Plant and Horticultural Science Studies: Crops

Enhanced characteristics for crop productivity and yield

Abstract Examples

McIntyre AC, Francis DM, Hartz TK, Gunter C. Fertility influence of the US Midwestern soils on yellow shoulder disorder in processing tomatoes. Hortscience 2007.

The economics of processing tomato production are driven by soluble solids content, viscosity, color, and color uniformity of the fruit. Ripening disorders that affect color are a major limitation to the economic success of processing whole-peel and diced products. The causes of ripening disorders are not completely understood, although it is clear that soil nutritional status, weather, plant genetics, and interactions among these variables are important factors. We sampled both soil and fruit from fields in Michigan, Ohio, and Indiana and were able to correlate soil fertility properties and fruit color. The correlation between soil properties and fruit color was different for fine- and coarse-textured soils. Fine-textured soils presented more frequent, but weaker, correlations with absolute color and within-fruit color differences when compared with coarse-textured soils. For fine-textured soils, exchangeable K correlated with a measure of within-fruit variation. Other measurements of K nutrition correlated to the same extent. The highest correlations were identified between soil-available P and L* and L*diff. In coarse-textured soils, exchangeable K correlated with L*, b* and Hue’. K center dot Mg-1/2 ratio and K., yielded higher correlation coefficients with absolute color measurements when compared with fine-textured soils. Soil-available P was correlated with L*, a*, Hue degrees, and C*. For coarse soils, K-Mg-1/2 ratio, K-act, and available P were important properties when the color of tomato fruit is of value. In all cases, higher exchangeable K and P nutrient status had a positive correlation with fruit color. Our sampling could not detect interactions among weather, genetics, and soil, and further work will be necessary to clearly describe the role of interactions in determining fruit quality in tomatoes.


Stanton MA, Scheerens JC, Funt RC, Clark JR. Floral competence of primocane-fruiting blackberries prime-jan and prime-jan grown at three temperature regimens. Hort Rev 2007.

We investigated the responses of staminate and pistillate floral components of Prime-Jan and Prime-Jim primocane-fruiting blackberry (Rubus L. subgenus Rubus Watson) to three different growth chamber temperature regimens, 35.0/23.9 degrees C (TIT), 29.4/18.3 degrees C (MT), and 23.9/12.8 degrees C (LT). Temperature was negatively related to flower size, and morphologically abnormal floral structures were evident in 41% and 98% of the MT- and HT-grown plants, respectively. Anthers of LT- and MT-grown plants dehiseed. The viability of pollen (as deduced through staining) from Prime-Jan grown at LT or MT exceeded 70%, whereas that of Prime-Jim pollen was significantly reduced (< 40%) by the MT regimen. In vitro pollen germinability (typically < 50%) was negatively influenced by temperature but was unaffected by cultivar. Pollen useful life was diminished under HT conditions; LT-grown pollen held at 23.9 degrees C retained 63% of its original germinability over a 32-h period, while the germinability of that held at 35.0 degrees C for 16 hours decreased by 97%. Virtually all flowers cultured under HT conditions were male sterile, exhibiting structural or sporogenous class abnormalities including petaloidy and malformation of tapetal cells or microspores; FIT anthers that were present failed to dehisce. Stigma receptivity, pistil density, and drupelet set were also negatively influenced by increased temperature; values for these parameters of floral competency among control plants were reduced by 51%, 39%, and 76%, respectively, in flowers cultured under HT conditions. In this study, flowering, fruiting parameters, and presumably the yield potential of Prime-Jan and Prime-Jim, were adversely affected by increased temperature. However, their adaptive response to heat stress under field conditions awaits assessment.


Kleinhenz M, Wszelaki A, Walker S, Ozgen S, Francis DM. Vegetable crop yield and quality following differential soil management (compost versus no compost application) in transitional- and certified-organic systems in Ohio [Abstract]. Hortscience; 2006.

Successful organic farming requires synchronizing soil-based processes affecting nutrient supply with crop demand, variable among and within crops. We report here on two studies conducted in transitional- (TO) and certified-organic (CO) systems containing subplots that, annually, were either amended with compost or not amended prior to vegetable crop planting. Dairy-manure compost was added at rates providing the portion of a crop’s anticipated nitrogen requirement not provided by a leguminous rotation crop and/or carryover from previous compost application. In the TO study, potato (2003), squash (2004), green bean (2005), and tomato (2006) were planted in main-season plots in open fields and high tunnels, and beet, lettuce, radish, spinach, and swiss chard were planted in high tunnels in early spring and late fall. Long-term CO open-field plots (±compost) were planted to multiple varieties of lettuce, potato, popcorn, and processing tomato in 2004–2006. Drip irrigation was used in all TO plots and CO lettuce and processing tomato plots. Treatment effects on crop physical and biochemical variables, some related to buyer perceptions of crop quality, were emphasized in each study. Yield in TO, compost-amended plots exceeded yield in unamended plots by 1.3 to 4 times, with the greatest increases observed in high-tunnel-grown mesclun lettuce and the smallest response observed in potato. Similar results were found in CO plots, although compost effects differed by crop and variety. The data suggest that: 1) compost application and the use of specific varieties are needed to maximize yield in organic vegetable systems in temperate zones, regardless of age; and 2) production phase management may influence buyer-oriented aspects of crop quality.