Genetic analysis of mesocotyl length and its relationship with other agronomic characters in rice (Oryza sativa L.)

Abstract

Mesocotyl length is an important character in promoting seedling emergence of direct-seeded rice. Genetic analysis of rice mesocotyl length was conducted using a six parent diallel cross. Generation mean analysis was carried out on parents (P), F1, F2 and backcrosses (B) of three crosses to complement the genetic information from the diallel analysis. Both analyses demonstrated the presence of significant additive and dominance effects. Duplicate type of non-allelic interaction was detected by the generation mean analysis and two crosses showed significant negative dominance gene effect. Dominance was partial and the narrow sense heritability estimate for mesocotyl length was high, indicating the preponderance of the additive effects.Mesocotyl length was negatively but weakly correlated with the coleoptile length and length of the second internode L2. There was no correlation between mesocotyl length and other mature plant characters such as plant height and internode lengths L1, (L~ being the peduncle with subsequent internodes to the base of the plant). Selection for mesocotyl length can therefore be carried out independent of these plant characters and semidwarf rice varieties with long mesocotyl can be developed.

Effect of Gibberellin and Uniconazole on Mesocotyl Elongation of Dark-Grown Maize under Different Seeding Depths

“…In wheat and barley, the first internode and coleoptile elongate (Suge et al, 1997;Schillinger et al, 1998;Takahashi et al, 2001;Matsui et al, 2002;Nishizawa et al, 2002;Rebetzke et al, 2004). In contrast, in rice the mesocotyl and coleoptile elongate (Turner et al, 1982;Mgonja et al, 1994;Zhang et al, 2005).…”

Genotypic variation in coleoptile or mesocotyl lengths of upland rice (Oryza sativa L.) and seedling emergence in deep sowing

“…The variation in seedling emergence roles of coleoptile and mesocotyl elongation could perhaps be related to their relative positions on a rice seedling, that is, mesocotyl at the base and joined to the coleoptile at the top. And as such, elongation of the mesocotyl serves to elevate the coleoptile to a point within a few millimetres of the soil surface where upon the coleoptile extends outwards to make contact with the atmosphere and allow the primary leaves to emerge (Mgonja et al, 1994). Thus, inability of the mesocotyl to elongate in deep seed placement would result in failed seedling emergence if the coleoptile is not capable of reaching the soil surface.…”

Components of variation of polygenic systems with digenic epistasis

“…)", although in the papers published by Balatero et al (1995), Gingera et al (1995) and Holtom et al (1995) there was no evidence of epistasis. In all cited papers, the methodology used was generation mean analysis with first degree epistasis, either exclusively or associated with diallel (Bartual et al, 1994;Mgonja et al, 1994) …”

“…In genetic studies it is commonly thought that epistatic effects contribute little to the genotypic values of individuals, and that epistatic variance is small or negligible compared to both additive and dominance variance. However, there is evidence from many analyses that epistatic effects cannot always be ignored (Rishipal, 1993;Ramsay et al, 1994;Saha Ray et al, 1994;Rahman et al, 1994;Mgonja et al, 1994;Bartual et al, 1994;Das and Griffey, 1995;Barakat, 1996).…”