Development of biotic stress resistant F1 interspecific hybrid rootstock derived from Solanum lycopersicum and Solanum habrochaites

Tomato is major horticultural plant consumed worldwide. Biotic stress (nematodes, fungus and bacteria) has negative effect on tomato production due to causing reduced yield or plant death. Rootstocks confer resistance to soil-borne pathogen are considered the most effective and environment friendly approach for such a stress management. Thus, development of genetic resources having multiple resistance genes is essential for sustainable tomato breeding. Solanum habrochaites is one of the most studied wild tomato species due to its high genetic potential for biotic and abiotic stresses. In the present study, rootstock potential of an interspecific F1 hybrid derived from S. habrochaites was evaluated as using resistance genes (Frl, I-2, I-3, Mi-3, Pto Ty-1, Ty-3 and Sw-5) specific molecular markers for 6 major tomato diseases and 31 fruit quality traits. The study reported that F1 hybrid had resistance alleles for 5 genes (Frl, I-2, I-3, Pto and Sw-5) confer resistance to fusarium crown rot disease, crown – root rot disease, race 2 and 3 of Fusarium oxysporum f. sp. radicis lycopersici, bacterial speck and tomato spotted wilt virus (TSWV), respectively. Despite high performance of F1 hybrid for biotic stress, the study pointed S. habrochaites specific graft incompatibility due to poor rate of grafting efficiency, small fruit formation and low yield. This is the first comprehensive study evaluated the horticultural performance of an interspecific hybrid in tomato.

Introgression of the sesquiterpene biosynthesis from Solanum habrochaites to cultivated tomato offers insights into trichome morphology and arthropod resistance

Main conclusion Cultivated tomatoes harboring the plastid-derived sesquiterpenes from S. habrochaites have altered type-VI trichome morphology and unveil additional genetic components necessary for piercing-sucking pest resistance. Abstract Arthropod resistance in the tomato wild relative Solanum habrochaites LA1777 is linked to specific sesquiterpene biosynthesis. The Sesquiterpene synthase 2 (SsT2) gene cluster on LA1777 chromosome 8 controls plastid-derived sesquiterpene synthesis. The main genes at SsT2 are Z-prenyltransferase (zFPS) and Santalene and Bergamotene Synthase (SBS), which produce α-santalene, β-bergamotene, and α-bergamotene in LA1777 round-shaped type-VI glandular trichomes. Cultivated tomatoes have mushroom-shaped type-VI trichomes with much smaller glands that contain low levels of monoterpenes and cytosolic-derived sesquiterpenes, not presenting the same pest resistance as in LA1777. We successfully transferred zFPS and SBS from LA1777 to cultivated tomato (cv. Micro-Tom, MT) by a backcrossing approach. The trichomes of the MT-Sst2 introgressed line produced high levels of the plastid-derived sesquiterpenes. The type-VI trichome internal storage-cavity size increased in MT-Sst2, probably as an effect of the increased amount of sesquiterpenes, although it was not enough to mimic the round-shaped LA1777 trichomes. The presence of high amounts of plastid-derived sesquiterpenes was also not sufficient to confer resistance to various tomato piercing-sucking pests, indicating that the effect of the sesquiterpenes found in the wild S. habrochaites can be insect specific. Our results provide for a better understanding of the morphology of S. habrochaites type-VI trichomes and paves the way to obtain insect-resistant tomatoes.

Response of whitefly to the wild tomato Solanum habrochaites

The whitefly Bemisia tabaci (Gennadius) causes severe damage to cultivated tomato in many regions of the world through direct feeding and indirectly through transmission of plant viruses. Field observations show that B. tabaci is rarely infested the non-host plants such as the wild tomato Solanum habrochaites; however, the molecular mechanism involved in the recognition of wild plant odors is still unclear. In this study, we assessed the effects of S. habrochaites on the survival, fecundity, and egg hatchability of the Mediterranean (MED) species of B. tabaci. Expression and splicing of stress-response genes in whitefly exposed to S. habrochaites was analyzed using RNA-sequencing data and alternative splicing analysis. These results indicated that the S. habrochaites treatment can induce the expression of environmental stress genes in B. tabaci. This study may help us to a better understanding of the molecular mechanisms involved in the olfactory recognition of non-host volatiles particularly wild tomato relative. Furthermore, the findings of this study may provide excellent chances of finding a suitable antagonist of eco-friendly properties which can block the perception of chemosensory signals. Thereby, the feeding behavior and food preferences of B. tabaci can be manipulated and thus insect populations can eventually be controlled.

Dissecting the Genotypic and Environmental Factors Underpinning the Quantitative Trait Variation in a Set of Wild Tomato (Solanum habrochaites LA1777) Introgression Lines

Exotic libraries have proven a powerful tool for the exploitation of wild relatives and quantitative trait loci (QTLs) detection in crop species. In early 2000, an introgression line (IL) population of the wild tomato Solanum habrochaites (SH) acc. LA1777 was developed and made publicly available. Despite the potentiality of the donor parent, so far, these lines have been poorly explored for their agronomic performance and for the identification of genomic regions underlying the variation of quantitative traits (QTLs). Here, we report the evaluation of 19 morpho-agronomic and chemical traits on a set of 39 ILs grown in three consecutive field seasons with the aim to: (a) Determine the overall phenotypic performances of the studied collection, (b) estimate the influence of the genotype (G) and the year of cultivation (Y) and their interaction on the traits analyzed, (c) investigate the plasticity of the traits, and (d) identify whole-genome QTLs in the wild SH background. The ILs showed lower productivity compared to the control genotype, while no major effects were found for the morphological fruit-related traits. Instead, a general increase in the soluble solids content was observed. The combined analysis of G × Y highlighted a major effect of the genotype on trait variation, although yield-related traits were more influenced by environmental factors. In total, 75 associations for 17 traits were detected. Major QTLs increasing soluble solids, pericarp thickness, and trichome density were respectively found on chromosomes 1, 5, and 11 with a percentage variation (PV) of 24.01%, 32.49%, and 200%. Furthermore, different QTLs increasing the color intensity and fruit shape were detected. These results suggest that SH could be a potential source of favorable alleles for qualitative traits despite its inferior phenotype compared to the cultivated parent. The evaluated set of SH LA1777 ILs is a potential for novel allele discovery in wild tomatoes and for breeding purposes towards the exploitation of the available introgressions and for the pyramiding of traits.

Molecular diagnosis of phytoplasma infection in some Moldavian tomato varieties

Relevance. The use of molecular methods allows reliable and fast determination of the resistance of genotypes (varieties) to pathogens, thereby reducing possible product losses and, at the same time, maintaining its environmental safety. It is very important in conditions of increasing demand for high-quality agricultural production. Aim: Using molecular diagnosis of ʹCandidatus Phytoplasma solaniʹ to compare the degree of infection in some Moldavian tomato varieties at different stages of plant development.Material and methods. The molecular analysis (nested-PCR) of plants of the four Moldavian tomato varieties (Elvira, Cerasus, Mary Gratefully, Desteptarea) created at the Institute of Genetics, Physiology and Plant Protection, and the wild formSolanum habrochaites, was carried out for the presence of the phytopathogen ʹCa. P. solaniʹ. Researches were made during two growing seasons. Results. The distribution of infection between the studied varieties was different in the process of plants development. The spread of infection in the tomato field was recorded under the climatic conditions of two growing seasons: the season of 2018, which was hot but with normal rains in the middle of summer, and the season of 2019, in conditions of a very hot and dry summer. During both seasons, Cerasus variety manifested the highest resistance to ʹCa. P. solaniʹ infection. A little more than half of plants of this variety were affected by stolbur only at the end of the growing season, after harvesting most of the crop. Varieties Elvira and Desteptarea had similar levels of infection of plants with phytoplasma during two years of research. These varieties manifested a higher sensitivity to phytoplasma infection compared with Cerasus. Mary Gratefully was the genotype with the highest dependence of the sensitivity toʹCa. P. solaniʹ infection from the climatic conditions of the growing season. Plants of the wild form Solanum habrochaites demonstrated complete immunity to phytoplasma infection during the growing season. Conclusion.The Cerasus variety, as well as the wild form Solanum habrochaites, can be recommended for including in breeding programs for the creating tomato varieties or hybrids resistant to phytoplasma. Thus, molecular diagnosis may be a useful tool for the breeding resistant genotypes.

Tổng hợp 2-methylketone nhờ cải biến biến dưỡng tế bào vi khuẩn

2-Methylketone là chất tạo hương quan trọng trong ngành công nghiệp thực phẩm và mỹ phẩm. Ở thực vật, 2-Methylketone chủ yếu có vai trò giúp cây trồng đối kháng với sâu hại. Gần đây, 2-Methylketone còn được xem là nguồn nguyên liệu tiềm năng cho sản xuất năng lượng sinh học. Việc khám phá ra hai gene methylketone synthase 1 (ShMKS1) và methylketone synthase 2 (ShMKS2) mã hóa cho hai enzyme chính tham gia trong sự sinh tổng hợp methylketone ở loài cà chua dại Solanum habrochaites và những gene tương đồng với chúng ở một số loài thực vật khác đã tạo nguồn gene cho nghiên cứu cải biến vi sinh vật nhằm tạo ra những chủng mới có khả năng sinh tổng hợp methylketone. Trong bài báo này, một số kết quả đạt được bước đầu trong nghiên cứu kỹ thuật biến dưỡng (metabolic engineering) hướng đến tối ưu hóa khả năng sản xuất methylketone nhờ vi khuẩn được cập nhật và phân tích. Trên cơ sở đó, chúng tôi bàn luận về những cơ hội và thách thức đi kèm, đồng thời thảo luận về một số đề xuất cải tiến cho các nghiên cứu tiếp theo.

Two novel 7-epi-zingiberene derivatives with biological activity from Solanum habrochaites are produced by a single cytochrome P450 monooxygenase

Secretions from glandular trichomes potentially protect the plant against a variety of aggressors. In the tomato genus, wild species constitute a rich source of chemical diversity produced at the leaf surface by glandular trichomes. Previously, 7-epi-zingiberene produced in several accessions of Solanum habrochaites was found to confer resistance to whiteflies (Bemisia tabaci) and other insect pests. Here, we identify two derivatives of 7-epi-zingiberene from S. habrochaites that had not been reported as yet. We identified them as 9-hydroxy-zingiberene and 9-hydroxy-10,11-epoxyzingiberene. Using a combination of genetics and transcriptomics we identified a single cytochrome P450 oxygenase, ShCYP71D184 that carries out two successive oxidations to generate the two sesquiterpenoids. Bioactivity assays showed that only 9-hydroxy-10,11-epoxyzingiberene exhibits substantial toxicity against B. tabaci. In addition, both 9-hydroxy-zingiberene and 9-hydroxy-10,11-epoxyzingiberene display substantial growth inhibitory activities against a range of microorganisms, including Bacillus subtilis, Phytophtora infestans and Botrytis cinerea. Our work shows that trichome secretions from wild tomato species can provide protection against a wide variety of organisms. In addition, the availability of the genes encoding the enzymes for the pathway of 7-epi-zingiberene derivatives makes it possible to introduce this trait in cultivated tomato by precision breeding.