Efficient Transformation of Catalpa bungei Shows Crystal Genes Conferring Resistance to the Shoot Borer Omphisa plagialis

Although Catalpa bungei is a forest plant with considerable economic and ornamental value in China, its wood and decorative qualities are constrained by insect pests such as the shoot borer Omphisa plagialis (Lepidoptera). Overexpressing insect resistance genes such as crystal genes to develop an insect-resistant variety of C. bungei is an environmental and ecological approach. However, genotype limitations and low regeneration rates of embryogenic calli (EC) inhibit the development of transformation and the insect-resistant gene expression system in C. bungei. Here, we first established embryogenic callus induction and regeneration systems of five genotypes using mature seed and stem segment explants; the highest induction and regeneration rates of EC were 39.89 and 100%, respectively. Next, an efficient and stable Agrobacterium-mediated genetic transformation system was developed from EC and its positive frequency was up to 92.31%. Finally, using the transformation system, 15 and 22 transgenic C. bungei lines that expressed Cry2A and Cry9Aa-like were generated, respectively. These transgenic lines that exhibited significantly higher resistance to O. plagialis in the laboratory and field have great promise for meeting the challenge of future pest management under changing climatic conditions. Additionally, this efficient, fast, and stable transformation system could be a potential tool for gene function analysis and forest tree genetic improvement.

Transgenic and genome-edited fruits: background, constraints, benefits, and commercial opportunities

Breeding has been used successfully for many years in the fruit industry, giving rise to most of today’s commercial fruit cultivars. More recently, new molecular breeding techniques have addressed some of the constraints of conventional breeding. However, the development and commercial introduction of such novel fruits has been slow and limited with only five genetically engineered fruits currently produced as commercial varieties—virus-resistant papaya and squash were commercialized 25 years ago, whereas insect-resistant eggplant, non-browning apple, and pink-fleshed pineapple have been approved for commercialization within the last 6 years and production continues to increase every year. Advances in molecular genetics, particularly the new wave of genome editing technologies, provide opportunities to develop new fruit cultivars more rapidly. Our review, emphasizes the socioeconomic impact of current commercial fruit cultivars developed by genetic engineering and the potential impact of genome editing on the development of improved cultivars at an accelerated rate.

Evaluation of cotton germplasm for morphological and biochemical host plant resistance traits against sucking insect pests complex

Background Sucking insect pests cause severe damage to cotton crop production. The development of insect resistant cotton cultivars is one of the most effective measures in curtailing the yield losses. Considering the role of morphological and biochemical host plant resistance (HPR) traits in plant defense, 12 cotton genotypes/varieties were evaluated for leaf area, leaf glanding, total soluble sugars, total soluble proteins, total phenolics, tannin and total flavonoids against fluctuating populations of whitefly, thrips and jassid under field conditions. Results The population of these insects fluctuated during the growing season and remained above threshold level (whitefly > 5, thrips > (8–10), or jassid > 1 per leaf) during late June and early July. Strong and negative association of whitefly (r = − 0.825) and jassid (r = − 0.929) with seed cotton yield was observed. Mean population of insects were the highest in Glandless-1 followed by NIA-82 and NIA-M30. NIAB-Kiran followed by NIAB-878 and Sadori were the most resistant, with the mean population of 1.41, 1.60, 1.66 (whitefly); 2.24, 2.32, 2.53 (thrips) and 0.37, 0.31, 0.36 (jassid), respectively. The resistant variety NIAB-Kiran showed less soluble sugars (8.54 mg·g− 1), soluble proteins (27.11 mg·g− 1) and more phenolic (36.56 mg·g− 1) and flavonoids (13.10 mg·g− 1) as compared with the susceptible check Glandless-1. Moreover, all insect populations were positively correlated with total soluble sugars and proteins. Whitefly populations exhibited negative response to leaf gossypol glands, total phenolics, tannins and flavonoids. The thrips and jassid populations had a significant and negative correlation with these four biochemical HPR traits. Conclusion The identified resistant resources and HPR traits can be deployed against sucking insect pests’ complex in future breeding programs of developing insect resistant cotton varieties.

Development of marker-free transgenic pigeon pea (Cajanus cajan) expressing a pod borer insecticidal protein

Pigeon pea, a grain legume of the semiarid tropics, is a rich source of high-quality protein. The productivity of this pulse is seriously affected by lepidopteron insect pests. To generate a sustainable insect-resistant plant, synthetically prepared bioactive key constituents of a crystal protein (Syn Cry1Ab) of Bacillus thuringiensis were expressed in pigeon pea under the guidance of a tissue-specific promoter of the RuBP carboxylase/oxygenase small subunit (rbcS) gene. Regenerated transgenic plants with the cry1Ab expression cassette (cry1Ab-lox-bar-lox) showed the optimum insect motility rate (90%) in an in vitro insect bioassay with second instar larvae, signifying the insecticidal potency of Syn Cry1Ab. In parallel, another plant line was also generated with a chimaeric vector harbouring a cre recombinase gene under the control of the CaMV 2 × 35S promoter. Crossing between T1 plants with a single insertion of cry1Ab-lox-bar-lox T-DNA and T1 plants with moderate expression of a cre gene with a linked hygromycin resistance (hptII) gene was performed to exclude the bialaphos resistance (bar) marker gene. Excision of the bar gene was achieved in T1F1 hybrids, with up to 35.71% recombination frequency. Insect-resistant pigeon pea plants devoid of selectable marker genes (syn Cry1Ab- bar and cre-hptII) were established in a consecutive generation (T1F2) through genetic segregation.