STURROCK:MANGO GENETICS 311 several growers in the area. The charts that Uniform velocity is important because sudden have been kept indicate to us the instruments changes can cause materials in suspension to are very reliable and accurate. We feel it is drop out and eventually block the lines. Inex unrealistic to install permanent irrigation with pensive standard mix materials have been used out instruments to measure moisture levels. exclusively for the last 18 months on a com Growers who have used them tell us they would mercial basis with excellent results. We hope to compare irrigation without instruments to a report on this in the future. doctor without a thermometer. Summary IV. Frost Protection Systems The data presented here is from company Our ten meager years of working with frost records and pertains to fruit crops and multi protection in extreme southern Florida have purpose design wherein uniformity is para taught us we have only scratched the surface in mount. It is possible to apply this to many the use of water and sprinklers for this purpose. crops and areas but if irrigation is the only Uniformity and complete coverage of the peri purpose of the sprinkler system the criteria are meters of crops is of great importance. Harri excessively strict. I feel it would be a serious son1 recommends .25 in/hour in our area and a mistake, however, to design and install a system spacing of 50'x50'. We did learn in 1962 that today without preparing for other uses in the wind can reverse the heat transfer and super future. In years to come most agricultural cool the crop. Sprinklers must rotate at least chemicals will be applied by sprinklers. one r.p.m. Acknowledgments V. Fertilizer Injection Appreciation is expressed to Dr. Simon E. Fertilizer has been injected into sprinkler Malo for his assistance in editing and encourag systems for at least 20 years in Florida. Most ing this effort. installations have been in nurseries and have been successful with the use of liquid fertilizer. LITERATURE CITED Uniformity is of utmost importance and will be 1. D. S. Harrison and J. F. Gerber Sprinkler Irrigation more important in the future when insecticides for protection of Tropical fruit crops in the Homestead Area from cold, Ext. Ag. Eng. Mineo Report No. 66-3 Nov. 1, and other forms of chemicals begin to be used. 1966. GENETICS OF MANGO POLYEMBRYONY Thomas T. Sturrock have raised some interesting questions concern ing the genetics of mango polyembryony. Department of Biological Sciences Mango breeding is a very slow process due Florida Atlantic University to the long time required for a seedling to reach Boca Raton fruiting age. Therefore, it is experimentally impossible to retrace what actually occurred in Following the presentation of a paper "Nu- the development of present varieties. An attempt cellar Embryos of the Mango" before this is made in this paper to piece together what evi society last year (6), a question was posed from dence is known regarding the lineage of selected the floor during the discussion period. The varieties. It is on this evidence that these theo writer was asked if there were any poly-embry retical genetic conclusions are based. onic mango varieties that were known to have Those mango varieties which are of Indian grown from monoembryonic seeds. The example origin are chiefly monoembryonic (2). Many of Simmonds was given (Haden X Carabao mango varieties of Indochinese origin have poly- grown by the late Edward Simmonds and named embryonic seeds. The crosses between those two after him) (7). Later thoughts on the subject races have resulted in some interesting genetic 312 FLORIDA STATE HORTICULTURAL SOCIETY, 1968 peculiarities. Characteristics of the progeny of vidual which is heterozygous for the character these crosses are now beginning to shed light on will not develop the phenotypic trait but may their genetics as described in the following pass it on to its offspring. This can be illustrated examples: by the model presented in Fig. 1. Mulgoba is EXAMPLE No. 1: The Mulgoba—Haden line monoembryonic and by itself produces seedlings The historical introduction of Mulgoba to which are also monembryonic. We can assume Florida by the United States Department of here that there are no recessive genes for poly- Agriculture is well documented. This mono- embryony in this variety as it is of Indian origin. embryonic variety is of Indian origin. Seeds When Mulgoba (homozygous dominant monoem taken from Mulgoba resulted in the well known bryonic) is crossed with an unknown pollen par monoembryonic Haden variety. The pollen par ent (perhaps Turpentine—homozygous recessive ent of Haden is unknown. Since the fruit is polyembryonic), the offspring (e.g., Haden) greatly different from the usual Mulgoba seed would be heterozygous monoembryonic. This lings, the assumption is that it resulted from a heterozygous monoembryonic variety when selfed natural cross. The presence of fibers together would produce an array of offspring which with the color and flavor of Haden suggest that would be expected to produce one-quarter homo Turpentine, which was prevalent in the area of zygous monoembryonic individuals, one-half the parent Mulgoba tree, was the possible pollen heterozygous monoembryonic individuals, and parent of that cross. Turpentine is a polyem- one-quarter homozygous polyembryonic individ bryonic variety which breeds true due to the for uals. When this heterozygous monoembryonic mation of nucellar embryos. individual (Haden) is crossed with a homozygous Haden has become the "standard" of the recessive polyembryonic pollen parent (Cara Florida mango industry. Its many problems bao), as illustrated in Fig. 2, the offspring with unfruitfulness are legion. Hundreds of would be expected to be one-half heterozygous "Haden Seedlings" have been produced in South monoembryonic and one-half homozygous poly Florida with varying degrees of success. This embryonic. If this is the case, then Simmonds brings us back to the original statement that probably developed from such a cross. Simmonds is a polyembryonic variety derived from a monoembryonic Haden seed. The name "Simmonds" was given to the pre viously designated "Haden X Carabao No. 1" seedling of Mr. Edward Simmonds by Wolfe and PISTIL PARENT POLLEN PARENT Lynch (7). Records at the U.S.D.A. Plant In troduction Garden in Miami do not indicate TURPENTINE whether these Haden X Carabao crosses of Mr. {Polyembryonic) Simmonds were hand pollinated or the results PP of open pollination of Haden flowers growing near Carabao flowers. Those who knew Mr. Simmonds and his work suggest that the latter is probably the case. Thus, we are assuming that Carabao is the pollen parent of Simmonds. HADEN Since Simmonds has some of the characteristics (Monoembryonic) of Carabao not found in Haden—yellow color, sub-acid flavor, and anthracnose resistance—it PP is fairly safe to assume that Carabao was, in fact, the pollen parent and that Simmonds is the result of a Haden X Carabao cross and not the result of a Haden X Haden cross. Whatever the origin, Simmonds is a polyembryonic variety and developed from a monoembryonic seed. For sake of argument, let us assume that the polyembryonic trait is a recessive character. An individual must then be homozygous for that 50% character before it will be manifested. An indi (THEORETICAL DISTRIBUTION) STURROCK: MANGO GENETICS 313 some of the seedlings exhibit enough of the PISTIL PARENT POLLEN PARENT shape, flavor, and color characteristics of Pico to assume that they resulted from an Edward X TURPENTINE Pico cross. {Polyembryonic) Paheri (also known as Pirie, Rajpuri, and other names) is a monoembryonic variety of Indian origin. Let us assume that it is a homo- zygous monoembryonic variety, as there is little evidence of polyembryony among the Indian va rieties. Carabao is a polyembryonic variety (and therefore, by our assumption, homozygous re cessive). The assumed cross (Fig. 3) of these two varieties resulted in the production of Ed PP ■>■ ward, which is a monoembryonic variety. If this assumed parentage is correct, Edward would then be heterozygous for the polyembry onic factor. If heterozygous Edward is self pollinated, it would theoretically produce an offspring popula tion of one-quarter homozygous monoembryonic individuals, one-half heterozygous monoembry onic individuals, and one-quarter homozygous polyembryonic individuals (see Fig. 3). If hete 50% 50% (THEORETICAL DISTRIBUTION) rozygous Edward is crossed with Pico (poly embryonic and therefore homozygous recessive for this characteristic), a theoretical offspring population of one-half heterozygous monoem EXAMPLE No. 2: The Edward line bryonic individuals and one-half homozygous Edward is another of the crosses supposedly made by the late Edward Simmonds which was assumed to be another of the Haden X Carabao crosses (5). Further observations of this va riety suggest that it resembles Paheri more PISTIL PARENT POLLEN PARENT than it does Haden and is probably a Paheri X Carabao cross. Regardless of its parentage, it is CARABAO a monoembryonic variety. (Polyembryonic) In 1962, David Sturrock reported before this PP society (3) on results of some Edward X Pico crosses (open pollination from adjacent inflores cences). At that time, the few seedlings from that cross which had produced fruit were all monoembryonic. Since that publication, a num EDWARD ber of other seedlings have fruited. From the (Monoembryonic) total of twenty-four individuals, five have been definitely confrmed to be polyembryonic. Sev Pp eral were discarded for various reasons before examination, and some did not survive long enough to bear fruit (4). The fact that any polyembryonic offspring were produced is sig nificant. Since these seeds were the result of open pollination, we cannot be sure that they are positively Edward X Pico crosses. They may be Edward X Edward (self pollinated) or the re 50% sult of some other accidental cross.