Potato Research

A panel of mouse monoclonal antibodies (MAbs) was prepared against potato virus A (PVA) and their reactivity was tested in various types of ELISA. The type of ELISA as well as the methods of MAbs purification played an essential role. All monoclonal antibodies reacted with PVA antigen in IDAS-ELISA but MAbs used in DAS1-ELISA and in DAS2-ELISA, in combination with polyclonal antibodies, showed different reactivity. The reactivity of MAbs in DAS-ELISA was dependent on the individual MAb used as a coating or as a conjugate. Two MAbs showed highest reactivity as coating antibodies but only one of them as a conjugate. The results demonstrate the importance of using different type of ELISA in selecting MAbs for routine diagnosis.

Virus infection is the key constraint to potato cultivation worldwide. Especially, coinfection by multiple viruses could exacerbate the yield loss. Transgenic plants expressing artificial microRNAs (amiRNAs) have been shown to confer specific resistance to viruses. In this study, three amiRNAs containing Arabidopsis miR159 as a backbone, expressing genes targeting P25, HC-Pro and Brp1 of potato virus X (PVX), potato virus Y (PVY) and potato spindle tuber viroid (PSTVd), were constructed. amiR-159P25, amiR-159HCPro and amiR-159Brp1 were cloned into the plant expression vector pCAMBIA1301 with a CaMV35S promoter, producing the p1301-pre-amiRP25−HCPro−Brp1 vector. Twenty-three transgenic plants (Solanum tuberosum cv. ‘Youjin’) were obtained by Agrobacterium tumefaciens–mediated transformation, and ten PCR-positive transplants were chosen for further analysis. Quantitative real-time PCR results indicated that 10 transgenic plants could express amiRNAs successfully. Southern blotting hybridization proved that amiR-159P25−HCPro−Brp1 had integrated into potato genome in transgenic lines. Viral (viroid) challenge assays revealed that these transgenic plants demonstrated resistance against PVX, PVY and PSTVd coinfection simultaneously, whereas the untransformed controls developed severe symptoms. This study demonstrates a novel amiRNA-based mechanism that may have the potential to develop multiple viral resistance strategies in potato.

Modified cry1Ca5 and cry1Ba1 genes, under the transcriptional control of a CaMV 35S promoter, were individually transferred into potato (Solanum tuberosum L.) cv. Iwa using Agrobacterium-mediated transformation. Thirty-six and thirty-eight independently derived cry1Ca5- and cry1Ba1-transgenic plants were regenerated respectively. Multiplex-PCR confirmed the presence of the nptII selectable marker gene and the specific cry gene in all regenerated lines. In greenhouse experiments, approximately 90% of each transgenic population produced phenotypically normal plants. More than 90% of the cry1Ca5-transgenic lines gave 100% larval mortality of potato tuber moth (PTM), Phthorimaea operculella (Zeller), on excised greenhouse-grown leaf and tuber bioassays. In contrast, only 40–50% of the cry1Ba1-transgenic lines gave 50 to 100% of larval mortality of PTM using the same bioassays, although all lines except one significantly inhibited larval growth. Southern blot analysis for eight selected cry1Ca5-transgenic lines revealed that they contained 1 to 6 copies of the cry gene. The amount of Cry1C protein, quantified by ELISA, ranged from 0.26 to 8.42 μg per g of leaf tissue and from 0.23 to 1.02 μg per g of tuber tissue. No relationship was apparent between cry1Ca5 gene copy number and amount of Cry protein expressed in leaves and tubers. Southern blot analysis for seven selected cry1Ba1-transgenic lines revealed that they contained 2 to 8 copies of the cry1Ba1 gene. Both the cry1Ca5 and cry1Ba1 genes offer additional sources of resistance that can be deployed with other effective cry genes to control tuber moth in potatoes.

Two hundred primary dihaploids (2n=2x=24) were obtained relatively easily from Dutch varieties and breeding stocks of the potato (2n=4x=48). Male fertility is rare in primary dihaploids but increases rapidly with further crossing. It is thus possible to inbreed and cross-breedSolanum tuberosum at the diploid level. Tetraploids were obtained by colchicine treatment. Tetraploids were also obtained by backerosses of dihaploids with tetraploids.

Progenies from crosses between cultivars varying widely in resistance to early blight (Alternaria solani Sor.), were assessed for resistance as true seedlings in a glasshouse in Scotland. The resistance of a representative sample of surviving genotypes from each progeny was compared with samples of the same progenies not previously exposed to the fungus, both in the glasshouse in Scotland and in the field in Israel. The exposed population was more resistant. Resistance was identified more effectively in adult plants from tubers in the glasshouse than in true seedlings and agreement between glasshouse and field assessment was better when progenies were compared rather than individual genotypes. The mid parent and progeny mean scores of the unexposed population were correlated at both sites, thus confirming that the resistance is heritable. Selecting resistant individuals at the seedling stage is suggested as a useful tool for resistance breeding, having first chosen the best parents for crossing.

Young seed tubers of several cultivars were exposed to storage temperatures of 4–24°C in light and dark intended to optimise their growth vigour following early plantings. In five experiments during four autumn and winter periods, the effects of storage conditions on subsequent initial plant development in the glasshouse were studied. Storage of seed potatoes for 2 months at temperatures of 12°C or higher greatly increased early plant development of five cultivars following early plantings. Light during storage had a favourable effect, but desprouting before planting was greatly disadvantageous.

The potato leafroll virus (PLRV) coat protein (CP) gene was directly cloned from the total RNA extracted from virus-infected plants. First strand cDNA synthesis was not necessarily specific; it was equally efficient using either random or CP-specific primers. The viral sequence encoding the coat protein was specifically amplified from the total population of cDNA molecules by polymerase chain reaction (PCR), using specific primers bordering the CP gene. The unique amplified product thus obtained was cloned blunt-end into the pT7T318U plasmid vector, and the authenticity of the cloned gene verified by sequence analysis. This cloning strategy obviates the need for virus purification. Sequence comparison of the CP gene of the Italian isolate and those of five other PLRV isolates revealed a close similarity to the three European and the Canadian isolates, and a more distant relationship with the Australian one.

Các khảo sát thực địa trên 2600 cây trong quá trình phát triển của vụ thu mùa và 1700 cây của vụ xuân cho thấy tỷ lệ cây bị bệnh héo do Fusarium lần lượt là 6.5% và 4.0%; trung bình, 40% củ từ các cây bị héo bị nhiễm bệnh. Các kết quả tương tự đã được thu nhận trong một ruộng được nhiễm bệnh nhân tạo. Kiểm tra 6105 vị trí trồng trong ruộng trong quá trình phát triển của vụ thu mùa cho thấy 28.7% củ giống bị thối là do Fusarium oxysporum f.sp.tuberosi gây ra, trong khi ở vụ xuân tỷ lệ này thấp hơn nhiều. Năng suất trong một ruộng được tiêm nhiễm nhân tạo giảm từ 10% đến 53% so với ruộng đối chứng, tùy thuộc vào giống.