Temperatura base, soma térmica, plastocrono e duração das fases fenológicas de cultivares de pimenta biquinho

Abstract

The objective of this study was to estimate the base temperature (Tb, ºC), degree day (STa, ºC day) and plastochron (ºC dia nó-1) of the development satges of the biquinho pepper cultivars. The study was conducted in the experimental area of the UFSM campus Frederico Westphalem-RS, Brazil, from August 2015 to May 2016. The experimental design was a randomized block design with factorial scheme 2x4, with two biquinho pepper cultivars (BRS Moema and Airetama Biquinho Amarela) and four growing seasons (24/08/2015, 01/10/2015, 13 / 11/2015 and 15/03/2016), with six replications. For the visual identification of different stages during the vegetative and reproductive phase, the following sub-phases were established: emergence-transplant (TR-FI), transplant-beginning of flowering (TR-IF), beginning of flowering-beginning of harvest (AN-FR), fruit-ripening-fruit (FR-MA), early harvesting (IC-PC), floral bud-anthesis (BO-AN), anthesis-fruiting. In the subphases was estimated its duration (in days), STa and Tb. The subphase Tb was calculated by the methods of the standard deviation in days, the standard deviation in degrees days, the coefficient of variation in days, the coefficient of variation in degrees day, x-intercept, and relative development. The plastochron was estimated for the vegetative and reproductive phase. For each phase, we estimated the base temperature, degree day and the emission of nodes on a plant stem. The Tb was estimated by the mean error square method (QME). The plastochron was estimated from the inverse of the coefficient of simple linear regression between the number of nodes and STa. The development was similar between the two cultivars, being dependent on the cultivation times and not on the genotype. The air temperature influences only the duration of the period for the EM-TR and TR-IF phases. Tb for the EM-TR, TR-IF, IF-IC, IC-PC phases is 16.5 °C , 14.8 °C and 20.2 °C, respectively. For the sub-phases (BO-AN, AN-FR, FR-MA) the base temperature is 20.2 °C. The STa was 446.2 °C day, 377.1 °C day, 558.0 °C day, 781.8 °C day for the phases EM-TR, TR-IF, IF-IC, respectively, and 104.0 °C day, 162.8 and 342.1 °C day for the sub-phases BO-AN, AN-FR, FR-MA, respectively. With the established phases a phenological scale was proposed that indicates the duration in days and the thermal needs in each phase. In the estimation of the plastochron base temperature as well as the emission of nodes was not influenced by the cultivar. In the vegetative phase, Tb and plastochron had on average a Tb of 16.8 ºC and a plastochron of 43.6 ºC day node-1. In the reproductive phase both Tb and plastochron were similar at the evaluated times, showing in average a Tb of 16.7 ºC and plastochron of 64.4 ºC day node-1.