LIBRO-CONGRESO-CITRUS

eshni), Citrus volkameriana, Citrus macrophylla, ‘Swingle’ citrumelo [Citrus paradisi x P. trifoliata], and six
new hybrids obtained at the Instituto Valenciano de Investigaciones Agrarias (IVIA): ‘Forner-Alcaide 5’, ‘Forner-
Alcaide 13’, ‘Forner-Alcaide 41’ and ‘Forner-Alcaide 31’ are hybrids of ‘Cleopatra’ mandarin and P. trifoliata,
‘Forner-Alcaide V17’ is a hybrid of C. volkameriana and P. trifoliata, and ‘Forner-Alcaide 2324’ is a hybrid of
‘Troyer’ citrange and ‘Cleopatra’ mandarin. The plot is located in the Experimental Field of ANECOOP, the
“Masia del Doctor”, sited ten km north of Valencia (Spain). The trial was planted in 2004 and yield has been
weighed during the first five harvests. In the first yield recorded, ‘Forner-Alcaide 5’ was the rootstock which
produced more (80% higher than ‘Carrizo’ citrange), and after five years, it has the highest cumulative yield
of all the rootstocks tested. ‘Carrizo’, ‘Forner-Alcaide V17’ and ‘Forner-Alcaide 13’ showed a high productivity
and ‘C-35’, ‘Cleopatra’ mandarin, ‘Swingle’ citrumelo and C. volkameriana had the lowest. Fruit quality was
analysed in the last two harvests. Rootstock significantly affected fruit quality variables. ‘Forner-Alcaide 5’,
‘Former-Alcaide 13’ and ‘Forner-Alcaide V17’ would appear to induce higher fruit size, juice content and fruit
quality.
S18P11
Influence of rootstock hydraulic conductance in the response to water stress and its relationship
to aquaporin expression in citrus
Rodríguez-Gamir J. 1 , Ancillo G. 2 , Bordas M. 3 , Primo-Millo E. 1 and Forner-Giner M.A. 1
1 Instituto Valenciano e Investigaciones Agrarias (IVIA), Centro de Citricultura y Producción Vegetal, Spain; 2 Instituto Valenciano e
Investigaciones Agrarias (IVIA), Centro de Protección Vegetal y Biotecnología, Spain; and 3 Agromillora Research S.L, Spain.
forner_margin@gva.es
Recent climate projections by the International Panel for Climate Change (IPCC, 2007) predict that water
scarcity will increase in the near future in many regions of the globe. Therefore, climate change poses an
acute problem to the citrus crops because the sector is expected to maintain its yield/quality standards under
more adverse climate conditions. Agronomic strategies such as the use of new rootstocks better adapted
to dryer conditions are needed. Plant water relations may be affected by drought stress and root hydraulic
conductance determines the ability of the rootstock to supply water and nutrients to the plant. This ability
could be the main factor influencing plant tolerance to abiotic stresses. Aquaporins are involved in regulating
root hydraulic conductance by mediating water flow through the cell membranes. Hypothesizing that
aquaporins could play a role in citrus response to water stress, responsiveness of photosynthetic parameters
and water balance to moderate water stress in different citrus rootstocks was evaluated. The plant materials
used were the rootstocks Poncirus trifoliata, ‘Cleopatra’ mandarin (Citrus reshni and ‘030115’ (a hybrid of
the two former rootstocks), all grafted with the citrus variety ‘Valencia Late’ (Citrus sinensis). Results showed
that down-regulation at transcriptional level results in decreased root hydraulic conductance. This facilitates
water maintenance in the cells and adequate levels of leaf water potential and photosynthesis in plants under
water stress. Thus, the decrease of aquaporin expression could be a water stress tolerance mechanism in
citrus.
S18P12
Micropropagation for evaluation of new citrus somatic hybrid rootstocks
Bordas M. 1 , Torrents J. 1 and Navarro L. 2
1 Agromillora Research, S.L, Spain; and 2 Instituto Valenciano de Investigaciones Agrarias (IVIA), Centro de Protección Vegetal y
Biotecnología, Spain. mbordas@agromillora.com
In citrus, virtually no rootstocks have tolerance or resistance to all the main biotic and abiotic stresses present
in a given growing area of the world and at the same time induce high yields and fruit quality. Although
several breeding programs are currently active to produce such rootstocks, propagation and evaluation of new
hybrids continues to be an important component of the development process. The development of somatic
hybridization by protoplast fusion in citrus has helped reach improvement goals that seemed unattainable
by conventional methods. It is possible to add the genomes of the parents in the hybrids without or with
very little recombination. At IVIA, a collection of somatic hybrids between ‘Carrizo’ citrange (Citrus sinensis
x Poncirus trifoliata) and Citrus macrophylla and Citrus taiwanica have been obtained. These hybrids are
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