Estresse hídrico e expressão de genes no início de crescimento de algodoeiro naturalmente coloridos

Abstract

The culture of naturally colored cotton in the Brazilian Northeast has great part of its production due to small farmers, what makes it of vital importance for the local economy, generating employment and income. Considering the climate peculiarities of the region, mainly frequent droughts, it is important the identification of genotypes tolerant to water stress. With this focus, the objective of this research was to study the tolerance of naturally colored cotton genotypes, in the initial growth phase, based on physiologic parameters and gene expression. Were used seeds of 6 naturally colored cotton genotypes, originated from the BAG of Embrapa Cotton: CNPA 2009-6 , CNPA 2009-11 , BRS SAFIRA , BRS TOPÁZIO , CNPA 2009-13 e CNPA 200950 . The seeding was done in root trainers, in a protected environment. Two handlings were tested, without water stress and with water stress, initiating this when the first real leaves measured 6 cm², allowing the evaluation of gas exchange. For the NCED and LEA genes expression studies, leaves were collected in the day that occurred the fall of stomatal conductance, two days after and in the recovery. The reduction of stomatal conductance was a good indicator of the humidity deficiency in the soil. The genotypes CNPA 2009-11 and CNPA 2009-13 didn t express the gene NCED in the reduction of stomatal conductance from 61% to 31%, and of 83% to 28%, respectively; it was observed the presence of LEA proteins in the genotypes CNPA 2009-6 and BRS SAFIRA, on the sixth day of water stress and in the genotypes CNPA 2009-3 and BRS SAFIRA on the recovery. In the end of the water stress, the root trainers containing these genotypes had a similar rate of soil humidity. The genotypes CNPA 2009-13 and CNPA 2009-50 were more tolerant to water stress, as they were the last to show signs of weakness due to water stress. However, the genotype CNPA 2009-6 reacted better to the rehydration, possessing higher indexes of number of leaves, leaf area, leaf phytomass. Nonetheless, in the end of the treatment without water stress, the genotypes CNPA 2009-11, CNPA 2009-13 and CNPA 2009-50 obtained greater phytomass, leaf, stem and root.