A 1975 fig crop reference chapter written by W.B. Storey contains pedigree information involving 30 cultivars from the University of California breeding program and early California. The data were compared with the records from the US Department of Agriculture and statements from two other sources. Graphical representations were used to determine differences among the authors. All data are supplied in this article and supplemental materials. An estimate of correct parentage is presented in the final graph.
Almond growers are seeking ways to reduce costs but maintain yield. Intensive planting systems with greater planting densities using trees on growth-controlling rootstocks, combined with mechanical pruning and shake-and-catch harvesting are becoming popular. In this study we examined the responses of six almond cultivars with distinctive architecture grafted onto five rootstocks with varying degrees of vigor control. Trees were planted in 2018 in a nursery row and left to grow without pruning until Winter 2021. Pruning involved a rudimentary hedging treatment akin to mechanical pruning. Branching and tree structure were recorded in 2020, before pruning, and again at the end of 2021, after one season’s growth following pruning. A rating system was developed to record qualitative data on central leader dominance and the number, length, basal diameter, and, in some cases, branching angle of axillary shoots and including scaffold branches. Relatively few changes were recorded in the basic growth habit of these trees in response to pruning. Before pruning, the most common rootstock effect was on axillary shoot production. After pruning, the most common rootstock effects were on scaffold branching and the length of subterminal axillary shoots. Further studies are required to determine how these differences produced by the interaction between pruning and rootstock may affect the productivity of fruit-bearing trees. Although in this study with young trees we were not able to record crop yield, the results highlight that it is mainly the scion–rootstock combination, with or without pruning, that determines the potential productivity of fruiting canopies. Scion–rootstock combinations that produce narrow upright canopies naturally with strong central leader dominance and highly branched canopies are preferred for superintensive growing systems with or without use of mechanical hedging.
Different sources of cytoplasmic male sterility (CMS) are used to produce hybrid onion seed. The most commonly used source of CMS in onion is S cytoplasm (S-CMS), and male fertility is restored by a dominant allele at the nuclear male-fertility restoration locus (Ms). Male-sterile plants possess S cytoplasm and have the homozygous recessive genotype at Ms; seed propagation of male-sterile plants is possible by crossing with a male-fertile maintainer plant or inbred possessing normal (N) male-fertile cytoplasm and the homozygous recessive at the Ms locus (N msms). Some commercially important onion populations possess S-CMS and high frequencies of the dominant Ms allele, eliminating the possibility to develop maintainer lines. An alloplasmic source of CMS (Gal-CMS) was developed by backcrossing the cytoplasm of Allium galanthum into the nuclear background of onion. The advantage of Gal-CMS is that the dominant allele at Ms does not restore male fertility, making this source of CMS useful for the development of male-sterile lines from populations possessing S cytoplasm and dominant allele(s) at Ms. In this research, a single nucleotide polymorphism unique to the cytoplasms of A. galanthum and Gal-CMS was identified, useful to distinguish Gal-CMS from other onion cytoplasms.
Knowledge of the genes underlying a given trait is highly useful for developing molecular markers for breeding and is the foundation for future genomic crop improvements. The cultivated strawberry, F. ×ananassa, is a valuable horticultural crop. Genome sequencing revealed that of the four diploid strawberry subgenomes contributing to the F. ×ananassa octoploid genome, the woodland strawberry, F. vesca, subgenome is dominant. Thus, F. vesca is an important system for determining gene function and should be used as a source of genetic diversity for F. ×ananassa breeding. Ethyl methanesulfonate mutagenesis of H4 F7-3, an inbred line of F. vesca, resulted in one M2 line that did not produce any strawberries over a 3-year period in the greenhouse. This line was named fruitless 1. The fruitless 1 phenotype results from a single gene recessive mutation. Microscopic characterization revealed that fruitless 1 failed to produce fruit because anthers fail to develop properly before meiosis, resulting in no pollen production. This report of fruitless 1 facilitates further studies of the line.
Lettuce drop caused by Sclerotinia minor is a damaging disease of romaine lettuce (Lactuca sativa L.) production in California. Introgression of partial resistance from wild, primitive, or heirloom accessions into modern cultivars could improve integrated management approaches to the disease. Breeding methods for lettuce drop resistance are not well developed and hinder the development of new lettuce drop–resistant cultivars. The objective of this work was to develop a pedigree-based breeding method for introgression of lettuce drop resistance into modern romaine germplasm. Progeny from crosses between the partially resistant cultivar Eruption and the susceptible romaine cultivars Darkland and Hearts Delight were selected in a modified pedigree breeding scheme. Families were evaluated for disease incidence and selected for lettuce drop resistance in artificially infested field experiments conducted in the summer and fall. Infected plants of partially resistant lines commonly do not produce seed, and therefore selection of resistant plants from infested nurseries is not possible. Noninfested field experiments were used to select individual plants with improved horticultural characteristics for seed production, but from within resistant families only. Evaluation and selection of progeny using this breeding scheme occurred from the F2:3 through the F5:6 generations. In all generations, superior resistance was identified in the ‘Eruption’ × romaine crosses. The breeding scheme generated eight green romaine-type inbred lines with better resistance than the romaine parent and better head weight than ‘Eruption’. Use of the new romaine lines as parents in backcrosses to romaine produced F2:3 families with high levels of resistance. The pedigree method used in this research can be implemented with any source of resistance, but is constrained by the use of family selection and the inability to select individual plants for resistance directly. Breeding schemes that use single seed descent or molecular markers are alternative approaches that would enable selection for resistance on individual genotypes.
Chrysanthemum ‘Bai Tian Xing’, ‘Huang Ching Chin’, ‘Pink Pearl’, and ‘NCHU-001’ plants were preheated at 35 °C for 24 hours to induce heat tolerance. The recently fully expanded leaves were detached, kept in a moist Ziploc bag, and then subjected to 35, 40, 45, 47.5, 50, 52.5, 55, 60, or 65 °C for 20 minutes. After dark-acclimatized at room temperature for 30 minutes, leaves were measured for Fv/Fm value with a chlorophyll fluorescence parameter. Results showed that ‘Bai Tian Xing’ had the highest critical (Tcrit) and midpoint temperature (Tmid). Mean Tcrit and Tmid were shown to be 47 and 50 °C, respectively, and Tmid gave greater distinguishment of Fv/Fm value among cultivars. Plants of four cultivars were acclimatized at 15 to 40 °C for 3 days and 35 °C being the most effective temperature to induce a heat-tolerant response in chrysanthemum. Required inducing time to reach a stable leaf Fv/Fm value ranged from 4.6 to 11.1 hours among cultivars. All cultivars had similar required time to reach visible bud between summer and autumn crops (except NCHU-001), but all had delayed flowering in the summer crop. There is a negative linear relationship between flowering heat delay and leaf Fv/Fm value (R2 = 0.93). Progenies from reciprocal crossing of ‘Bai Tian Xing’ × ‘NCHU-001’ and ‘Huang Ching Chin’ × ‘Pink Pearl’ were also subjected to treatments for Fv/Fm measurements and observed for time to flowering in the summer crop. All combinations showed negative linear relationship between time to flowering and leaf Fv/Fm value (R2 = 0.70–0.87). Two plants, 109-W001Y and 109-W003Pi, showed early flowering habit and good flower performance under heat conditions were selected. All four cultivars and the two selected lines were measured for photosynthetic parameters under day/night temperatures of 35/30 or 25/20 °C in growth chambers. All cultivars and lines showed decreased net photosynthetic rate and dark respiration rate under 35/30 °C when compared with 25/20 °C. Relatively higher net photosynthetic rate and lower dark respiration rate in ‘Bai Tian Xing’, ‘109-W001Y’, and ‘109-W003Pi’ under 35/30 °C, when compared with the other three cultivars, might have contributed to better flowering performance in the summer.