Search Results
You are looking at 1 - 5 of 5 items for
- Author or Editor: Roger L. Vallejo x
Cultured cotyledon and leaf pieces of five cultivars of Lycopersicon esculentum Mill. were tested in six culture media for their ability to produce shoots for transformation studies. The no. of tissue pieces with callus/total tissue pieces, quality of callus (size and vigor), no. of tissue pieces with shoots/total tissue pieces, and shoot quality (size and vigor) were measured. Cultivars tested were `Campbell 28', `Flora-Dade', `UC82b', and two breeding lines, Fla.7171 and Fla.7324. The six media used were Murashige and Skoog medium supplemented with six combinations of indole acetic acid (IAA) and cytokinins: A) 1 mg/l IAA + 1 mg/l kinetin, B) 0.5 mg/l IAA + 2 mg/l kinetin, C) 0.02 mg/l IAA + 1 mg/l zeatin, D) 0.2 mg/l IAA + 2 mg/l zestin, E) 1 mg/l IAA + 2.5 mg/l BAP (6-benzyl amino purine), and F) 0.2 mg/l IAA + 1 mg/l BAP. Standard procedures were followed for culturing 4 - 5 mm pieces of cotyledon and leaves. Callus and shoot regeneration were greater, less variable and faster, in cotyledon than in leaf pieces. Media C and F gave the highest rates of callus and shoot production, respectively, in cotyledon tissue. Medium E gave the highest rate for both callus and shoot production in leaf discs. The best rates of shoot production were achieved with cotyledon tissue from cultivar UC82b cultured on media C (85.3%) and F (77.2%).
The objective of this research was to determine optimum plot size and number of replications to evaluate yield of sweetpotato (Ipomoea batatas Lam.) clones. The optimum plot size was estimated using the methods of maximum curvature and comparison of variances. The adequate number of replications was determined using the Hatheway method. Using the maximum curvature method, the estimated optimum plot size was 10 basic units (b.u. = six plants or 1.2 m2) for La Molina and San Ramon, and 5 b.u. for Tacna, Peru. Using the comparison of variances method, the optimum plot size was 15 b.u. for all locations tested. The adequate number of replications with a plot size of 15 b.u. was four.
A hybrid diploid potato population (Solanum phureja x Solanum stenotomum) with superior horticultural traits has been developed for breeding purposes. Because this highly advanced population has no resistance to potato virus Y (PVY), and because PVY pressure is very high in North Carolina, glandular trichomes from another diploid species, Solanum berthaultii, were introduced as a defense against aphids, the PVY vector. Two types of glandular trichomes, A and B, were transferred. Preliminary results show that genetic diversity and broad-sense heritability are adequate to transfer these traits; however, non-additive gene action was indicated in narrow-sense heritability estimates. Spearman's coefficients of rank correlation showed a low level of association between A and B trichomes; density of both types is postulated to be under the control of a Small number of genes.
Preliminary data on the genetics of glandular trichomes and the feasibility of incorporating A and B glandular trichomes and polyphenol oxidase (PPO) activity from Solanum berthaultii Hawkes (Ber) into an advanced S. phureja Juz. et Buk.-S. stenotomum Juz. (Phu-Stn) diploid potato population are presented. A random sample of four Phu-Stn clones was intercrossed with a sample of three Ber progenies (pollen bulk per progeny) segregating for high density of A and B glandular trichomes. Nine F1 families [(Phu-Stn) × Ber] were evaluated over two experiments in the greenhouse for A and B trichome density (5 mm2 of abaxial surface) and PPO activity 45 days after planting. A completely randomized design in an experimental hierarchical classification arrangement was used to quantify the genetic variability and to estimate broad-sense heritabilities (defined on an individual basis) for the attributes under study. To characterize the inheritance of these attributes further and to estimate narrow-sense heritabilities, fifteen backcross (BC) families were evaluated in a randomized complete-block design with three replications and analyzed by half-sib family analysis. Phenotypic and genotypic correlations between these attributes were also estimated. In the F1 families, broad-sense heritabilities were 0.59 and 0.41 for density of A and B trichomes, respectively. In the BC population, narrow-sense heritabilities were 0.15 and 0.08 for A trichome density and PPO activity, respectively; expression of B trichomes was almost absent in this generation. Genotype × environment interaction was significant for density of A trichomes and highly significant for density of B trichomes in F1 families. There was some level of positive association between density of A and B trichomes and PPO activity. Additive genetic variance of these attributes was very low in this study; therefore, selection schemes based on family selection and progeny testing would be an appropriate breeding strategy for improving these traits.
Glandular trichomes from some Solanum species have suppressed infestation by insects including green peach aphid, which is a main vector of potato virus Y (PVY) and potato leaf roll virus (PLRV), both of which contribute to a serious loss in potato production. Eight Solanum phureja Juz. et Buk.-S. stenotomum Juz. (Phu-Stn), three S. berthaultii Hawkes (Ber), nine F1 [(Phu-Stn) × Ber], fifteen backcross (BC) [(Phu-Stn) × F1], and seventeen reciprocal BC (BCR) [F1 × (Phu-Stn)] families were evaluated to determine the genetic variability and heritability of A and B glandular trichome density and polyphenol oxidase (PPO) activity. Experiments were carried out in completely randomized and randomized complete-block designs in the greenhouse. Genetic analysis was done using half-sib family and parent-offspring regression analysis. Phu-Stn showed a higher density of A trichomes than Ber and F1, while the BC and BCR had densities of A trichomes similar to Phu-Stn. B trichomes were not observed in Phu-Stn. Ber showed a high B trichome density, which was transmitted to the F1. In the BC, B trichomes were almost absent, but, in the BCR, the density of B trichomes was higher than that of BC. Ber and F1 had similar or higher PPO activity than Phu-Stn. PPO activity decreased in the BC, but, in the BCR, it was high and similar to Ber and F1. Broad-sense heritability estimates for A and B trichome density and PPO activity were from medium to high (0.48 to 0.77) in Phu-Stn, Ber, and F1. Narrow-sense heritability estimates for A and B trichome density and PPO activity were very low (0.04 to 0.24) in BC and BCR. In the BC families, additive genetic variance was very low for A and B trichome density and PPO activity. Half-sib family selection based on progeny testing and combined with BCs to Phu-Stn in subsequent generations would be a suggested breeding procedure to improve these traits. Phenotypic correlations between A and B trichome densities were 0.26 (F1) and 0.44 (BCR), between A trichome density and PPO activity 0.20 (F1) and 0.31 (BCR), and between B trichome density and PPO activity 0.04 (F1) and 0.27(BCR. Positive associations found between traits might facilitate simultaneous improvement for high levels of A and B trichome density and PPO activity.