Genetic behavior analysis for phytochemical traits in coriander: Heterosis, inbreeding depression and genetic effects

Increasing fruit yield, fatty acids and essential oils content in coriander are the main objectives. Reaching them need to understand the nature of gene action and quantifying the heterosis and inbreeding depression. Six genetically diverse parents, their 15 F1 one-way hybrids and 15 F2 populations were evaluated under different levels of water treatments. Beside the water treatment and genotype effects, the genetic effects of general (GCA) and specific (SCA) combining ability and their interactions with water treatment were significant for all traits. Water deficit stress decreased all traits in both F1 and F2 generations except for essential oil content which were significantly increased due to water deficit stress. Under water deficit stress, a non-additive gene action nature was predominant in F1 generation while an additive gene action nature was more important in F2 generation for all the traits except fruit yield under severe water deficit stress. There was a positive high heterosis for the traits examined in some hybrids. Also, in F2 generation even after inbreeding depression, some promising populations displayed appropriate mean performance. These show that the parents used for crossing had rich gene pool for studied traits. Therefore, selection between the individuals of relevant F2 populations could be led to develop high yielding hybrids or transgressed lines.

1 block design with three replications at the research field of Tarbiat Modares University (51° 09 2 ʹ E; 35° 44 ʹ N; altitude 1265 m), Iran during the growing season of 2017. In WW experiment, a set 3 of genotypes were well watered overall the experiment period. In MWDS experiment, a set of 4 genotypes were well watered until an appearance of the stem when watering was withdrawn until 5 the end of the flowering stage at which point one recovery watering applied. In SWDS 6 experiment, watering was similar to WW experiment until an appearance of flowering stage and 7 after which watering was cut off completely. The research field soil physical and chemical 8 characteristic presented in Table 2. The datasets were firstly tested for normality using the Anderson and Darling normality test. The 3 analysis of variance for GCA and SCA effects were done according to Griffing's (1956) method 4 2, model 1 using a SAS program suggested by Zhang et al. (2005). Mean values of traits in water 5 treatments were compared using the least significant difference (LSD) method at 5% level of 6 probability. Estimates of (general combining ability variance) and (specific combining 7 ability variance) were computed according to the random-effects model (Zhang et al., 2005). The 8 GCA /SCA ratio was computed according to the method proposed by Baker (1978) (Equation 1).

12
(2) 13 where F 1 and BP are target hybrid and best parent values, respectively. Also, the observed 14 inbreeding depression (ID) was estimated as a percent of the decrease in F 2 mean when 15 compared with F 1 hybrid mean according to the formula suggested by Khan et al. (2009)

16
(Equation 3). The is the mean value of F 1 hybrid and is the mean value of F 2 generations 17 mean of parents.

18
(3) 19 All statistical analysis were done using Statistical Analysis System (SAS) (SAS Institute, 1992) 20 and graphs generated using Excel Microsoft Office Software. The combined analysis of variance revealed the presence of a significant difference between 4 water treatments for all of traits in both F 1 hybrids and F 2 generations (Table 3). There was a 5 high significant difference between F 1 hybrids and also between F 2 generations for all of studied 6 traits. These observations indicate that parent selection for diallel crosses had been properly 7 done. Along with the main water treatment and genotype effects, the genotype × water treatment 8 interaction effect was significant for all traits in both F 1 hybrids and F 2 generations (Table 3).

9
Being significant genotype (F 1 hybrids + F 2 generations) × water treatment interaction refers to 10 different growth response of genotypes in differently watered growth conditions.

11
Analysis of variance for genetic effects revealed that both additive and non-additive gene actions 12 are involved in the expression of traits in both F 1 hybrids and F 2 generations. Also, significant 13 GCA × environment and SCA × environment interactions effect for all traits in both F 1 and F 2 14 generations (Table 3) reveal that general combing ability of parents and specific combining 9 1 Effect of water deficit stress on fruit yield 2 As shown in table 4, fruit yield was significantly affected by water treatments. The highest fruit 3 yield obtained in well-watered condition while the minimum fruit yield obtained in severe water 4 deficit stress in both F 1 hybrids and F 2 generations. A reduction in fruit yield of coriander under 5 water deficit condition also reported by Nadjafi et al. (2009) andKhodadadi et al. (2016b). In 14 Effect of water deficit stress on essential oil content and essential oil yield 15 The largest value of essential oil content obtained in the moderate water deficit stress while the 16 lowest essential oil content recorded in well-watered for both F 1 hybrids and F 2 generations.

17
Results indicate that drought stress has a positive effect on the essential oil content in coriander.

18
Increasing in the essential oil content by progress in drought stress has also been documented by  Whereas, drought stress leads to decrease in essential oil yield in both F 1 hybrids and F 2 2 generations ( Table 4). So that the highest value of essential oil yield obtained in the well-watered 3 condition and the lowest essential oil yield observed in severe water deficit stress for both F 1 4 hybrids and F 2 generations (Table 4). Similar results were reported by Singh and Ramesh (2000), that both additive and non-additive gene actions are contributed to determine these traits.

1
GCA/SCA ratio reflects the degree of trait which transmitted to the progeny. When the 2 GCA/SCA ratio are closer to unit and zero show that additive and non-additive gene actions are 3 mostly involved in inheritance of the trait, respectively. Consideration the GCA/SCA ratio, non-4 additive gene action was predominant for fruit yield, essential oil yield and fatty oil yield traits in 5 F 1 and F 2 generations under well-watered condition ( Table 5). The same gene action in F 1 and F 2 6 may be because of coupling phase linkage (Ramachandram and Goud, 1981). In advanced 7 generations, when a coupling linkage present, additive genetic variance decrease and when the 8 repulsion linkage present, additive genetic variance increase Robinson et al. (1960). Therefore, to 9 improve fruit yield, essential oil yield and fatty oil yield traits under well-watered condition, 10 selection should be delayed to the later generations of segregation. For fatty oil content, non-11 additive gene action nature was predominant in F 1 hybrids, while in F 2 generations the additive 12 genetic effects were more important under well-watered condition ( Table 5). The inconsistency 13 in F 1 and F 2 results is due to the breakdown of dominance effects and gen linkages. Also, 14 essential oil content was predominantly governed by additive gene action in both F 1 hybrids and 15 F 2 generations. Presence of mostly additive gene action in F 2 generation for fatty oil content and 16 in both F 1 and F 2 generations for essential oil content suggests that selection programs can be 17 effective in the F 2 and later generations for improvement of fatty oil content and essential oil 18 content traits under well-watered conditions.

19
In severe water deficit stress, results of GCA/SCA ratio for fruit yield showed that non-additive 20 type of gene action was predominant in both F 1 hybrids and F 2 populations (Table 5). Therefore, 21 to improve fruit yield under severe water deficit stress condition, selection should be delayed to 22 the later generations of segregation to loss of non-additive gene actions. For fruit yield under 23 moderate water deficit stress and essential oil content, fatty oil content, essential oil yield and 1 fatty oil yield under both moderate and severe water deficit stress conditions, the non-additive 2 gene action in F 1 hybrids while an additive gene action in F 2 generation were more important 3 (Table 5). Therefore, breeding programs based on selection can be effective in the F 2 and later 4 generations for improvement of these traits under water deficit stress. In well-watered condition, fruit yield varied from 2.40 (P 6 ) to 9.71 g (P 2 ) between the parents 8 and ranged from 5.26 to 18.10 g (H 2 × 4 ) between the F 1 hybrids (Fig. 1A). Parental genotypes of 9 the H 2 × 4 had approximately half yield (6.80-9.71 g) as compared to their hybrid. In F 2 10 generation, the fruit yield varied from 3.75 to 10.71 g between the hybrids (Fig. 1A). Similar to 11 F 1 generation, in F 2 the highest fruit yield obtained by H 2 × 4 . Also, in F 1 generations, almost all 12 hybrids exhibited positive heterosis (7.82-115.40 %) in which P 4 involved hybrids mostly 13 showed high heterosis (+80.91 to +89.74 %). Inbreeding depression from F 1 hybrids to F 2 14 generations ranged from −7.94 % to −42.80 % for fruit yield (Fig. 1A).

15
In moderate water deficit stress condition, fruit yield varied from 1.14 (P 5 ) to 5.27 g (P 4 ) between 16 the parents and ranged from 1.17 to 10.03 g between the F 1 hybrids (Fig. 1B). A large fruit yield 17 obtained in five F 1 hybrids including H 4 × 6 (10.03 g), H 1 × 4 (9.58 g), H 2 × 4 (8.93 g), H 4 × 5 (8.71 g) 18 and H 3 × 4 (8.85 g). In F 2 generation, fruit yield varied from 1.08 to 9.29 g (Fig. 1B In severe water deficit stress, fruit yield varied from 0.58 (P 5 ) to 2.24 g (P 6 ) between parents and 2 from 0.22 to 4.77 g between F 1 hybrids ( Fig. 1C). In F 2 generation, fruit yield varied from 0.21 to 3 4.28 g (Fig. 1C) and a large fruit yield obtained from F 2 populations derived from the P 4 and P 6 4 contributed hybrids. The heterosis values for fruit yield ranged between -64.68 and +154.54 % 5 (Fig. 1C) and many of the hybrids exposed positive heterosis. Similar to moderate water deficit 6 stress, inbreeding depression from F 1 hybrids to F 2 populations in severe water stress showed 7 larger range (−0.59 to −22.66 %) than well-watered (Fig. 1C).

8
Higher heterosis and lower inbreeding depression in water deficit stressed conditions than those 9 in well-watered condition reveal that the respective parents of hybrids probably were carriers of 10 drought tolerance alleles could be homozygous recessive (Musembi et al., 2015). Therefore, their 11 hybrids appeared superior in water deficit stressed conditions compared with the high yielding 12 hybrids being superior in well water. In case of inbreeding depression from F 1 hybrids to F 2 13 generations, the heterozygote loci can maximally be 50 % breakdown. Therefore, an appearance 14 of drought tolerance in F 2 generations could yet be kept by heterozygote genes.

15
Essential oil content 16 In well-watered treatment, the essential oil content ranged from 0.140 % (P 2 ) to 0.550 % (P 4 ) 17 between the parents and from 0.250 to 0.563 % between the F 1 hybrids ( Fig. 2A). The highest 18 essential oil content obtained in five hybrids of P 4 (0.440-0.563 %), followed by H 1 × 3 hybrid. In 19 F 2 generation, essential oil content ranged from 0.237 to 0.545% ( Fig. 2A) and five of the F 2 20 populations that a P 4 was one of mating partner exposed the highest essential oil content (0.431-21 0.545 %). In F 1 generation ( Fig. 2A)  In moderate water deficit stress, the essential oil content ranged from 0.257% (P 5 ) to 0.653 % 2 (P 4 ) between the parents and from 0.343 to 0.997 % between the F 1 hybrids (Fig. 2B). The 3 highest essential oil content recorded in five hybrids relevant to P 4 (0.667-0.997 %). In F 2 4 generation, essential oil content ranged from 0.258 to 0.907 % between the populations (Fig. 2B) 5 and similar to the F 1 hybrids, five populations derived from P 4 showed the highest essential oil 6 content (0.542-0.907 %). In F 1 generation all crosses exposed positive heterosis (+2.04 to +63.74 7 %) (Fig. 2B). Also, almost all the F 2 populations showed inbreeding depression (−9.00 to −36.52 8 %) (Fig. 2B).

9
In severe water deficit stress, the essential oil content ranged from 0.227 % (P 5 ) to 0.580 % (P 4 ) 10 between the parents and from 0.320 to 0.770 % between the F 1 hybrids (Fig. 2C). The highest 11 essential oil content obtained by five hybrids of P 4 (0.593-0.770 %). In F 2 generation, essential indicates that non-additive action genes play major role in the inheritance of essential oil content. Our results are in accordance with previous researches on inbreeding depression under water 2 deficit stressed conditions (Cheptou et al., 2000;Armbruster and Reed, 2005). In F 2 , even after 3 inbreeding depression, some crosses exhibited good performance indicating the potential of these 4 crosses to develop high essential oil content cultivars. The derivatives of the P 4 parent displayed 5 better mean performance as compared to their parents even after segregation and inbreeding 6 depression. Therefore, P 4 population could be used in the segregating generations to obtain 7 genotypes with high essential oil content under different water treatments. In well-water, fatty oil content varied from 15.33 (P 4 ) to 22 % (P 6 ) between the parents and 10 ranged from 16.33 to 26.67 % between the F 1 hybrids (Fig. 3A). The highest fatty oil content 11 recorded for hybrids of P 6 (H 1 × 6 (26.67 %), H 4 × 6 (26.0 %), H 3 × 6 (25.0 %) and H 2 × 6 (23.0 %)) 12 followed by H 1 × 4 hybrid. Parental genotypes of these promising hybrids also had nearly high .54 % between the populations (Fig. 3A). The highest fatty oil content obtained in F 2 15 generation by P 6 hybrids and followed H 1 × 4 , H 2 × 5 , H 1 × 2 hybrids. In F 1 generation, heterosis 16 ranged from +0.00 to +36.36 % for fatty oil content (Fig. 3A) and in F 2 generation, inbreeding 17 depression for fatty oil content observed from −8.32 to −25.75 % (Fig. 3A).

18
In moderate water deficit stress, the fatty oil content varied from 11.67 (P 2 ) to 25.33 % (P 6 ) and 19 15.00 to 25.0 % between parents and F 1 hybrids, respectively (Fig. 3B). The highest fatty oil 20 content observed in eight F 1 hybrids that P 6 involved in four crosses. In F 2 generation, fatty oil 21 content varied from 14.68 to 25.98 % between hybrids (Fig. 3B) and the highest fatty oil content

3
In severe water deficit stress, the fatty oil content varied from 10.33 (P 2 ) to 19.67 % (P 6 ) and 4 13.33 to 22.67 % between parents and F 1 hybrids, respectively (Fig. 3C). The highest fatty oil 5 content were recorded in F 1 hybrids involving P 6 and followed by H 1 × 4 hybrid. In F 2 generation, 6 fatty oil content varied from 12.85 to 20.41 % between the hybrids (Fig. 3C) and the highest fatty 7 oil content was obtained from hybrids of P 6 . The heterosis values for fatty oil content ranged 8 from +4.26 to +30.77 % (Fig. 3C) and many of hybrids showed positive heterosis. The F 2 9 generations displayed inbreeding depression (−3.64 to −13.30 %) for fatty oil content (Fig. 3C).

10
Overall, it was revealed that P 6 involved F 2 populations could be utilize for developing cultivars 11 with high fatty oil content under different water treatments.

12
The ranges of heterosis and inbreeding depression were higher in well-watered than water 13 stressed conditions. High heterosis is well-known to be a result of the effects of non-additive In well-watered treatment, the essential oil yield ranged from 0.005 (P 6 ) to 0.037 g (P 4 ) among 22 the parents and from 0.014 to 0.096 g between the F 1 hybrids (Fig. 4A). High essential oil yield 23 was obtained for four P 4 crosses (0.057-0.096 g). In F 2 generation, essential oil yield ranged 1 from 0.010-0.055 g between the cross generations ( Fig. 4A) and four crosses of P 4 showed a 2 high essential oil yield (0.033-0.055 g). In F 1 generation (Fig. 4A) almost all crosses indicated 3 positive heterosis for essential oil yield (+7.48 to +213.91 %). Also, all of the F 2 populations 4 showed inbreeding depression (−15.06 to −47.80 %) (Fig. 4A).

13
In severe water stress, the essential oil yield ranged from 0.002 (P 5 ) to 0.010 g (P 4 ) between the 14 parents and from 0.001 to 0.032 g between the F 1 hybrids (Fig. 4C). The highest essential oil 15 yield was obtained in crosses of P 4 (0.021-0.032 g), followed by H 1 × 6 , H 3 × 6 , H 5 × 6 hybrids. In F 2 16 generation, essential oil yield ranged from 0.001-0.023 g between the cross generations ( Fig.   17 4C) and progenies of P 4 and P 6 showed the highest essential oil yield. In F 1 generation, almost all 18 crosses displayed positive heterosis (+26.01 to +208.31 %) (Fig. 4C). The F 2 generation showed 19 inbreeding depression (−21.96 to −40.85 %) (Fig. 4C). Overall, results indicated that P 4 20 population could be used in the segregating generations to obtain genotypes with essential oil 21 yield potential under different water treatments.

22
In well-water, the fatty oil yield varied from 1.12 to 3.41 g between parents and F 1 hybrids (Fig.   23 5A). The highest fatty oil yield was obtained from H 2 × 4 , H 1 × 4 hybrids. In F 2 generation, fatty oil 1 yield varied from 0.71 to 1.82 g between the generations (Fig. 5A) and highest fatty oil yield was 2 noticed in generations derived from the hybrids of P 4 . The heterosis values for fatty oil yield 3 were ranged from -26.95 to +204.96 % (Fig. 5A) and all hybrids showed positive heterosis. F 2 4 populations displayed inbreeding depression for fatty oil yield (−21.88 to −49.31 %) (Fig. 5A).

5
In moderate water stress, the fatty oil yield ranged from 0.13 (P 2 ) to 0.85 g (P 4 ) between the 6 parents and from 0.24 to 2.48 g between the F 1 hybrids (Fig. 5B). High values of fatty oil yield 7 were recorded in hybrids involving P 4 and P 6 . In F 2 generation, fatty oil yield ranged from 0.20-8 0.2.27 g between the cross generations ( Fig. 5B) and the crosses of P 4 and P 6 showed high fatty 9 oil yield. In F 1 generation (Fig. 5B) almost all of the hybrids showed positive heterosis (+3.42 to 10 +191.18 %). Also, almost all of the F 2 population showed inbreeding depression (−4.14 to 11 −31.64 %) (Fig. 5B).

12
In severe water stress, the fatty oil yield varied from 0.06 (P 2 ) to 0.45 g (P 6 ) and 0.04 to 1.04 g 13 between parents and F 1 hybrids, respectively (Fig. 5C). High values of the fatty oil yield were 14 recorded in F 1 hybrids involving P 6 and followed by hybrids of P 4 . In F 2 generation, fatty oil indicated that P 6 and P 4 population could be used in the segregating generations to obtain 20 genotypes with high fatty oil yield potential under different water treatments.

21
Inbreeding depression was higher in well water condition compare to water deficit stressed 22 conditions for essential oil yield and fatty oil yield indicating that inbreeding depression was 23 unstable across environments. Also, results revealed the higher heterosis values for essential oil 1 yield and fatty oil yield than other traits indicating that non-additive genes were more responsible 2 for the expression of these traits. These findings can be confirmed by the results of the 3 GCA/SCA ratio in Table 5.

4
The utilization of hybrid vigor is one of the ways to improve yield in plant breeding. The 5 existence of considerable degree of natural outcrossing had made these possible to use genetic 6 diversity through production heterotic hybrids (Saxena et al., 1990). In coriander, heterosis 7 cannot be exploited for higher production through commercial hybrids due to the nature of 8 flower and poor seed recovery during hybridization. But estimation of heterosis for fruit yield, 9 fatty oil and essential oils content will help in recognition crosses that can lead to isolate of coriander. In present study, the significant SCA effect indicates that there was non-additive gene 16 effect, which could be the cause of the heterosis on the progenies observed and selection will not 17 be effective in early generations. Hence, selection could be practiced in advance generations 18 confirming to earlier reports.

19
The results showed that many of the F 2 population exposed inbreeding depression and it was 20 higher for fruit yield, essential oil yield and fatty oil yield. Inbreeding depression mostly was 21 higher in hybrids with high performing than hybrids with low and moderate performing. Soomro performing were also correlated with higher inbreeding depression. Showing heterosis in F 1 and 1 inbreeding depression in F 2 reveal the nature of gene action involved in the expression of the 2 vigor in F 1 and depression in F 2 . In F 2 generation, the offspring's of the parental genotypes P 4 3 and P 6 displayed better mean performance as compared to their parents and the selection in these 4 crosses can provide transgressive gene recombinants for studied traits. P 4 and P 6 crosses are 5 required to be subjected to the pedigree/progeny selection directly for reaching to the high 6 potential cultivars. Also, P 4 and P 6 parents can be used as source of elite parents for synthetic Results indicated that water deficit stress negatively affected the fruit yield, essential oil yield, 10 fatty oil content and fatty oil yield of coriander in both F 1 and F 2 generations. On the contrary, 11 water deficit stress significantly increased the essential oil content of the coriander. Analysis of 12 variance for genetic combining ability indicate that mean square due to GCA and SCA for all 13 traits were highly significant in both F 1 and F 2 generations. Revealing the importance of additive crosses can provide a better base for future. The progenies of the P 4 and P 6 parents displayed 2 better mean performance as compared to their parents and the selection in these crosses provided 3 transgressive gene recombinants for studied traits. It is also indicated that combined performance 4 of F 1 hybrids and F 2 populations could be an appropriate criterion to recognizing the most 5 promising populations to be used either as F 2 hybrids or as a resource population for further 6 selection in advanced generations.      ** , * and ns are significant at 1% and 5% level of probability and not significant, respectively. General combining ability (GCA), specific combining ability (SCA), fruit yield (FY), essential oil content (EOC), essential oil yield (EOY), fatty oil content (FOC), fatty oil yield (FOY).