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Jonathan H. Crane, Bruce Schaffer and Richard J. Campbell

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Jonathan H. Crane, Bruce Schaffer and Richard J. Campbell

Southern Florida has experienced numerous hurricanes, of which Hurricane Andrew was the most recent. Six years after this storm, nearly one-third of the 8093 ha of tropical fruit that existed in Miami–Dade County before the storm has never been replanted. The damage, reaction, and recovery from the storm varied among fruit species. The effect of heat stress and high light intensity was minimal on avocado, `Tahiti' lime, carambola, mamey sapote, guava, sapodilla, and longan. In contrast, mango trees experienced severe heat stress. Root damage caused by toppling and subsequent re-setting of sugar apple, atemoya, mango, and grafted `Tahiti' lime trees was severe; thus, trees not re-set were less likely to recover than trees left toppled or leaning. The extent and rate of recovery from hurricane-related wind stress also varied among species. Avocado, carambola, guava, and longan refoliated within 3 to 4 weeks after Hurricane Andrew. In contrast, mango, sugar apple, and atemoya trees went through two or more cycles of refoliating and dying back until tree death occurred. Iron and nitrogen deficiencies were common for mango, sugar apple, atemoya, and guava. Other consequences of hurricanes in south Florida include increased weed and vine growth and increased susceptibility to drought stress and insect infestations. Recovery to prehurricane crop production levels has varied among crops. For example, avocado and carambola production is near and exceeds pre-1992 levels, respectively. In contrast, `Tahiti' lime and mango production are about 20% pre-1992 levels. The long-term effect of the most recent hurricane on fruit production in south Florida has been a change in the crop species and/or cultivars planted.

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Richard J. Campbell, Kendrick N. Mobley, Richard P. Marini and Douglas G. Pfeiffer

The relationship between SPAD-501 meter readings (SPAD) and total chlorophyll content (TCHL) was evaluated for `Delicious' apple (Malus domestica Borkh.) leaves grown in various environments. Regression models were developed between SPAD and TCHL for each of six separate experiments and were evaluated for statistical coincidence. SPAD was linearly related in a positive manner to TCHL in five of the six experiments; however, models differed between experiments, particularly between field- and greenhouse-grown trees. Thus, the relationship between SPAD and TCHL must be determined for each experiment.

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Raymond Schnell, J. Steven Brown, Cecile Olano, Alan Meerow, Richard Campbell and David Kuhn

Mangifera indica L. germplasm can be classified by origin with the primary groups being cultivars selected from the centers of diversity for the species, India and Southeast Asia, and those selected in Florida and other tropical and subtropical locations. Accessions have also been classified by horticultural type: cultivars that produce monoembryonic seed vs. cultivars that produce polyembryonic seed. In this study, we used 25 microsatellite loci to estimate genetic diversity among 203 accessions. The 25 microsatellite loci had an average of 6.96 alleles per locus and an average PIC value of 0.552. The total propagation error in the collection, i.e., plants that had been incorrectly labeled or grafted, was estimated to be 6.13%. When compared by origin, the Florida cultivars were more closely related to Indian than to Southeast Asian cultivars. Unbiased gene diversity (Hnb) of 0.600 and 0.582 was found for Indian and Southeast Asian cultivars, respectively, and both were higher than Hnb among Florida cultivars (0.538). When compared by horticultural type, Hnb was higher among the polyembryonic types (0.596) than in the monoembryonic types (0.571). Parentage analysis of the Florida cultivars was accomplished using a multistage process based on introduction dates of cultivars into Florida and selection dates of Florida cultivars. Microsatellite marker evidence suggests that as few as four Indian cultivars, and the land race known as `Turpentine', were involved in the early cultivar selections. Florida may not represent a secondary center of diversity; however, the Florida group is a unique set of cultivars selected under similar conditions offering production stability in a wide range of environments.

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Chad E. Finn and John R. Clark