To determine the earliest developmental stage at which isozyme screening could be accomplished, 10 isozyme systems were examined in peach [Prunus persica (L.) Batsch] for differential expression during development. Differences in isozyme expression based on stage of development were detected in nine systems. The earliest stage for complete screening of most isozymes examined is in l-month-old seedlings. The significance of these results relative to genetic mapping is discussed.
Thirty-six peach and nectarine [Prunus persica (L.) Batsch] cultivars were evaluated for flower bud number (flower buds/node) over 2 years. Cultivar, year, and year × cultivar effects were highly significant. Cultivars released from California breeding programs generally had fewer flower buds than those from eastern U.S. programs, suggesting that selection for cropping consistency in eastern breeding programs has resulted in release of cultivars with many flower buds. Variance component estimates from this study and from 2 years of sampling trees of ‘Redhaven’ indicates that sampling over years and increasing the number of shoots sampled per tree is warranted. Variability among trees within cultivar was low.
Eighteen isozyme systems were surveyed in the peach [Prunus persica (L.) Batsch.] plant introduction collection. Seven systems were polymorphic. Three previously unreported isocitrate dehydrogenase (IDH; EC 18.104.22.168), three malate dehydrogenase (MDH; EC 22.214.171.124) and two shikimate dehydrogenase (SDH; EC 126.96.36.199) banding patterns were detected in the clones. Isocitrate dehydrogenase was dimeric in structure, with two alleles present at a single locus. Malate dehydrogenase was dimeric in structure, with three alleles present at the fast locus, while a second locus was monomorphic. Shikimate dehydrogenase was monomeric, with one allele present in most clones, while PI 113452, PI 113650, and PI 117679 were heterozygous for a slow SDH allele. Electrophoretic evidence suggests PI 113452, PI 113650, and PI 117679 are peach × almond (P. dulcis Webb) hybrids, since they were heterozygous for alleles previously reported only in almond.
In the article “Chilling Requirement of Post-rest Heat Accumulation as Related to Difference in Time of Bloom Between Peach and Western Sand Cherry,” by Dennis J. Werner, Bruce D. Mowrey, and Eric Young [J. Amer. Soc. Hort. Sci. 113(5):775-778, September 1988], in the legend of Fig. 2, second line, “14 hr” should read “1400 hr”.
The basis for the difference in time of bloom between ‘Redhaven’ peach [Prunus persica (L.) Batsch] and western sand cherry (Prunus besseyi Bailey) clone ‘Cornell-Geneva (CG) 3-24’ was investigated. Based on 3 years of field observation, average bloom date (50% of buds) of ‘Redhaven’ was 9 days earlier than ‘CG 3-24’. Greenhouse forcing of field-collected shoots and artificially chilled trees suggested that the flower bud chilling requirement of these two clones is similar. Forcing of artificially chilled trees under different post-rest temperature regimes revealed that the base temperature for flower bud heat accumulation was lower in ‘Redhaven’ than in ‘CG 3-24’ (4.3° vs 7.0°C, respectively). Values of Q10 for flower bud development were 2.2 and 2.8 for ‘Redhaven’ and ‘CG 3-24’, respectively. These results suggest that the basis for difference in time of bloom is due to a difference in the base temperature for heat accumulation and is not related to chilling requirement.
Four isozyme systems, glucosephosphate isomerase (PGI, EC 188.8.131.52), phosphoglucomutase (PGM, EC 184.108.40.206), isocitrate dehydrogenase (IDH, EC 220.127.116.11), and malate dehydrogenase (MDH, EC 18.104.22.168), were identified as useful in detecting intergeneric Vitis vinifera × Muscadinia rotundifolia hybrids. Polymorphism between and within the two genera was observed at the PGI-2, PGM-2, and IDH-1 loci. However, the two appeared fixed for different alleles at the MDH-3 locus. The combination of any two of the enzyme systems allowed for rapid identification of F1 hybrids at the young, pre-fruiting seedling stage.