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2008 Artigo Milton Egyptian Journal of Agricultural Research, V. 86, p. 1197-1206,

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   Egypt. J. Agric. Res, 86(3), 2008 1197 PHOTOSYNTHESIS, LEAF AREA INDEX AND PRODUCTIVITY OF TOMATO ( Lycopersicon esculentum Mill.) GERMPLASM Milton E. Pereira Flores 1 ; Derly J. Henriques da Silva 1 ; Marco Oliva 2 ; Francisco  X.R. Do Vale 3 ; Jorge G. Aguilera 4 ; Ahmed Y. Elsayed 4,5   1 Plant Sciences, 2 Plant Physiology, 3 Phytopathology and 4 Genetics and Breeding Depts., University Federal of Viçosa, MG, Brazil. 5 Hort. Res. Inst., Agric. Res. Center, Giza, Egypt.  (Author for corresponding: miltonpereira2001@yahoo.com)    ABSTRACT Nine accessions of tomato ( Lycopersicon esculentum   Mill.) indeterminate growth habit belonging to BGH-UFV bank with high variability were evaluated for leaf net photosynthesis (A), leaf area index (LAI), total dry matter production, dry matter partitioning and productivity. Santa Clara cultivar was used as well-adapted standard tomato variety with high production, LAI and total dry matter. The genotypes were grown under optimal irrigation and nutrition conditions. Optimal environmental conditions occurred over all experiment. The results showed significant genetic variability for all the evaluated traits. No correlation was found between A, total dry matter and productivity. Positive correlation between total dry matter, production and harvest index, but A correlated negatively with LAI. Favorable combination of physiological traits with production was found in BGH-320 and BGH-1020 accessions. INTRODUCTION The physiological breeding has considered the study of morpho-physiologic characteristic with the aim of identifying quantitative traits or combinations used in indirect selection with high efficiency (3, 4). In this context and in different cultivars has been frequent the seeking for genetic variability of leaf net photosynthesis (A) measured by CO 2  gas exchange and its effective contribution with improved the production (1, 15, 17, 21, 22, 28). Early research in this area has related linear increases, with different rates, from A, harvest index (HI), stomatal conductance and chlorophylls content in genetic improvement of cultivars as soybean (22), rice and wheat (21). In contrast, other studies (28, 30) have indicated that the large increases in production do not require increase of A, but only of the morpho-agronomic characteristics as biomass, plant architecture and size, colour of the canopy and the harvest index, resulting in productive cultivars with high leaf area index (LAI) and reduced photosynthetic capacity per leaf unit (9, 28). It has been reported genetic variability, heritability and transgressive F1 hybrids in A for diverse environmental conditions in tomato (5, 6, 11, 31). However, the correlations between A and yield, total dry mass, content of chlorophyll and fruit quality   Egypt. J. Agric. Res, 86(3), 2008 1198 are contradictory among scientific research and have needing for more knowledge in this area. Thus, the result of the present paper arise the knowledge of the genetic variability of photosynthetic capacity and its relation to production, total dry matter, IAF and harvest index of tomato plants. MATERIALS AND METHODS In this study it was used 9 tomato accessions ( Lycopersicon esculentum Mill.) and Santa Clara cultivar belonging to Vegetables Germplasm Bank of University Federal of  Viçosa, BGH-UFV (http://www.ufv.br/bgh/files/pag/tomate.htm) with high morpho-agronomic variability. 'Santa Clara' was used as a standard well-adapted and productivity reference of the Santa Cruz type cultivars and because of its wide diffusion in Brazil (26, 29). The experiment was conducted in greenhouse under favourable environmental, nutrient and irrigation conditions (8, 12, 14). The soil was plough up with 8 kg MS -2  m of manure tanned until 0.40 m depth, to improve the porosity of soil for avoid any hypoxic conditions than affect severely the photosynthesis along the A assessment. The irrigation was calculated using lysimeter (18) and the average water soil potential in 10 and 30 cm of depths was 10.63 ± 8.34 and 27.8 ± 48.4 Kpa, respectively (19). The seedlings were transplanted at 31 days-old (four to five extended leaves), 0.5 m x 1.0 m space, a randomized block design with five replications and 2 plants per block was used. The plants were grown in vertical system with one shoot per plant and pruned above the second pair of leaves of the fifth bunch. The A was measured with IRGA analyzer (LI-6400, LI-COR Biosciences, Inc. Lincoln, Nebraska) in the second pair of leaflets of the fourth leaf from 7:30 to 11:00 AM at 51 to 56 day after transplanting. The IRGA was configured as following: air flow of 500 mmol s -1 , 1200 µmol photons m -2  s -1  and 25 o C for the chamber and leaves temperatures (15, 16, 24). This measurement period was chosen in agreement with (11) that found in 54 DAT the highest A values in 12 tomato genotypes, measurements over different development stages. The fourth leaf was used in previous test which had highest and stable value of A. The leaf area index (LAI), leaf area (LA), total dry matter (TDM) and harvest index (HI) were calculated by conventional methods and expresses in standard units. The root biomass was extracted of a soil cube (30x30x30 cm) by washing with running water on sieve. Statistical Analysis:  The data was submitted to analyzed of variance using F-test (p <0.01), discrimination of means by Tukey (p <0.05) and correlations by Pearson with SAEG 0.9 statistical software.   Egypt. J. Agric. Res, 86(3), 2008 1199 RESULTS AND DISCUSSION Production The production, as it predicted, had significant variation among the genotypes (F test, p <0.01). The BGH-1020, `Santa Clara’ and BGH-994 were superiors than other genotypes. Contrary, the BGH-322 and BGH-406 had lowest production (two kg pta -1 ) representing 31% or less than productive genotypes. The productivity of ‘Santa Clara’, BGH-1020, BGH-994, BGH-970 and BGH-320 was equivalent to 116; 117; 105; 84 and 84 ton ha -1 , respectively. This production was superior to the average tomato yield in Brazil 60 ton ha -1  (20) thus the best accessions could be used as progenitors to increase tomato productivity. Leaf net photosynthesis The leaf net photosynthesis (A) of the genotypes was wide variability (F test, p <0.01) between 25 and 17 µmol CO2 m -2  s -1  (Table 1); these values was related in early research for accessions (11) and hybrids (31) of the specie. The accessions BGH-320 and BGH-1020 had largest A, with 25 and 23 µmol CO 2  m -2  s -1 , respectively, although BHG-1020 did not differ from other accession. All the accessions were higher than the commercial tomato `Santa Clara’ which reached 17 µmol CO 2  m -2  s -1 . Table 1, Santa Clara had lowest A value whereas BGH-320 with the highest A value it means less production than Santa Clara or BGH-994. The Pearson correlation (Table 2), did detect any relation between these traits, indicating there is no direct influence of photosynthesis on the production in tomato. This results is coherent with previous research with tomato (5) but is contrary with other pre-breeding research of tomato germplasm (11) which related positive correlation between A and total dry mass and production. These antagonist reports may be understand due to A is highly variable over development stages of plant not integrative measurement of whole net photosynthesis, and highly influenced by the environmental conditions, in addition, the true maximum values of A is ever recorded and not standard homogenized protocols are applied for the  A assessment. In this experiment, it was applied similar development stage (11) but not similar experimental conditions. On the other hand, the inheritance of this trait have related transgressive inheritance, significant general combining ability and the potential selection of A in tomato (31, 5) which suggest this character is controlled by additive gene action. This fact implicates the possibility of accessions BGH and particularly BGH-320 and BGH-1020 can be used as parents to increase A in tomato breeding. Total dry matter and Harvest Index The total dry matter (TDM) and harvest index (HI) had wide variation among the genotypes (F test, p <0.01). The total dry matter of BGH-1020 was superior to all the other genotypes, except BGH-994 and ‘Santa Clara’. These genotypes had superior production too. Correspondingly the BGH-406 had the less TDM and production. The others accessions showed moderate TDM and production (Table 1). Indeed the Pearson correlation was positive for relation of TDM and Production (Table 2). Contrary didn’t   Egypt. J. Agric. Res, 86(3), 2008 1200 have correlation among A, production and total dry matter as reported in previous study in pre-breeding tomato genotypes (11). Our data coincident with the results obtained from cotton (17) and tomato (6, 31). In these cultivars didn’t found any positive correlation among these traits. The harvest index varied significantly (F test, p < 0.01) between 25 and 64% (Table 1). The accessions BGH-320 with HI 64% allocated 10% more than the dry matter fruit reached for Santa Clara between 10 and 40% of the rest accessions. The value of HI for tomato plant ranged between 60 and 70% (12) despite of the experiment conditions were similar. The high TDM and its correlated with the production implies plants with high TDM, potentially may allocate more units of mass to fruit, even though the HI being the same if compared with other plant that has less TDM. The BGH-1020, Santa Clara and BGH-994 with the largest TDM had the highest productions too, but its HI was 10 to 16% units below BGH-320 had IH 64% and 6.5% lower production. In this case, the production of BGH-320 would be limited by its TDM. Similarly, the BGH-322 and BGH-406 with the lower production had TDM and HI of 25 and 40% which means that high TDM improved the probability to obtain high HI in tomato breeding as well as it related in other cultivars (14, 28, 30). On the other hand, the lack of correlation between A and productive traits, suggest that the A variability will be important only if exist inheritance and significant correlation with production or other traits. Between the F1 hybrids, consequently the A variability may be desirable over the correlation with production, for the improvement the productive efficiency of the tomato plants. Leaf area Index (LAI) There was significant variation of LAI among genotypes (F test, p <0.01) at 83 DAT and the EPC (Table 2). `Santa Clara’, with the least A had a LAI superior to all accessions at 83 DAT and the EPC, but only has different with BGH-320, BGH-987, BGH-970 and BGH- 406 accessions at the EPC (Table 1). This superiority of the ‘Santa Clara’ in LAI over the accessions is consistent with the fact of the selection for production in the new cultivars would reduce A and increase IAF to compensate the reduced exchange of CO 2  per unit area (28,30) as effectively was observed in ‘Santa Clara’ (Table 1). The BGH-320 with high A had the lowest LAI to 83 DAT (1.4) and intermediate value in the EPC (2.3), but was significantly lower than the IAF in Santa Clara. BGH-1020 with the largest production had intermediate values of IAF in both evaluations, but only reached the EPC values equal to `Santa Clara’. In this context the ideal limit of LAI in tomato is between 3.0 and 3.5 (12) even though in most commercial cultivars ranges between 90 and 120 DAT, from which occurs reduction of leaf area by the end of the production cycle (7, 10, 27). Above this optimal level of LAI, the shelf-shaded decrease the efficiency in the use of radiation, this effect

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Jul 23, 2017
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