Abstract
HIGHLIGHTS In an abortive ovary of hazel, an integument seldom differentiated and a mature embryo sac never developed.In an abortive ovary of hazel, pollen tube growth was arrested at the style base about 40 days after blooming. Thus, fertilization of the ovule was precluded.Ovary abortion in the four hybrid cultivars was indicated to be associated with insufficient resource availability to support fruit set by all flowers, whereas ovary abortion in C. heterophylla was at least partly determined by pollen availability.In Northeast China, a high frequency of ovary abortion contributes to serious losses in yield of hazelnut. The development of pistillate inflorescences and fruit clusters of four large-fruited hybrid hazel cultivars and the small-fruited Corylus heterophylla were used to study ovary abortion and its possible causes during the progamic phase in hazel. The average number of pistillate (ANP) flowers per inflorescence and average number of fruit (ANF) per cluster of four hybrid hazel cultivars were 7.6–8.5 and 2.4–3.0 respectively; in C. heterophylla, its ANP and ANF was 5.8–6.2 and 3.5, respectively. The total drop varied from 50 to 67%. Ovary abortion in hazel initiated from about 30 days after blooming. The percentage of abortive ovaries (PAO) in the four hybrid hazel cultivars ranged from 63 to 72%, and was significantly higher than that of C. heterophylla (29–42%). Only the abortive ovary ratio of C. heterophylla was significantly reduced after artificial pollination. Fruit number per cluster was positively and negatively correlated with yield and nut mass, respectively. In abortive ovaries, the diameter remained less than 2 mm during the entire fruit development, an integument seldom differentiated and a mature embryo sac never developed. In addition, pollen tube growth was arrested at the style base about 40 days after blooming. Thus, fertilization of the ovule was precluded. Compared with abortive ovary, starch content in developing ovary of four hybrid hazel cultivars and C. heterophylla were significantly higher. This study suggests that abortive ovary was incapable to finish fertilization process due to the absence of mature embryo sac and arrested pollen tubes, and this is likely associate with insufficient resource availability to support fruit set by all flowers in four hybrid hazel cultivars, whereas ovary abortion in C. heterophylla is at least partly determined by pollen availability.
Highlights
Hazel (Corylus spp.) is the most widely distributed and economically important member of the Betulaceae family in China
The percentage of abortive ovaries (PAO) and average number of fruit (ANF) per cluster of C. heterophylla were reduced and promoted by artificial pollination, respectively (Table 3). These results indicated that fruit set was at least partly determined by pollen availability
Besides loss due to pistillate inflorescence and fruit cluster drop, the development of most of the pistillates flower will stop and form abortive ovaries, and this process occurs during progamic stage of hazelnut
Summary
Hazel (Corylus spp.) is the most widely distributed and economically important member of the Betulaceae family in China. The hazel forest area in China exceeds one million hectares, which is much higher than all other hazelnut-producing countries in the world. The northeast is the traditional hazelnut production region in China. Development of the hazelnut industry plays an important role in increasing farmers’ income, especially in mountainous areas (Liu et al, 2012). Compared with yields of 600–1000 kg ha−1 in Turkey, 2000–3000 kg ha−1 in Italy and. 1700–2500 kg ha−1 in the United States (Aydinoglu, 2013), yields in China are less than 450 kg ha−1.
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