Rice (Oryza sativa. L) genetic diversity for early vigor and drought ...

IntroductionChapter I: Developmental dynamics and early growth vigor in rice.Relationship between Developmental rate (1/phyllochron) and growthMaria Camila Rebolledo 1 , Michael Dingkuhn 1 , Pierre Péré 1 , Kenneth L. Mc Nally 2 , Delphine Luquet* 11 CIRAD, UMR AGAP, F-34398 Montpellier, France2 IRRI, Plant Breeding Genetics and Biochemistry Division, DAPO Box 7777, Metro Manila, PhilippinesKeywords: Oryza sativa L., phenotyping, developmental rate, Relative growth rate (RGR), early vigor,tillering, leaf dimensions.Running TitleDevelopmental dynamics and early growth vigor in riceAccepted (January, 2012) in Journal of Agronomy and Crop Science.ABSTRACTAchieving early vigor, i.e. rapid dry matter accumulation is a priority in rice crop improvement, butthis trait is complex and not well understood genetically and physiologically. This study tested thehypothesis that developmental rate (DR) contributes to early vigor.Two diversity panels were phenotyped during vegetative stage for traits constituting early vigor(shoot dry weight, SDW; relative growth rate, RGR), or contributing to early vigor (tillering, leaf size,DR). The first panel comprised 169 genotypes from all major genetic groups of O. sativa and wasphenotyped under irrigated upland conditions in the field (Philippines, Exp1). The second panel with190 genotypes representing the diversity of the tropical japonica group was phenotyped in pots in agreenhouse (Montpellier, France, Exp2).Results from field and pot experiment pointed out that DR, tillering and leaf size were positivelycorrelated with RGR and SDW, although the contribution of leaf size was small. DR was positivelycorrelated with tillering but both were negatively correlated with leaf size. DR vs. RGR correlationwas conserved in subsets of genotypes with similar leaf size and tillering, suggesting an effect of DRon RGR independent of the other traits.DR is a promising, still underexploited trait contributing to rice early vigor, requiring further geneticand physiological characterization.31