Global Journal of Science Frontier Research, G: Bio-Tech & Genetics, Volume 22 Issue 2

provenance/adaptation to the agroecology of origin, i.e., durations of the dry or rainy season, but instead the duration of dormancy varied, depending on genotype, growing and storage conditions. Inductive environmental and endogenous factors, such as air temperature, photoperiod, relative humidity, and exogenously applied/endogenous PGRs, etc., can slightly shorten the duration of dormancy. From this school of thought, yam tuber dormancy seems to be regulated more by genetic factors than environmental factors. Therefore, this scenario tends to be more wholistic in viewing of yam tuber dormancy induction. However, its deficiency lies on the fact that even Hamadina (22) established that some of tuber initiating and development phytohormones (endogenous PGRs) also have dormancy inducive effects; inhibiting sprouting even on physiologically mature tuber and these substances are in their peak concentrations during tuber development and gradually decrease, even after the tuber development has come to an end and tubers attain maturity. This implies that phytohormones involve in tuber initiation, growth and development are also part of the hormones involve in tuber dormancy induction and maintenance, this might be the tuber internal mechanism of ensuring that growing tuber cannot initiated sprouting process which will limit its growth potential and as well affect it food quality. The pictorial summary of the postulations of the two scenarios of dormancy induction and duration n yam tuber and actual empirical observation is presented in figure 2 below. Fig. 2: Diagrammatical representation of yam tuber developmental phenology. Showing the proposed tuber dormancy induction and duration according the two lines of hypotheses, and the actual dormancy induction phenophase and duration based on empirical observation It is necessary to find the agronomical ideal time of commencement and duration of tuber dormancy in order to design research towards its efficient management. This will lead to striking a balance between the two schools of thought, even though, each of them has its merit, but fact remains that an ideal definition lies somewhere in the middle. As already stated here, tuber initiating and development hormones are also dormancy inducing or sprouting inhibiting substances, it implies that tubers are at early developmental stages are designed to be dormant, therefore, tubers are produced dormant and the production hormonal machinery helps to maintain that dormancy during early development to ensure optimum tuber development, food quality and shelf life. Hence, in designing research targeted at reducing the long tuber dormancy duration, this growth and developmental stages should be excluded, because tilting the concentrations of those tuber developmental PGRs during early tuber development stage in order to induce sprouting at such developmental stage might have some serious negative implications on tuber economic yield, food quality and shelf life. In view this, the question of when is agronomically ideal commencement of dormancy induction needs to be answered, to clearly define what part of this long yam tuber dormancy period has constitute a constraint to yam production, productivity and genetic improvement. And this, an average yam researcher and producer will agree that it is from physiological maturity or onset of senescence. If tubers can be made to be able to initiate the processes of sprouting from physiological maturity, a reasonable dormancy period reduction would have been achieved. On the other hand, contrary to the position of first school of thought (scenario A) which seems to be inferring that yam tuber dormancy is absolutely controlled by environmental and eco-physiological factors, scenario B 1 Year 2022 53 © 2022 Global Journals Global Journal of Science Frontier Research Volume XXII Issue ersion I VII ( G ) Physiological and Molecular basis of Dormancy in Yam Tuber: A Way Forward towards Genetic Manipulation of Dormancy in Yam Tubers