CHARACTERIZATION OF COFFEE CULTIVARS LEAF RUST-RESISTANT SUBJECTED TO FRAMEWORK PRUNING

The goal of our work was to evaluate physiological and agronomic traits, as well as the relationship between these traits in coffee cultivars coming from a germplasm supposedly resistant to leaf rust, and their response to framework pruning. The experiment was conducted at the Federal University of Lavras in randomized blocks with three replicates, with spacing of 3.5 x 0.7 m and plots of 12 plants. An amount of 25 coffee cultivars was evaluated, from which 23 were considered resistant and two susceptible to leaf rust. Traits analyzed were the plagiotropic branch length and number of nodes, net photosynthetic rate, transpiration rate, water use efficiency, fluorescence and chlorophyll index, leaf area index, leaf rust incidence and yield. Catucaí Amarelo 20/15 cv 479, Araponga MG1 and Tupi IAC 1669-33 cultivars show highly responsive to framework pruning. These cultivars have high yield associated to high net photosynthetic rate, water use efficiency and low transpiration rate. Moreover, the last two cultivars show a low incidence of leaf rust. The Acauã cultivar has a good response to framework pruning, showing high yield associated to lower incidence of leaf rust. Catucaí Vermelho 785/15 cultivar is not responsive to framework pruning because show lower yield, high incidence of leaf rust, low vegetative growth and low water use efficiency.

A randomized block design was used with three replicates and plots of 12 plants.Spacing was 3.5 m between rows x 0.70 m between plants.
Framework pruning was performed in September 2014.Posteriorly, the reduction of orthotropic stem was made at 2 meters of soil, with a single budding top at the terminal portion of plants.
To evaluate the physiological traits were used leaves in the third node from the apex of the branch, in the middle third of the plant.They were free from pest and disease attack, nutritional deficiencies and environmental stresses.The evaluations were performed nine months after framework pruning in June 2015, at the end of the vegetative period, beginning at 8 a.m. and ending at 11 a.m.
Leaf area index (LAI) was determined according to the methodology proposed by Barbosa et al. (2012).
recovering the vegetative vigor of these plants over the years.
Framework pruning is a technique that consists of the removal of a large terminal portion of all plagiotropic branches and is considered a relatively drastic operation because it reduces a large portion of shoot and consequently of root system (QUEIROZ-VOLTAN et al., 2006).Therefore, for the adequate application of this technique, it is necessary to associate the use of appropriated cultivars with a correct management in order to increase yield, in the short term, in relation to the free growth.
Therefore, the use of techniques to improve conventional selection methods of coffee plants is extremely important, favoring the identification of cultivars that are more productive and responsive to management practices, especially pruning usually employed in crop management.
It should also be considered that physiological studies have been highlighted as important ways for optimizing breeding studies (BATISTA et al., 2010).Moreover, agronomic traits associated with physiological methods allow identifying cultivars with favorable aspects to growth and development vegetative and productive.
Thus, the goal of our work was to evaluate physiological and agronomic traits, as well as the relationship between them in coffee trees cultivars originating from germplasm supposedly resistant to leaf rust and their response to framework pruning.

MATERIAL AND METHODS
The experiment was conducted at the Department of Agriculture, Federal University of Lavras, MG, Brazil, from August 2014 to July 2016.
Physiological and agronomic traits were evaluated in 25 Coffea arabica L. cultivars developed by the main genetic improvement programs in Brazil.The selected cultivars developed by PROCAFÉ with their respective source materials were: Catucaí Amarelo 2 SL (Icatu x Catuaí), Catucaí Amarelo 24/137 (Icatu x Catuaí), Catucaí Amarelo 20/15 cv.479 (Icatu x Catuaí), Catucaí Vermelho 785/15 (Icatu x Catuaí), Catucaí Vermelho 20/15 cv.476 (Icatu x Catuaí), Sabiá 398 (Catimor x Acaiá), Palma II (Catimor x Catuaí), Acauã (Sarchimor x Mundo Novo).The selected cultivars developed by EPAMIG were Oeiras MG 6851 (Caturra Vermelho (CIFC 19/1) The plagiotropic branch length (cm) was evaluated in June 2015, at the end of the period of vegetative development and differentiation of buds for later production.An evaluation was performed using a graduated ruler by measuring three branches (lower, middle and upper third) on each side of the plant, with measures from the apex to the base of the branch developed after pruning, disregarding the first plagiotropic branch.
Leaf rust incidence was evaluated monthly through leaf sampling collected in the middle third of the third and fourth pairs of leaves from the plagiotropic branches, totaling 100 leaves per plot from December 2015 to March 2016.It was determined as a percentage, counting the number of leaves with sporulated pustules.
Harvesting was performed in the first production after framework pruning in all plants.It was made the measured in liters of harvested coffee and divided by the number of plants to obtain the average production (liters/plant).There was extrapolation (liters of coffee harvested/plot) and then conversion to 60 kg bags of processed coffee/ha through actual yield, calculated according to Moraes (2013) using a sample of four liters of coffee.
The statistical analyses were performed using the R software version 3.3.1(RCORE TEAM, 2016).

RESULTS AND DISCUSSION
For net photosynthetic rate (   According to Rezende et al. (2014), leaf area is related to yield crop.The estimated leaf area index is a central component of crop growth models, as well as for yield prediction (POCOCK; EVANS; MEMMOTT, 2010;WHITE et al., 2010).The results of our work corroborate partially with those found by these authors, since the cultivar Catucaí Amarelo 20/15 cv.479 showed higher leaf area index values and yield, showing that this parameter is a good indicator for predicting the yield of this cultivar.For the cultivars Catucaí Amarelo 2 SL,Catucaí Amarelo 24/137,Catucaí Vermelho 20/15 cv. 476,Sabiá 398,Catiguá MG 1,Pau Brasil MG 1,IPR 99,IPR 103 and IPR 104, the leaf area index was directly related to the growth of plagiotropic branches (TABLE 1).
Plagiotropic branch length was higher in the following cultivars: Catucaí Amarelo 2 SL, Catucaí Amarelo 24/137,and Catucaí Vermelho 20/15 cv. 476,Sabiá 398,Catiguá MG 1,Sacramento MG 1,Catiguá MG 2,Pau Brasil MG 1,IPR 99,IPR 103 and IPR 104 (TABLE 1).Carvalho et al. (2010) found that phenotypic traits such as number of plagiotropic branches, plant height and plagiotropic branch length showed high correlation with yield.These results do not corroborate with those observed in our work, once cultivars with great plagiotropic branch length showed low relationship with the highest yield observed (TABLE 1).This may occur because most of the cultivars with great plagiotropic branches had a higher leaf area index (TABLE 1), indicating an investment in vegetative growth in detriment to the reproductive growth.
The performance of certain cultivars after framework pruning was already evaluated in some studies.Carvalho et al. (2013) observed a satisfactory response to this pruning in progenies derived from the cross between Mundo Novo and Catuaí.Silva et al. (2016) analyzed the recovery capacity of four and a half years old coffee cultivars after framework pruning and verified that the Sabiá 398, Topázio MG1190 and Catiguá MG3 highlighted in the first biennium after pruning.
Carbon availability from the photosynthetic process for plant growth can be increased due to increasing photosynthesis depending on nutrient availability and the growth capacity of each species (KIRSCHBAUM, 2011).Photoassimilates produced along this process can be mainly redirected to the growth of reproductive organs such as beans (DING et al., 2007), resulting in higher yield and/or directed to vegetative organs such as leaves, stems and roots (COVRE et al.

2016), reflecting higher vegetative growth.
A different behavior of redirecting photoassimilates was observed in the cultivars that showed high net photosynthetic rates (TABLE 1).According to Covre et al. (2016), the reproductive growth of Coffea canephora limited the vegetative growth.The results found in the present work corroborate with this assertion for cultivars with the largest yield, 'Acauã', 'Araponga MG 1' and 'Tupi IAC 1669-33', which showed lower vegetative growth, with small plagiotropic branch length and leaf area index in relation to others cultivars.Thus, it can be suggested that these cultivars may be a good option for the zero-crop system, in which cultivars are pruned again after harvesting, since they would possibly exhibit low yields in the following year due to their low vegetative growth.
The cultivar Catuaí Amarelo 20/15 cv.479, which belongs to the group with higher yield, also obtained higher average values for leaf area index (TABLE 1).Therefore, this cultivar can be a good cultivar for management in which a programmed pruning system or pruning in longer cycles is used due to high vegetative growth combined with yield.
The cultivars that showed lower yield were: Catucaí Vermelho 785 /15, Catucaí Vermelho 20/15 cv. 476, Sacramento MG1, Obatã 1669-20, IPR 98, Catiguá MG 3 and Catuaí Vermelho IAC 144 (TABLE 1).When was compared the net photosynthetic rate (A) with vegetative growth (PBL and LAI) and yield, it was found that, for these cultivars, targeting of photoassimilates may have predominated for vegetative organs.This is true, for example, for Catucaí Vermelho 20/15 cv.476, Sacramento MG1 and Obatã 1669-20.In addition, the photoassimilates production may have be insufficient for vegetative growth and a satisfactory yield, which is the case of Catucaí Vermelho 785/15, IPR 98, Catiguá MG 3 and Catuaí Vermelho IAC 144 cultivars. Campostrini and Maestri (1998) performed studies comparing photosynthesis and yield of five coffee genotypes (C.canephora), observed that all genotypes showed the same photosynthetic efficiency, but obtained different yield levels, showing that the difference between these two variables may not be correlated.Carvalho et al. (2012) found that, among leaf rust-resistant coffee plants, the Catucaí Vermelho 785/15 cultivar showed yield below 44.9% in relation to the average of four crops from superior cultivars in the studied sites, and were not pruned.Such research corroborates with the results obtained in the present work, being that this cultivar showed a decreased yield of 66% in relation to the average of the group from superior cultivars after the first production after pruning.
There are also reports of the occurrence of resistance breakdown by new races in cultivars previously considered as leaf rustresistant, including those originated from Catimor germplasm (VARZEA et al., 2002).Carvalho (2011) verified that the Oeiras MG 6851 cultivar, released as leaf rust-resistant, show high susceptible to the disease, in addition to high deterioration and lower vegetative vigor.
Plants from the 'Híbrido de Timor' have at least the major genes SH 5 to SH 9 (BETTENCOURT; LOPES; PALMA, 1992).Besides these ones already identified, it is likely that other genes will be present in these genotypes (VARZEA;MARQUES, 2005), conferring greater resistance to the materials coming from this crossbreed.
Observing the relationship between leaf rust-incidence and yield in coffee can be suggested that even cultivars that showed high or low disease incidence obtained different yields (TABLE 1).This fact can be explained due the fact that most part of studied materials showed leaf rustresistance genes.Therefore, the leaf rust-incidence (fungal sporulation) may have occurred when the fruits already showed satisfactory fruiting filling, not influencing the leaf area index that could compromise the photoassimilates production that would be directed to fruit development.The high disease incidence affects mainly the production of the following year, since the loss of leaves decreases photoassimilates production and consequently the yield.This fact was verified in the present work, in which the annual yield was not compromised.

CONCLUSIONS
Cultivars such as Catucaí Amarelo 20/15 cv.479, Araponga MG1 and Tupi IAC 1669-33 are highly responsive to framework pruning because they show high yield associated to high net photosynthetic rate and low transpiration rate.Moreover, the last two cultivars have a low leaf rust-incidence.The Acauã cultivar shows a good response to this pruning, showing high yield associated to the lower leaf rust-incidence.
Catucaí Vermelho 785/15 cultivar is not responsive to framework pruning showing lower yield, besides high leaf rust-incidence and low vegetative growth.
a 1.20 c 9.33 b 3.93 b 45.67 a 77.c 0.45 d 15.79 a 4.22 a 38.33 b 69.70 b 39.47 a Catucai Vermelho IAC 144 8.89 b 0.84 d 9.97 b 3.66 b 41.33 b 46.73 c 41.33 a Means followed by the same letter in columns do not differ by the Scott-Knott test at 5% probability.

TABLE 1 )
Carvalho et al. (2014)he highest averages were obtained by 'Acauã' and 'Catucaí Vermelho 785/1' (TABLE1).Transpiration is the loss of water vapor by plants, occurring mostly through the diffusion of water vapor through the stomata.In situations of water abundance, there is high water loss by transpiration, since water supply is constant, which is advantageous for the production of photoassimilates.However, when soil water is less abundant, the stomata will open less or remain closed to avoid plant dehydration (TAIZ; ZEIGER, 2013).The plant efficiency in managing water loss while allowing sufficient CO 2 absorption for photosynthesis can be determined by water use efficiency (WUE).The highest WUE values were obtained by Catucaí Amarelo 24/137, Catucaí Vermelho 20/15 cv.476, Sabiá 398 and Topaz MG 1190 (TABLE1).The WUE consists of the ratio between the net photosynthetic rate and the transpiration rate, i.e., plants with greater WUE produce more dry matter in relation to transpired water(RAMALHO et al., 2013).Carvalho et al. (2014)also observed that Catucaí Amarelo 2 SL cultivar showed high WUE due to its lower transpiration rate, resulting in a lower water loss in relation to the amount of dry matter produced.Catucaí Vermelho 20/15 cv.476 were in the two groups of cultivars with higher WUE.They were also in the two groups with higher net photosynthetic rate and in the group with lower transpiration rate in relation to others cultivars (TABLE1).However, Sabiá 398, Catiguá MG 1 and Topázio MG 1190 showed high WUE mainly due to their low transpiration rate, despite having low net photosynthetic rates (TABLE1).It is worth noting that Catucaí Vermelho 785/15 and Acauã showed low WUE due to their high transpiration rates, despite obtaining high net photosynthetic rates.This is also true for PalmaII, Pau Brasil  MG1, Obatã IAC 1669-20, Iapar 59, IPR 98, IPR  103 and Catiguá MG 3, but only because of the low net photosynthetic rates (TABLE1).