Jean-Michel Legave

Effects of pollination by irradiated pollen in Hayward kiwifruit and spontaneous doubling of induced parthenogenetic trihaploids

Abstract Parthenogenesis induced by irradiated pollen was investigated for the main cultivar Hayward of Actinidia deliciosa as a possible means of genetic improvement. Pollinations were carried out for two years involving two different sources of pollen which were previously irradiated with gamma rays in the dose range of 200–1500 Gy. Although pollen irradiation decreased the number of viable seeds formed, high rates of trihaploid seedlings were detected early on using flow cytometry after a direct sowing of these seeds in a greenhouse. The best efficiency was obtained with the male genotype M2 at dosages of 500–1500 Gy. Hexaploid seedlings were also found but mainly at the lowest dosage of 200 Gy. Some trihaploids kept in the shadehouse remained stable after two years. However, some of them underwent a spontaneous doubling after a short stage of in-vitro propagation by adventitious regeneration. This is the first evidence of spontaneous doubling of Actinidia deliciosa trihaploids.

Use of flow cytometry for rapid determination of ploidy level in the genus Actinidia

Abstract Measurement of ploidy levels in the genus Actinidia , using flow cytometry, was the subject of this preliminary research. Compared with other methods (chromosome counts, length of stomata), flow cytometry promises quicker and easier determination of the ploidy level. The use of this method in plants produced in vitro from seeds of ‘fruiting male’ of Actinidia deliciosa revealed the existence of individuals of high ploidy level, probably 9 ×. In general, these individuals were characterized by low vigor and an abnormally long juvenile period. Plants of this ploidy level, which to our knowledge have never before been noticed, do not seem to have any varietal potential.

Detecting QTLs and putative candidate genes involved in budbreak and flowering time in an apple multiparental population

Highlight QTLs and candidate genes for the regulation of budbreak and flowering time reveal new hypotheses on temperature perception in growth resumption at spring time in apple.

Differentiated dynamics of bud dormancy and growth in temperate fruit trees relating to bud phenology adaptation, the case of apple and almond trees

Few studies have focused on the characterization of bud dormancy and growth dynamics for temperate fruit species in temperate and mild cropping areas, although this is an appropriate framework to anticipate phenology adaptation facing future warming contexts which would potentially combine chill declines and heat increases. To examine this issue, two experimental approaches and field observations were used for high- and low-chill apple cultivars in temperate climate of southern France and in mild climates of northern Morocco and southern Brazil. Low-chill almond cultivars offered an additional relevant plant material for comparison with apple in northern Morocco. Divergent patterns of dormancy and growth dynamics were clearly found in apple tree between southern France and southern Brazil. Divergences were less pronounced between France and Morocco. A global view outlined main differences in the dormancy chronology and intensity, the transition between endordormancy and ecodormancy and the duration of ecodormancy. A key role of bud rehydration in the transition period was shown. High-chill cultivars would be submitted in mild conditions to heterogeneous rehydration capacities linked to insufficient chill fulfillment and excessive forcing linked to high temperatures. This would favor bud competitions and consequently excessive flowering durations and weak flowering. Low chilling requirements in apple and almond would conversely confer biological capacities to tolerate superficial dormancy and abrupt transition from endordormancy to ecodormancy without important heterogeneous rehydration states within buds. It may also assume that low-chill cultivars can also tolerate high temperatures during ecodormancy as well as extended flowering durations.

The PERPHECLIM ACCAF Project – perennial fruit crops and forest phenology evolution facing climatic changes

Phenology is a bio-indicator of climate evolution. Measurements of phenological stages on perennial species provide actually significant illustrations and assessments of the impact of climate change. Phenology is also one of the main key characteristics of the capacity of adaptation of perennial species, generating questions about its consequences on plant growth and development or on fruit quality. Predicting phenology evolution and adaptive capacities of perennial species needs to override three main methodological limitations: 1) existing observations and associated databases are scattered and sometimes incomplete, rendering difficult implementation of multi-site study of genotype-environment interaction analyses 2) there are not common protocols to observe phenological stages 3) access to generic phenological models platforms is still very limited. In this context, the PERPHECLIM project, which is funded by the Adapting Agriculture and Forestry to Climate Change Meta-Program ( ACCAF) from INRA ( French National Institute of Agronomic Research), aims to develop the necessary infrastructure at INRA level ( observatories, information system, modeling tools) to enable partners to study the phenology of various perennial species ( grapevine, fruit trees and forest trees). Currently, the PERPHECLIM project involves 28 research units in France, mainly from INRA institutes. Five activities have been developed: define protocols and observation forms to observe phenology for various species of interest for the project : organize observation training, develop generic modeling solutions to simulate phenology ( Phenological Modelling Platform software and modelling platform solutions), support the building of research projects at national and international levels, develop environment/genotype observation networks for fruit-tree species, and develop an information system to manage data and documentation concerning phenology. Finally, the PERPHECLIM project aims to build strong collaborations with public ( Observatoire des Saisons) and private ( technical institutes) sector partners in order to allow a more direct transfer of knowledge.