Greenhouse Tomato Fruit Quality

Fruit cracking is an important problem in horticultural crop production. Polygalacturonase (SlPG) and expansin (SlEXP1) proteins cooperatively disassemble the polysaccharide network of tomato fruit cell walls during ripening and thereby, enable softening. A Golden 2-like (GLK2) transcription factor, SlGLK2 regulates unripe fruit chloroplast development and results in elevated soluble solids and carotenoids in ripe fruit. To determine whether SlPG, SlEXP1, or SlGLK2 influence the rate of tomato fruit cracking, the incidence of fruit epidermal cracking was compared between wild-type, Ailsa Craig (WT) and fruit with suppressed SlPG and SlEXP1 expression (pg/exp) or expressing a truncated nonfunctional Slglk2 (glk2). Treating plants with exogenous ABA increases xylemic flow into fruit. Our results showed that ABA treatment of tomato plants greatly increased cracking of fruit from WT and glk2 mutant, but not from pg/exp genotypes. The pg/exp fruit were firmer, had higher total soluble solids, denser cell walls and thicker cuticles than fruit of the other genotypes. Fruit from the ABA treated pg/exp fruit had cell walls with less water-soluble and more ionically and covalently-bound pectins than fruit from the other lines, demonstrating that ripening-related disassembly of the fruit cell wall, but not elimination of SlGLK2, influences cracking. Cracking incidence was significantly correlated with cell wall and wax thickness, and the content of cell wall protopectin and cellulose, but not with Ca2+ content.

/pdf/disassembly-of-the-fruit-cell-wall-by-the-ripening-2o2byklf0c.pdf

Disassembly of the fruit cell wall by the ripening-associated polygalacturonase and expansin influences tomato cracking.

The effects of spraying sweet cherry trees with calcium nitrate and naphthalene acetic acid (NAA) and their combination during the rainy season were investigated.1. Spraying with 0.5% calcium nitrate solution significantly reduced the cracking index of 'Napoleon' sweet cherries and the percentage of cracked fruits under rain without any visble residue and damage from the chemicals.2. Application of NAA at 0.5, 1 and 2 ppm on 'Satohnishiki' reduced the cracking index and the percentages of cracked fruits to 15 to 30% and 13 to 40% of the control, respectively. In 'Napoleon' sprayed with Ca (NO3)2 and NAA, the cracking index and % cracked fruit decreased to 20 to 38% and 26 to 66%, respectively.3. Spraying with the combination of the 2 reagents more effectively reduced the cracking of 'Napoleon' than did either reagents as a single spray; and the minimum value of the index and the % cracked fruits was about one eighth of the control.

The Effects of Calcium and Naphthalene Acetic Acid Sprays on Cracking Index and Natural Rain Cracking in Sweet Cherry Fruits

Preharvest rainfall that occurs when fruit are fully ripe or approaching full ripeness can result in detrimental fruit splitting in rabbiteye and southern highbush blueberries. This study was initiated to develop a laboratory method to model rain-related incidence of splitting in cultivated blueberries with the goal of predicting the incidence of splitting in blueberry cultivars and selections. Multiyear field surveys of rabbiteye and southern highbush cultivars show that the incidence of rain-related splitting is strongly cultivar-dependent. Laboratory values for forced splitting and naturally occurring rain-related field splitting data show a strong correlation indicating that the incidence of fruit splitting can be accurately estimated by this laboratory method. Soaking the berries in distilled water 14 h at room temperature gives a confident determination of splitting tendencies. Blueberry breeders and geneticists can use this method to evaluate new potential blueberry cultivars for splitting tendencies as part of routine screening. This would lead to a long-term goal of reducing splitting susceptible blueberry cultivars in commercial plantings.

/pdf/laboratory-method-to-estimate-rain-induced-splitting-in-4aekn77ict.pdf

Laboratory Method to Estimate Rain-induced Splitting in Cultivated Blueberries

To improve the quality of berries during handling and shipping, blueberry breeders have strived to develop a fruit that is firm in texture. However, some previous studies have suggested that blueberry cultivars with firmer fruit were more susceptible to splitting. This study was conducted to further investigate the correlation between splitting susceptibility and fruit firmness. Various cultivars and selections of rabbiteye (Vaccinium ashei) and southern highbush (interspecific hybrids primarily consisting of V. corymbosum) blueberry were used to determine whether berries displaying higher fruit firmness also have a higher incidence of splitting. Three distinctly different measurements of berry firmness were obtained using two instruments: QTS25 and FirmTech2. Berries were subsequently submitted to laboratory procedures to induce splitting. In general, firmness measured as either deformation (FirmTech2) or modulus of elasticity (QTS25) correlated with splitting tendencies. There are exceptions, however, that need to be further examined.

/pdf/blueberry-splitting-tendencies-as-predicted-by-fruit-3e5j0a9iuy.pdf

W. B. Ackley

Papers

Overhead irrigation water quality and the cracking of sweet cherries.