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A. Beshir El Ahmadi and M. Allen Stevens

Abstract

The genetics of high-temperature fruit set was studied with a complete diallel cross using 5 cultivars with excellent high temperature tolerance and a California cultivar lacking stigma exsertion. The cultivars differed genetically for number of flowers per cluster, percent fruit set, number of seeds per fruit and stigma exsertion. At normal and high temperatures recessive genes are associated with greater flower number and heritability for this character was high. Percent fruit set is under the control of a largely additive system with a moderate heritability at high temperature. Nonallelic gene interaction was involved in seed set and dominance components exceeded additive at both temperatures. Heritability for seed set was low at high temperature. Stigma exsertion at high temperature is controlled by partially dominant genes with a high diallel additive component and heritability. The results suggest that a scheme of selection for specific combining ability would be useful to combine the strengths of the high temperature tolerant lines with needed characters from a successful cultivar.

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D.I. Leskovar, J.C. Ward, and A. Meiri

109 ORAL SESSION 28 (Abstr. 572–579) Fruit Set & Seed Quality–Vegetables

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A. Maaike Wubs, Yuntao Ma, Lia Hemerik, and Ep Heuvelink

-growing fruits, this leads to alternating periods of high and low fruit set. These fluctuations in fruit set are believed to be the cause of cyclic fluctuations in fruit yield. Irregular fruit yield causes difficulties in the planning of activities throughout the

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Yoshishige Furukawa and Martin J· Bukovac

Abstract

The development of the embryo sac was followed during the pollination period in ‘Montmorency’ sour cherry (Prunus cerasus L.) and related to fruit set. Twenty five percent to 40% of the embryo sacs were incomplete, degenerating, or contained four nuclei or fewer at anthesis and were considered nonfunctional. The effective pollination period extended for 3 to 5 days in each of two growing seasons, and fruit set ranged from 14% to 26%. The incidence of nonfunctional ovules at anthesis did not appear to be sufficient to fully account for the limited fruit set observed. Other factors, most likely physiological, play a contributing role.

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S. Z. Berry and M. Rafique Uddin

Abstract

Selected F3 and F4 lines of different origin were evaluated at high temperature (26° night and 35°C day) in the greenhouse along with several known heat-sensitive and heat-tolerant tomato (Lycopersicon esculentum Mill.) cultivars. A number of the selected lines had fruit set comparable to the tolerant cultivars Saladette, Ohio 7663, BL 6807, and Chico III. The expected greater fruit set of the tolerant cultivars vs. that of the sensitive cultivars was observed. High fruit set in this study was not associated with high seed number in the majority of tolerant cultivars evaluated.

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Chunxian Chen, William R. Okie, and Thomas G. Beckman

brown and abscise, and can dramatically affect peach fruit set ( Rieger et al., 1991 ; Smith et al., 1994 ). A late spring frost can wipe out an entire peach crop. A mild spring frost may be helpful by thinning the fruitlets naturally, because many

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Carlos Miranda, Luis G. Santesteban, and José B. Royo

The apical or king (K) flower in the apple (Malus ×domestica L. Borkh.) cluster usually develops and blooms first and also has a greater sink potential. For this reason, resources are primarily used by the K fruit, and this is also one of the reasons why most thinning practices tend to favor K fruit set. However, it is not always possible to retain the K flower and remove the lateral ones. This study was undertaken to determine if the removal of the most developed flowers in the cluster influences yield or quality compared to that obtained in a whole cluster. The treatments were made in `Golden Delicious' and `Royal Gala' apple cultivars, within a wide range of flower densities for each cultivar. The factor tested was the intensity of flower removal (FRI); the treatments consisted in removing one, two, or three flowers in each cluster. Flower density was used as a covariate in an analysis of covariance to account for differences in flower densities in response to FRI treatments. In all experiments the covariate was not significant; therefore FRI effect was not affected by flower density. `Golden Delicious' and `Royal Gala' had similar responses to flower removal, so that when at least three flowers in a cluster remained, fruit set and cluster yield were similar to whole clusters. Only when two or fewer poorly developed flowers remained after FRI treatments, yield was reduced by as much as 25%. Fruit from FRI clusters were even heavier than those from whole clusters, due to reduced competition among the fruit, so that the growth potential of fruit from the first and second lateral flowers was similar to clusters with K fruit, in clusters where the K flower had been removed.

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Khalil R. Jahed and Peter M. Hirst

Pollination is an essential process for fruit set, fruit growth, fruit quality, and seed set of most apple cultivars. The first step of successful apple pollination is the transfer of pollen to the stigmatic surface (typically vectored by bees

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Carlos Miranda, Luis G. Santesteban, and José B. Royo

The lowest flower in the pear (Pyrus communis L.) cluster usually develops and blooms first and also has a greater sink potential. For this reason, resources are preferentially utilized by the lowest fruit, and this is also one of the reasons why most thinning practices tend to favor their set. However, it is not always possible to perform selective thinning. This study was undertaken to determine if hindering pollination in the most developed flowers in the cluster influences yield or quality compared to that obtained in a whole open-pollinated cluster. The treatments were made in `Blanquilla' (Spadona, Agua de Aranjuez) and `Conference' pear within a wide range of flower densities for each cultivar. Pollination was hindered by cutting off the flower styles. The factor tested was style removal intensity (SRI). Treatments consisted in removing the styles of two, four(always the most developed), or all flowers in each cluster. Flower density was used as a covariate in an analysis of covariance to account for differences in flower densities in response to SRI treatments. In all experiments the covariate was not significant; therefore, SRI effect was not affected by flower density. `Blanquilla' and `Conference' had similar responses to treatments, so that when at least three flowers are susceptible to be openly pollinated, fruit set, seed content, and cluster yield were similar to control clusters, therefore the growth potential of fruit from partially damaged clusters in their most developed flowers is similar to undamaged open pollinated clusters. The reduced set of parthenocarpic clusters implies yield reductions ranging between 40% and 60% in `Conference', and up to about 60% in `Blanquilla'.

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Qin Yang, Er Liu, Yan Fu, Fuqiang Yuan, Tingting Zhang, and Shu Peng

changes occurred frequently during the 2014 to 2018 period and were associated with erratic fruit set in blueberry. Production practice in recent years has shown that temperature stress constitutes the biggest obstacle to flowering and fruit setting in