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Cacao (Theobroma cacao L.) is an important cash crop in tropical growing regions of the world and particularly for small cacao farmers. Over the past two decades, ‘CCN 51’ has become one of the most planted cultivars in Ecuador, mainly as a result of its high productivity and disease resistance. Intermixing of Nacional fine flavor Ecuadorian beans with beans of ‘CCN 51’ has become common practice, reducing overall bean quality and decreasing value. The primary goals of this study were to determine the genetic identity, structure, and allelic richness of ‘CCN 51’, its maternal origin and to compare ‘CCN 51’s’ agronomic characteristics against a composite group of Nacional cultivars. To investigate the complex genetic background of this cultivar, 70 simple sequence repeat loci were used. The high heterozygosity observed (56 of 70 loci) for ‘CCN 51’ is not characteristic of traditional Nacional cultivars. Comparison of agronomic characteristics between ‘CCN 51’ and several Nacional cultivars indicates significant differences in cacao dry bean weight, yield potential, production efficiency, percent healthy pods, and witches' broom [Moniliophthora perniciosa (Stahel) Aime & Phillips-Mora] disease incidence. Additionally, physical, chemical, and organoleptic characteristics suggest that ‘CCN 51’ is different from those of Nacional lineage. Based on population structure analysis, the predominant ancestries for ‘CCN 51’ are Iquitos (45.4%), Criollo (22.2%), and Amelonado (21.5%) genetic groups. A lesser proportion of its genome was accounted for by genetic groups Contamana (3.9%), Purús (2.5%), Marañon (2.1%), and Nacional (1.1%) admixtures. Results of phylogenetic analyses using the unweighted pair group method with arithmetic mean yielding high bootstrap values strongly support the relatedness of ‘CCN 51’ with Iquitos, Criollo, and Amelonado genetic groups. Moreover, seven mitochondrial simple sequence repeat loci revealed that ‘CCN 51’ maternally inherited the ‘IMC 67’ cytotype. ‘CCN 51’ constitutes a valuable cacao genetic resource that is currently used not only in its country of origin, but also in many other national breeding and selection programs worldwide.

Avocado (Persea americana Mill.) possesses a unique flowering mechanism, thought to promote out- crossing, in which the male and female parts of the perfect flower function at different time periods. Cultivars are classified as Flowering Type A, where flowers are functionally female the morning of one day and functionally male the afternoon of the next day, or Flowering Type B, where flowers are functionally female in the afternoon and func- tionally male the next morning. Avocado growers typically interplant cultivars of opposite flowering types to maxi- mize yield. Recently, it has been hypothesized that 90% to 95% of avocado flowers are self-pollinated in southern Florida. However, this hypothesis does not address whether mature, marketable avocado fruit in Florida are the result of outcrossing. To determine whether avocado fruit in southern Florida result from self-pollination or out- crossing, fruit were harvested from a commercial orchard in Miami-Dade County, Florida, from a block consisting of two cultivars, Simmonds (Flowering Type A) and Tonnage (Flowering Type B), interplanted in approximately equal numbers. Seeds were germinated and the resulting progeny were genotyped using eight fully informative, micro- satellite markers. Seventy-four percent of the 'Simmonds' progeny and 96% of the 'Tonnage' progeny were judged to be the result of cross-pollination, with an estimated overall outcrossing rate of 63% to 85% within this particular block of the orchard. Seedlings judged to be the result of cross-pollinations between 'Simmonds' and 'Tonnage' are being maintained at the U.S. Department of Agriculture-Agricultural Research Service, Subtropical Horticulture Research Station and are being evaluated for segregation of important agronomic and horticultural traits. Avocado is an evergreen tree native to Mesoamerica.Persea americana is a polymorphic species consisting of several botanical varieties, or subspecies, adapted to geographically distinct microenvironments. These include wild botanical varieties (var. floccosa Mez, var. steyermarkii Allen, var. nubigena (Williams) Kopp) and three horticulturally important botanical varieties, also known as ''races'' (var. americana Mill. (''West Indian''), var. guatemalensis Williams (''Guate- malan''), and var. drymifolia (Schlecht. and Cham.) Blake (''Mexican''); Scora and Bergh 1990). Because of the adapta- tion to microclimates, hybrids of Guatemalan-Mexican botan- ical varieties are cultivated in the dry Mediterranean-like environments of California, Israel, Chile, South Africa, and the upland areas of Asia. West Indian or hybrids of West Indian-Guatemalan botanical varieties are cultivated in the more humid tropical environments of Florida, Hawaii, South- east Asia, and the Caribbean. Mexico is the primary producer of avocados, centered around the state of Michoacan, and 'Hass' is

Identifying genetic markers linked to disease resistance in plants is an important goal in marker-assisted selection. Using a candidate-gene approach, we have previously developed genetic markers in cacao (Theobroma cacao L.) for two families of genes involved in disease resistance: non-TIR-NBS-LRR (Toll/Interleukin-1 Receptor-nucleotide binding site-leucine rich repeat) resistance gene homologues and WRKY transcription factor genes; however, we failed to isolate TIR-NBS-LRR genes. Using a novel algorithm to design degenerate primers, we have now isolated TIR-NBS-LRR loci as determined by DNA sequence comparison. These loci have been developed as genetic markers using capillary array electrophoresis (CAE) and single-strand conformational polymorphism (SSCP) analysis. We have mapped three distinct TIR-NBS-LRR loci in an F2 population of cacao and demonstrated that one is located on linkage group 3 and the other two on linkage group 5.

Knowledge of genetic differences among commonly cultivated cacao clones, as well as the type of gene action involved for disease resistance, yield, quality, and horticultural traits, are essential for cacao breeders to select parental clones efficiently and effectively. This information is also critical for quantitative geneticists in designing and improving quantitative trait loci (QTL) localization strategies using breeding populations, whether they involve analysis of multiple populations crossed to one common parent or association genetic analysis. The objectives of this research were to 1) verify the genetic identity of parental cacao clones used to produce hybrids for field evaluation at the Centro Agrónomico Tropical de Investigación y Enzeñanza (CATIE), Turrialba, Costa Rica, using molecular marker analysis, and 2) estimate general and specific combining ability (GCA and SCA) of the parental clones for resistance to frosty pod (Moniliophthora roreri Cif. and Par.) and black pod [Phytophthora palmivora (Butl.) Butl.] diseases, total number of pods, vigor (as measured by trunk diameter), and measures of maturity (months to first flowering and pod production). Misidentification of cacao clones was found at three levels. Molecular marker analysis revealed that six parental clones differed in identity to supposedly identical accessions from other germplasm collections. Trees of the parental clone UF 273 consisted of two clearly different genotypes, resulting in two types of progeny, requiring separate designation for correct statistical analysis. Out-crossed progeny, presumably from foreign pollen, and selfed progeny were also found. Two of the traits measured, percent healthy pods and percent pods with frosty pod, showed predominantly additive gene action, while the traits total number of pods and trunk diameter, demonstrated regulation by both additive and nonadditive gene action. Number of months to first flowering and first fruit both showed evidence of predominant regulation by nonadditive gene effects. Crosses of two parental clones, UF 712 and UF 273 Type I, were identified as potential candidates for QTL analysis as breeding populations, given their favorable GCA estimates for frosty pod resistance and total pod production, respectively.

The native American genus Annona contains many species that are cultivated for their edible fruit, including the custard apple (A. reticuluta L.), soursop (A. muricata L.), cherimoya (A. cherimola L.), sugar apple (A. squamosa L.), and interspecific hybrids, the atemoyas. RAPD analysis of A. cherimola. 'Campa' and 'Jete,' A. squamosa 'Lessard,' and the atemoyas 'Ubranitzki,' 'Malali,' and 'Kaspi' resulted in very distinctive patterns, indicating that RAPD markers, may be an efficient method of fingerprinting genotypes within and between Annona species. All 15 primers used generated repeatable, polymorphic patterns. An F1 population of 'Jete' x 'Lessard' was analyzed to determine the inheritance of the RAPD banding patterns. Fifty-two polymorphic loci were identified, which segregated in an expected Mendelian fashion. Annona contains more than 50 species and interspecific hy- brids, many of which are cultivated in tropical and subtropical America for their edible fruit. The genus has been divided into five groups and 14 sections based on morphological characters (Safford, 1914). Cherimoya (A. cherimola) originated in the highlands of Ecuador and Peru (Zeven and Zhukovsky, 1975). Cultivars of this early-maturing species have a superior flavor and are cold-tolerant 'Jete' and 'Campa' are two Spanish cultivars representative of this species. Sugar apple (A. squamosa) is native to the Central Ameri- can lowlands and the West Indies, and is suited to tropical climates. The fruit is considered inferior to cherimoya, but is exceptionally high in calcium, phosphorous, and iron (Sturrock, 1959). This species is drought tolerant and grows well in alkaline soils. A. squamosa is less variable than the other Annona species (Sturrock, 1959). 'Lessard' is a representative commercially grown cultivar. Other species, such as A. muricata (soursop) and A. reticulata (custard apple; Bullock's heart) vary widely in fruit quality, flavor

Additional index words. cocoa, DNA Abstract. RAPD markers have been used successfully in genetic analysis of several crop plants. This method poses difficulties with a highly heterozygous species such as Theobroma cacao because of the dominant phenotypic expression of bands. A backcross family derived from ctultivars Catongo and Pound 12 was analyzed to determine the efficacy of RAPD markers in analyzing cacao populations. A preliminary screen of the parents and the F 1 plant used as the backcross parent was conducted with 180 RAPD primers; of these, 26% were polymorphic and reproducible and produced 104 storable loci. Genomic DNA from 54 individuals of the backcross population was then amplified with these primers; 68.3 % of the loci segregated as expected in a Mendelian fashion. Separation of RAPD fragments on acrylamide revealed an additional polymorphic locus from one primer that was indistinguishable on agarose. The results demonstrated that RAPD markers can be used to study the cacao genome. The seed of Theobroma cacao, the cocoa bean, is a major crop in the tropics of Central and South America, Asia, and Africa. The commercial cultivars grown in these areas are derived principally from three main morphological types: Forasteros, Criollos, and Trinitarios. These types differ greatly in flavor, yield, and suscep- tibility to diseases such as witches' broom (Crinipellis perniciosus (Stahel) Singer), cacao swollen shoot virus, Ceratocystis wilt, pod rot (Monilia roreri Cif.), and other cankers and pod rots (Phytophthora spp.). For example, the fine-flavored Criollos lack vigor and are highly disease susceptible, the more robust Forasteros produce the bulk, or ordinary, cocoa, and the Trinitarios are highly variable (Wood and Lass, 1985). Cacao breeding through traditional methods has been slowed by the long generation time and large multiyear field plot testing requirements. F1 hybrids from current commercial clones, released as synthetics, resulted in seedlings with variable field performance and yields well below the midparent values for cacao (Hunter, 1990). Although much variability exists, most breeding work has used only a narrow genetic base (Wood and Lass, 1985). Improve- ment has focused on traits that, for the most part, are under polygenic control and have low heritabilities, such as yield and resistance to witches' broom disease. Lockwood et al. (1991) used a factorial mating design (NC Design II) to estimate genetic variation for girth, yield, and height of jorquette (low branches arising near the apex of the main 'axis). They demonstrated that most variation was additive and that heterosis was unimportant. Soria et al. (1974) also demonstrated that most important traits have low heritabilities. These results indicate that some type of cyclical selection program should be used to improve the general