**6. Effect of temperature (maximum) during blooming period on fruit yield**

The maximum temperature during the flowering period has a negative effect on the yield at the Ain-Draham site. The cultivar "Van" is characterized by the lowest yield (3.2 Kg/tree) during 2013 and a highest temperature during blooming (17.43°C), while "Bouargoub" produced 8 Kg/tree in 2015 and bloomed during a period characterized by a low temperature (13.37°C) (**Figure 4**).

In Tibar site, the year 2015 was characterized by a low temperature during blooming and by a better yield. The cultivars "Moreau" and "Sunburst" registered 6.5 and 7 Kg/tree and a maximum blooming temperature of 20 and 22°C, respectively. While "Napoleon" records the lowest yield and a low blooming temperature (18, 19°C) (**Figure 10**).

Bousalem site, the blooming periods of the cultivars "V2" and "V5" in 2013 and 2014 were characterized by almost the same maximum temperature. The cultivars "V3" and "V1" were also characterized by the same blooming temperature, whereas they showed a difference in yield throughout the 3 studied years. The cultivar "V4" was characterized by the highest yield during the 2 years, 2014 and 2015, while its flowering period was overlapping with that of "V2" (**Figure 11**).

The temperature at the blooming period is a determining parameter for the yield. If the blooming period coincides with a low mean maximum temperature the yield is high, whereas if the blooming coincides with a high mean maximum temperature the yield will be low, which is the case for the local cultivar "Bouargoub" in the site of Ain-Draham and the cultivar "V5" in the Bousalem site. "V5" is characterized by spreading blooming and a low yield despite the highest number of stamens. However, the other cultivars such as "V1" and "V3" bloom during a period characterized by a low mean maximum temperature (19.61–17.51°C and 19.8–18.85°C, respectively) and record low yield.

These results show that the temperature during blooming determines the fruit yield in the sweet cherry tree, but there are other factors that influence

Prunus

**Figure 11.**

*Yield (Kg/tree; Rdt) and Maximum temperature during blooming at BouSalem site.*

this parameter such as the genetic potential and self-fertility of the cultivar. The difference in yield between cultivars and sites can be explained by several factors including the behavior of the flower pieces depending on environmental conditions. The duration of the stigma's viability is influenced by weather factors. Regarding sour cherries, Nyeki [34] observed that the viability of the stigma was 2–3 days during sunny and hot days (mean daily temperature is 15–22°C). The viability was longer (4–6 days) in cool weather and daily temperatures of 4–12°C.

Low temperatures and rainy weather reduce the receptivity of the stigma. This was reported by Davarynejad [39] for apples and, in 1996, for pear trees. Although temperature is the main driver of phenological development, other ecogeographic factors can influence the date of flowering.

Thus, the cold temperature during blooming reduces the rate of growth of the pollen tube and can shorten the effective pollination period [40]. Caprio and Quamme [41] have shown a negative effect of high temperatures before blooming

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*Flowering of Sweet Cherries "*Prunus avium*" in Tunisia DOI: http://dx.doi.org/10.5772/intechopen.93234*

bees and, consequently, the setting rate [42].

**7. Conclusion**

**Acknowledgements**

**Conflict of interest**

**Author details**

Tunisia

(above 27°C) on the longevity of the ovum and on the efficiency of pollination. In addition, rain and low temperatures negatively affect the activity of pollinating

Sweet cherry is sensitive to temperature profiles during the blooming period. The low productivity is largely due to the nonoverlap of flowering periods and pollen incompatibility among different cultivars in the same experimental site. Our study is based on a mixture of introduced and local cultivars with different characteristics to diversify Tunisian orchards. While, the introduction of foreigner sweet

This work has been supported by the National Research Institute of Rural Engineering Water and Forests (INRGREF), Tunisia. The authors are grateful to the

National Researches Institute of Rural Engineering, Water and Forests, Ariana,

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

cherry cultivars in areas with mild winters leads to increased yields.

engineers and technicians who contributed to this work.

The authors declare no conflict of interest.

Thouraya Azizi-Gannouni\* and Youssef Ammari

provided the original work is properly cited.

\*Address all correspondence to: najeh.esak@gmail.com

(above 27°C) on the longevity of the ovum and on the efficiency of pollination. In addition, rain and low temperatures negatively affect the activity of pollinating bees and, consequently, the setting rate [42].
