Leaf-color mutation induced by ethyl methane sulfonate and genetic and physio-biochemical characterization of leaf-color mutants in pepper (Capsicum annuum L.)

Abstract

Limited genetic germplasm has been a problem for diversity of pepper for some years. Despite many mutants of plant have been reported in recent years, leaf anthocyanin or chlorophyll mutants were rarely identified in pepper, and the developmental and genetic characteristics of leaf-color remain poorly understood in pepper. Here, pale green leaf mutant, such as zylm mutant that was identified in an ethyl methane sulfonate mutagenized population of wild pepper (Capsicum annuum L.) ‘Zunla’, can be used to study the effect of leaf-color on pepper plants. Under natural field conditions, the leaves of zylm mutant plants exhibited impaired growth and pale green leaf throughout the entire growth season. Physiological and biological analysis of zylm mutant and other leaf-color mutants (yellow-green mutant bmy and purple leaf mutant Z1) revealed that chlorophyll deficiency was affected by down-regulation of chlorophyll synthesis gene expression, and resulted in impaired growth of pepper by inhibiting root activity, decreasing photosynthesis capacity, disturbing accumulation of soluble sugar and protein. Anthocyanins accumulation caused by up-regulation of anthocyanin synthesis gene expression increased root activity and contents of soluble sugar and protein, while its excessive accumulation limited the increase of photosynthesis capacity. Genetic analysis showed that formation of pale green leaf and purple leaf was controlled by nucleus. Green leaf is dominant over pale green leaf, and green leaf is recessive over purple leaf. Pale green leaf gene ZYLM and purple leaf PL were mapped in chromosome 3 and chromosome 9, indicating the diversity of leaf-color in pepper.