Three selections from different bud sources of Bartlett pear were planted in a split block experiment grafted to five rootstocks in 1971. In 1992 and 1993, significant yield and yield efficiency differences occurred between the three selections. The highest yielding selection produced 51 and 40% greater weight then the lowest. The lowest yielding selection also had smaller fruit and lower soluble solids.
Differences of 37 and 52% occurred between the highest and lowest yielding rootstocks. There were also significant differences in trunk cross sectional area, yield efficiency. fruit pressure and soluble solids between rootstocks.
Meiotic asynchrony, lagging chromosomes, chromosome bridges, and variable chromosome numbers were associated with reduced pollen fertility in a red raspberry (Rubus idaeus L.) selection ‘Ore-US 1314’.
Mass selection for improved tenderness was conducted in the corn (Zea mays L.) cultivar ‘Hawaiian Super-sweet No. 9’. Two selection criteria were applied separately—a pericarp thickness measurement of mature kernels, and a bite test of immature ears on the plant. Selection was carried out at 10% intensity among 400 ears each for 3 cycles by pericarp thickness and for 4 cycles by bite test. Selection based on pericarp thickness led to a genetic advance of 9.2% per cycle (from average 73.6 to 53.3 μm), with a concomitant 2.9% increase per cycle in tenderness as evaluated by the bite test. Genetic advance following selection based on the bite test was 3.9% per cycle as evaluated by the bite test and 2.9% per cycle as evaluated by pericarp micrometry, the germinal and abgerminal sides of pericarp differed consistently, with germinal 14.5% thinner than the abgerminal, but correlated so well for all cycles that only one side is advised in a selection program. A significant correlation (r=0.98) was found between average bite-test scores and immature pericarp thickness, but correlations based on individual ears were low (r=0.24). Bite-test scores were subject to high error variability (CV =25%) as opposed to pericarp micrometry (CV=12%). Both techniques deserve recommendation for tenderness-selection programs, possibly as tandem criteria for successive cycles of selection.
Apricot production in México is limited; actually, the area devoted to this crop is ≈880 ha, from which 230 ha are established in Sonora State. The main cultivar is `Canino'. The fruit yield ranges from 15 top 20 t·ha-1. The present study tested 20 low-chilling (300-400 chill hours) requirements of apricot selections; `Nemaguard' was the rootstock used. On the fourth production year, from the 20 apricot selections tested, 7-23, 1-81, and 15-1 yielded 31.8, 20.2, and 15.5 t·ha-1, respectively. all of these selections showed higher yields than `Canino' (14.6 t·ha-1). The fruit of these apricot selections ripened by mid-May, exhibiting a similar fruit quality (size, flavor, color, and °Brix) in all the tested selections. We have not recorded any important insect pests or diseases during this trial.
A “gynoecious synthetic” (GS) population, developed by random mating of 50 adapted Cucumis sativus L. cultivars and breeding lines, and a “hardwickii semi-exotic” (HSE) population, developed by open-pollinating an F2 population derived from a cross between a Cucumis sativus var. hardwickii (R.) Alef. accession LJ 90430 and a gynoecious inbred line GY 14, were subjected simultaneously to S1 line (S1 and reciprocal full-sib (RFS) recurrent selection. S1 selection resulted in increased fruit number per plant in the GS and HSE populations, and in the GS × HSE population hybrid. In contrast, RFS selection did not result in increased fruit number per plant in the GS and HSE populations or their hybrid. The contrasting responses to S1 compared to RFS selection suggests that additive gene effects were more important than nonadditive effects in the expression of fruit number per plant. Correlated responses to selection resulted in increased number of days to harvest in the GS population, and in reduced percentages of gynoecious plants and pistillate flowers in the HSE population. No change in fruit firmness, and a reduction in length : diameter ratio of fruit only in the GS × HSE population hybrid developed through S1 selection, suggests that selection for increased fruit number per plant should not adversely affect these fruit quality characteristics in either the GS or HSE populations.
A base population of high specific gravity clones was established from a diploid hybrid population of Solarium tuberosum Group Phureja and Solarium tuberosum Group Stenotomum previously adapted to the long-day growing conditions in North Carolina. This base population was subjected to two 2-year cycles of recurrent selection. During each cycle, selections in the field were made on the basis of tuber smoothness, shape, and size. Tubers from unselected clones were bulked by plots. Tuber specific gravity was determined for the selected and unselected (bulk) clones. Tuber specific gravity was significantly greater in the selected than in the unselected clones in each cycle of selection.
Apricot production in México is limited; actually, the area devoted to this crop is ≈880 ha, of which 230 ha are established in Sonora State. The main cultivar used is `Canino'. The fruit yield ranges from 15-20 t·ha-1. The present study tested 20 low-chilling (300 to 400 chill hours) requirments of apricot selections; `Nemaguard' was the rootstock used. On the 4rth production year from the 20 apricot selection tested, 7-23, 1-81, and 15-1 yielded 31.8, 20.2. and 15.5 Ton.Ha-1, respectively; all of these selections showed higher yields than the Canino cultivar (14.6 t·ha-1). The fruit of these apricot selectiosn ripened by mid-May, exhibiting all the tested selection a similar fruit quality (size, flavor, color, and °Brix). We have not recorded any important insect pests or diseases during this trial.
Amplified fragment length polymorphisms (AFLPs) were used to analyze the relationships between sweet cherry (Prunus avium L.) cultivars and selections from the breeding program at the Pacific Agri-Food Research Centre in Summerland, Canada. Six pairs of preselected primers were used for the analysis of a total of 67 cultivars and selections. Scoring the absence and presence of 118 polymorphic DNA fragments produced a unique binary code for each cultivar and selection. Two phylogenetic trees were constructed using these 118 polymorphic fragments, one tree for 55 related cultivars and selections from the Summerland breeding program and the other for 23 self-incompatible cultivars of differing origins. The reliability of AFLP DNA fingerprints was confirmed by correlating relationships revealed by AFLP profiles with known genetic relationships of some sweet cherry cultivars and by a blind test for cultivar identification. Results indicate that AFLP analysis is a good technique to evaluate genetic distance and relationships in a sweet cherry breeding population.
‘Haida’ was the most effective of 15 red raspberry (Rubus idaeus L.) cultivars or selections in transmitting spur blight (Didymella applanata (Niessl) Sac.) resistance to progeny. Inheritance of the resistance reaction was quantitative and predominantly additive in nature.
Tandem mass selection in a sweet com (Zea mays L.) composite produced a 5-day gain in maturity, increased the percentage of plants with light-colored silks, and increased the number of kernel rows per ear. Although the differences in earworm resistance between generations were not statistically significant, they suggest a slight but steady increase through the first four cycles of selection. Because infestation of earworm [Heliothis zea (Boddie)] was very low in 1972, no selection was applied to the fifth generation for resistance, and the level of resistance based on mean larval weights and larval instars dropped. Tandem mass selection improved the sweet com population for certain agronomic characters, and maintained its level of earworm resistance.