Effects of Foliar Application of Methanol on Yield and Yield Components of Two Cultivars of Canola (Brassica napus L.) under Rainfed Conditions

Canola (Brassica napus L.) is an annual plant of the Brassicaceae or Cruciferae family and is regarded as an important oil seed crop in the world. Water deficiency is one of the most limiting factors for plant growth and production in dry regions. The positive effects of methanol application on growth and yield of C3 plants under drought stress are well documented. Methanol can rapidly metabolize to water and CO2 in plant tissues and can affect dry matter accumulation by decreasing photorespiration. The foliar application of methanol also can stimulate the methyltrophic bacteria, indirectly. Methyltrophic bacteria usually live on plant leaves and consume some of the methanol on the leaves and affect plant growth via the production of different plant growth regulators such as auxin and cytokine.
To evaluate the effects of foliar application of methanol on yield and morpho-physiological characteristics of rapeseed cultivars under rainfed conditions a split plot experiment was conducted based on randomized complete block design (RCBD) with four replications. Experimental treatments were two cultivars of canola (Hayola 401 and Delgan) and four levels of methanol foliar application (control, 5, 10 and 15% of volume), respectively. In the stage of stem elongation, foliar application of methanol repeated 2 times with 10 days interval. At maturity, the plant height and number of lateral branches were measured. At the end of growth season, the plants were harvested by hand-cutting at the soil surface and subsequently, the number of pod per plant, number of seed per pod, 1000 seed weight, seed yield and aboveground biological yield of canola were determined.
The results showed that the effects of experimental treatments on plant height and numbers of lateral branches were significant. There was no significant different between cultivars for 1000 seed weight. For all of the studied traits Hayola 401 was better than Delgan cultivar. The highest amounts of 1000 seed weight, pod number per plant, seed number per pod, number of lateral branches and plant height were observed in treatment with 10% methanol. According to the results, the effect of experimental treatments and also the interaction of these treatments on the seed yield, biological yield and also harvest index were significant. The highest and lowest seed yield were observed in Hayola 401 cultivar treated with 10% methanol (1114 kg ha-1) and Delgan cultivar in the control condition (785 kg ha-1), respectively.
For all of the studied traits, the performance of Hayola 401 cultivar was better than Delgan cultivar. Although foliar application of methanol has positive effects on studied traits but the relationship between the dose of application and observed response was not linear and the highest amounts of seed yield, number of pod per plant, number of seed per pod, number of produced lateral branches and plant height were obtained in 10% (V/V) methanol. Therefore, application of methanol in concentrations higher than 10% is not recommendable.