Heterosis and Combining Ability for Fruit Yield, Sweetness, β-Carotene, Ascorbic Acid, Firmness and Fusarium Wilt Resistance in Muskmelon (Cucumis melo L.) Involving Genetic Male Sterile Lines

Ten genetically diverse inbred lines, including two genic male sterile lines, of muskmelon (Cucumis melo L.) were crossed in a half-diallel to generate 45 F1 hybrids. These hybrids, along with the parental lines and commercial check, were evaluated for their fruit yield, level of phytochemicals and Fusarium wilt resistance. Both additive and non-additive genetic variances were important in governing the expression of all of the traits; however, the additive gene action for the fruit weight (g), flesh thickness (cm), rind thickness (mm), firmness (lb inch−2), β-carotene content (mg/100 g), non-additive variance for fruit yield (t ha−1), fruit number, total soluble solids (TSS, °Brix), ascorbic acid (mg/100 g) and reaction to Fusarium wilt were comparatively more important. The parental line MM-625 was the best general combiner for fruit yield, rind thickness and β-carotene content (mg/100 g). The exotic line Riogold was the best combiner for flesh thickness and firmness. The netted inbred line MM-610 was the best general combiner for fruit weight, ascorbic acid and reaction to Fusarium wilt. The inbred lines KP4HM-15 and MM-916 were the best general combiners for the number of fruits per vine and TSS. The best cross-combinations for fruit yield ha−1 and TSS were MS-1×M-610 and Kajri×MM-904, respectively. The hybrids KP4HM-15×MM Sel-103 and KP4HM-15×MM-1831 recorded the highest standard heterosis for fruit yield and TSS. The landrace-derived inbred lines Kajri, MM Sel-103 and KP4HM-15 produced moderate-to-highly FW-resistant hybrids. Out of the 121 SSR markers applied, 70 exhibited parental polymorphism. The markers DM0561, CMAAAGN14, TJ147, CMMS35_3, CMAGN45 and DE1337 identified specific/unique alleles in certain parental genotypes. Thus, the findings of this study revealed that the novel inbred lines can effectively be combined to generate heterotic F1 hybrids for yield and other traits, such as rind and flesh thickness, TSS, β-carotene content and firmness. Furthermore, SSR markers can potentially be utilized to confirm the genetic diversity among the parental lines, and for the DNA fingerprinting of F1 hybrids.

Integrated cyto-physiological and proteomic analyses reveal new insight into CMS mechanism in a novel upland cotton CMS line LD6A

Cytoplasmic male sterile (CMS) system has extensively been exploited for hybrid vigor in plant breeding programs. However, its application in many crops is limited due to poor understanding of molecular mechanism of fertility restoration. Using advanced analytical approaches, we elucidated molecular pathways regulating CMS induction and fertility restoration in cotton. Reproductive structures of a novel CMS (LD6A) and its maintainer (LD6B) line were analyzed for physiological and proteomic changes during the development process. Significant differential expression of proteins, such as Abrin, malate dehydrogenase, malic enzyme, isocitrate dehydrogenase, histone acetyltransferase was observed in CMS and its maintainer line. Transmission electron micrographs of anther tapetum showed that inner ridge of CMS mitochondria was relatively indistinct than that of LD6B with narrower membranous space at tetrad stage. Further, relatively higher reactive oxygen species were accumulated in the anther of CMS than its maintainer line at pollen mother cell and tetrad stage. We suggest that abnormal sequence of mitochondrial ribosome gene rps4 and rpl10 and high expression of ribosome-inactivating protein gene Abrin in CMS line damaged mitochondrial membrane and consequently induced pollen sterility. These data provide new insight into CMS mechanism in cotton crops and a tool to develop new CMS germplasm resources.

Generating Novel Male Sterile Tomatoes by Editing Respiratory Burst Oxidase Homolog Genes

Hybrid breeding of tomatoes (Solanum lycopersicum), an important vegetable crop, is an effective way to improve yield and enhance disease and stress resistance. However, the efficiency of tomato hybridization is hindered by self-fertilization, which can be overcome using male sterile lines. It has been reported that reactive oxygen species (ROS) act as a key regulator for anther development, mediated by RBOH (Respiratory Burst Oxidase Homolog) genes. Here, two tomato anther-expressed genes, LeRBOH (Solyc01g099620) and LeRBOHE (Solyc07g042460), were selected to cultivate novel tomato male sterile strains. By using a CRISPR/Cas9 system with a two-sgRNA module, the lerboh, lerbohe, and lerboh lerbohe mutant lines were generated, among which the lerbohe and lerboh lerbohe mutants displayed complete male sterility but could accept wild-type pollens and produce fruits normally. Further analysis uncovered significantly decreased ROS levels and abnormal programmed cell death in lerboh lerbohe anthers, indicating a key role of ROS metabolism in tomato pollen development. Taken together, our work demonstrates a successful application of gene editing via CRISPR/Cas9 in generating male sterile tomatoes and afforded helpful information for understanding how RBOH genes regulating tomato reproduction process.

Mitochondrial Proteomics and Transcriptional Analysis of Cytoplasmic Male Sterility in Sugar Beet using iTRAQ and qRT–PCR

Sugar beet (Beta vulgaris L.) is an important raw material for the sugar industry, and its output is second only to sugar cane. Cytoplasmic male sterility (CMS) is a phenomenon of pollen abortion that has important implications in sugar beet hybrid breeding. Male plant sterility is usually considered to be associated with mitochondrial dysfunction. Although mitochondrial genes associated with male sterility have been well explored, the different mitochondrial proteomics of CMS in sugar beet are still poorly understood. In this study, differentially expressed mitochondrial proteomic analysis was performed on the flower buds of the male sterile line (DY5-CMS), its maintainer line (DY5-O) and a fertility restorer line (CL6), using an isobaric tag for relative and absolute quantitation (iTRAQ) technology. A total of 2260 proteins were identified by mass spectrometry, of which 538 were differentially expressed proteins. Most of them were involved in protein metabolism, carbohydrate and energy metabolism, and binding. More specifically, some cysteine and methionine metabolism proteins (A0A0J8BGE0, A0A0J8CZM6, A0A0J8D7W0 and A0A0J8BCR7) may play important roles during the formation of CMS. This study provided an in–depth understanding of the CMS molecular mechanism at the protein level in sugar beet.

Heterotic groups for identifying of suitable combiners in sunflower using top-cross

The study was conducted in order to identify the suitable parental inbred lines using top cross method for improvement of new sunflower F1 single cross hybrids at research field of Seed and Plant Improvement Institute in Karaj, Iran during two Crop season (2018 and 2019). Experimental materials consisted of 31 restore lines and 43 cytoplasmic male sterile lines which were crossed with A1221 and R14 as the testers respectively. The developed F1 hybrids were evaluated for GCA of three breeding objectives i.e. flowering time, plant height and grain yield during two years replicated trials. Cluster analysis revealed two heterotic groups in which the restorer lines; R22, R24 and R38 (Grain yield of 33, 32 and 31 g head-1 respectively) and three CMS lines; A32, A370 and A110 (Grain yield of 47, 44 and 43 g head-1 respectively) were identified as the suitable restorer and cytoplasmic male sterile line for improvement of new sunflower single cross hybrids. Evaluation of specific combing ability of the resulted combinations will reveal the efficiency of this selection in the following generation.