We thank Mitzi Aguirre for assistance with the fruit quality analyses and Richard A. Jones, Oscar Lorenz, and Vincent Rubatzky for constructive comments on the manuscript. Mention of company names and products is for the benefit of the reader and
Bell pepper (Capsicum annuum L.) cultivars were grown in nine Florida environments to evaluate phenotypic stability of marketable fruit yield (t-ha-') and mean fruit size (g/fruit). A stable cultivar excelled for a particular trait when grown in either favorable or unfavorable environments. A stable cultivar for a given trait was defined as one with an individual mean greater than the grand mean (mean of all cultivars) (x > X), a regression coefficient (b1) ≤ 1 (individual genotypic mean regressed against environmental means), nonsignificant deviation mean squares from regression (S2d), coefficient of linear determination (R2) > 0.50, and coefficient of variation (cv) < the pooled cv. `Ssupersweet 860', `Whopper Improved', and `Ranger' were stable for mean marketable fruit weights and fruit size, and `Ssupersweet 860' and `Whopper Improved' were stable for mean fruit size. Bell pepper cultivars were differentiated for phenotypic stability of yield and fruit size or adaptability to diverse environments. Therefore, through stability analyses, bell pepper plant breeders can identify cultivars or select advanced breeding lines that express adaptability for fruit yields or size to diverse environmental conditions or cultural practices.
1 Soil scientist; e-mail: firstname.lastname@example.org . 2 Entomologist; e-mail: email@example.com . 3 Horticulturist. 4 Entomologist. 5 Agronomist. 6 Entomologist. 7 Horticulturist. The authors wish to thank the Washington State Tree Fruit
In a 2-year study (1993-94), tomato (Lycopersicon esculentum Mill. `New Yorker') plants grown in a sandy loam soil in field lysimeters were subjected to four water table depth (WTD) treatments (0.3, 0.6, 0.8, and 1.0 m from the soil surface). In 1994, precipitation during the flowering stage was far above average and apparently led to waterlogging in the shallowest WTD treatment, while in the drier year (1993), the deepest WTD treatment suffered from drought stress. In general, over the 2 years, the 0.6-m WTD showed the best yields and largest fruit, while the 1.0-m WTD showed the lowest yields and smallest fruit. However, the incidence of catfacing, cracking, and sunscald was generally higher in the 0.6 m WTD treatment and lower in the 1.0-m WTD treatment. Furthermore, fruit firmness was generally greatest for the two deeper WTD than for the shallower WTD. To strike a balance between yield and quality, a WTD of between 0.6- and 0.8-m is recommended for tomato production on sandy loam soils.
Selection criteria to identify primocane-fruiting red raspberry seedlings (Rubus idaeus L.) with high, early yield are desirable in regions with short growing seasons. To identify possible parents contributing these desirable characteristics, ‘Heritage’, ‘Redwing’, and two genotypes from the Minnesota breeding program were subjected to yield component analysis. In all genotypes, yield was determined by canes/meter of row, fruit per node, and fruit weight. Over the 3-year period, ‘Heritage’ had the highest yield/meter of row, yield per cane, fruit per cane, and number of fruit per fruiting node among all genotypes. Component compensation was highest for ‘Redwing’, while MN 652 had the greatest degree of independence among components. In selecting seedlings for early fruiting and high yield, high cane densities and/or large fruit size will be needed.
Whole-tree sprays of Release LC [predominantly gibberellic acid] (GA,) were applied in a commercial peach [Prunus perisca (L.) Batsch.] orchard in the California Central Valley on three dates from mid-June (about 90 days after full bloom = 28 days before harvest) to late July (14 days postharvest) 1993 at 50, 75, 100, and 120 mg·liter-1. Gibberellin (GA) reduced the number of flowers differentiated in 1993, thereby reducing fruit density in 1994, when sprays were applied by early July 1993. Sprays in late July did not reduce flowering and fruiting density in the following year. In 1994, there were fewer fruit located on the proximal third of the shoot after GA sprays of 75,100, and 120 mg-liter' applied on 15 June compared to hand-thinned controls, and reduction was linear with increase in GA rate. Fruit numbers in the middle and distal sections of shoots were reduced by all 15 June and some 9 July GA sprays, with fewer fruit as concentration increased. However, the distribution of fruit within shoot sections, after GA treatments during floral differentiation, expressed as a percentage of the total number of fruit along fruiting shoots, showed even fruiting compared with hand thinning. Due to reduced flowering in response to GA treatments in June and early July 1993, the hand-thinning requirement was significantly reduced, with no thinning required in 1994 from 15 June 1993 GA sprays. All sprays applied in early July resulted in 40% to 60% fewer fruit removed during thinning than the nontreated controls. Sprays in late July were ineffective. Sprays of GA applied in mid-June at 50,75, 100, and 120 mg·liter and sprays of 120 mg·liter-1 GA applied in early July (4 days preharvest) increased the firmness of `Loadel' cling peach (about 26% improvement in June sprays) in 1993. The salable yield of fruit (after removal of the undersized fruit) was the same on hand thinned and on non-hand thinned trees treated with GA on 15 June at 50 mg·liter-1. The salable yield of fruit was increased by GA sprays of 50 and 75 mg·liter applied on 9 July 1993 compared to controls. There were no differences in fruit size (by weight or diameter) among the aforementioned treatments and hand thinning. GA sprays of 75,100, and 120 mg-liter' applied on 15 June 1993 tended to reduce salable yield, but fruit size increased with decreased yield. Based on the results obtained in 1993 and 1994, we believe that Release LC has good potential for chemically thinning peaches in California.
In 3 ‘McIntosh’ apple (Malus domestica Borkh.) orchards, yield was positively related to fruit numbers, but negatively related to fruit size. Increases in fruit size from thinning were proportionately less than decreases in fruit numbers. Fruit thinning increased the percentage of larger fruits, but reductions in yield were such that the actual number of large fruits was either unchanged or reduced.
A multiple regression analysis of yields of ‘6718 VF’ tomato (Lycopersicon esculentum Mill.) from 11 field plots along an ambient ozone gradient in southern California indicated that ozone was responsible for a significant reduction in fruit size. Ozone dose accounted for 85% of the reduction in fruit size and was at least 3.3 times more important than any of the monitored meteorological variables in predicting the percentage of marketable fruit. High ambient ozone depressed production and caused a significant decrease in fruit size over time. A model describing the reduction in marketing container yield (% reduction = 0 + (.0232 x dose)) predicted a 50% reduction at a dose of 2000 pphm-hours > 10 pphm.
Ten fresh market tomato (Lycopersicon esculentum Mill.) genotypes were evaluated for yield stability in 7 environments within Florida. Genotype × environment interaction was significant for yield of marketable fruit. Linear relationships between mean yields of individual genotypes and environmental mean yields were evaluated to determine genotype stability. Mean square deviations from linear regression (s2d), regression coefficients (b1) and coefficient of linear determination (R2) were used to evaluate phenotypic stability. ‘Sunny’, Castlehy 1035’, ‘Burgis’, ‘FTE 12’, and ‘Duke’ were considered stable and high yielding. An advanced breeding line, 827015-IBK, was considered stable but low yielding. ‘Hayslip’, D76127, ‘Flora-Dade’, and ‘Walter PF’ were considered unstable. This study suggests that yield stability differences occur among fresh market tomato genotypes. Therefore, selection of tomato genotypes for improved adaptability should be considered in tomato breeding programs.