Chemical factors influencing dry bean yield

English: The abscission of the reproductive organs (flower buds, flowers and pods) of the common bean, Phaseolus vulgaris L., has proved to be a very serious problem affecting bean yields. The yield reductions are mainly significant under conditions of environmental stress, which aggravate production of the abscission causing hormones such as ethylene. The study therefore evaluated the effect of certain nutrients, other chemicals and ethylene (growth regulator) applied as foliar sprays to determine their effect in as far as abscission of the reproductive organs in beans is concerned. Glasshouse trials were carried out during the 1998/99 and 1999/00 seasons to investigate the possible preventative role of some micro and macro-nutrients, abscission inhibitors (e.g. Silver) and growth regulators (e.g. ethylene) all applied as foliar sprays. In another trial, three cultivars were compared where no treatments were applied. Data were collected and the following parameters were measured; number of flowers and pods that abscised, pods formed and abscised, pods that matured and could be harvested, dry pod mass at harvest, seed number per pod, dry seed mass per pod and total yield per hectare. Data were analyzed using a SAS software system and interpreted accordingly. The results of this study indicated that flower and pod formation might not be considered as the major factor affecting bean yields. The reason being that flowering percentage was not very different between the treated and the untreated plants. The abscission of flower buds, flowers and pods, however, was relatively high in general, indicating that this is possibly a primary factor affecting poor yields in beans. Ethrel, an ethylene releasing compound, applied as a foliar spray, aggravated the problem of flower and pod abscission. An ethylene antagonist (silver salt) had a slight alleviating effect on organ abscission but did not improve the final yield significantly. Molybdenum and potassium salts improved flower formation to a certain extent but had no real alleviating effect on organ abscission. This was also revealed in the lack of yield improvement. Foliar application of a copper salt as well as treatment with ComCat®, a natural product with biocatalytic properties, did not influence flower and pod abscission significantly, but increased the final yields to some extend. The latter indicates that other factors besides organ abscission could have had an effect on determining the final yield outcome. In the light of these findings, it is suggested that further studies be undertaken to test a wider range of chemicals for their potential to circumvent flower and pod abscission and improve bean yields. The latter could also include treatment at other growth stages, including post flowering. Other attempts could include an investigation into the effect of other known ethylene antagonists such as AVG (L-a.-(2-arninoethoxyvinyl)-glycinehydrochloride), an inhibitor of ethylene synthesis and NBD (2,S-norbornadiene), an inhibitor of ethylene action, on organ abscission and yield outcome in beans. As the results also showed that other factors besides organ abscission could have played a role in yield improvement, it might be worthwhile to investigate the effect of promising chemicals on physiological processes.