kingston's position can be correlated to published data reporting its consistently good yields even when temperatures are high. The results of this study indicate RAPD markers may be used to screen for cultivars that have high yield potentials despite high temperatures. Further studies to screen F, and inbreeds will determine the usefulness of these markers in breeding programs.
R.L. Fery and P.D. Dukes
The USDA has released a new cream-type southernpea [Vigna unguiculata (L.) Walp.] cultivar that is well adapted for productionthroughout the southern United States. The new cultivar, named `Tender Cream', is the product of a backcross breeding procedure to transfer the dominant Rk gene for root-knot nematode resistance from `Floricream' into `Carolina Cream'. `Tender Cream' is resistant to cowpea curculio, root-knot nematodes, southern bean mosaic virus, cercospora leaf spot, southern blight, rust, and powdery mildew. `Tender Cream' outyielded the cream control in the 1992, 1993, and 1994 Regional Southernpea Cooperative Trials by 5.4%, 11.0%, and 18.8%, respectively. It outyielded its root-knot-nematode-susceptible `Carolina Cream' isoline by 22.3% in a replicated 1994 test conducted in a field infested with a natural population of the southern root-knot nematode. Canned samples of fresh `Tender Cream' peas scored well during 3 years of testing at the Univ. of Arkansas.
Mark J. Bassett
The inheritance of an induced mutant for spindly branch and male sterility (SBMS) was investigated in common bean (Phaseolus vulgaris L.) in F2 and backcross populations. The results support the hypothesis that the mutant is controlled by a single recessive gene. Extensive breeding work with SBMS, involving several thousand F2 progeny, produced no recombinant of the types expected if two closely linked genes controlled the character. Therefore, a single pleiotropic gene apparently controls SBMS. Allelism tests demonstrated that SBMS is allelic with sb but not with sb-2 and sb-3. The gene symbol sb ms is proposed for SBMS because it is a new allele at sb, with the order of dominance being Sb > sb > sb ms. Various ways to exploit the new mutant for marked male sterility are discussed.
Jesse Vorwald and James Nienhuis
and Nienhuis, 1997 ; Tohme et al., 1995 ). In a temperate-adapted, photoperiod-insensitive nuña bean breeding line, ‘PB24’, the effects of seed moisture content and chamber temperature were greater than the effects associated with popping time on the
H. M. Ariyarathne, D. P. Coyne, Anne K. Vidaver, and K. M. Eskridge
30 POSTER SESSION 4 (Abstr. 460-484) Breeding/Genetics/Molecular Markers
Paige Hanning, Dyremple B. Marsh, and Mohsen Dkhili
Chemically fixed nitrogen is a costly import for Caribbean Basin Countries. Increased cost of fertilizer only serves to reduce crop yields in these areas. This greenhouse research was undertaken to evaluate the N2 fixing capabilities and yield potential of several Phaseolus vulgaris lines developed for use in Caribbean Basin countries. Ten common bean lines from breeding programs at the Universities of Puerto Rico and Wisconsin and two efficient Rhizobium phaseoli strains were used for the study. Plants treated with Rhizobium UMR 1899 and UMR 1632 had significantly higher stem and leaf dry weight than the control plants. Bean lines WBR 22-34, WBR 22-50, WBR 22-55, PR9056-98B and the cultivar Coxstone showed increased dry matter accumulation over that of the control plants. Plants treated with the Rhizobium strain UMR 1899 had the highest stem and leaf dry matter accumulation. Nodulation was significantly higher when plants were treated with UMR 1632. The lines WBR 22-34 and PR 9056-98B produced more nodules than the other lines used. Pod yield as measured by number of immature pods was highest for PR 9056-98B when inoculated with Rhizobium UMR 1899.
D. P. Coyne, E. Arnaud-Santana, J. Beaver, and H. Zaiter
128 ORAL SESSION 37 (Abstr. 263–266) Vegetables: Breeding and Genetics
H.M. Ariyarathne, D.P. Coyne, A.K. Vidaver, and K.M. Eskridge
Biometry. University of Nebraska Agricultural Research Division journal series paper no. 11970. Research was conducted under Title XII Bean/Cowpea CRSP Project, Univ. of Nebraska, Univ. of Puerto Rico, and Dominican Republic under AID Contract No. DAN 1310
Soon O. Park, Dermot P. Coyne, Nedim Mutlu, James R. Steadman, and Geunhwa Jung
91 POSTER SESSION 10 (Abstr. 050-084) Genetics/Breeding/Biotechnology Friday, 30 July, 1:00-2:00 p.m.