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A fruit anomaly, pillowy (P), has been identified in processing cucumber This physiological disorder has been shown to be accelerated by water stress.
A series of experiments were conducted to determine postharvest handling procedures which minimize the appearance of pillowy after induction by water stress. Isogenic lines evaluated in RCB design with 3 replications where subjected to water stress during fruit enlargement. Fruits were then subjected to various storage temperatures and times before hydrocooling to 8°C. Cucumbers were then fresh pack processed and evaluated for % pillowy after 12 weeks,
The postharvest control treatmcnt (2 days, 26°C, 60% RH) produced 32%P to 51%P in fruit subjected to stress and 23%P to 39%P in unstressed fruit. In the optimal postharvest treatment (1 day, 26°C, 60% RH, then hydrocool to 8°C, 2 days, 15°C, 85% RH) fruits from stress plants exhibited 23%P to 39%P and those from nonstress plants showed 13%P to 26%P. Fruits from miniature leaf lines exhibited higher percent (37%) P ratings when compared to normal leaf lines.
A study was designed to determine whether temperature alone or temperature and relative humidity (RH) interactions affect the development of pillowy fruit disorder (PFD) in cucumber (Cucumis sativus L.). Fruit of `Calypso', `Flurry', `Carolina'? and inbred breeding line 39 were matured in four environments: cyclic and high (22 to 45C) and moderate (22 to 30C) temperatures at two RHs (35% and 75%). PFD symptoms were most severe at high temperature and RH; thus, both contribute to the development of this disorder. Line 39 had the highest PFD ratings, regardless of growing environment, a result indicating that cultigens respond differently to these imposed stresses.
Two experiments (1989 and 1990) were designed to characterize the response of cucumber (Cucumis sativus L.) plants with different leaf types [normal leaf (LL) vs. little leaf (ll)] to high soil moisture tension (SMT) and to determine whether hydrocooling would reduce the severity of pillowy fruit disorder (PFD). Comparisons were made among nine cultivars (7 LL and 2 ll) for aboveground vegetative and fruit response, and between two irrigation regimes. High SMT generally caused increased wilt ratings and stomatal conductance and decreased plant dry weight. PFD severity of fruit from watered plots was less [61% (Expt. 1, 1989) and 26% (Expt. 1, 1990)] than of fruit harvested from plots in which water was withheld. The response of the two ll cultivars to moisture stress differed depending on environmental conditions. Increased PFD severity was associated with increased temperature, lower relative humidity (RH), and excluding hydrocooling during postharvest handling. Of the four storage treatments examined, hydrocooling to ≈8.5C then storage at 15C and 85% RH for 4 days produced fruit with the least PFD symptoms. Fruit of `Carolina' (LL) exhibited the highest PFD ratings, while those of `Calypso' (LL) were consistently low compared to other cultivars. Processors can lower PFD incidence and severity by ensuring that adequate moisture is available to plants during fruit enlargement and that harvested fruit are hydrocooled before shipping and storage.
Three orange-mesocarp derivatives of the xishuangbannan cucumber (Cucumis sativus L. var. xishuangbannanesis Qi et Yuan), P100, P101, and P104; and NPI (P105), an unrelated cucumber (Cucumis sativus L.) reported to have orange flesh, were selected as parents for a diallel experiment to evaluate inheritance of orange cucumber mesocarp pigment over 3 years. Visual color intensity and carotenoid content were closely related. A preponderance of additive genetic effects for cucumber mesocarp pigmentation was observed in grade size 2 fruit (immature fruit used for pickling). Both additive and nonadditive genetic effects were important in grade size 4 fruit (mature). Years and yea× genotype interactions were highly significant for pigmentation of size 2 fruit, indicating the importance of environment on the expression of pigmentation in this size class. In contrast, color development was stable among years for size 4 fruit. P104 exhibited high general combining ability (GCA) estimates for size 4 fruit pigmentation across years, while P101 had high GCA estimates for size 2 fruit. The diallel analysis illustrated high fruit carotene content of parents per se. However, most hybrid combinations of the diallel reduced carotenoid content relative to parents, indicating both dominance for low carotenoid content for both fruit sizes and lack of genetic complementation among parents to enhance fruit color. Genetic control of pigmentation in size 2 fruit appeared to be independent of that for size 4 fruit.
Local production of organic tomatoes marketed directly to consumers is growing rapidly in the U.S. Midwest. Growers serving this market need cultivars that are well adapted to local climatic conditions, are competitive under organic management, and have end-use quality characteristics desired by their customers. Participatory plant breeding is a powerful, cost-effective approach with potential to engage growers in development of new cultivars optimally adapted to organic farming systems. To initiate a participatory breeding program for organic tomatoes an online grower survey was conducted to identify key plant traits, and a diverse set of tomato germplasm was evaluated under organic management to better understand horticultural constraints and identify adapted germplasm for further development. Tomato growers rated flavor as their top breeding priority, followed by disease resistance with late blight (LB) (Phytophthora infestans), early blight (EB) (Alternaria solani), and septoria leaf spot (SLS) (Septoria lycopersici) identified as the most problematic diseases. In field trials, foliar diseases were problematic in both years, though many entries exhibited partial resistance. Differences among entries in resistance to insect pests such as hornworms (Manduca sexta) were also observed. Yield varied widely among entries with some of the F1 hybrids and heirloom cultivars performing well despite significant disease pressure. Overall, we identified existing cultivars and F1 hybrids with potential to meet the immediate needs of Midwest organic tomato growers, and segregating breeding populations for further selection to be conducted on working organic farms.
Four nearly isogenic cucumber lines (Cucumis sativus L.) differing in leaf size [standard leaf (LL) vs. little leaf (ll)] and plant habit [indeterminate (DeDe) vs. determinate (dede)] were compared for their response to high soil moisture tensions in 1990 and 1996. Comparisons were made between lines for aboveground vegetative and fruit response, between two irrigation regimes, and among three postharvest treatments. Differences in vegetative plant response between lines were documented by wilting ratings, plant dry weight, fruit number and fresh weight, and fruit quality [i.e., fruit shape, seed size, seed cavity size, and pillowy fruit disorder (PFD)] ratings depending upon the stress environment. Postharvest treatment affected the quality of fruit recovered from plants subjected to water stress. Exposure of fruit at 15 °C and 85% relative humidity (RH) for 4 days after hydrocooling, resulted in lower PFD than storage of fruit at 26 °C and 60% RH for 2 days without hydrocooling. Cucumber genotypes showed differential response to water stress indicating that plant habit and leaf size can be important genetic determinants of plant response to water stress. Although plant productivity was not affected by water stress, PFD, shape, seed size, and seed cavity size of fruit from lldede plants were more severely affected by water stress than its llDeDe counterpart. Plants homozygous ll, in either a determinate or indeterminate background, were less susceptible to wilting under water stress conditions than their normal leaf (LL) counterparts. However, plant dry weight and fruit number and weight were higher in LLDeDe plants when compared to their llDeDe counterparts. Fruit recovered from LLDeDe plants were of higher quality than those recovered from llDeDe plants. Thus, wilting response to water stress is not necessarily indicative of a cucumber plant's tolerance to water stress in the reproductive stage.