Evaluation of Aminoethoxyvinylglycine (AVG) for Flower Retention In Paprika (Capsicum annuum L.)

Chile is an important vegetable crop in the desert southwest, and is grown in a geographic area called the “chile belt” (west Texas, New Mexico, and Arizona).  Paprika is the general term for red chile varieties that are grown specifically for dehydration and subsequent pigment extraction.  These pigments are used as safe colorants in a wide range of consumer products including cosmetics and processed meats. However, the pigments associated with deep coloration also appear to be associated with premature fruit (pod) ripening and abscission.  In addition, high daytime temperatures in the chile belt during the bloom period (June and July) can cause flower abscission, possibly due to release of the plant growth regulator (PGR), ethylene.  Both flower and premature fruit abscission can cause yield losses under field conditions.  Aminoethoxyvinylglycine hydrochloride (AVG- trade name ReTain®, Valent BioSciences), blocks the biosynthesis of ethylene in plant tissues. In this study, we evaluated the effectiveness of the ethylene inhibitor ReTain® for flower retention in the paprika cultivar ‘NuMex Garnet.’  ReTain® was applied at 250 parts per million (ppm) active ingredient with a non-ionic surfactant (0.05% v/v) to direct seeded chile for all treatments in this study.  Application dates were timed to correspond with first, early, and peak bloom and were calculated based on heat units accumulated after planting (HUAP with 86/55^oF thresholds).  After treatment, no significant differences (P=0.05) among treatments or the untreated control for number of red pods, number of green pods, fresh weight red pods, fresh weight green pods, fresh weight dropped pods, fresh weight of diseased (unmarketable) pods, or dry weight of red pods.  However, there were significant differences among treatments for the number of dropped pods and the dry weight of these dropped pods.  When ReTain® was applied at early bloom (~1700 HUAP), the number of dropped pods were significantly lower (1.5/plant) than when the product was applied at first bloom (2.25 dropped pods/plant).  Also, when applied at early bloom, the dry weight of dropped pods/plant was significantly lower than the control or when the product was applied at first bloom.  Although ReTain® applications at early bloom had an impact on number and weight of dropped pods, there were no corresponding significant differences in yield.  Ethylene may play a role in fruit and flower abscission in paprika, however the application timing of ReTain® used in this study did not produce results that indicate a significant benefit to using this product.