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  • Author or Editor: J.W. Franklin x
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Abstract

Low levels of abscisic acid (ABA) were found at 10 days after anthesis in fruits of a normal cultivar (‘Rutgers’) and of the abnormal ripening mutants (Nr, rin and nor) of tomato (Lycopersicon esculentum Mill). Thereafter the levels increased to peak values which preceded or coincided with coloring in all strains. Peak levels of ABA coincided with the completion of growth in ‘Rutgers’ and rin but followed completion of growth in Nr and nor. Phaseic acid (PA) and gibberellin (GA) activity were highest in all strains about 10 days after anthesis. Subsequently the levels decreased then rose to a second peak except for PA in rin which remained at a relatively high level from 20 days until completion of growth. The second peak in PA in Rutgers, Nr and nor coincided approximately with peak levels of ABA, the second peak in gibberellin activity preceded the peak of ABA in Rutgers, Nr and rin but coincided with it in nor. The results showed that the patterns in the levels of ABA, PA and gibberellin from about 14 days after anthesis are related to ripening or senescence in the four strains and not to growth.

Open Access

This report summarizes the results of irrigation studies conducted from 2000 to 2005 at the Sweet Potato Research Station, Chase, La. These studies investigated the role of various scheduling methods, soil moisture measurement devices, and irrigation delivery methods in sweetpotato production. The studies indicate that 15 to 20 inches of total rainfall and supplemental irrigation is required to produce 400 to 525 bu/acre of US#1 storage roots in Beauregard. Supplemental irrigation can be scheduled based on this benchmark, potentially reducing over-irrigation during dry periods. We have also found that during dry periods, irrigating every furrow can bring about 50% difference in US#1 yield vs. supplying irrigation to alternate furrows. During growing seasons characterized by optimum rainfall patterns, we did not detect any response in US#1 yield to various irrigation treatments. We evaluated several moisture measurement devices including granular matrix sensors, evaporation pan, time domain reflectometry (TDR)-based instrument, and tensiometers. We found the TDR-based device easy to use and convenient in terms of its portability. Based on studies conducted in 2001 and 2002, this device demonstrated potential as a management tool in sweetpotato production. For instance, a management allowable deficit (MAD) of 25% available moisture as measured using the TDR-based device can potentially result in the same yield as weekly irrigation and a MAD of 50% available moisture. When used properly, irrigation scheduling can reduce over-irrigation and contribute to overall efficiency in the use of production inputs.

Free access

Transplant survivability is important in achieving consistent economic yields in sweetpotatoes. We are conducting a series of studies that investigate the role of transplant quality in sweetpotato yield. In 2004, in addition to investigating the role of transplant diameter, we also investigated the influence of transplant water (about 6 oz per hill) on stand and yield. Even though rainfall events were regular and mean rainfall during the growing season was above average for the year, there was a significant increase in US#1 yield (23.57%) among plots derived from thick transplants (≥0.25 inches, no transplant water) versus thin transplants (no transplant water). There was a 44.16% increase in US #1 yield among plots planted with thick transplants vs. plots with thin transplants (with transplant water). In 2005, there was also a significant difference (14%) in US #1 yield between plots planted to thick and thin transplants, respectively. This indicates the possible role of transplant thickness on stand and yield. We also investigated the relationship between root spacing during bedding on cutting diameter as well as a farmer's practice of planting two transplants per hill. In both preliminary tests, no differences among the treatments were observed. Additional studies are planned to investigate the possible use of chemical-based treatments to enhance transplant thickness and survivability.

Free access

Yield tests and evaluation of selected storage root and vine characters were conducted among 12 `Beauregard' sweetpotato [Ipomoea batatas (L.) Lam.] mericlones. Maximum yield differences were 43%, 48%, 79%, and 40% for U.S. #1, canners, jumbos, and total marketable yield, respectively. Additive main effect and multiplicative interaction (AMMI) biplot analysis was useful in graphically presenting the yield differences and stability patterns of mericlones. Differences were also detected in vine length, internode diameter, and internode length. Digital image analysis of U.S. #1 storage roots also revealed differences in storage root minor axis length, roundness, and elongation attributes. The results provide valuable information for enhancing current methods of evaluation and selection of mericlones for inclusion in sweetpotato foundation seed programs.

Free access