Reserve mobilization, dry matter partitioning and specific leaf area in seedlings of African rice cultivars differing in early vigor

Asch Folkard, Sow Abdoulaye, Dingkuhn Michaël. 1999. Reserve mobilization, dry matter partitioning and specific leaf area in seedlings of African rice cultivars differing in early vigor. Field Crops Research, 62 : 191-202.

https://doi.org/10.1016/S0378-4290(99)00020-9

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Autre titre : Mobilisation des réserves, répartition de la matière sèche et surface foliaire spécifique chez des plantules de cultivars de riz africain qui différent par leur vigueur juvénile

Résumé : Rice breeding for weed competitiveness requires improved screening tools. An ongoing breeding program uses #O. glaberrima# as genetic donor for growth vigor and weed competitiveness. This study investigates morphophysiological characteristics relevant to seedling vigor, namely, the kinetics of reserve mobilization, dry matter partitioning among organs, and specific leaf area (SLA). Five diverse cultivars (#O. glaberrima" upland rice, improved and traditional tropical #O. sativa# japonica upland rices, an improved #O. sativa# indica cultivar and an interspecific progeny) were grown in the screenhouse for 18 days on wet soil. Dry matter fractions of plant organs were measured daily, leaf area (LA) and SLA were measured 9, 14 and 18 days after seed soaking (DAS). SLA measurements were repeated using crowded populations simulating farmers' seedbed nurseries. Seedlings achieved photo-autotrophic growth between 7.6 and 9.3 DAS, and had compensated for respiration losses during heterotrophic growth at 10.3-12.4 DAS, with #O. glaberrima# and improved indica cultivars requiring shorter periods than tropical japonica cultivars. For all cultivars, dry matter partitioning coefficients (PC) for roots were initially large but dropped temporarily to near zero during the transition from heterotrophic to autotrophic growth. The #O. glaberrima# cultivar had the largest PC for laminae and the largest SLA among the cultivars. It is concluded that the superior early growth vigor of the #O. glaberrima# cultivar, as documented in previous studies, is partly due to (1) early onset of autotrophic growth, (2) high PC for leaves, and (3) large SLA. Based on the previous observation that SLA is correlated with weed competitiveness, it appears that SLA measured at about 14 days after germination might be employed as a rapid screen for weed competitiveness.

Mots-clés Agrovoc : Oryza glaberrima, Oryza sativa, hybride, variété, taux de croissance, plantule, relation source puits, surface foliaire, critère de sélection, compétition végétale, mauvaise herbe, vigueur