Water is a main factor in agriculture activities and almost 70 percent of world water resources are consumed in agriculture. The present research has been done to investige response of Citrus rootstocks to drought as factorial test based on randomized completely design with three replications. Factors included rootstocks in 10 levels [Poncirus (PT), Troyer citrange (TC),Citrumello (CR),Sour orange (SO),Cleopatra mandarin (CM), Rough Lemon (RF), Bakraii (B), Chang-sha (CH), Machrophylla (M) and Mexican Lime (ML)] and irrigation in two levels [optimum irrigation (fixed in field capacity) and withholding irrigation]. Results showed that drought induced increament of ion leackage percentage in all of the rootstocks and  the root to shoot dry weight ratio in PT, M and B and decrease of leaf water relative content in all of the rootstocks, leaf fresh weight in SO, stem fresh weight in CR, root fresh weight in TC, SO, CR and M, shoot fresh weight in SO and CR, total fresh weight in SO, CR and M, root to shoot fresh weight ratio in TC, CR, M and CM. Therefore, TC, CH and PT had good tolerance to drought because of lower ion leackage in TC, higher water storage in CH leaves and the higher root to shoot dry weight ratio in PT.

Vegetative reactions of six citrus different rootstocks (Swingle citromelo; Troyer citrange; Carizo citrange, C-35; Smooth flat sevill and Gou tou) and their effect on early mature Miyagawa Satsuma mandarin was evaluated during 8 years (2010-2017). Experiment was done in randomized complete block design with 4 replications and 4 trees in each replication. Results showed that after vegetative phase (third year) trees on Gou tou had the least canopy volume and height but in the last three years, trees on C-35 had minimum volume and height. In contrast, trees on Swingle citromelo rootstock had the most canopy volume. The most rootstock trunk cross-sectional area (TCSA) and girth was related to Swingle citromelo and the most mandarin trunk girth and TCSA was on Smooth flat sevill. Results of rootstock and scion affinity showed that in Smooth flat sevill it was more than 1, in citranges it was about 1 and in Swingle and Gou tou it was less than 1. Rootstock TCSA had the most correlation with canopy volume and scion trunk girth had the most correlation with canopy height and width; so these can be used to estimate the canopy volume.

In this study, the effects of six citrus rootstocks: Swingle citromelo; Troyer citrange; Carizo citrange, C-35 citrange; Smooth flat sevill and Gou tou) on reproductive reactions of Miyagawa Satsuma mandarin was investigated during 5 years (2013-2017). Experiment was done in randomized complete block design with 96 trees. Results showed that trees on Swingle citromelo at the beginning of fruiting phase (2013 and 2014) was more productive (58 and 48 kg/tree respectively) than other rootstocks and they had the most annual mean yield (52 kg/tree), cumulative yield during 5 years (261 kg/tree) and minimum alternate bearing index (22.1%), statistically. Also, cold tolerance in this rootstock was more than others due to maintaining the flower and fruit and high final yield in the year after the frost (2014). Annual mean yield and cumulative yield during five years on Citranges (Troyer, Carizo and C-35) and Smooth flat sevill was statistically similar. But, the highest yield efficiency was obtained on C-35 (6.72 kg/m3). Fruits on Swingle citromelo, were more spherical (length/width: 0.953) and juicy (46.22%), on Carizo were more oblate (length/width: 0.939) and thinned peel (2.21 mm) and on C-35 were heavier (150.2 g) and more premature (harvest index: 11.21) than fruits on other rootstocks. Gou tou significantly increased the thickness of the peel (2.83 mm), reduced fruit juice (41.65%) and extended fruit ripening time (harvest index: 8.52). Also, trees on Gou tou had the highest alternate bearing index (42.4%) during five years.

The diversity of cultivars is very important for the sustainable production of citrus. Also, there is little information about the effect of common sour orange substitute rootstocks on new cultivars. The present research was conducted to investigate the vegetative growth of six navel orange cultivars ('Fucumoto'; 'Navelina'; 'Navelate'; 'Thomson navel'; 'Cara cara' and 'Lane late navel') on three poncirus hybrids rootstocks ('Carrizo citrange'; 'Swingle citrumelo' and 'C-35 citrange'), during seven years. Traits related to vegetative growth such as tree volume, rootstock and scion morphological compatibility, leaf nutrient concentration and tree survival were measured. All measured vegetative traits were affected by year, rootstock and cultivar. The rootstocks affected the concentration of all nutrients in the leaves. Tree height and volume and the required area for orange trees on the 'Carrizo citrange' were less than the other two rootstocks. 'Navelate' and 'Lane late navel' cultivars had the highest and 'Fukumoto' had the lowest tree volume. The compatibility of the graft union decreased with the increasing age of the trees. In the last year, there was the lowest compatibitity between 'Fukumoto' cultivar and 'citrumelo' rootstock (0.60) and the highest between 'Navelate' cultivar and 'Carrizo citrange' rootstock (0.77). One tree of 'Fukumoto' and 'Navelina' with 'C-35' rootstock declined in the last year of the experiment, but other rootstocks and cultivars did not show any signs of yellowing. The maximum area required for seven-year-old trees of 18 studied rootstock and cultivar combinations with regular annual pruning was about 9.5 m2, which was recorded in 'Navelate' cultivar on 'C-35 citrange' rootstock.

Today, the existence of various biotic and abiotic stresses has necessitated research with different rootstocks in different climatic and soil conditions. So, the growth trend and some characteristics of Miyagawa Satsuma mandarin on Swingle citrumelo rootstock in alluvial and piedmont plain in East Mazandaran during 10 years were evaluated. The results showed that the trees on this rootstock were vigorous and had high yield (62 kg per tree). The affinity of scion and rootstock in both locations was 0.8. The tree canopy volume at the end of the experiment was 19.09 in alluvial and 11.62 m3 in piedmont plain. So it is recommended to increase the number of alluvial and piedmont plain trees to more than 600 and 800 plants/hectare, respectively. Despite several frost stresses during 10 years, the survival of rootstock and scion compound was 100 % in both locations, however, the piedmont trees entered the alternate bearing cycle as at the end of the experiment, the trees alternate bearing index was 0.23 % in alluvial and 0.67 % in piedmont plain. The best harvest time for both locations was early October. Fruits of the alluvial plain had more weight and extract (7.6 g and 5.8 %), smoother peel, and higher harvest index (1.64 units); In contrast, fruits of the piedmont was more oblate and had thicker peel (0.35 mm) and higher peel weight, sugar, total acid and vitamin C (8.7, 25, 62 and 28.6 %, respectively). In general, the trees in alluvial location had higher visual quality fruits and a more regular and stable annual yield.