Background Cytoplasmic male sterility (CMS) is a maternally inherited failure to produce functional pollen that most commonly results from expression of novel, chimeric mitochondrial genes. In Zea mays, cytoplasmic male sterility type S (CMS-S) is characterized by the collapse of immature, bi-cellular pollen. Molecular and cellular features of developing CMS-S and normal (N) cytoplasm pollen were compared to determine the role of mitochondria in these differing developmental fates. Results Terminal deoxynucleotidyl transferase dUTP nick end labeling revealed both chromatin and nuclear fragmentation in the collapsed CMS-S pollen, demonstrating a programmed cell death (PCD) event sharing morphological features with mitochondria-signaled apoptosis in animals. Maize plants expressing mitochondria-targeted green fluorescent protein (GFP) demonstrated dynamic changes in mitochondrial morphology and association with actin filaments through the course of N-cytoplasm pollen development, whereas mitochondrial targeting of GFP was lost and actin filaments were disorganized in developing CMS-S pollen. Immunoblotting revealed significant developmental regulation of mitochondrial biogenesis in both CMS-S and N mito-types. Nuclear and mitochondrial genome encoded components of the cytochrome respiratory pathway and ATP synthase were of low abundance at the microspore stage, but microspores accumulated abundant nuclear-encoded alternative oxidase (AOX). Cytochrome pathway and ATP synthase components accumulated whereas AOX levels declined during the maturation of N bi-cellular pollen. Increased abundance of cytochrome pathway components and declining AOX also characterized collapsed CMS-S pollen. The accumulation and robust RNA editing of mitochondrial transcripts implicated translational or post-translational control for the developmentally regulated accumulation of mitochondria-encoded proteins in both mito-types. Conclusions CMS-S pollen collapse is a PCD event coincident with developmentally programmed mitochondrial events including the accumulation of mitochondrial respiratory proteins and declining protection against mitochondrial generation of reactive oxygen species.

The experiment was performed at Maharajpur Farm under the Department of Horticulture, College of Agriculture, J.N.K.V.V., Jabalpur (M.P.) during the Kharif season 2019-2022 and planted in Randomized Complete Block Design (RCBD) with three replications. The characterization of thirty genotype for thirty-five qualitative traits articulated no variability for trait i.e., the monomorphic trait was non-enveloping fruit calyx cover, two descriptors were found to be moderately diverse, which were with medium fruit intensity of the red colour (at the mature unripe stage) and the narrow triangular shape of fruit with the Shannon-Weaver diversity index H'=0.46 & H'=0.50, both of these are fruit related traits. The descriptor intensity of pubescence (hairiness) of the stem had the highest diversity index of 1.82. The studies highlighted some of the genotypes with the distinctness, MPKC-1(Katni collection) addressed unique features with green with purple tinge leaf colour, purple petal colour, upright fruit orientation, absence of fruit curvature, purple fruit colour at ripening maturity, ovate leaf and erect plant habit, depicting it like a wild relative of capsicum and could be utilized as the morphological descriptor.