Search Results
You are looking at 1 - 5 of 5 items for :
- Author or Editor: Larry D. Knerr x
- HortScience x
The available U. S. Cucumis sativus germplasm collection (754 Plant Introductions) was electrophoretically screened for genetic diversity using 39 enzymes representing a total of 57 loci. Polymorphisms were observed at 18 loci which included g2dh, gpi1, gpi2, gr1, gr2, idh, mdh1, mdh2, mdh3, mpi2, pep-la2, pep-pap2, per4, pgd1, pgd2, pgm1, pgm3, and skdh. Appropriate crosses were set up to verify the inheritance of and test linkages among these loci. Four allozyme linkage groups have currently been identified. Representative linkages and their genetic distances include: gpi1 - mdh3 (20); pgm1 - pgd1 (25); and g2dh - pgd2 (19). Additionally, crosses were made to marker stocks to test for linkages between some allozyme loci and loci coding for resistance to downy mildew and anthracnose, long hypocotyl, divided leaf, short petiole, glabrous, compact plant, determinate, little leaf, and bitter free (bi).
A new malate dehydrogenase (MDH) locus (Mdh) was identified in cucumber (Cucumis sativus L.) by using an extraction buffer containing sucrose and 2-mercaptoethanol. This fourth locus localizes on starch gels between the previously described Mdh-2 and Mdh-3 loci, necessitating the renaming of existing loci. Given previous MDH nomenclature in cucumber, this locus should be Mdh-3, and the former Mdh-3 is more correctly labeled Mdh-4. Mdh-x designates the interlocus heteromer formed between Mdh-2 and Mdh-4. Interpreting our data in terms of previous work, we hypothesize that Mdh-1 codes for a microbody isozyme; Mdh-2, Mdh-4, and Mdh-x code for cytosolic isozymes; and Mdh-3 codes for a mitochondrial isozyme.
Thirty-eight cultivated accessions of the diverse Cucurbitaceae were electrophoretically surveyed using 13 enzyme systems. Included were representatives from 6 of the 6 Cucurbitaceae tribes, 9 genera, and 17 species. Additionally, several cultivars or groups were included for those species possessing marked morphological diversity such as the 7 groups of Cucumis melo var. melo and 7 of the numerous cultivars representing Cucurbita pepo. Zymograms were scored for the presence or absence of bands measured in mm from the origin. Cluster analysis (complete linkage method) was used to detect affinities among the accession surveyed. Data suggest that: 1) Cucumis melo (x=12) possessed greater biochemical affinity with C. sativus (x=7) than with either C. anguira or C. metuliferus (both x=12); 2) Sechium edule and Cyclanthera pedata. both members of the tribe Sicyeae, were more closely associated with members of other tribes than with each other; 3) Some cultivars of Cucurbita pepo shared greater affinity with Cucurbita moschata than with other cultivars of C. pepo. Additional observations as well as their possible implications will be presented.
The U.S. cucumber germplasm collection (753 accessions) and U.S. adapted processing cucumber (Cucumis sativus L.) inbreds and hybrids were surveyed for response to 6.7 kg ae/ha of chloramben. Nine plant introductions (PI 165952, 173892, 179676, 275411, 277741, 279464, 279465, 436609, and 482464) were classified as tolerant to chloramben, based on percentage and rate of field emergence and seedling vigor. All adapted strains evaluated were susceptible to chloramben injury. The chloramben-tolerant accessions (C0) were subjected to two cycles of recurrent half-sib family selection that resulted in 11 C2 families. These families, a susceptible adapted line (WI 2870), and the resistant PI 436609 were evaluated in the field (6.7 kg ae/ha) and laboratory (0.0, 0.01, and 0.0001 M) for response to chloramben challenge. Significant (P = 0.05) differences between families were observed for percentage emergence and phytotoxicity ratings. Correlations between emergence and phytotoxicity ratings at two dates were low (r2 = -0.32 and – 0.05). Significant (P = 0.05) interfamily differences were also recorded for percentage germination, hypocotyl length, primary root length, and number of lateral roots in the laboratory. Correlated responses between these growth variables were high (r2 = 0.78 to 0.84), but correlations between field and laboratory observations were low (r2 = -0.31 to 0.24). We hypothesize that the genetic response to chloramben challenge under laboratory conditions depends on the concentration of the chemical administered. Chemical name used: 3-amino-2, 5-dichlorobenzoic acid (chloramben).