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The lychee fruit is in high demand worldwide. However, the yields of many cultivars are low, including the high-quality cultivars "Nuomici" (NMC) and "Fei Zi Xiao" (FZX), which are very tasty and produce large fruit with a small seed, but tend to shed their fruitlets. In a previous work, we found that cross-hand pollination of "Mauritius" (MA) with pollen of another cultivar increased fruit set and reduced fruit-drop in comparison to self-hand pollination. In the current research, we aimed to identify the optimal pollen donor for three of the main cultivars grown in Israel: MA, FZX, and "Tamuz" (TA). We compared the effect of different pollinizers and found that the Vietnamese cultivar "Hong Long" (HL), which is becoming an important cultivar in Israel, was the optimal pollinizer for the three cultivars. In addition, we found that FZX and TA were not self-fertile under the Israeli environmental conditions since they tend to shed fruitlets that originated from self-fertilization. In contrast, MA is able to fertilize itself, although cross-pollination greatly increased its fruit number and size. We also identified a new PCR marker for lychee, M3, that enabled us to distinguish between self- and cross-fertilized FZX fruits pollinated by HL. Our results indicate that cross-pollination, particularly by HL, has beneficial effects on the production of lychee and it is especially important for cultivars that generate small seeds and tend to shed their fruitlets. [ABSTRACT FROM AUTHOR]

The European apricot (Prunus armeniaca) cultivar 'Earlicot' has high economic potential due to its high-quality fruit and early yields. 'Earlicot' has recently been introduced into Israeli orchards. The climate in Israel is relatively warm, although cold enough for cultivating high-quality stone fruit. However, the full potential of this new apricot cultivar was not being realised. The aim of this work was to understand the reasons for the low performance of 'Earlicot' and to identify methods to overcome them. In a 2-year study, we observed that 'Earlicot' flowered poorly. The problem of poor flowering and hence fruit-set was improved and yields tripled following application of the gibberellin inhibitor, uniconazole, at 500 mg 1-1 [1% (v/v) Magic™] during the period of floral differentiation (mid-May). In addition, we found significant positive relationships between the proximity of 'Earlicot' trees to the polleniser 'Earlygold' and the efficiency of fertilisation, as determined by the genetic marker S8-RNase, the fruit-set percentage, and fruit yield. We also identified the early apricot flowering cultivar '311' to be a fully-compatible polleniser for 'Earlicot'. Full-compatibility for cross-pollination will assure high fruit yields in 'Earlicot'. [ABSTRACT FROM AUTHOR]

The current understanding of the RNase-mediated Gametophytic Self-Incompatibility (GSI) system in pears is presented. A practical outcome of GSI research is the ability to S-genotype cultivars molecularly. In Israel the main pear cultivar is ‘Spadona’; ‘Cocsia’, ‘Gentile,’ and ‘Spadochina’ serve as its pollenizers. However, yields are relatively low, probably, at least in part, because of genetic semi-compatibility, which causes rejection of half of the pollen grains that reach the ‘Spadona’ flowers. The wild pear Pyrus syriaca, which is endemic to Israel, flowers in parallel to the cultivated European pear varieties, and is expected to be compatible with them. We are currently examining P. syriaca trees in the northern part of Israel, to see if they could serve as efficient pollenizers for the cultivated pears in Israeli orchards. [ABSTRACT FROM AUTHOR]

Abstract: Japanese plum belongs to the Rosaceae, which carry the S-RNase-based gametophytic self-incompatibility system. Therefore, these plum cultivars depend on cross-pollination for setting fruit. However, cultivar combinations may be genetically semi- or fully compatible. In apples and pears cultivated in Israel, where conditions for pollination are usually unfavorable, it was demonstrated that yields may be correlated with compatibility levels of pollinators. In the present study fruit-set of semi- and fully compatible plum couples was determined for a wide range of cultivars, in unfavorable and favorable conditions. Full compatibility was found superior to semi-compatibility, in both unfavorable and favorable conditions for pollination. These findings should be taken into consideration in determining the orchard designs of cultivars. [Copyright &y& Elsevier]

Apple (Malus domestica) has a gametophytically determined self-incompatibility system, which limits inbreeding. As a consequence, apple trees depend on cross-fertilization for fruit-set, which may be enhanced by honeybees (Apis mellifera). In this study honeybee pollination effectiveness and setting potential of two important apple cultivars, 'Smoothee Golden Delicious' and 'Topred Red Delicious', were investigated to shed light on the high fruit-sets and yields of 'Smoothee', as compared with 'Topred'. Analysis of floral features and honeybee behaviour revealed that the differences between the two cultivars in flower size and nectar traits did not affect honeybee visitation frequency, which was the same for both cultivars. Due to the wide basal gaps between the stamen filaments in 'Smoothee' and 'Topred' flowers, which enabled "sideworking", a low proportion of "topworkers" was found in both cultivars. Yet, more than double the number of "topworkers" was found in 'Smoothee', as compared to 'Topred', probably because of the wider diameter of the stamen filament spread of the 'Smoothee' flowers, facilitating nectar collection from the top and thus increasing pollination effectiveness. 'Smoothee' fruit-set was significantly higher than 'Topred' in all stages of flower development, in accordance with the assumption that 'Topred' has a shorter ovule longevity than 'Smoothee'. However, higher fruit-set of 'Smoothee' flowers pollinated before anthesis, at the "Balloon" stage, was also found. This implies that the high fruit-set and fertility of 'Smoothee' are also due to additional genetic features. [ABSTRACT FROM AUTHOR]

Pollination is limiting for avocado production. We examined whether adding bumblebees (BBs; ca. 10 hives/ha) to conventional honeybees (HB; 5 hives/ha) would improve 'Hass' avocado pollination and yields. A preliminary trial (2017/18) in an avocado orchard with four consecutive rows of 'Hass' followed by one row of 'Ettinger' serving as a pollenizer (20% 'Ettinger') showed a considerable increase in 'Hass' yield in rows adjacent to (up to 80 m from) the BB hives vs. distant rows (=controls). In 2018/19, the trials were extended to three additional orchards. A significant yield increase was obtained in the BB hive-adjacent trees compared to BB hive-distant ones. Similar results were obtained in 2019/20, in experiments conducted throughout the country. The SNP analysis, to determine the parents of 'Hass' fruit at varying distances from the BB hives, showed no differences in the cross-pollination rate ('Hass' × 'Ettinger'). However, pollination rates and the number of germinating pollen grains per stigma decreased with distance from the hives, and correlated to the negative gradient in yield. Taken together, our data suggest that adding BB hives to 'Hass' avocado orchards, at ca. 10 hives/ha resulting in 0.5–1.0 BB visits/tree per min, increases pollination and, accordingly, total yield. [ABSTRACT FROM AUTHOR]

Apple (Malus domestica) has a gametophytic self-incompatibility (GSI) system. Consequently, fertilization is achieved by cross-pollination with a compatible pollinator. Compatibility is governed by a multiallelic S locus. Cultivars are fully compatible when both of their S-loci differ and are semi compatible when one locus is identical and the other differs. In a previous study we found that the fruit set and yield of the apple cultivar 'Topred' was reduced when it was pollinated by a semi compatible cultivar. To examine if this occurrence is a general feature in apples grown under suboptimal conditions, three additional cultivars, 'Golden Delicious', 'Granny Smith' and 'Royal Gala', were studied as pollen recipients of semi and fully compatible pollinators. Based on PCR analysis of the S-RNase allele, it was determined that the pollination rate of the semi compatible was significantly lower than that of the fully compatible pollinator in all cases. This was reflected by the lower fruit set and seed set of 'Golden Delicious' and 'Royal Gala', but not of 'Granny Smith'. In hand pollination experiments, where pollen was in excess, no difference was found between the semi and fully compatible pollinators in all three cases. These results indicate that the low yield, conferred by semi compatible pollinators, is due to insufficient cross-pollination (and not to cultivar characteristics). Thus, low yields due to semi compatibility may be avoided by appropriate honeybee management that will increase pollination. Still, under suboptimal conditions, for growth and pollination, full compatibility is preferable. [ABSTRACT FROM AUTHOR]

Highlights • SNP markers were identified for 'Hass', 'Ettinger' and 'Iriet'. • 98% of the 'Hass' fruit were due to cross pollination. • Honeybee visitations in 'Iriet' was relatively high. • 'Iriet' could serve as pollinator of 'Hass' beside of 'Ettinger'. Abstract Avocado (Persea americana M.) exhibits a two-type 'synchronous dichogamy' form of flowering that promotes outcrossing. In 'type A,' the flower opens in the female phase from morning till noon, then closes and re-opens on the afternoon of the following day in the male phase. In 'type B,' the flower opens in the female form on the afternoon of the first day, closes at the end of the day, and re-opens in the male form on the following morning. In both types, the female and male forms may overlap and self-fertilize. Planting an A type and B type cultivar adjacently to each other increases yield in most cases. 'Hass' (A type) is the most favorable avocado cultivar worldwide, however, the cultivar that serves as its pollinator varies between regions and countries. In Israel, for more than 30 years, the 'Ettinger' cultivar (B type, a seedling of 'Fuerte' selected in Israel) is its only pollinator, hence, adding another pollinator for 'Hass' should be beneficial. 'Iriet' (B type) is an Israeli-bred cultivar and its fruit has a 'Hass'-like appearance (a marked change in color from green when not ripe to black at full ripe). For accurate comparison between 'Iriet' and 'Ettinger' as a pollinator of 'Hass,' an orchard with the two pollinators was planted and a SNP analysis was developed for the identification of the paternal parents of the 'Hass' fruits. In addition, the flowering phenology and honeybee visits were determined. The results suggest that 'Iriet' is a good pollinator for 'Hass' and could be added alongside 'Ettinger' as a pollen donor for 'Hass'. [ABSTRACT FROM AUTHOR]

Abstract: ‘Orri’, a selection of ‘Orha’ mandarin [Temple (Citrus temple hort. ex Y. Tanaka)×Dancy (Citrus tangerina hort. ex Tanaka)], is a new high-quality Israeli mandarin which, in the last decade, has become one of the leading varieties in Israel. ‘Orri’ has an excellent taste, the rind is deep orange in color and easily removed, and it contains few or no seeds. However, ‘Orri’ grown in Israel suffers from inadequate yield and no published studies have yet addressed this problem. In the present study we determined that ‘Orri’ productivity depended on conditions being favorable to cross-pollination. Under cross-pollination conditions a positive correlation (R 2 =0.97) was found between yield per tree and number of fruits per tree, and more than 90% of the fruits exceeded 60mm: the most profitable size range. These data suggest that the number of fruits per tree, and not fruit size, is the limiting factor for yield improvement in ‘Orri’ orchards. Studying seed set showed that ‘Michal’ mandarin (Citrus reticulata Blanco) is a compatible pollenizer for ‘Orri’ flowers: the number of seeds per ‘Orri’ fruit increased as the distance from ‘Michal’ trees decreased. The present study demonstrated that cross-pollination of ‘Orri’ resulted in yield improvement, yet at the price of increased seed set. [Copyright &y& Elsevier]