Reactive Oxygen Species Accumulation Strongly Allied with Genetic Male Sterility Convertible to Cytoplasmic Male Sterility in Kenaf

Male sterility (MS) plays a key role in the hybrid breed production of plants. Researchers have focused on the association between genetic male sterility (GMS) and cytoplasmic male sterility (CMS) in kenaf. In this study, P9BS (a natural GMS mutant of the kenaf line P9B) and male plants of P9B were used as parents in multiple backcross generations to produce P9SA, a CMS line with stable sterility, to explore the molecular mechanisms of the association between GMS and CMS. The anthers of the maintainer (P9B), GMS (P9BS), and CMS (P9SA) lines were compared through phenotypic, cell morphological, physiological, biochemical observations, and transcriptome analysis. Premature degradation of the tapetum was observed at the mononuclear stage in P9BS and P9SA, which also had lower activity of reactive oxygen species (ROS) scavenging enzymes compared with P9B. Many coexpressed differentially expressed genes were related to ROS balance, including ATP synthase, electron chain transfer, and ROS scavenging processes were upregulated in P9B. CMS plants had a higher ROS accumulation than GMS plants. The MDA content in P9SA was 3.2 times that of P9BS, and therefore, a higher degree of abortion occurred in P9SA, which may indicate that the conversion between CMS and GMS is related to intracellular ROS accumulation. Our study adds new insights into the natural transformation of GMS and CMS in plants in general and kenaf in particular.

Developing rice hybrids for temperate conditions using three line approach

Exploitation of heterosis in the form of hybrid rice is yet to be exploited at commercial level in the temperate regions of India. The present study is attempted to develop rice hybrids for the temperate conditions of Kashmir valley by utilizing the cytoplasmic genetic male sterility system (CGMS). Among the four CMS lines evaluated, the genotype SKUA-7A and SKUA-11A had desirable performances. The 24 test crosses developed involving these CMS lines were evaluated for spikelet fertility and pollen fertility. Moreover, the highest standard heterosis for grain yield and other yield attributes over the check varieties (Jehlum and Shalimar Rice-3) was recorded in the cross combination K15-34 followed by K15-31 and K15-40. Pollen parents of all the three test crosses on screening with RM-6100, DDRMRf3-10 and DRCG-Rf4-14 markers revealed presence of both Rf3 and Rf4 genes responsible for fertility restoration. Besides, 39 genotypes were screened for fertility restoration and the lines RL-2, RL-5, RL-6, RL-7, RL-10, Pusa Sugandh3 and Kohsar were identified to carry homozygous alleles at both Rf3 and Rf4 loci. These genotypes can thus be used as promising restores for the development of temperate rice hybrids.

Male sterility induction of sorghum using chemical hybridizing agent TFMSA, trifluoromethanesulfonamide

In sorghum, male sterility has been induced mainly using mechanical and genetic means with minimal use of chemical methods. Mechanical sterility induction is limited to producing small quantities of seed and genetic male sterility is limited to specific germplasm. An effective chemical hybridizing agent could be used to produce large amounts of seed and would not be limited by genotypes. The chemical trifluoromethanesulfonamide (TFMSA) was evaluated as a male gametocide in sorghum. In greenhouse conditions, TFMSA induced varying degrees of male sterility contingent on the dosage, timing of application, and sorghum genotype. If applied at or after the flag leaf emergence, panicles were male fertile but male sterile when applied at least 2 d before the flag leaf emerged. In terms of dosage, 2 mg of TFMSA rendered a BTx623 male sterile if applied 2–6 d prior to flag leaf emergence. However, 30 mg of TFMSA applied as much as 34 d before the flag leaf emerged also induced complete sterility of the panicle. There may be a genotypic effect as less TFMSA was necessary to induce complete male sterility in BTx623 than in BTxArg-1. No phytotoxic effects or reductions in female fertility were observed in dosages of TFMSA up to 40 mg. Germination of hybrid seed made on treated plants was equal to that of the parents and the hybrid seedlings were phenotypically normal. The results indicate that male sterility can be induced effectively in sorghum using TFMSA at appropriate dosages and application timings.