The Response of Phenological Stages of Quinoa Promising Lines to Temperature and Photoperiod Regimes

One of the important factors in the adaptation of plants to new environmental conditions is the appropriate response of development stages to temperature and photoperiod regimes. The thermal time, growing degree days (GDD) or heat unit concept is commonly the basis for modeling phenological development in crop models for different common crops and under-utilized crops. The GDD concept describes crop development as a function of temperature accumulation above the base temperature (lower limit) and in some cases below a cut off temperature (upper limit). Evaluation of plant photoperiod sensitivity is often beneficial help to use appropriate cultivars which in turn to ensure cultivation success. Considering that adaptation of quinoa to new regions demands acclimation to appropriate temperature range also day-length, this study aimed to investigation of quinoa response to Yazd weather condition as an arid region to assess the possibility of quinoa cultivation under these conditions.

This research was conducted through 10 separate experiments and were based on a randomized complete block design with three replications. The experimental treatment consisted of five lines (1, 2, 3, 4 and 5), and one cultivar (Titikaka) which belong to different maturing groups including early, middle and late maturing. Ten planting dates selected to be serial as following: March 29, April 29, May 28, June 28, July 26, August 23, September 6, September 20, January 29, and February 29. Every three days, phenological stages of each line including planting distance to each stage of development including emergence, four leaves, flower bud, panicle formation, pollination, seed filling, seed hardening and ripening were recorded accordingly. Using local weather data and equation 1 the needed GDD for every development stage was calculated:GDD= (Tmax-Tmin)/2-T(1)MS-Excel Ver. 15 was employed to arrange recorded data and required calculating. Fitting equations and plotting the graphs were done using Slide Write Ver. 2 and Minitab Ver. 20 software.  

The results showed that the mean of flowering temperature up to seed formation stage was between 25 and 30 °C for five lines and was between 20 and 25 °C in cultivar 6. The mean length of photoperiod for flowering and seed formation stage of these lines was between 12 and 12.5 hours. The relationship between temperature and day length was inversely related to the number of days of flowering stage, i.e., with decreasing day length and increasing temperature, the number of days for flowering stage was increased. The time required for flowering stage, between 20 to 30° C, for the early maturing cultivar was about 35 days, for the middle maturing lines including 1, 2, 3 and 6 was about 40 days and for the late maturing line 4 was about 45 days. At temperatures higher than 30 °C, a decreasing trend was observed in the number of days required for flowering stage. From the budding stage to the end of the growth period, a significant difference in the GDD was observed for the quinoa lines. The GDD of quinoa was the highest (2530 °C) for late maturing line (4) and was the lowest (1805 °C) for the early maturing cultivar. The effect of planting date on the GDD of quinoa lines showed that moving from March planting date to July, there was an increasing trend on the GDD of quinoa lines and by moving from July planting date to October, a decreasing trend was observed.

In general, quinoa is a short-day plant which is affected by the day length from flowering to seed maturity stages. Line 6 responded qualitatively to day length; however, the other lines responses were quantitatively. The study of the simultaneous effect of temperature and day length showed that temperature has a compensatory effect for day length during flowering stage. According to the results, it seems that the most suitable planting date for early lines suggests in September, for middle maturing lines suggests in August and for late maturing lines suggests in August. The results also showed that line 6 is more suitable than other lines for cultivation in cold regions.