JWSS - Journal of Water and Soil Science

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OF2 and VAP genes, probably involved in signal transduction of sugarbeet nematode resistance, have already been cloned in bacterial vector by AFLP molecular marker and a two-hybrid system, respectively. To examine their capability to introduce resistance in sugarbeet, the genes were transferred to plant expression vectors. For this reason, OF2 gene after isolation was inserted within T-DNA of pAM194 binary vector, downstream of CaMV35S constitutive promoter and also inserted within T-DNA of modified pBin121 binary vector, downstream of HS1^pro-1 gene inducing promoter (responsible for nematode resistance). VAP gene after isolation was inserted within T-DNA of pAM194 plasmid, downstream of CaMV35S constitutive promoter. Thus, three new constructs were made in which genes of signal transduction pathway were expressed to give beet cyst nematode resistance. These plasmids were separately transferred to Agrobacterium rhizogenes, strain AR15834. In the next step, petiole explants of sugarbeet were inoculated with the bacterial cells. Transformation-derived hairy roots were analyzed by GUS staining and/or PCR and were then inoculated with nematode larvae. Primary results showed partial resistance against nematode larvae in some hairy roots. As a result, this resistance can be related to OF2 and VAP genes effect.

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The first Iranian hybrid monogerm cultivar of sugarbeet was developed in 2000 after an 8-year period of R&D activity. The cultivar is not only a high yielding variety but enjoys a good resistance to bolting and Sercospora. The study sought to estimate the rate of return to the public investment made to develop this variety, using the economic surplus approach. The results revealed that the investment has got an internal rate of return of 117 percent and that it has produced an exchange saving of $28.7 million. This finding indicates that the investment has been highly productive and that the field suffers underinvestment.

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Due to yield increase, some farmers in Iran plant sugarbeet in 50-cm row spacing instead of conventional 60-cm row spacing. Low row spacings force farmers to harvest three consecutive rows instead of two alternate rows. This would increase the amount of draft requirement to pull the lifter through the soil. In order to use common medium tractors for pulling the three-unit sugarbeet lifter and properly lifting the sugarbeet tubers out of the soil, applying vibration to the shanks of the lifter was taken into considertion. In this study, the effects of vibration frequency and share rake angle of a vibratory lifter on its performance were investigated. Draft, slippage, percentage of broken and non-harvested tubers were determined for four vibration frequencies (0, 9, 10 and 12 Hz) and three share approach angles (11, 24 and 36 deg.), using a factorial experiment arrangement in a randomized complete block design with three replications. The results showed that the variations in draft and slip with frequency and rake angle were similar. Although the minimum value of draft resistance was obtained at 24 deg. of share rake angle with non-vibrated shanks, 50 percent of tubers remained in the soil and were not harvested. However, the non-harvested tubers reduced to only 20 percent when vibration was applied to the lifter. So using the vibrating shanks improved the removal of the tubers out of the soil. A ratio (K) of draft to the harvested tubers (whole and broken tubers) was defined for selecting the optimum combination of the rake angle and vibration frequency. The K ratio was calculated and analyzed for different combinations of the rake angle and vibration frequency. K ratio comparison showed that, for minimizing percentages of broken and non-harvested tubers, the sugarbeet lifter should have share rake angle of 24 deg. and vibrate with frequency of 9 Hz.