Response of evergreen perennial tree crops to gibberellic acid is crop load-dependent: II. GA₃ increases yield and fruit size of ¡®Hass?avocado only in the on-crop year of an alternate bearing orchard

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• 作者：Lauren  ; Garner¹ ; Grant  ; Klein ; Yusheng  ; Zheng ; Toan  ; Khuong ; Carol J.  ; Lovatt  ; ;   ; ^{carol.lovatt@ucr.edu}
• 关键词：Persea americana Mill. ; Flower and fruit abscission ; Off-crop year ; Fruit size ; Crop value ; Phenology
• 刊名：Scientia Horticulturae
• 出版年：2011
• 出版时间：31 October 2011
• 年：2011
• 卷：130
• 期：4
• 页码：753-761
• 全文大小：449 K

文摘

Despite problems of low fruit set, small fruit size and alternate bearing, the Hass cultivar dominates commercial avocado production worldwide. To increase yield and fruit size, gibberellic acid (GA₃) (25 mg L^?) was applied at different stages of ¡®Hass?avocado tree phenology: (i) mid¨Clate April (flower abscission), end of June¨Cbeginning of July (fruit abscission and beginning of the exponential phase of fruit growth), and mid-January (beginning of pre-harvest fruit drop); (ii) end of June¨Cbeginning of July; and (iii) mid-September (near the end of the major fruit abscission period; period of exponential fruit growth). In both years of the research, applications of GA₃ in April and June¨CJuly were within the periods of intense flower and fruit abscission, respectively; fruit abscission was low in September and January. Maximum air temperature was not related to flower or fruit abscission. In the on-crop year (391 fruit per untreated control tree), a single application of GA₃ at the end of June¨Cbeginning of July significantly increased total yield (kilograms only) and yield of commercially valuable fruit (178?25 g/fruit) (as kilograms and number per tree) compared with the control (P < 0.0001). GA₃ applied in September increased total yield (kilograms only) and yield of commercially valuable fruit (kilograms and number per tree) to values intermediate to and not significantly different from all other treatments, except trees receiving multiple applications of GA₃. This treatment reduced total yield and yield of commercially valuable fruit (kilograms and number per tree) relative to all treatments (P ?0.0002). In contrast, during the off-crop year (32 fruit per control tree), no GA₃ treatment had a significant effect on yield or fruit size compared with the control and all other GA₃ treatments. For ¡®Hass?avocado, there was no negative effect from applying GA₃ at the end of June¨Cbeginning of July in both the off- and on-crop years; 2-year cumulative total yield and yield of commercially valuable fruit were increased by 27 kg (128 fruit) and 22 kg (101 fruit) per tree, respectively, above the yield of untreated control trees (P < 0.0001).