213 Adv. Hort. Sci., 2018 32(2): 213-219 DOI: 10.13128/ahs-21365 The effect of polyamines and SICS on the compatibility, fertility and yield indices of apple cv. Golden Delicious P. Sayyad-Amin, G.H. Davarynejad (*), B. Abedy Department of Horticultural Sciences and Landscaping, Agriculture College, Ferdowsi University of Mashhad, P.O. Box 9177948978, Mashhad, Iran. Key words: fruit set, putrescine, spermidine, spermine. Abstract: The most critical problems of temperate fruit trees are poor fruit set and low yield. To solve the problem, some major chemical compounds such as polyamines and SICS (self-incompatibility control substance, Mn+B) can be used. Popular polyamines including Putrescine (0.1 and 0.25 mM), both Spermine and Spermidine (0.05 and 0.25 mM), and SICS (1 and 2 mg L-1) were used alone or with cotton coverage bags to cover branches in order to investi- gate self-incompatibility in Malus domestica. Results showed that Spermidine (0.25 mM) led to higher yields in comparison with that of the control. SICS (2 mg L-1), also, demonstrated the highest yield compared with that of the control. At June fruit set, treatment with Spermidine (0.25 mM) led to the highest per- centage of fruit set and also the highest index of self-incompatibility and per- centage of final fruit set among treatments. 1. Introduction Alternate bearing and self-incompatibility are the main issues in apple. Alternate bearing is vigorous in some apple cultivars like ‘Golden Delicious’. Most apple cultivars are self-incompatible and self-unfruitful; therefore, they need another cultivar for pollination and fertilization. Gametophytic self-incompatibility (GSI) occurs when the S allele of the pollen grain matches either of the S alleles of the stigma. In such a case, the pollen tube begins to develop but stops before reaching the micropy- le (Asatryan and Tel-Zur, 2013). Gametophytic self-incompatibility is con- trolled by glycoprotein with RNase (S-RNase) activity expressed in the pis- til. S-RNase (Qing-qing et al., 2009; Duca et al., 2010; Uchida et al., 2012) encoded by the S-locus gene is named SFB (S-haplotype-specific F-box gene) in the Rosaceae. To date, in Rosaceae family, SI has mainly been studied in Japanese pear (Pyrus pyrifolia) and almond (Prunus dulcis) (Qing-qing et al., 2009; Uchida et al., 2012). However, some requirements are necessary for suitable cross pollination: having (1) compatible pollen grains with enough quantity and high quality (in fact, pollination with (*) Corresponding author: davarynej@um.ac.ir Citation: SAYYAD-AMIN P., DAVARYNEJAD G.H., ABEDY B., 2018 - The effect of polyamines and SICS on the compatibility, fertility and yield indices of apple cv. Golden Delicious. - Adv. Hort. Sci., 32(2): 213- 219 Copyright: © 2018 Sayyad-Amin P., Davarynejad G.H., Abedy B. This is an open access, peer reviewed article published by Firenze University Press (http://www.fupress.net/index.php/ahs/) and distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Competing Interests: The authors declare no competing interests. Received for publication 7 November 2017 Accepted for publication 18 April 2018 AHS Advances in Horticultural Science Adv. Hort. Sci., 2018 32(2): 213-219 214 semi-compatible pollen resulted in lower fruit-set than that with fully compatible pollen) (Sapir et al., 2008), (2) an overlap period of pollination between pollinizer and pollinator (pollinizer trees must be cul- tivated along with the pollinator trees) (3) proper time of flowering and blooming, and finally, (4) hav- ing attractive flowers in order to reduce the number of bees visiting weeds on the orchard floor (the pollen grain of fruit trees is sticky and heavy causing not to be carried by the wind) (Bekey and Burgett, 1981). Hand pollination is a type of cross pollination that can be effective on producing crop in adverse weath- er conditions. When the king flower opens, it is nec- essary to place bee colonies in order to do cross polli- nation by bees and then remove them at petal fall in fruit orchards: however, this method is also time- consuming and needs a big number of workers (Bekey and Burgett, 1981; Maib et al., 1996). Despite the presence of hives, pollen transfer limitation and subsequent seed set reductionwas observed in orchards (Quinet et al., 2016). The other suitable technique applied to do pollination involves chemical methods; in fact, some chemical compounds can be used in order to achieve enough fruit set and high yield. Plant bio regulators (PBRs) had significant effects on increasing pollen germination and pollen tube length in almond pollen: the action of these PBRs significantly increased the percentage of fruit set at both the bud pink and petal fall phenological stages (Maita and Sotomayor, 2015). As an alterna- tive, the use of polyamines (putrescine, spermine, spermidine), that are natural compounds involved in plant growth and development process, has been s u g g e s t e d r e d u c e f l o w e r s a n d f r u i t s d r o p ; polyamines competes with ethylene synthesis with whose they share the same precursor called s-adeno- syle methionine (Crisosto et al., 1988; Khezri et al., 2010). Polyamines as plant bio regulator revealed to increase pollen tube growth and fruit set by stimulat- ing pollen germination (Crisosto et al., 1988; Liu et al., 2006) and were effective on pollen tube elonga- tion (Aloisi et al., 2015). Also, self-incompatibility control substance (SICS), which is a mixture of man- ganese and boron (Son et al., 2009), could be useful for increasing fruit set. Polyamines and SICS were effective on increasing yield and fruit set in crops such as pear (Crisosto et al., 1988; Son et al., 2009), apple and apricot (Asadi et al., 2013), olive (Costa et al., 1986), sweet cherry (Grant Sheard, 2008), sweet orange (Saleem et al., 2008), pistachio (Khezri et al., 2010), mango (Malik et al., 2005), and date palm (Tavakoli and Rahemi, 2014). With regard to the effect of these compounds on pollen tube growth, Spermidine (Spd) and Spermine (Spm) influence the p r o m o t i o n o f t h e p o l l e n t u b e e l o n g a t i o n a t Polyamines concentrations up to 50 mM in Rosaceae family, whereas higher concentration of Spd and Spm resulted inhibitory for pollen tube elongation in Rosaceae family and correlate with male sterility in Actinidia deliciosa (Aloisi et al., 2015). They are com- pounds useful in enhancing ovule longevity (Crisosto et al., 1988; Liu et al., 2006), without having any deleterious and toxic effects on human life (Azh et al., 2014). In the initial stage of fruit development, an active cell division takes place, which possibly needs sufficient polyamines. At the later stage of fruit development, polyamine synthesis is reduced. As biosynthesis of polyamines takes place before pollen tube emergence, low level of free polyamines in cytoplasmic male sterile plants influences cell divi- sion and its enlargement, leading to abnormal devel- opment and low viability of pollens (Liu et al., 2006). Polyamines increase pollen tube growth and fruit set by stimulating pollen germination. As well, they play a role in carbohydrates and nitrogen regeneration, followed by increasing chlorophyll content and leaf a r e a ( B a n i n a s a b a n d R a h e m i , 2 0 0 8 ) . U s e o f polyamines (Put, Spm, Spd) at bloom improves ovule longevity in fruit crops such as apricot and pear. Higher endogenous polyamine contents have been correlated with improved ovule viability in apricot and sour cherry (Grant Sheard, 2008). Boron increased pollination activity (Nyomora et al., 1997). In boron deficiency, phenolic compounds aggregates on stigma. The accumulation of these com- pounds due to the activation of dehydrogenase enzyme led to the pollen grain not to be germinated. Boron increases pollen grain viability by increasing the flavenoids content of pollen grain (Marschener, 1995). The percentage of fruit set as a vital factor is as important as other quantitative and qualitative traits to achieve an acceptable yield in apple (Malus domestica). It seems the contemporary application of polyamine and SICS together can enhance their effects. Although there are numerous researches on the individual application of polyamine and SICS, there was not found any literature comparing the effect of polyamines and SICS on yield indices, espe- cially along with cotton coverage bags on the index of fertility (IF) and the index of self-incompatibility (ISI). The aim of this study was to increase yield indices in apple cultivar ‘Golden Delicious’, accompanying the decrease of fruit drop using polyamines and SICS. Sayyad-Amin et al. - Polyamines and SICS effect on compatibility, fertility and yield indices of apple cv. Golden Delicious 215 2. Materials and Methods The study was carried out on thirteen year-old apple trees cv. Golden Delicious in an orchard locat- ed in Mashhad (latitude of 36°20’and altitude 59° 34‘). It is an area with arid and semiarid climate and annual average precipitation of 255 mm. The foliar application was done with 5 l sprayer on four select- ed branches between bud swollen and flower open- ing pheological stages at early morning. The com- pounds included polyamines [putrescine (Put) 0.1 or 0.25 mM; spermine (Spm) 0.05 or 0.25 mM; spermi- dine (Spd) 0.05 or 0.25 mM] and SICS [1 mg/L (3.5 mg boric acid, 6.8 mg manganase sulphate) and 2 mg/L (6.8 mg boric acid, 13.6 mg manganese sulphate)] (Son et al., 2009) with (+) or without (-) cotton cover- age bags (ccb), and control (untreated) plants. Cotton coverage bags were used in order to prevent cross and open pollination. In this study, the following traits were measured: yield, percentage of fruit set [initial (2 weeks after petal fall); June (fruit drop in June); final (at harvest)] and fruit drop. Index of fertility (IF) was measured based on the percentage of initial fruit set ratio in each treatment compared to control. Index of self-incom- patibility (ISI) was evaluated based on the percentage of final fruit set ratio in each treatment in comparison with control; in this regard, the ratios of 0.2, between 0.2-1, and higher than 1 represent incompatibility, semi-compatibility and full self-compatibility, respec- tively (Zeinanlo et al., 2001; Azimi et al., 2008; Seifi 2008; Taslimpour and Aslmoshtaghi, 2013). The randomized complete block design with four replicates was applied in this study. At final, the data w e r e a n a l y z e d b y S A S s o f t w a r e v e r . 9 . 1 ( S A S Institute, 2004) and the means were compared using LSD test at 0.05. Fruit diameter and length were measured with non destructive method during the fruit growth peri- od until the harvest time. This method was better than the destructive technique. Non destructive method are less time consuming and no need to lab- oratory space, and without harvesting. According to this method, fruit length and diameter were mea- sured every 2 weeks without harvest, whereas in destructive method, these parameters are measured in fruits harvested every 2 weeks and their length a n d d i a m e t e r w e r e m e a s u r e d . T h e r e f o r e , n o n destructive method was used in the present study (Arzani et al., 1999; Dehghani et al., 2012). 3. Results The effects of polyamines and SICS on yield and fruit set Without cotton coverage bags. Data showed that Spd treatment (0.25 mM) led to a higher yield in comparison to the control (P<0.05). SICS (2 mg L-1) demonstrated the highest yield among all of the treatments (P<0.05). It was also found that Put (0.1 mM) and Spm (0.05 mM) showed increase in yield compared with the control, but it was statistically non-significant at 0.05 level. SICS (1 mg L-1) increased initial fruit set when com- pared to control. The highest June and fruit set related to Spd (0.25 mM) among all of the treatments (P<0.05). With cotton coverage bags. There was significant increase in percentage of initial fruit set by applica- tion of SICS (2 mg L-1), and Spm (0.25 mM) (Table 1) in comparison to the control. The results also demon- strated the higher percentage of initial fruit set under treatment with Spd (0.05 mM) than the control, but it was statistically non-significant at 0.05 level. Percentage of final fruit set showed statistically significant difference (P <0.05) in most of the treat- ments in comparison with the control, except for Put (0.1 mM), SICS (2 mg L-1), Spm (0.25 mM), Spm (0.05 mM) and Spd (0.25 mM). The effects of polyamines and SICS on IF and ISI The index of fertility increased in treatments with Spm (0.25 mM + ccb) and SICS (2 mg L-1 + ccb). All of the treatments could led to semi or full fer- tility and compatibility, due to the percentage of fruit set ratio in each treatment compared to the control was larger than 0.2. The effects of polyamines and SICS on fruit drop In general, final fruit drop decreased significantly in treatments with Put (0.1 mM) and Spd (0.05, 0.25 mM). Without coverage. SICS (1, 2 mgL) decreased per- centage of initial fruit drop in comparison with the control of 12 and 10%, respectively (P <0.05). Final fruit drop decreased significantly in treatments with Put (0.1 mM) and Spd (0.05, 0.25 mM). With cotton coverage. Spm (0.25 mM) demon- strated the significantly (P<0.05) decrease of 14% in percentage of initial fruit drop in comparison with the control. Adv. Hort. Sci., 2018 32(2): 213-219 216 The effects of polyamines and SICS on fruit growth habit Based on figure 1, fruit growth totally increased in all of the treatments; in fact, fruit length and diame- ter increased gradually from July 9 to harvest (Fig. 1 b and d) whereas Spm (0.25 mM + ccb) showed a dif- ferent trend. 4. Discussion and Conclusions The effects of polyamines and SICS on yield and fruit set In the present study, application of polyamines [Put (0.1, 0.25 mM), Put (0.25 mM + ccb), Spd (0.05, 0.25 mM) and Spd (0.05 mM + ccb)] between periods of swollen buds and the start of flowering phenologi- cal stages could increase fruit set at final fruit set stage. Several researchers studied about the effects of polyamines on yield indices. Polyamines (Put, Spm, Spd) enhanced ovule longevity at bloom in fruit crops such as apricot, pear and sour cherry (Grant Sheard, 2008). Polyamine synthesis had also positive influ- ence on development and viability of pollen and it occurred before pollen tube emergence. Therefore, lower content of free polyamines caused male sterili- ty in flowers (Liu et al., 2006). Exogenous application of different polyamines at full bloom had influence on increasing fruit set and total yield in apples, olive, litchi and mango. Increase in fruit set and yield by polyamines was due to raising pollination, fertiliza- tion and fruit retention (Costa et al., 1986). Saleem et al. (2008) stated that polyamines significantly increased initial fruit set and yield and maximum fruit set was observed in Spd, Spm and Put, respectively. Put had positive effect on increasing ovule longevity, EPP (Effective pollination Period), N and B and might raise the pollen tube growth rate in the styles of pears (Crisosto et al., 1988), but their role on raising ovule longevity might be due to the improved nutri- tional status of the flower (Grant Sheard, 2008). Application of Put raised fruit set and yield of ‘Comice’ pear at the start of flowering (Crisosto et al., 1988). Fruit set, crop density and yield efficiency under low fruit set conditions were improved by Put application at flower opening stage in pear (Crisosto et al., 1988). According to our results, the effects of polyamines o n f r u i t s e t a n d y i e l d w e r e i n a g r e e m e n t w i t h Crisosto et al. (1988) on pear, Malik et al. (2005) on mango, Grant Sheard (2008) on sweet cherry, Saleem et al. (2008), Khezri et al. (2010) and Asadi et al. (2013) on pistachio. In present study, SICS (2 mg L-1) had also a positive influence on fruit set and yield. In boron deficiency, p h e n o l i c c o m p o u n d s a g g r e g a t e o n s t i g m a . Accumulation of these compounds due to activation of dehydrogenase enzyme did not lead to germina- tion of pollen grain. Boron increased pollen grain via- bility by increasing the flavenoids content of pollen grain (Marschener, 1995). Boron increased pollina- tion activity (Nyomora et al., 1997). Foliar application Table 1 - The effect of polyamines (putrescine, spermine and spermidine) and SICS on yield, fruit set and first drop Means with the same letters were not significantly different according to LSD (0.05). Spm= Spermine, Spd= Spermidine, Put= Putrescine, IF=index of fertility, ISI=index of incompatibility. Treatments yield (g) Initial fruit set (%) June fruit set (%) final fruit set (%) IF ISI first drop (%) final drop (%) Control 1230 cde 55.893 d-g 40.395 b-e 18.02 f 1 b-e 1 bcd 30.7 cde 68.25 a-e Without cotton coverage bag Put (0.1 mM) 1416.7 c 50.179 e-h 39.046 c-f 28.636 bc 0.8625 def 1.4872 b 34.091 cd 42.424 g Put (0.25 mM) 1101 def 15.152 j 37.231 c-f 27.778 bc 0.5565 f 0.3715 e 31.548 cde 55.357 efg Spd (0.05 mM) 728.5 ghi 34.953 hi 32.749 c-g 22.281 de 0.6352 ef 1.2683 bcd 25.417 d-g 51.25 fg Spd (0.25 mM) 1990.8 b 41.692 ghi 61.722 a 34.722 a 0.7621 def 2.4166 a 18.75 gh 20.313 h Spm (0.05 mM) 1274.5 cd 74.605 abc 43.367 bcd 29.592 bc 1.3588 ab 1.0409 bcd 24.107 efg 76.259 ab Spm (0.25 mM) 1130 def 69.86 bcd 23.077 g 19.268 f 1.2552 abc 1.529 b 64.245 a 68.593 a-e SICS (1 mg L-1) 452 ij 75.63 abc 52.241 ab 20.26 f 1.3693 ab 1.2772 bcd 19.063 fg 56.818 d-g SICS (2 mg L-1) 2349 a 59.127 c-e 40.857 b-e 29.241 b 1.0773 bcd 1.4317 bc 9.43 h 58.772 c-f With cotton coverage bag Put (0.1 mM) 556 ij 42.361 f-i 28.03 fg 18.374 f 0.8869 c-f 1.4954 b 35.714 c 64.249 b-e Put (0.25 mM) 1116 def 33.145 i 27.083 fg 22.917 de 0.7276 def 1.2771 bcd 48.889 b 72.222 a-d Spd (0.05 mM) 696 hi 60.348 cde 30.925 efg 20.049 c 1.0839 bcd 1.4104 bc 50.379 b 63.258 b-f Spd (0.25 mM) 984 efg 56.25 d-g 43.75 bc 18.5 f 1.015 b-e 0.7663 de 16.193 gh 77.399 ab Spm (0.05 mM) 355 j 51.667 e-h 43.089 bcd 20.365 f 0.9567 cde 0.8757 cde 56.034 ab 74.353 abc Spm (0.25 mM) 599 ij 84.858 ab 31.579 efg 17.526 f 1.5371 a 1.2116 bcd 22.5 efg 55 efg SICS (1 mg L-1) 900.7 fgh 57.143 defg 32.712 c-g 25.173 cd 1.054 bcd 1.3247 bcd 28.333 c-f 56.667 d-g SICS (2 mg L-1) 720 ghi 87.326 a 44.355 bc 19.903 f 1.5973 a 1.1082 bcd 49.958 b 83.953 a Sayyad-Amin et al. - Polyamines and SICS effect on compatibility, fertility and yield indices of apple cv. Golden Delicious 217 of boron increased yield (Mashayekhi and Atashi, 2008) and fruit set in comparison with control and fruit abscission was lower than control (Khoshghalb et al., 2011). Maz Ardalan and Savaghebi Firoozabadi ( 1 9 9 7 ) r e p o r t e d t h a t f o l i a r a p p l i c a t i o n o f M n increased fruit yield. High levels of boron in floral organs such as the stigma and style, may aid pollen germination and make faster pollen tube growth down the style and into the ovary. Application of SICS a day before full bloom at 1 or 2 mg L-1 on three pear cultivars increased fruit set especially at 1 mg L-1 SICS. Furthermore, SICS at 2 mg L-1 ascended the number of seeds (Son et al., 2009). In addition, regarding fruit yield, foliar application of Mn alone showed signifi- cant increase in fruit yield of sweet oranges due to its effect on increasing the number of fruit/tree as well as fruit average weight (Hasani et al., 2012). Our results for SICS were in accordance with Maz A r d a l a n a n d S a v a g h e b i F i r o o z a b a d i ( 1 9 9 7 ) , Khoshghalb et al. (2011) on pear, Mashayekhi and Atashi (2008) on strawberry, Son et al. (2009) on pear, Hasani et al. (2012) on pomegranate. The effects of polyamines and SICS on If and ISI In our experiment, all of the treatments could led to semi or full fertility and compatibilty. So, this result was in line with Duca et al. (2010) on pear. If the ISI is lower than 0.2 means (self or cross) incom- patibility, if it is between 0.2 to 1 interpret as semi (self or cross) compatibility, and if it is higher than 1, reveals full (self or cross) compatibility (Zeinanlo et al., 2001; Azimi et al., 2008.; Seifi, 2008). Duca et al. (2010) reported that, in compatible pollinated styles, the levels of Put and Spm were sim- ilar and higher than Spd, whereas in self-incompati- ble pollinated styles, Put was the highest. In the com- patible pollinated styles, these three polyamines showed higher content when compared to self- incompatible pollinated styles (Duca et al., 2010). Pollen germination and pollen tube development are important for fertilization (Kuruki et al., 2017). Extremely low pollen germination rates may cause fruit setting failure because of ovule degradation before the pollen tube reaches the ovary (Kuruki et al., 2017). Full compatibility is superior to semi-com- patibility for ensuring high fruit set, even when envi- ronmental conditions are favorable for growth and pollination (Sapir et al., 2008). Among the natural polyamines, Spm showed strongest effects on tube growth (Aloisi et al., 2015). The effects of polyamines and SICS on fruit drop Put treatments significantly reduced secondary Fig. 1 - Effects of foliar application of polyamines and SICS on fruit length without ccb - (a), with ccb (b) and fruit diameter without ccb (c) and with ccb (d) of apple (cv. ‘Golden Delicious’). Put= Putrescine, Spm= Spermidine, Spr= Spermine, ccb= cotton cove- rage bags. Adv. Hort. Sci., 2018 32(2): 213-219 218 fruit drop on date palm, apple, pear, mango, sweet orange and avocado (Asadi et al., 2013). A reduction in secondary fruit drop was observed in date palm, apple, pear, mango, sweet orange and avocado (Tavakoli and Rahemi, 2014). Due to preventing enzymatic conversion of 1- aminocyclopropane-l-carboxylic acid (ACC) to ethyl- ene by polyamines, the ethylene production reduced and is followed by fruit drop (Tavakoli and Rahemi, 2014). Decreased fruit drop one week before full bloom in the “on” year and increased yield per shoot two weeks before full bloom in the “off” year were observed by application of Spm (0.1 and 1 mM), but Spd (1 mM) just lowered fruit abscission one week before full bloom in the “on” year (Khezri et al., 2010). In our study, Spd (0.25 mM) was the best treat- ment on fruit set (June and final), yield, ISI and fruit drop. Asadi et al. (2013) reported that the most effective treatment on raising fruit set were Spm and Spd in apricot, respectively (Asadi et al., 2013). The content of Spd was the highest at four devel- opment stages, followed by Put and Spm, respective- ly (Valero, 2010). Tavakoli and Rahemi (2014) stated that treatment with Spd 1 mM led to the highest fruit yield. The effects of polyamines and SICS on fruit growth habit Regarding the effects of polyamines on fruit length and diameter, fruit growth totally increased because of increasing fruit length and diameter in all of the treatments in our study. In the case of fruit growth, Malik et al. (2005) demonstrated that the amount of polyamines increased during initial fruit growth period of apple, pear, apricot and strawberry followed by gradually decrease near maturity. Polyamine content of pericarp declined from fruit set to maturity. Spd and Spm were higher than Put dur- ing initial fruit growth compared to later during fruit development (Malik et al., 2005). Put application had a positive effect on fruit size and weight, which might due to its role in cell division leading to improved weight and diameter of fruit (Saleem et al., 2008). Mn application in SICS increased fruit diameter and length but only the 0.6% rate of manganese was significant on fruit diameter (Hasani et al., 2012) and influenced fruit growth habit. Control trees produced significantly lower fruit yield, so naturally the fruit size was greater com- pared to fruit from polyamines-treated trees (Saleem et al., 2008). S p e r m i d i n e i n c o n c e n t r a t i o n o f 0 . 2 5 m M , with/without cotton coverage bags, was the best polyamine treatment to increase yield, fruit set and to decrease fruit drop. Put in concentration of 0.1 mM, with/without cotton coverage bags, was effec- tive on improving percentage of final fruit set and IS. 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