Search Results
A tomato (Lycopersicon esculentum Mill.) breeding line (81B416) with' resistance to anthracnose caused by Colletotrichum dematium was crossed to three susceptible genotypes. Parental, F1, F2, and backcross populations were analyzed in the cross with `US28', while parental, F1, and F2 populations were tested in crosses of 81B416 with `US141' and 81B9. Inheritance of resistance was primarily additive, but 3- and 6-factor scaling tests indicated the presence of dominance and epistatic effects. The average broad-sense heritability estimate was 0.57; narrow-sense heritability was estimated at 0.42.
Abstract
A 6-parent diallel was used to study combining ability and type of gene action contributing to resistance in tomato (Lycopersicon esculentum Mill.) to anthracnose caused by Colletotrichum dematium (Pers. ex Fr.). The 6 parents, one set of F1, hybrids, and 5 selected reciprocal crosses were grown at 2 locations. Ripe fruit were harvested, puncture-inoculated with the pathogen, and subsequently evaluated for resultant lesion diameter. No reciprocal effects were found at either location for the 5 crosses studied. The analysis of variance for parent and F1 hybrid performance revealed a genotype × location interaction. Combining ability analysis based on the F1 hybrids alone indicated a significant general combining ability (GCA) effect. The specific combining ability (SCA) and GCA × location interaction mean squares were smaller than the GCA value but were still significant. Differential performance over locations of the hybrids of one line was primarily responsible for the GCA × location interaction. Analysis of variance and covariance of parental arrays indicated partial dominance in the direction of susceptibility. Narrow sense heritability for the trait was 70% over both locations.
Dormant coffee (Coffea arabica L.) flower buds require water stress to stimulate regrowth. A xylem specific watersoluble dye, azosulfamide, was used to quantify the uptake of water by buds after their release from dormancy by withholding water. In non-stressed flower buds, the rate of water uptake was generally slower and variable. In stressed flower buds, the rate of uptake tripled from one day to 3 days after rewatering and preceded the doubling of fresh and dry weight of buds. Free, ester, and amide IAA levels of developing flower buds were measured by GCMS-SIM using an isotope dilution technique with [13C6] IAA as an internal standard. Throughout development, the majority of IAA was present in a conjugated form and the dominant form was amide IAA. The proportions of amide and free IAA changed rapidly after plants were water stressed until day 3, and preceded the doubling of fresh and dry weight. Correlation coefficients of 0.9, 0.7, and 0.7 (p<0.l) were found between auxin content and fresh weight, dry weight, and rate of water uptake, respectively.
`Napoleon' grafted onto Colt, F/12-1, and MxM60 rootstock were planted into three types of tree holes: augered; backhoed, and backhoed plus fumigation. The auger treatment resulted in lower yields, smaller trunk cross-sectional area (TSCA), and smaller canopy volume when compared to backhoed holes. Fumigation had no significant effect. Trees on Colt rootstock were more precocious, had a smaller TCSA and canopy volume, greater cumulative yield efficiency, and, in 1987, the smallest fruit weight. The yield efficiency of Colt was the highest until 1988, when it was surpassed by MxM60, but was still similar to F/12-l. Yields were highest on trees of MxM60 in 1987 and 1988.
Abstract
‘Redskin’ peach (Prunus persica Batsch.) trees, planted at a high-density spacing (3 × 5 m), were fertilized annually with urea at rates of 45, 90, or 135 kg·ha−1. Trees were trained to a trapezoidal hedge by annual, mechanized, summer pruning. Within each fertilizer plot, subplots of five summer-pruning treatments were applied. Single pruning treatments were made at 120 days after full bloom (DAFB) and 150 DAFB. Paired pruning treatments were applied 30 + 60 DAFB, 60 + 120 DAFB, and 60 + 150 DAFB. Pruning at 120 DAFB alone, and in combination with pruning at 60 DAFB, decreased trunk cross-sectional area (TCA), fruit soluble solids content, and weight, while increasing the percentage of surface that was red. Pruning at 30 DAFB followed by a second pruning at 60 DAFB decreased leaf Ca concentration in comparison to pruning treatments applied later in the season. Increasing N fertilization also decreased leaf Ca. Year, N level, and pruning treatments gave a statistical interaction on mean fruit weight and yield.