Pollenizer

Abstract: SUMMARY (2) Experimental pollination showed that c. 150 pollen grains per flower were required to achieve the average natural full seed-set in the plant population. Although 57% of the flower-visiting moths deposited pollen, only about 10% of the moth visits delivered - 150 pollen grains in one visit to virgin female flowers, indicating that seed-set usually originated from multiple pollinator visits. (3) Pollen receipt indicated pollination by a guild of noctuid and sphingid moths. The abundance of the dominating pollinator species varied strongly between years. (4) Most species deposited about the same mean number of pollen grains, although they were taxonomically diverse and had different flower-visiting behaviours and proboscis lengths. Even noctuid moths of the genus Hadena, known as associated larval seed predators of S. vulgaris, were not especially frequent or efficient polli- nators despite the fact that these moths influence their larval food resource through pollination. (5) The annual and seasonal variation in abundance among pollinator species and lack of variation in pollination efficiency among them are factors which counteract specializational trends and control evolutionary retention of plastic and unspecialized floral traits in S. vulgaris. They thereby provide an option for opportunistic responses in this species.

Abstract: SummarySelf- and cross-incompatibility of the olive cultivars Frantoio, Manzanillo, Kalamata, Pendolino, and Picual were investigated using a 5 × 5 diallel matrix. Pistils were collected seven days after controlled pollinations on the day of flower opening, and pollen tubes were detected by fluorescence microscopy. Diallel analysis showed significant specific combining ability, general combining ability and reciprocal effects between cultivars for pollen tube growth in the pistil. ‘Frantoio’ was cross-compatible, as either a male or female parent, with each of the other cultivars, but showed a high degree of self-incompatibility. ‘Manzanillo’, ‘Kalamata’, ‘Pendolino’, and ‘Picual’ were crossincompatible, and all except for ‘Manzanillo’, were self-incompatible. It is concluded that ‘Frantoio’ is a good general polleniser for the other cultivars investigated. Pollen tube growth decreased in discrete steps from stigma to upper style, and from upper style to lower style, with the result that only one, and rar...

Abstract: The effect of boron (B) on in vivo and in vitro development of almond ( Prunus dulcis (Mill.) D.A. Webb (syn. P. amygdalus Batsch)) pollen and pollen tubes and the resultant effect on fruit set was studied in mature trees. The cultivars Mono (pistil donor) and Butte (pollinizer) in an orchard with low soil B in Fresno, California were sprayed with B at 0, 0.8, 1.7, or 2.5 kg·ha -1 during Fall 1993. Pollen viability as indicated by the fluorescein diacetate method (FDA) was >85% and was not affected by field-applied B, however, in vivo pollen germination and tube growth were enhanced by foliar-applied B. More effect of applied B on in vivo growth appeared as pollen tubes progressed toward the ovary. For in vitro germination, foliar-applied B reduced bursting of tubes, and addition of B to the culture media significantly increased pollen germination and pollen tube growth. Most commercial almond (Prunus dulcis (syn. P. amygdalus)) cultivars are self-unfruitful (Griggs 1953) and therefore need to be interplanted with cross-compatible, pollinizer cultivars to produce an appreciable crop (Hill et al., 1985). Important factors that a grower must consider when selecting cultivar and pollinizer combinations include bloom overlap and the capacity to produce pollen in sufficient quantity and quality. While genetic factors determine the ultimate potential of the pollinizer (Hill et al., 1985), environmental variables, including mineral nutrition of the plant, can influence the quantity and quality of the pollen produced and its subsequent performance. In some Prunus sp., including almond, the presence of pollen tubes in the transmitting tissue activates the final phases of ovule and megagametophyte development that lead to ovule receptivity (Herrero and Arbeloa, 1989; Pimienta and Polito, 1983). In almond, pollen tubes arrive at the obturator and there is a temporary cessation of their growth at this point. While pollen tube growth is arrested at the obturator, megagametophyte devel- opment is completed. Pollen tube growth resumes after megaga- metophyte differentiation is complete (Pimienta and Polito, 1983). Williams (1965) introduced the term effective pollination period (EPP) to describe the window of time during which pollination may result in fertilization. EPP incorporates stigma receptivity, ovule longevity and the time needed for pollen tubes to reach the ovule, i.e., the rate of pollen tube growth. Research leading to yield models by Brain and Landsberg (1981) in apple (Malus sylvestris (L.) Mill. var domestica (Borkh.) Mansf.), and DeGrandi-Hoffman (1989) in almond shows that fruit set is determined by the number of flowers per tree and EPP. In these models, the time taken by pollen tubes to reach the ovule is a primary attribute used to calculate predicted yields. In view of these relationships, optimal orchard management practices in a species such as almond, where maximum fruit set is desired, should aim at extending EPP to maximize fertilization success.