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Brad G. Howlett, Samantha F.J. Read, Maryam Alavi, Brian T. Cutting, Warrick R. Nelson, Robert M. Goodwin, Sarah Cross, Trevor G. Thorp and David E. Pattemore

Macadamia is partially self-incompatible ( Sedgley, 1983 ), although self-pollinated nut set is known to occur in at least some cultivars ( Meyers, 1997 ; Vithanage et al., 2002 ; Wallace et al., 1996 ). Cross-pollination has been considered

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Gabriela Vuletin Selak, Slavko Perica, Smiljana Goreta Ban, Mira Radunic and Milan Poljak

productivity depends on the combination of planted cultivars. Simultaneous flowering periods enable cross-pollination, fertilization, and fruit set of different cultivars if the recipients and pollenizers are compatible ( Lavee et al., 2002 ). The knowledge of

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Dario J. Chavez and Paul M. Lyrene

of interspecific hybrid swarms ( Camp, 1942 ; Vander Kloet 1983 , 1988 ). Studies of self-pollination and cross-pollination in several Vaccinium species have provided varying results. In most cases, partial to complete self-incompatibility was

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E. James Parrie and Gregory A. Lang

Pollen deposition on the stigmatic surface of blueberry pistils was studied with regard to maximum pollen load and stigmatic fluid production (stigma receptivity). Three hybrid southern highbush cultivars (Vaccinium corymbosum L. with V. darrowi Camp, V. ashei Reade, and/or V. angustfolium Aiton), two northern highbush cultivars (V. corymbosum), and one hybrid half-high cultivar (V. corymbosum with V. angustifolium) were selfand cross-pollinated with counted pollen tetrads until saturation of the stigmatic surface occurred. Stigmatic saturation generally required 200 to 300 tetrads and was characterized by the cessation of stigmatic fluid production and the inability to absorb further tetrads. The loss of stigmatic receptivity was irreversible. Cross-pollination resulted in cessation of stigmatic fluid production at lower levels of tetrad deposition than did self-pollination, suggesting a potential pollen-stigma recognition phenomenon. Northern highbush, half-high, and southern highbush cultivars required 7% to 10%, 12% to 17%, and 14% to 21%, respectively, more self-pollen to develop the stigmatic saturation condition. The potential relation of the pollenstigma phenomenon to self-incompatibility mechanisms is discussed.

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Cecil Pounders, Sandra Reed and Margaret Pooler

Crapemyrtle (L. indica and L. indica × L. fauriei hybrids) is one of the most popular flowering landscape plants in the U.S. Although many cultivars have been developed through breeding efforts, little has been published on the reproductive biology of the genus. The objective of this study was to evaluate barriers to successful self-seed production in crapemyrtle. Self-compatibility was assessed by comparing pollen tube growth, fruit and seed production, and seed germination following controlled self- and cross-pollinations. Observations of pollen tube growth at intervals up to 24 hours after self- and cross-pollination indicated no barriers to self-fertilization acting at the stigmatic or stylar level in L. indica, L. fauriei or cultivars derived from inter-specific hybrids of these two species. Self-pollinations of `Catawba', `Whit IV', `Tonto' and `Tuscarora' had lower percent seed pod set and seed germination than did cross-pollinations of these cultivars. The number of seeds per pod was lower when `Catawba', `Whit IV' and `Tuscarora' were self-rather than cross-pollinated, but no difference between `Tonto' self- and cross-pollinations was observed. When decreased pod set is combined with much lower seed germination for self-pollinations, selfing of crapemyrtle is extremely unproductive when compared to cross-pollination. A late-acting self-incompatibility system or inbreeding depression is indicated for L. indica and inter-specific crosses with L. fauriei.

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Gregory A. Lang and Robert G. Danka

Southern highbush (“low chill tetraploid”) blueberries are an earlier-ripening, self pollen-compatible alternative to rabbiteye blueberries. `Sharpblue', the first southern highbush cultivar planted on a commercial scale, has been shown to require cross-pollination for optimal fruit size and earliness of ripening. `Gulfcoast', a recently released cultivar for Gulf states growers of about latitude 30 to 32 N, differs in heritage from `Sharpblue', incorporating about 50% more self-compatible northern highbush germplasm. `Gulfcoast' fruit development after honey bee-mediated self- or cross-pollination with `Sharpblue' was similar in terms of set (85.5 vs. 82.2%), weight (1.26 vs. 1.18g), and seed number (32.8 vs. 33.6), respectively. Cross-pollination did not result in significantly earlier ripening. Thus, `Gulfcoast' appears to be more self-fertile than `Sharpblue'. Other closely-related cultivars are being examined to determine the genetic influence on potential for self-fruitfulness.

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Charles A. McClurg

Recommendations for culture of sweet corn (Zea mays) suggest separation of genotypes for color and/or sweetness by considerable distance since corn is generally wind-pollinated and unwanted pollination may result in undesired color or sweetness effects. Many small-scale producers lack adequate acreage to separate plantings by more than a short distance. To determine the extent of cross-pollination, `Golden Queen' yellow sweet corn was seeded in a circular pattern of 16 rows in 1989 and eight rows in 1990. White `Silver Queen' was then planted in 20 rows around the yellow genotype. The circular pattern enabled detection of pollen carried by wind in any direction. Yellow kernels on `Silver Queen' were attributed to cross-pollination. Depending on wind speed and direction, cross-pollination ranged from 50% on adjacent rows to none as close as eight to 10 rows from the yellow type. Consumer acceptance of a white genotype with a few yellow kernels was not determined.

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Guanxing Hu, Chao Gao, Xiaoming Fan, Wenfang Gong and Deyi Yuan

. The main objective of the study was to screen compatible pollen and optimal pollination combinations of four C. oleifera cultivars (HS, HJ, HX, and XL). Cross-pollination, self-pollination, and natural pollination were carried out in the four

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Bruce W. Wood

Pecan is wind pollinated, exhibits heterodichogamy and are either protandrous (I) or protogynous (II). Orchards are typically established using two complimentary flowering types but with no further scrutiny as to the degree of compatibility of these two types. Additionally, orchards are sometime established with a very low frequency of pollinator. An evaluation of several orchards revealed that yield losses are due to poor pollination is likely common. Data indicate that trees beyond about 46 m (150 feet) from a complementary pollinator exhibit substantial reductions in fruit-set; therefore, large block-type plantings are disadvantaged. Flowering data over several years show that Type I and Type II cultivars are often functionally noncomplementary, suggesting that pecan cultivars should also be identified with a seasonal identification (i.e., early, mid, and late). Data also indicate that dichogamy patterns substantially change as trees age or with abnormally warm or cool springs; hence, pollination patterns will vary depending upon orchard age. Data indicate that orchards should be comprised of 3+ cultivars. RAPD-DNA analysis of “hooked-nuts” indicates that this trait is not reliable as an indicator of selfing.

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Derek W. Barchenger, Danise L. Coon and Paul W. Bosland

insects. However, before caging can be implemented, all open flowers and possibly cross-pollinated fruit on the chile pepper plants must be removed. This is currently accomplished through laborious and time-consuming hand removal, which is exacerbated in