Title : Phenology of two Carica Papaya L. genotypes with response to tropical climate
Abstract:
Carica papaya L. is a gynodioecious plant that has three sex forms: female (F), male (M), and hermaphrodite (H). The nutraceutical and antimicrobial properties of papaya varieties are highly beneficial during pharmaceutical production. The study's objectives were to evaluate the performance of the two papaya varieties in the tropical climate and to establish a relationship between the growth of the two papaya varieties and the ambient conditions. The experiment was conducted at the Faculty of Technology, University of Ruhuna, Karagoda-Uyangoda, Kamburupitiya (6.0635° N, 80.5420° E; 14 m a.s.l.) of IL1A agroecological region. The experiment design was Randomized Complete Block Design (RCBD) of 16 replicates in two varieties with 1.8 m X 1.8 m spacing. The morphological characteristics of the H and the F plants of the papaya red lady (R) (a commercial variety) and a local variety (L) were observed for the plant height (PH), stem diameter (SD), leaf number (LN), leaf length (LL), chlorophyll content (SR), flower number (FN) and the fruit number (FR) were measured at 3rd, 6th, 9th, 12th and 15th month of growing (MG). The weather data of the daily min and max temperature, min and max relative humidity (RH), bright sunshine hours, evaporation and rainfall were obtained and averaged on monthly basis. The dates to flowering (FLD), dates to fruiting (FRD) and the total growing degree days (GDD) were calculated. An average of 13 GDD was observed throughout the planting period of 15 months. FLD of H and F of R was significantly lower with compared to the H and F of L variety and the same pattern was observed for the FRD. PH, SD, LL, SR and FR were significantly negatively correlated with GDD for H and F of Local variety. While the LN, LL, SR and FN showed a significantly positive correlation for F of R. All plant types were significantly positively correlated for the PH, SD and FR. All seven morphological characters of F and H of local variety are significantly positively correlated with the 08:30 am RH, 03:30 pm RH and average RH. All plant types of FN were negatively correlated with evaporation while LL and FR were negatively correlated with rainfall. The study summarises the fact of morphological and phenological factors are highly associated with environmental variables such as temperature, relative humidity, bright sunshine hours, and rainfall which would ultimately affect the vegetative development and the development of papaya fruit. The study would provide an understanding of the yield potential of local varieties and associated environmental factors that could be important in developing related industrial products such as papain enzyme.
