Improving Efficacy of GA 3 to Increase Fruit Set and Yield of Clementine Mandarins in California

Transcription

1 26 Annual Report Plant Management & Physiology Citrus Research Board Project Concluding: Summary Report Improving Efficacy of GA 3 to Increase Fruit Set and Yield of Clementine Mandarins in California C. Thomas Chao and Carol J. Lovatt Botany and Plant Sciences, UC/Riverside The Nules Clementine (Citrus reticulata Blanco) (also called Clemenules or De Nules ) is a seedless mandarin of great fruit quality. It is the leading Clementine cultivar produced around the world. In recent years, California growers have planted thousands of acres of Nules Clementine and more may be planted in the future. The oldest plantings of Nules Clementine in California are now in production. One of the major challenges to California growers is the problem of low fruit set and small fruit size associated with the production of seedless Nules and other seedless Clementine mandarins. To overcome this problem, mandarin growers apply GA 3 during bloom and post-bloom to enhance fruit set and yield. However, the current registration of gibberellic acid (GA 3 ) (ProGibb, 4%, Valent BioSciences Corp., Libertyville, IL) for fruit set of Clementine mandarins in California was based on experiments conducted in foreign countries and by private companies in California. In Spain, Morocco and South Africa, GA 3 is routinely used in the production of seedless mandarins to increase both fruit set and fruit size but these strategies have not proven reliable in California. The label provides no detailed information telling growers how to use GA 3 to increase fruit set and yield or yield of commercially valuable large size fruit annually and, thus, results for Clementine mandarin production have been variable. Moreover, improper use of GA 3 results in low fruit set, canopy damage, and potential reduction of flower formation in following years. The goal of this research is to identify the proper dose and best timing of GA 3 application for increasing fruit set and packout of commercially valuable large size fruit of Nules Clementine mandarin and to demonstrate the negative effects resulting from use of high rates of GA 3 or from numerous applications of lower rates of GA 3 on yield and fruit size in the current and following years. A comprehensive experiment testing the efficacy of combinations of GA 3 concentrations and application times and urea, the effect of which was unknown on mandarins, was undertaken to maximize the yield of commercially valuable large size fruit of Nules Clementine mandarin. The treatments included in the study are numbered and presented in Tables 1 and 2 for easy reference when studying the yield data in the remaining tables. Figures depicting flower, fruit and leaf abscission as biomass and number biweekly from May through preharvest in Decem-ber for 25 and 26 are presented after the yield results. Year 1 The research was initiated in a commercial orchard in Selma in the San Joaquin Valley in spring 24. The effects of the GA 3 and urea treatments on yield and fruit size for the December 24 harvest are reported in kilograms fruit per tree (Table 3) and number of fruit per tree (Table 4). (1 kg = 2.2 lbs.) This experiment included a winter prebloom foliar application of 1% and 3% low biuret urea. Results: Application of GA 3 (25 mg/l) at 6% and 9% full bloom, 75% petal fall and 1 days after 75% petal fall resulted in retention of significantly more small fruit (kilograms and number) per tree of packing carton sizes tiny and small (fruit 51-<44 mm in diameter) compared to untreated control trees (Tables 3 and 4). Trees receiving GA 3 at 15 mg/l at the same application times produced significantly more tiny and small fruit (kilograms and number) per tree than control trees, whereas trees treated with GA 3 at 1mg/L at these same times produced significantly more small size fruit (kilograms and number) per tree, but not more tiny fruit. GA 3 strategies that increased retention of small fruit resulted in significantly lower yields (kilograms and number) of commercially valuable large fruit of packing carton sizes large, jumbo and mammoth (57-76 mm in diameter) per tree compared to the control (Tables 3 and 4). Trees receiving GA 3 (1 mg/l) at 9% full bloom, 1 days after 75% petal fall and in early July, a winter prebloom foliar application of low-biuret urea (1% or 3%) and the untreated control produced more commercially valuable large size fruit (kilograms and number) with no reduction in total kilograms or number of fruit per tree. GA 3 (25 mg/l) at 6% and 9% full bloom, 75% petal fall and 1 days after 75% petal or GA 3 (1 mg/l) at 6% full bloom, at 75% petal fall and in early July fall produced significantly less total kg fruit per tree with no increase in yield of large size fruit. Our data show that most GA 3 treatments produced more tiny and small size fruit and less large, jumbo, mammoth, and colossal size fruit than the untreated control. The correlation between total rate of GA 3 applied per season and fruit weight in different size classes is shown in Table 5. There was a negative correla-tion between treatments that applied higher concentrations of GA 3, especially in multiple applications, and the yield of large size fruit per tree (Table 5). Higher concentrations and/or greater frequency of GA 3 applications also had a negative effect on fruit set and total yield of Nules Clementine mandarins in the San Joaquin Valley of California. There were no significant effects of the GA 3 treatments on fruit quality (Table 6). Year 2 In Winter 24, a new set of experiments was established at an isolated Nules Clementine mandarin orchard near Grapevine, CA, to prevent theft of our nets and fruit from the data trees. The effects of the GA 3 treatments on yield and fruit size for the December 25 harvest are reported in kilograms fruit per tree (Table 7) and number of fruit per tree (Table 8). Winter prebloom low biuret urea treatments were initiated in year 2 at this site.

2 26 CRB AR Efficacy of GA3 in Clementine Mandarins Chao and Lovatt continued Results: The different GA 3 treatments had no significant effect on total yield as kilograms per tree (Table 7), with the exception that the control in which water alone was applied as a foliar spray in the same manner as the application of GA 3 resulted in a significant reduction in total yield. This finding is consistent with previous findings demonstrating that foliar sprays remove flowers and young fruit and that foliar treatments that success-fully increase yield clearly overcome the negative effect of the spray application itself. In contrast, the GA 3 treatments resulted in significant effects on the total number of fruit per tree. Treatments using the higher rates (15 and 25 mg/l) of GA 3 applied most frequently (four applications) resulted in the greatest total number of fruit per tree, which were significantly greater than trees receiving GA 3 at 1 mg/l applied only three times, the control and the water spray control (Table 8). Trees receiving 25 mg/l GA 3 applied at 6% bloom, 9% bloom, 75% petal fall, and 1 days after 75% petal fall produced the greatest kilograms and number of fruit of packing carton sizes medium, large, jumbo, and in the combined pool of large, jumbo and mammoth and fruit greater than large, but produced fewer fruit of packing carton sizes colossal or super-colossal compared to control and water control (Tables 7 and 8). Trees receiving these treatments, including the control, were not significantly different from trees receiving all other GA 3 treat-ments with regard to the kilograms and number of fruit per tree for the combined pool of packing carton sizes large, jumbo and mammoth and fruit greater in size than packing carton size large. The water spray control produced fewer fruit in most size categories, but yielded the highest kilograms and number of colossal and super-colossal fruit. The water spray control trees had 2% to 3% less crop than trees in other treatments. It is clear that fruit size is a function of crop load. In this site for this year, total yield and yield of commercially valuable large size fruit through packing carton size jumbo, the combined pool of large, jumbo and mammoth, and the combined pool of fruit greater than packing carton size large was significantly posi-tively correlated with increasing concentration and frequency of GA 3 applied, i.e., total amount of GA 3 applied. This relationship was, however, negative for the yield of fruit of packing carton sizes colossal and supercolossal (Table 9). Several GA 3 treatments had significant effects on fruit quality compared to both the control and water control (Table 1). All GA 3 treatments that were initiated early at 6% bloom reduced the weight of individual fruit. Treatments applied four times, with the exception of 15 mg/l, increased the total soluble solids concentration ( Brix) of the juice (Table1). Year 3 The effects of GA 3 treatments on yield and fruit size for the December 26 harvest are reported as kilograms fruit per tree (Table 11) and as number of fruit per tree (Table 12). Results: The 26 yield was greater than 25 yield at this site and number of fruit per tree for the control trees (1162 fruit per tree) in 26 was very similar to the number of fruit per tree for the control trees (1189 fruit per tree) in 24 at the first site. No GA 3 treatment increased total yield or yield of commercially valuable large size fruit compared to the control. Frequent applications of GA 3 at rates from 5 to 15 mg/l reduced total yield as kilograms fruit per tree (Table 11) and as number of fruit per tree (Table 12). Even two applications of GA 3 at 15 mg/l made at 6% bloom and 75% petal fall reduced the kilograms fruit per tree compared to the control. The negative effect of GA 3 application on kilograms fruit per tree is clearly seen by comparing trees treated in both 25 and 26 with trees treated only in 25 for each GA 3 rate and application schedule: 5 mg GA 3 /L, treatment 1 with 2; 1 mg GA 3 /L, treatment 3 with 4; 15 mg GA 3 /L, treatment 7 with 8; 25 mg GA 3 /L treatment 9 with 1; and 15 mg GA 3 /L but only 2 times, treatment 13 with 14 (Table 11). With only one exception (treatment 9 versus treatment 1), all trees receiving a GA 3 treatment in 25 but not in 26 (the on-crop year) yielded more kilograms fruit per tree in 26 than trees treated for two consecutive years. The greatest yields of commercially valuable large size fruit (fruit in the combined pool of packing carton sizes large, jumbo and mammoth) were obtained in 26 from trees treated with GA 3 at 1 mg/l four times or 15 mg/l only two times in 25 and not treated in 26, but the yields of large size fruit were not significantly better than the control (Tables 11 and 12). These result provide clear evidence that there is no negative effect of applying as many as four applications of 25 mg GA 3 /L carried over to the next year. All negative effects resulting from GA 3 application occurred in the year of application. The relationship between the total amount of GA 3 applied and total yield and yield of large size fruit was negative, but only significant for total yield and yield of mammoth and supercolossal size fruit (Table 13). There were no effects from any GA 3 treatment on fruit quality (Table 14). The winter prebloom low-biuret urea treatments had no effect on yield, consistent with urea not be recommended for on-crop years (data not shown). Numerical increases in total yield were achieved with earlier applications (Nov. and Dec.) and in yield of commercially valuable large size fruit with later applications (Jan. and Feb.). Additional research with urea is being continued at our own expense. Effect of GA 3 treatments on flower, fruit and leaf abscission All GA 3 treatments reduced flower abscission through the end of May and fruit abscission through early June compared to the control. Trees receiving a GA 3 1 mg/l or greater applied 1 days after 75% petal fall or in July dropped an increased amount of fruit equaling that of control trees during the mid- to late-part of July. The effect of GA 3 on leaf abscission was variable, but four applications of GA 3 at 25 mg/l was consistently the best treatment for reducing leaf drop from the end of May through harvest in December. 2

3 26 CRB AR Efficacy of GA3 in Clementine Mandarins Chao and Lovatt continued Conclusion The results, thus, far strongly suggest that results obtained with the use of GA 3 are variable due in part to differences in crop load (alternate bearing). In the light crop year (approximately 55 fruit per tree), application of GA 3 early (starting at 6% bloom), frequently (four applications) and at a higher rate (15 or 25 mg GA 3 /L) increased the total number of fruit per tree, but not total yield as kilograms fruit per tree, and increased the yield as both kilograms and number per tree of commercially valuable large size fruit (packing carton sizes large, jumbo and mammoth). In the on-crop year (approximately 12 fruit per tree), it was better not to apply any of the GA 3 treatments tested in this study. In both on-crop years, these GA 3 treatments either reduced both total yield and yield of commercially valuable large size fruit (packing carton sizes large, jumbo and mammoth) or had no effect at all. The results of this study provided no evidence of a negative effect from four applications of GA 3 at 25 mg/l applied one year on yield the next year. NOTICE The research results included in this publication are summary reports for the benefit of the Citrus Research Board and the growers it serves. They are not to be taken as recommendations from either the individual reporting or the agency doing the research. Some of the materials and methods mentioned are neither cleared nor registered for commercial use. The summaries were written by the project leaders identified. Both technical names and registered trademarks of materials are used at the discretion of the authors and do not constitute any endorsement or approval of the materials discussed. Questions on possible applications should be directed to the local University of California Extension Specialist, a licensed PCA, or the appropriate regulatory agency. Note: Page 5 in this file is blank. Data tables on pages 6 thru 13 are in landscape format. Leaf, Flower, Fruit and Total Biomass 25 Biomass (g) Number /3/25 5/17/ /3/25 5/17/25 Max. temp. Total Leaf Fruit Flowers 5/31/25 6/14/25 6/28/25 7/12/25 7/26/25 8/9/25 8/23/25 9/6/25 9/2/25 Number 25 Date 5/31/25 6/14/25 6/28/25 7/12/25 7/26/25 8/9/25 8/23/25 1/4/25 1/18/25 11/1/25 11/15/25 11/29/25 12/13/25 Max. temp. Fruit Flowers Date /6/25 9/2/25 1/4/25 1/18/25 11/1/25 11/15/25 11/29/ /13/ Max. air temperature (ºC) Max. air temperature (ºC) 3

4 Leaf, Flower, Fruit and Total Biomass 26 Biomass (g) /9/26 5/23/26 Max. temp. Total Leaf Fruit Flower 6/6/26 6/2/26 7/4/26 7/18/26 8/1/26 8/15/26 8/29/26 9/12/26 Date Number 26 9/26/26 1/1/26 1/24/26 11/7/26 11/21/26 12/5/ Max. air temperature (ºC) Number /9/26 5/23/26 6/6/26 6/2/26 7/4/26 Max. temp. Fruit Flowers /18/26 8/1/26 8/15/26 8/29/26 9/12/26 Date 9/26/26 1/1/26 1/24/26 11/7/26 11/21/26 12/5/ Max. air temperature (ºC) 4

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6 Table 1. Schedule of GA 3 and urea treatments applied to Nules Clementine mandarin trees in commercial orchards in Selma and Grapevine, Calif. 24 (Parlier) 25 (Grapevine) 26 (Grapevine) Treatment 6% Bloom Petal fall Bloom Petal fall Bloom Petal fall 9% 75% 75% +1 d July Dec. 6% 9% 75% 75% +1 d July 6% 9% 75% 75% +1 d July (1) 5 mg/l GA 3 x (2) 5 mg/l GA 3 x4 (1 yr) (3) 1 mg/l GA 3 x (4) 1 mg/l GA 3 x4 (1 yr) (5) 1 mg/l GA 3 x3 6% (6) 1 mg/l GA 3 x %/9% (7) 15 mg/l GA 3 x (8) 15 mg/l GA 3 x4 (1 yr) (9) 25 mg/l GA 3 x (1) 25 mg/l GA 3 x4 (1 yr) (11) 1% urea 1% (12) 3% urea 3% (13) 15 mg/l GA 3 x (14) 15 mg/l GA 3 x2 (1 yr) (15) Water H 2 O H 2 O H 2 O H 2 O H 2 O H 2 O H 2 O H 2 O H 2 O H 2 O (16) Control Table 2. Schedule of urea treatments applied to Nules Clementine mandarin trees in a commercial orchard in Grapevine, Calif. 26 (Grapevine) Treatment November 25 December 25 January 26 February 26 (1) 1% urea (Nov.) 1% (2) 1% urea (Dec.) 1% (3) 1% urea (Jan.) 1% (4) 1% urea (Feb.) 1% (5) Control 6

7 Table 3. Effect of GA 3 and urea treatments on total yield (average kg fruit per tree) and fruit size distribution as average weight (kg) of fruit in different fruit size categories (based on transverse diameter) of Nules Clementine mandarin trees in a commercial orchard in Selma, Calif. jumbo + Treatments Total Tiny Small Medium Large Jumbo Mammoth mammoth Colossal kg/tree (1) 5 mg/l GA 3 x4 94. abc y 1.3 bc 1.1 bcd c 12.2 bc 1.7 bcd 6.2 bcd 1.1 (3) 1 mg/l GA 3 x bc 1.3 bc 11.3 abc c 12. bc 8.3 def 57.9 d.8 (5) 1 mg L -1 GA 3 x3 6% 88.9 c 1.3 bc 9.3 bcd c 13.5 ab 9.5 cde 59.7 cd 1.1 (6) 1 mg L -1 GA 3 x3 9% 99.1 abc.9 c 9.2 cd abc 15.6 a 13.6 ab 68.6 ab 1.3 (7) 15 mg/l GA 3 x abc 2.9 a 13.9 a c 1.2 c 7. ef 54.1 d.7 (9) 25 mg/l GA 3 x4 9.2 c 2.1 ab 12.8 ab c 1.4 c 5.7 f 52.7 d.5 (11) 1% Urea 14.9 a.8 c 9.3 bcd a 15.3 a 13.8 ab 73.1 a 1.5 (12) 3% Urea 98.7 abc 1.1 c 1.5 abcd bc 15.3 a 13. abc 66.8 abc 1.6 (16) Control 13.8 ab.8 c 7.8 d ab 16.2 a 15.1 a 74.2 a 1.8 P-value <.1 <.1 < z Fruit sizes categories based on fruit transverse diameters (mm): tiny (< 44.45), small ( ), medium ( ), large ( ), jumbo ( ), mammoth ( ), colossal ( ), and large + jumbo + mammoth ( ). y Average weights followed by different letters are significantly different at P =.5 based on Fisher s Protected LSD Test. Table 4. Effect of GA 3 and urea treatments on total yield (average number of fruit per tree) and fruit size distribution as the average number of fruit in different fruit size categories (based on transverse diameter) of Nules Clementine mandarin trees in a commercial orchard in Selma, Calif. Treatments Total Tiny Small Medium Large Jumbo Mammoth jumbo + mammoth Colossal No./tree (1) 5 mg/l GA 3 x bc y 174 bcd c 17 bc 81 bcd 584 bcd 6 (3) 1 mg/l GA 3 x bc 196 abc c 16 bc 63 def 567 cd 4 (5) 1 mg L -1 GA 3 x3 6% bc 161 bcd c 119 ab 72 cde 581 bcd 6 (6) 1 mg L -1 GA 3 x3 9% c 159 cd abc 137 a 13 ab 658 ab 7 (7) 15 mg/l GA 3 x a 24 a c 9 c 53 ef 534 d 3 (9) 25 mg/l GA 3 x ab 222 ab c 92 c 43 f 523 d 3 (11) 1% Urea c 161 bcd a 135 a 15 ab 76 a 8 (12) 3% Urea c 182 abcd bc 134 a 99 abc 641 abc 8 (16) Control c 134 d ab 142 a 114 a 713 a 9 P-value <.1 <.1 < z Fruit sizes categories based on fruit transverse diameters (mm): tiny (< 44.45), small ( ), medium ( ), large ( ), jumbo ( ), mammoth ( ), colossal ( ), and large + jumbo + mammoth ( ). y Average weight followed by different letters are significantly different at P =.5 based on Fisher s Protected LSD Test. 7

8 Table 5. Pearson correlation coefficients (r) between total amount of GA 3 applied per season and total yield (kg/tree) and yield of fruit (kg/tree) in different fruit size categories of Nules Clementine mandarin. jumbo + Total Tiny Small Medium Large Jumbo Mammoth mammoth Colossal Rate of GA P-value <.1 <.1.18 z Fruit sizes categories based on fruit transverse diameters (mm): tiny (< 44.45), small ( ), medium ( ), large ( ), jumbo ( ), mammoth ( ), colossal ( ), and large + jumbo + mammoth ( ). Table 6. Effect of GA 3 and urea treatments on fruit quality parameters of Nules Clementine mandarin trees in a commercial orchard in Selma, Calif. Treatments Fruit weight (g) Juice weight (g) Percent acid ºBrix Brix:acid (1) 5 mg/l GA 3 x (3) 1 mg/l GA 3 x (5) 1 mg L -1 GA 3 x3 6% (6) 1 mg L -1 GA 3 x3 9% (7) 15 mg/l GA 3 x (9) 25 mg/l GA 3 x (11) 1% Urea (12) 3% Urea (16) Control P-value

9 Table 7. Effect of GA 3 on total yield (average kg fruit per tree) and fruit size distribution as average weight (kg) of fruit in different fruit size categories (based on transverse diameter) of Nules Clementine mandarin trees in a commercial orchard in Grapevine, Calif in 25. Treatment Tiny + Jumbo + Super- Total Tiny Small Small Medium Large Jumbo Mammoth Mammoth Colossal colossal Large kg/tree (1) 5 mg/l GA 3 x a y bc bc abc ab 6.78 c 1.67 c a (3) 1 mg/l GA 3 x a ab abc 25.2 bc ab 6.97 bc 1.44 c a (5) 1 mg/l GA 3 x3 6% a bc bc abc ab 4.98 c 1.85 c a (6) 1 mg/l GA 3 x3 6%/9% a ab bc ab ab 6.93 bc 1.31 c a (7) 15 mg/l GA 3 x a ab ab ab a 5.53 c 1.31 c a (9) 25 mg/l GA 3 x a a a a a 4.72 c.68 c a (13) 15 mg/l GA 3 x a ab 13.4 abc 28.2 abc ab 6.4 c 1.98 bc a (15) Water b d 6.7 d d c a 3.44 a b (16) Control a cd 1.32 c c b 9.24 b 3.25 ab 6.9 a P-value <.1 <.1.31 <.1 z Fruit sizes categories based on fruit transverse diameters (mm): Tiny (<44.45), Small ( ), Medium ( ), Large ( ), Jumbo ( ), Mammoth ( ), Colossal ( ), and Supercolossal ( ). y Average weight followed by different letters are significantly different at P =.5 based on Fisher s Protected LSD Test. 9

10 Table 8. Effect of GA 3 on total yield (average number of fruit per tree) and fruit size distribution as the average number of fruit in different fruit size categories (based on transverse diameter) of Nules Clementine mandarin trees in a commercial orchard in Grapevine, Calif in 25. Treatment Total Tiny Small Tiny + Small Medium Large Jumbo Mammoth Jumbo + Mammoth Colossal Supercolossal Large Fruit no./tree (1) 5 mg/l GA 3 x4 62 abc y bc 123 bc 218 abc ab 37 c 7 c 58 ab (3) 1 mg/l GA 3 x4 63 abc ab 137 abc 2 bc ab 39 bc 6 c 486 ab (5) 1 mg/l GA 3 x3 6% 569 bc bc 116 bc 226 abc ab 28 c 8 c 485 ab (6) 1 mg/l GA 3 x3 6%/9% 623 ab ab 124 bc 23 ab ab 38 bc 6 c 56 ab (7) 15 mg/l GA 3 x4 637 a ab 151 ab 234 ab a 31 c 6 c 524 a (9) 25 mg/l GA 3 x4 653 a a 163 a 237 a a 26 c 3 c 535 a (13) 15 mg/l GA 3 x2 613 abc ab 132 abc 225 abc ab 33 c 9 bc 59 ab (15) Water 448 d d 68 d 143 d c 67 a 15 a 353 c (16) Control 548 c cd 15 c 193 c b 51 b 14 ab 463 b P-value < <.1 <.1.31 <.1 z Fruit sizes categories based on fruit transverse diameters (mm): Tiny (<44.45), Small ( ), Medium ( ), Large ( ), Jumbo ( ), Mammoth ( ), Colossal ( ), and Supercolossal ( ). y Average number followed by different letters are significantly different at P =.5 based on Fisher s Protected LSD Test. Table 9. Pearson correlation coefficients (r) between total amount of GA 3 applied per season and total yield (kg/tree) and yield of fruit (kg/tree) in different fruit size categories of Nules Clementine mandarin trees in a commercial orchard in Grapevine, Calif. in 25. Treatment Total Tiny Small Tiny + Small Medium Large Jumbo Mammoth Jumbo + Mammoth Colossal Supercolossal Large Rate of GA P-value <.1 < <.1 <.1.26 z Fruit sizes categories based on fruit transverse diameters (mm): Tiny (<44.45), Small ( ), Medium ( ), Large ( ), Jumbo ( ), Mammoth ( ), Colossal ( ), and Supercolossal ( ). 1

11 Table 1. Effect of GA 3 and urea treatments on fruit quality parameters of Nules Clementine mandarin trees in a commercial orchard in Grapevine, Calif. in 25. Treatment Fruit weight (g) Juice weight (g) Percent acid ºBrix Brix:acid (1) 5 mg/l GA 3 x c z a (3) 1 mg/l GA 3 x bc a (5) 1 mg/l GA 3 x3 6% bc ab (6) 1 mg/l GA 3 x3 6%/9% a ab (7) 15 mg/l GA 3 x c bc (9) 25 mg/l GA 3 x bc a (13) 15 mg/l GA 3 x abc ab (15) Water abc c (16) Control ab bc P-value z Values followed by different letters are significantly different at P =.5 based on Fisher s Protected LSD Test. Table 11. Effect of GA 3 on total yield (average kg fruit per tree) and fruit size distribution as average weight (kg) of fruit in different fruit size categories (based on transverse diameter) of Nules Clementine mandarin trees in a commercial orchard in Grapevine, Calif in 26. Treatment Tiny + Jumbo + Super- Total Tiny Small Small Medium Large Jumbo Mammoth Mammoth Colossal colossal Large kg/tree (1) 5 mg/l GA 3 x cdef y.46 ab 6.36 e 6.82 e bcd abcd abc ab.42 b abcd (2) 5 mg/l GA 3 x4 (1 yr) a.47 ab ab ab a abcd bc 4.49 ab.48 ab abc (3) 1 mg/l GA 3 x f.77 a 8.26 bcde 9.3 bcde cd 28.2 bcde c bcd. b def (4) 1 mg/l GA 3 x4 (1 yr) 93.6 abc.44 ab 8.86 bcde 9.3 bcde bcd ab ab a 1.9 a a (5) 1 mg/l GA 3 x3 6% cdef.55 ab 1.57 abc abc abc de c cd. b ef (6) 1 mg/l GA 3 x3 9% 87.8 bcdef.16 b 7.68 cde 7.84 de abcd abc abc 38.5 abc. b abcde (7) 15 mg/l GA 3 x def.59 ab 8.67 bcde 9.27 bcde d cde c bcd.52 ab cdef (8) 15 mg/l GA 3 x4 (1 yr) 91.9 abc.53 ab 1.57 abc 11.1 abc ab abcde c abc.23 b abcde (9) 25 mg/l GA 3 x bcd.3 ab 8.19 bcde 8.49 bcde abcd abc bc abc.39 b abcde (1) 25 mg/l GA 3 x4 (1 yr) bcde.42 ab 8.94 bcde 9.36 bcde ab bcde a abcd. b bcdef (13) 15 mg/l GA 3 x ef.31 ab 1.39 abcd 1.7 bcd bcd e c 28.5 d. b f (14) 15 mg/l GA 3 x2 (1 yr) abc.61 ab 7.43 de 8.3 cde 4.79 bcd a c 44.1 a.59 ab ab (15) Water bcde.35 ab 8.75 bcde 9.1 bcde bcd abc abc ab.35 b abcd (16) Control ab.64 ab a a ab abc bc ab.39 b abcd P-value z Fruit sizes categories based on fruit transverse diameters (mm): Tiny (<44.45), Small ( ), Medium ( ), Large ( ), Jumbo ( ), Mammoth ( ), Colossal ( ), and Supercolossal ( ). y Average weight followed by different letters are significantly different at P =.5 based on Fisher s Protected LSD Test. 11

12 Table 12. Effect of GA 3 on total yield (average number of fruit per tree) and fruit size distribution as the average number of fruit in different fruit size categories (based on transverse diameter) of Nules Clementine mandarin trees in a commercial orchard in Grapevine, Calif in 26. Treatment Tiny + Jumbo + Super- Total Tiny Small Small Medium Large Jumbo Mammoth Mammoth Colossal colossal Large Fruit no./tree (1) 5 mg/l GA 3 x4 951 cde y e 125 e 451 bcd 311 abcd 55 6 abc 372 abc 2.2 b abc (2) 5 mg/l GA 3 x4 (1 yr) 1199 a 11 2 ab 212 ab 6 a 31 abcd 68 5 bc 383 abc 2.5 ab abc (3) 1 mg/l GA 3 x4 911 e bcde 166 bcde 43 cd 277 bcde 36 3 c 315 cde. b 315 cde (4) 1 mg/l GA 3 x4 (1 yr) 169 abcd bcde 169 bcde 479 bcd 339 ab 67 9 ab 414 ab 5.7 a ab (5) 1 mg/l GA 3 x3 6% 119 cde abc 22 abc 521 abc 243 de 51 2 c 295 de. b 295 de (6) 1 mg/l GA 3 x3 9% 12 cde cde 141 de 515 abcd 317 abc 4 6 abc 363 abcd. b 363 abcd (7) 15 mg/l GA 3 x4 922 e bcde 169 bcde 428 d 27 cde 5 1 c 322 cde 2.7 ab 322 cde (8) 15 mg/l GA 3 x4 (1 yr) 187 abc abc 22 abc 528 ab 291 abcde 64 2 c 357 abcd 1.2 b 357 abcd (9) 25 mg/l GA 3 x4 945 de abcd 193 bcd 479 bcd 235 e 35 3 c 272 e. b 272 e (1) 25 mg/l GA 3 x4 (1 yr) 172 abcd de 147 cde 52 bcd 355 a 63 3 c 42 a 3.1 ab 42 a (13) 15 mg/l GA 3 x2 145 bcde bcde 153 cde 519 abcd 325 abc 4 4 bc 369 abcd 2.1 b 1 37 abcd (14) 15 mg/l GA 3 x2 (1 yr) 149 bcde 1 16 bcde 17 bcde 538 ab 286 bcde a 342 bcde. b 342 bcde (15) Water 123 bcde bcde 165 bcde 478 bcd 314 abc 57 7 abc 378 abc 1.8 b abc (16) Control 1162 ab a 252 a 531 ab 315 abc 57 4 bc 375 abc 2.1 b abc P-value z Fruit sizes categories based on fruit transverse diameters (mm): Tiny (<44.45), Small ( ), Medium ( ), Large ( ), Jumbo ( ), Mammoth ( ), Colossal ( ), and Supercolossal ( ). y Average number followed by different letters are significantly different at P =.5 based on Fisher s Protected LSD Test. 12

13 Table 13. Pearson correlation coefficients (r) between total amount of GA 3 applied per season and total yield (kg/tree) and yield of fruit (kg/tree) in different fruit size categories of Nules Clementine mandarin trees in a commercial orchard in Grapevine, Calif. in 26. Treatment Total Tiny Small Tiny + Small Medium Large Jumbo Mammoth Jumbo + Mammoth Colossal Supercolossal Large Rate of GA P-value z Fruit sizes categories based on fruit transverse diameters (mm): Tiny (<44.45), Small ( ), Medium ( ), Large ( ), Jumbo ( ), Mammoth ( ), Colossal ( ), and Supercolossal ( ). Table 14. Effect of GA 3 and urea treatments on fruit quality parameters of Nules Clementine mandarin trees in a commercial orchard in Grapevine, Calif. in 26. Treatment Fruit weight (g) Juice weight (g) Percent acid ºBrix Brix:acid (1) 5 mg/l GA 3 x (2) 5 mg/l GA 3 x4 (1 yr) (3) 1 mg/l GA 3 x (4) 1 mg/l GA 3 x4 (1 yr) (5) 1 mg/l GA 3 x3 6% (6) 1 mg/l GA 3 x3 9% (7) 15 mg/l GA 3 x (8) 15 mg/l GA 3 x4 (1 yr) (9) 25 mg/l GA 3 x (1) 25 mg/l GA 3 x4 (1 yr) (13) 15 mg/l GA 3 x (14) 15 mg/l GA 3 x2 (1 yr) (15) Water (16) Control P-value z Values followed by different letters are significantly different at P =.5 based on Fisher s Protected LSD Test. 13