Chemical-induced androsterility by imidazolinone herbicide treatment: evidence of sporogenerus tissue damage in Imisun sunflower genotypes

DUARTE, C.; NESTARES, G.; OCHOGAVÍA, A. C.; MENENDEZ, A.; BIANCHI, M. B.; PICARDI, L.

Foz do Iguazu

Congreso; XXII International Congress of Genetics; 2018

Sociedade Brasileira de Genética

Imidazolinones (IMI) are powerful herbicides that inhibit branched-chain amino acid biosynthesis by targeting the acetohydroxyacid synthase (AHAS). Imisun sunflowers (Helianthus annuus L.) were the first commercial imidazolinone-resistant cultivars developed. A digenic model with a major semidominant gene Imr1 and a modifier gene Imr2 was postulated to explain the genotypic resistance. IMI application in the advanced vegetative developmental stages is associated with androsterility in Imisun sunflowers; however, the underlying mechanism for this sterility remains unknown. The aim of our work was to describe anatomical and physiological alterations in male reproductive tissue induced by two different imazapyr treatments (1x and 2x doses) in two Imisun genotypes: resistant (R; Imr1Imr1Imr2Imr2) and intermediate resistant (I; Imr1Imr1imr2imr2). Pollen viability was assessed by lactophenol-aniline blue stained, viable seeds were counted, and treatments were compared with X2 test. Immature anthers were collected and fixed 11 days after treatment in order to be observed by Confocal Laser Microscopy (CLM). Pollen viability was 87.14 and 91.04% for R and I genotypes respectively. No significant differences were observed. Nonetheless the number of viable seeds was significantly reduced by the 2x IMItreatment in both genotypes (p