French prunes growing on marianna 2624 (P. cerasifera × P. munsonianna; M 2624), myrobalan seedling and 29C (P. cerasifera; MS and M 29C, respectively) were planted in 1981 on a clay type soil, and evaluated for growth and yield components over a 10 year period. Thirty replicate trees per treatment were pruned and grown under uniform irrigation and fertility regimes. There were no tree size differences among rootstocks after 10 years growth even though initial and seasonal trunk cross sectional area differences were observed. Trees on MS rootstock were highest yielding in the initial 2 years of fruiting, but cumulative yields were not different as a function of rootstock. More rootstock suckers were counted on M 2624 than myrobalan rootstocks. Excavations revealed that trees on MS had a deeper root distribution. No statistical differences were observed with regard to fruit size and fresh to dry fruit weight ratios.
William H. Olson, Steve Southwick and Jim Yeager
Leland E. Francois
Garlic (Allium sativum L.) salt tolerance was determined in a 2-year field plot study. Saline treatments were imposed by irrigating with water that was salinized with 1 NaCl: 1 CaCl2 (w/w). The electrical conductivities of the irrigation water was 1.4 (control), 3.1, 5.8, 8.8, 12.0, and 14.8 dS·m–1 in 1990 to 1991 and 1.4, 2.0, 3.9, 5.8, 7.8, and 9.9 dS·m–1 in 1991 to 1992. Considering both years, relative bulb yield was reduced 14.3% with each unit increase in soil salinity >3.9 dS·m–1. Increasing soil salinity significantly reduced all yield components (i.e., bulb weight and diameter; plants per unit area). Percentage of solids in the bulb was significantly reduced as soil salinity increased. Leaf tissue accumulated significantly higher Cl, Na, and Ca concentrations then did bulb tissue.
Greenhouse and field experiments were conducted to determine the influence of transplant age on growth and yield of `Dixie' and `Senator' summer squash (Cucurbita pepo L.). Dry weight and leaf area measurements indicated that 28- to 35-day-old greenhouse-grown transplants grew more slowly after transplanting than plants that were 10, 14, or 21 days old. Older transplants flowered earlier; however, earlier flowering did not result in higher early yields. Transplants of varying ages did not differ greatly in yield and yield components in the field, although all transplants had higher early yields than the directly seeded controls. Results from these experiments suggest that 21 days may be a reasonable target age for transplanting summer squash. If transplanting were delayed by adverse planting conditions, 21-day-old transplants would likely have at least a 10-day window of flexibility before yields would be reduced notably by additional aging.
Gina E. Fernandez and Marvin P. Pritts
The objective of this experiment was to determine the effects that altering the probable source-sink relationships would have on subsequent growth and yield components under field conditions. The balance between vegetative and reproductive growth was altered by imposing light stress (shading) on various growth phases, or removing primocanes, floricanes or fruit. Removal of primocanes significantly increased yield the year of removal. However, if primocane removal coincided with canopy shading, this increase in yield was not achieved. Overall, a significant negative correlation existed between 1991 and 1992 yields. Treatments with high yields in 1991 had low yields in 1992, and visa verca. This evidence-suggests that: 1) primocanes and floricanes are competing for light, not photosynthates during the flowering and fruiting period and 2) altering the balance of vegetative and reproductive growth one year had a significant effect on growth the subsequent year.
Teryl R. Roper and Marianna Hagidimitriou
Carbohydrate concentration may be important for flower initiation and fruit set in cranberry (Vaccinium macrocarpon Ait.). Fruit set has been shown to be a major limiting factor in yield component analysis. The objective of this research was to identify carbohydrate concentrations in cranberry tissues at various stages of development under field conditions. Samples of two cranberry cultivars, `Stevens' and `Searles' were collected during the 1989 season using a 13 cm diameter probe. Samples were divided into fruit, uprights, woody stems and roots. Carbohydrates were quantified by HPLC. Nonstructural carbohydrates were primarily sucrose, glucose, fructose and starch. Soluble carbohydrate concentration was stable throughout the season in tissues analyzed, while starch content was high early in the season then decreased during blossom and fruit set. This work shows that starch reserves in leaves and stems apparently are remobilized to support fruit set in cranberry.
Christophe N. Kouamé, Hortense A. Djidji and Koffi Goli
Pepper (Capsicum spp.) is an important component of various cropping systems and dishes in Cote d'Ivoire. The need to meet local market demand has prompted the development of high-yielding hot pepper varieties. Three local selections and 20 AVRDC-introduced breeding lines were evaluated in a three-replicate randomized complete block design. Data were collected on fruit and plant characteristics as well as on fruit yield and yield components. Large variations were found in all studied variables. Date of 75% flowering occurred between 52 and 77 days after sowing. First harvest date varied from 99 to 134 days after sowing, while plant height at first harvest ranged from 42 to 92 cm. Fruit size and fruit form were quite diverse. Maximum total fresh fruit weight (5490 g/plot) was about 10 times higher than that of the lowest-yielding (557 g/plot) entry. Selection within those lines has potential to contribute to the improvement of pepper productivity in Cote d'Ivoire.
J.T. Baker, D.R. Earhart, M.L. Baker, F.J. Dainello and V.A. Haby
Triploid watermelon (Citrullus lanatus Thunb.) was grown on the same plots in 1990 and 1991 and fertilized with either poultry litter or commercial fertilizer. Additional treatments included bare soil or plots mulched with black polyethylene, and plots with or without spun-bonded fabric row covers over both bare soil and mulch. Watermelon yields were unaffected by fertilizer source in 1990 butwere significantly higher for poultry litter than for commercial fertilizer treatment in 1991. Polyethylene mulch significantly increased postharvest soil NO3 and leaf N concentrations in 1990 and increased yield and yield components in both years. There were no beneficial effects of row covers on yield in either year, presumably because no early-season freezes occurred.
J.M. Mutisya, J.A. Sullivan, S. Couling, J.C. Sutton and J. Zheng
The relationship between severity of leaf scorch epidemics, caused by Diplocarpon earlianum, and components of vegetative growth and fruit yield was examined in `Kent' strawberry (Fragaria ×ananassa Duch.). Plants were treated in July with six densities of initial inoculum of the pathogen, and severity of leaf scorch was assessed at 2-week intervals from late July to late October. After an analysis of vegetative growth in late October, plants were overwintered in the field or grown in a greenhouse, and later assessed for yield components. Relationships between area under the disease progress curve (AUDPC) and plant growth and yield components were examined by regression analysis. Significant negative linear relationships were found between AUDPC values and number of green leaves, leaf area, leaf dry weight, crown number, crown dry mass, and root dry weight. Significant negative relationships were also found between AUDPC values and number of flowers and inflorescences, and total and marketable berries in the subsequent season, in plants maintained in the field or in the greenhouse. Mean berry weight was not significantly affected. Reduction in the number of crowns in plants affected by leaf scorch was a major factor limiting the yield of diseased plants. In an analysis of regrowth at seven weeks after fruit harvest, a significant negative linear relationships was found between AUDPC values and each growth component except crown dry weight. Collectively, the data provide a rationale to optimize timing of treatments, such as chemical fungicides or microbial agents, to control leaf scorch in August, September and October and thereby promote berry yield in the subsequent season.
Matthew D. Robbins, Jack E. Staub and Zhicheng Fan
To increase yield in cucumber (Cucumussativus L.), we designed a recurrent selection program utilizing phenotypic (PHE) and marker-assisted (MAS) selection for the development of multiple lateral branching (MLB; branches per plant), gynoecious, early genotypes possessing high fruit length to diameter ratio (L:D). These yield components are under genetic control of few quantitative trait loci (QTL; 2-6 per trait), which have been placed on a moderately saturated molecular linkage map. Four inbred lines, complementary for the target traits, were intermated and the resulting population underwent MAS and PHE, as well as random mating (RAN), for three cycles. Selections by PHE were visually made for all four traits at the whole plant level. Selections based on MAS contained the highest number of desired marker genotypes from 20 marker loci (SSR, RAPD, SCAR, SNP). Using the same selection scheme and intensity allowed a direct comparison of MAS to PHE. Selection was equally effective for MLB and L:D by MAS (3.5 and 3.0) and PHE (3.6 and 3.0), which were both superior to RAN (2.8 and 2.8). For earliness (days to anthesis) and gynoecy (percent female), MAS (41.8 and 26.6) was less effective than PHE (40.5 and 81.8) and RAN (41.0 and 80.9), which were equal. For yield (fruit per plant), RAN (1.90) and MAS (1.88) were equal, but less than PHE (2.15). After three cycles of PHE, further selection by MAS identified superior genotypes, which were intermated. Superior hybrids were selected by MAS and underwent one backcross generation. In some backcrosses, gains were made in every trait compared to the PHE Cycle 3 mean, while in other backcrosses, gains were made only in some traits. Improvement by MAS was very effective during line extraction for these yield components.
The grapevine shoot consists of nodes without clusters (inflorescences) basal to a zone in which leaf-opposed clusters are found at the nodes. Beyond the cluster zone leaf-opposed tendrils are borne at the nodes. The numbers and possible relationship of basal nodes and clusters are important in grapevine breeding and improvement. Basal node number influences cluster placement within the canopy, which relates to light penetration to the fruit and fruit maturation and to application of cultural practices, including harvest and cluster treatments. Cluster number is a primary yield component. Basal node and clusters numbers were counted on ten primary shoots each of forty grapevine (Vitis) accessions. The accessions analyzed are cultivars and wild species collections held in the United States National Plant Germplasm System. The correlation coefficient of the number of basal nodes and number of clusters was calculated using the means of the ten observations per accession. Basal node and clusters numbers were negatively correlated; the correlation coefficient was -0.763, which is significant (P <0.001). The negative correlation of basal node and cluster number has implications for grapevine improvement.