C.R. Hampson and H.A. Quamme
Sensory evaluation methods were used to establish tentative guidelines for screening apple (Malus ×domestica Borkh.) breeding selections for four visual attributes. A panel of 42 regional consumers rated sample selections for fruit size on the 7-point “Just Right” (JR) scale, for fruit shape on a 7-point hedonic (liking) scale, and for the appearance of lenticels and stem bowl russet (SBR) on a 7-point affective (acceptability) scale. The panel most preferred a fruit about 7.5 cm in diameter. No evidence was found for range bias or for differences between yellow and red apples in size preference. Women and panelists over 55 years of age tended to prefer a slightly smaller apple. Panelists liked all the most common apple shapes. Lenticels generally became unacceptable when they exceeded 1.0 mm in diameter, but lenticel density was not related to acceptability. For red or yellow apples, SBR was acceptable on average, provided its maximum extent did not exceed about 55% of the fruit diameter. The panel's tolerance to SBR resembled that of a larger regional population, and their fruit size preferences resembled those reported elsewhere for European consumers. Similar methods could be used by other breeders to assess the preferences of their target consumer population.
H.A. Quamme, Wei Ai Su and L.J. Veto
Excision of the flower from the peach [Prunus persica (L.) Batsch.] flower bud raised the 50% injury temperature of flowers (cooled at 1C/hour) from -18 and -20C to -10 and -13C on two test dates, 26 Feb. 1988 and 5 Dec. 1990, respectively. Ice inoculation of the excised flowers at -3C further raised the 50% injury temperature to -7 and -8C for the two dates, respectively. These observations suggest that supercooling is a true mechanism for avoiding freezing injury. Low temperature scanning electron microscopy of freeze fractured cells verified that the flower froze intracellularly, whereas the subtending tissue froze extracellularly. Ice inoculation of the flower and the flower bud axis from which the scales were removed demonstrated that a barrier to ice propagation (effective to -11C) from the flower bud axis to the flower was present. This barrier may involve the provascular strands and a cell zone at the flower base (BZ) that were devoid of intercellular spaces. These tissues also had smaller cells, smaller vacuoles, greater ratio of cell wall thickness to cell size than tissue just below the BZ, which may result in greater cell rigidity and restriction of extracellular freezing. The cells outside the provascular strands at the base of the flower were also lacking in intercellular space, were smaller in size, and had a higher ratio of cell wall thickness to cell size compared to cells near the base of the scales. In the intact flower buds in which the flowers supercool below -11C, the presence of the first and second scales was important to full expression of supercooling because their removal raised the supercooling point, whereas the removal of lower scales did not. Sequestration of ice by the first two subtending scales during the early stages of freezing may be important to the creation of a dry region at the flower base that prevents ice propagation into the flower at temperatures below -11C.
J.M. Caprio, H.A. Quamme and R. Berard
Winter freeze events, identified by horticulturists to lower yields or kill trees (estimates vary by year from 1000 to >200,000 trees), have occurred in the Okanagan Valley of British Columbia 18 times in 94 years (1 in 5 years). To determine the association of winter temperatures and production, 72 years (1920–91) were separated into quartiles by level of production. Then, a maximum χ2 value was produced by a scanning iterative technique comparing each of the extreme quartiles with the combined mid-quartiles. A strong association was found between level of production and the low minimum temperatures in November, December, and February but not January. This result agrees with the historical records that indicate three winter-kill events occurred in November, five in December, one in January, and three in February during the same time period. Warm temperatures in September were associated with low production, indicating the possibility that warm temperatures at this time delay acclimation. Warm temperatures in January also were associated with low production, indicating a possible effect in hastening deacclimation.