Fine root lifespan has previously been estimated at 3 to 4 weeks for apple trees growing in England. We used nondestructive belowground imaging technology to investigate the accuracy of this estimate for apple trees growing in central Pennsylvania. Eight root observation tubes (minirhizotrons) were installed beneath each of six 20-year-old `Red Delicious' apple trees on M26 rootstock. Videos of roots growing against the tubes were taken at intervals of 14 to 28 days between October to June, depending on the amount of root activity. Images were used to construct a database of life history information for over 500 individual roots. A flush of fine roots was produced in the early fall, followed by a period of low but constant mortality that lasted through December. Roots that survived to this time were generally maintained throughout the winter and following spring. A second flush of root production occurred in the spring, coinciding with bud burst and flowering. Root mortality was highest in late spring following this flush. In contrast to earlier estimates of apple root lifespan, we found that >30% of the fine roots produced in the fall lived for ≥200 days. Most of these roots developed red-brown pigmentation, a feature that previously has been associated with cortical cell death. However, the ability of these pigmented roots to produce new white laterals in the spring argues against categorizing these as dead roots. The information on root demographics provided by this study adds to our understanding of seasonal carbon and nutrient allocation patterns in apple.
Christina E. Wells and David M. Eissenstat
Jennifer R. DeEll and Robert K. Prange
This paper reports preliminary results on the postharvest quality and storage characteristics of several scab-resistant apple cultivars. `Novaspy', `Moira', `Priscilla', `Novamac', `Nova Easygro', `Prima', and `Macfree' were stored for 3 months at 3C in air or standard controlled atmosphere (CA; 4.5% CO2 and 2.5% O2) in 1990 and for 4 months at 0C in air, standard CA, or low-O, CA (LO; 1.5% CO2 and 1.5% O2) in 1991. `Moira', `Prima', and `Priscilla' had very limited storage life. `Moira' was susceptible to bitterpit, scald, core browning, vascular breakdown, and storage rots. `Prima' was susceptible to core browning and vascular breakdown and had a high incidence of storage rots in air storage. `Priscilla' had several defects as a result of insect damage and was susceptible to bitterpit and scald. `Novaspy' stored very well and had virtually no physiological disorders or storage rots. `Novamac, `Nova Easygro', and `Macfree' developed few storage rots and were essentially at the end of their storage life after 4 months, regardless of storage conditions. Firmness in `Novamac' decreased substantially in all storage atmospheres, while `Nova Easygro' and `Macfree' were susceptible to core browning and scald.
Yousheng Duan, Zhiqiang Ju, Liye Ju, and Aixin Guo
Effects of 10% plant oils (corn, soybean, peanut, canola, sunflower, safflower, rape seed, linseed, and cottonseed), 100 mg·L-1 chlorine, or 100 mg·L-1 chlorine plus 10% oil combinations on pathogen (B. cinerea, P. expansum, or G. cingulata) infection and fruit decay in `Delicious' apples and `Ya Li' pears were studied. None of the oils showed inhibition on spore germination of the three pathogens by in vitro test. In inoculated fruit, oil treatments did not affect incidence but reduced severity of decay after 6 months storage at 0 °C plus 7 days at 20 °C, but no difference was found among the oils at the same concentration. In non-inoculated fruit, oils reduced fruit decay to low levels (4%) even in the most severe season. Oils also maintained fruit quality attributes, reduced water loses, and controlled scald in apples and internal browning in pears. Chlorine reduced incidence but did not reduce severity in decayed fruit. Fruit first drenched with chlorine then dipped in oil emulsions without pathogen inoculation remained decay free, while control fruit developed 10% to 15% or 13% to 23% decay after 6 months at 0 °C plus 7 days at 20 °C in both apples and pears, respectively.
P. Guy Lévesque, Jennifer R. DeEll, and Dennis P. Murr
Sequential decreases or increases in the levels of O2 in controlled atmosphere (CA) were investigated as techniques to improve fruit quality of `McIntosh' apples (Malus ×sylvestris [L.] Mill. var. domestica [Borkh.] Mansf.), a cultivar that tends to soften rapidly in storage. Precooled fruit that were harvested at optimum maturity for long-term storage were placed immediately in different programmed CA regimes. In the first year, CA programs consisted of 1) `standard' CA (SCA; 2.5–3.0% O2 + 2.5% CO2 for the first 30 d, 4.5% CO2 thereafter) at 3 °C for 180 d; 2) low CO2 SCA (2.5–3.0% O2 + 2.5% CO2) at 3 °C for 60 d, transferred to low O2 (LO; 1.5% O2 + 1.5% CO2) at 0 or 3 °C for 60 d, and then to ultralow O2 (ULO; 0.7% O2 + 1.0% CO2) at 0 or 3 °C for 60 d; and 3) ULO at 3 °C for 60 d, transferred to LO at 0 or 3 °C for 60 d, and then to SCA or low CO2 SCA at 0 or 3 °C for 60 d. In the second year, the regimes sequentially decreasing in O2 were compared with continuous ULO and SCA. After removal from storage, apples were held in ambient air at 20 °C for a 1-week ripening period. Fruit firmness was evaluated after 1 and 7 d at 20 °C, whereas the incidence of physiological disorders was assessed only after 7 d. Lowering the temperature while decreasing O2 was the best CA program with significant increased firmness retention during storage and after the 1-week ripening period. Reduced incidence of low O2 injury in decreasing O2 programs and absence of core browning at the lower temperature were also observed.
W.D. Lane, D.-L. McKenzie, and M. Meheriuk
Nodules associated with the main cortical vascular bundles in fruit of the `Gala' apple (Malus ×domestica Borkh.) strains `Royal' and `Regal' were observed in several growing seasons. The nodules were found in 68% (n = 586) of the fruits examined, with a mean of 2.5 nodules per fruit. The nodules were first detected in developing fruit 2 months after bloom and were normally 1-2 mm in diameter by commercial harvest maturity. The nodules, like the vascular bundles, were pale green. They were inconspicuous at first, but became conspicuous and unattractive and changed to brown or red as the fruit became overmature. Nodules in the fruit of the `Gala' × `Splendour' hybrid `8S 27-2' were dark brown or red at picking maturity, and occurred with high frequency. Nodules were also observed in `Splendour', but were small, pale green, and infrequent in this cultivar. Microscopic examination of the nodules revealed that they typically contained a central cavity surrounded by a lignified wall with small pigmented cells outside the wall adjacent to the cortex. Low-frequency irrigation cycle times generally promoted the development of nodules in both `Gala' strains but nitrogen treatments did not affect nodule frequency in `Royal Gala'. Mean fruit nodule frequency tended to be higher, overall, in `Regal Gala' (3.9) than in `Royal Gala' (1.4).
Rui Sun, Hui Li, Qiong Zhang, Dongmei Chen, Fengqiu Yang, Yongbo Zhao, Yi Wang, Yuepeng Han, Xinzhong Zhang, and Zhenhai Han
antioxidants in the cells, inhibits enzymatic browning, and its content is an important factor influencing apple browning ( Nicolas et al., 1994 ). Several techniques are currently used to control flesh browning, e.g., thermal treatment, low O 2 –high CO 2
C.B. Watkins and F.W. Liu
between storage disorders of ‘Empire’ apples and major minerals reveal few strong relationships ( Table 4 ) and none for external CO 2 injury and flesh browning. Lau and Looney (1978) found an association of low potassium and Mg, but not Ca, with
Daniel Ferreira Holderbaum, Tomoyuki Kon, Tsuyoshi Kudo, and Miguel Pedro Guerra
human health ( Heim et al., 2002 ), varieties with high polyphenol content are interesting for fresh consumption, whereas low enzymatic browning potential is relevant for apple processing ( Podsedek et al., 2000 ) as a way to avoid the formation of off
Ian McIvor, Alexander Lang, W. David Lane, and Paula E. Jameson
The new apple (Malus ×domestica Borkh.) cultivar Sciros™, resulting from a cross of 'Gala' with 'Splendour', is marketed internationally from New Zealand. A characteristic of this cultivar is the presence of dense, dark green or black nodules in the fruit cortex, located in close proximity to the five sepal vascular bundles. Nodules are visible as green spots beginning about 40 days after bloom and they continue to develop, reaching a length of up to 8 mm at fruit maturity, although there is considerable variation in their size. Large vascular nodules often develop dark brown centers and reduce the visual quality of the fruit flesh. The frequencies of vascular nodules in 61 'Gala' × 'Splendour' hybrids from New Zealand and British Columbia, Canada, were examined. These ranged from a mean of 0 to 12.1, depending on the hybrid. Thirteen hybrids were in the high frequency class (2.76-12.1), 28 in the low frequency (0.04-1.86), and 20 were without nodules. The mean nodule frequency in Sciros™ was 12.1 nodules per fruit, the highest of all hybrids examined. Our survey of 44 other cultivars confirmed the occurrence of vascular nodules in 'Gala' and 'Splendour', with mean vascular nodule frequency of 1.9 and 0.5 nodules per fruit, respectively. Nodules were also found in 'Newtown Pippin' (frequency 0.8), and in a 'Newtown Pippin' × 'Granny Smith' hybrid (frequency 0.1).
Jennifer DeEll and Behrouz Ehsani-Moghaddam
stress-related disorders in apples; increased incidence of CO 2 injury or flesh browning has been found in 1-MCP-treated ‘McIntosh’ and ‘Empire’ apples ( DeEll et al., 2003 ; Fawbush et al., 2008 ; Jung and Watkins, 2011 ). Efficacy of 1-MCP treatment