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    Assessing drought tolerance in field-grown sunflower hybrids by chlorophyll fluorescence kinetics
    (Soc Botanica Sao Paulo, 2019) Cicek, Nuran; Pekcan, Veli; Arslan, Ozlem; Erdal, Sekure Culha; Nalcaiyi, Ayse Suna Balkan; Cil, Ayse Nuran; Sahin, Vakas
    Drought is one of the most damaging abiotic stress factors commonly experienced by plants, resulting in a significant loss of crop yield worldwide. The aim of the study was to assess drought tolerance of sunflower (Helianthus annuus) hybrids and find out potentially underlying photobiological traits. Experiment was conducted in the agricultural field of Eastern Mediterranean Agricultural Research Institute in Adana. To evaluate the drought tolerance of twenty-six sunflower hybrids polyphasic chlorophyll fluorescence measurements were performed at the three growth stages named as vegetative, head formation and milky seed (stress 1, S1; stress 2, S2; stress 3, S3, respectively). The hybrids were classified from drought tolerant to drought sensitive based on their drought factor index (DFI) values calculated from photosynthetic performance index. 9444 A X 9947 R and 9444 A X 8129 R were determined as the most tolerant hybrids, whereas 2453 A X 8129 R and 7751 A X TT 135 R were determined as the most sensitive hybrids. Severe drought stress (S2) inhibited severely both the donor and the acceptor sides of photosystem II in sensitive hybrids. Photosynthetic structures of drought-tolerant hybrids were less damaged by drought stress, consequently these hybrids could maintain their photosynthetic performances (minor changes in phi(Po), psi(o), delta(Ro), specific and/or phenomenological energy fluxes) approximately control levels under severe drought condition. As a result, results, 9444 A X 9947 R and 9444 A X 8129 R hybrids could be recommended to be used in the breeding programs and further studies as genetic material and to be grown in drought-prone areas.
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    Oil content determination on sunflower seeds in drought conditions
    (Wiley-Hindawi, 2022) Pekcan, Veli; Yilmaz, M. Ibrahim; Evci, Goksel; Cil, Ayse Nuran; Sahin, Vakas; Gunduz, Oguz; Koc, Hasan
    Sunflower (Helianthus annuus L.) is one of the most important oil crops in the world and mostly produces oil. Due to the global warming and unexpected climatic changes especially extreme heat and droughts in recent years, as a spring crop sunflower affects severely by these climatic conditions in the vegetation period and loses seed yield hardly. Plant breeding longer process taking at least ten years to develop cultivars. Therefore, sunflower breeders should consider future climatic conditions, hence it seems that drought tolerance should consider primarily in their breeding programs. Oil content is the most important trait in sunflower than the major goal in the breeding studies; likewise, it is the most affected yield trait in sunflower from drought conditions. The study was conducted to determine the oil contents from drought some inbred lines and their hybrids developed lately in National Sunflower Project conducting by Trakya Agriculture Research Institute (TARI). Based on the study results; the significant relationships were observed between oil content and other yield traits in drought conditions. Oil content of male lines exhibited more variability than female lines changed as 13.16%-54.05% male lines and 19.12%-52.46% in female lines, and 30.17%-53.68% in the hybrids. While oil content of inbred lines affected negatively mostly from thousand seed weight and head diameter, leaf number, leaf area, and seed yield followed this trait, respectively. Based on path analysis for the contribution of yield traits on determining of oil content; it determined that seed and oil yield were the most directly affected traits then followed by oil yield in sunflower inbred lines in a negative way, and other yield traits mostly affected oil content determination in drought stress conditions over these two traits. The seed and oil yield, leaf area, and thousand seed weight reduced about over 90% in the drought in inbred lines. Severe droughts resulted heavy decreases in sunflower oil content as well as in the seed and oil yield and other yield traits so no need to focus on increasing oil contents over 40%-43% and it should be sacrified from this trait in that kind of conditions. The sunflower hybrid evaluations in three different locations mentioned that thousand seed weight, seed yield, and leaf area as well as leaf number are the most important yield traits affecting positively of oil content determination in drought stress conditions. Practical applications Sunflower is commonly influenced by the environmental conditions, such as hot temperatures and drought as being a spring growing crop. These environmental stresses mostly appear during mid-summer then sunflower suffers from these stressess resulting of seed and oil yield losses with lower oil content. Especially the stress in the grain filling period results in lower oil content in the sunflower growing season. The study results mentioned that sunflower breeders should consider more male inbred lines to develop better oil content hybrids for drought stress. Furthermore, thousand seed weight is also the most important seed characteristics other than seed and oil yield for consisting of oil content in sunflower. Therefore, we have to focus on developing higher seed yield instead of higher oil content because sunflower sacrifice from seed yield to give higher oil content over 40%-43% during the stress conditions.