Herança da tolerância ao estresse salino em tomateiros derivados de Solanum galapagense e Solanum pennellii

Abstract

The cultivated tomato, Solanum lycopersicum, is a glycophyte species and is severely damaged even at low salinity levels. As areas for growing tomatoes are becoming narrower around the world due to the increased salinization of arable lands, breeding for salt-tolerant crops is a pressing issue. Salt tolerant genotypes could attenuate these losses, however, in spite of the substantial efforts, progress towards this goal has been limited, mainly due to the lack of a screening criteria for salt tolerance viable for routine breeding. In this study, a new screening methodology to select salt tolerant genotypes is proposed, as well as a trait that can predict salt tolerance at the seedling stage.Also, to elucidate the genetic control of stress symptoms caused by salinity in Solanum galapagense, segregating populations were obtained from Solanum lycopersicum‘TOM-684’ x Solanum galapagense ‘LA1401’. 35 days after sowing, the plants were exposed to a salt stress of 300 mM, and were evaluated based on stress symptoms. The area under the stress symptoms progress curve was used to test a hypothesis of monogenic inheritance under different presumed degrees of dominance, and genetic models were tested using maximum likelihood tests of genetic control. Broad-sense heritability was of 0.66 and narrow-sense heritability was of 0.27. Stress symptoms in S. galapagense ‘LA1401’ is controlled by more than one locus, and might be under polygenic control.S. lycopersicum 'BPX-441E-88', a genotype previously identified as drought-tolerant (tolerance obtained from S. pennellii), was identified as salt-tolerant. In this study, populations P1 (BPX-441E-88), P2 (TOM760), F1, F2, F1BC1(1), and F1BC1(2) were grown under saline conditions (300 mM NaCl) in a hydroponic system, and assessed for stress symptoms, which were converted to area under the stress symptoms progress curve. This trait was found to be controlled by a major gene plus modifier genes, with both additive and non-additive gene effects. The estimates of broad-sense and narrow-sense heritability are 0.26 and 0.10, respectively.