Relationship of intra- and interpopulation tropical maize single cross hybrid performance and genetic distances computed from AFLP and SSR markers

Two sets of tropical maize inbred lines, one derived from the BR-105 population and another derived from the BR-106 population, were assayed for Amplified Fragment Length Polymorphism's (AFLP) and for Simple Sequence Repeat (SSR), in order to investigate genetic distances among lines and their relationship to heterotic group assignment and single cross yield performance. Genetic distances were on average greater for interpopulation than intrapopulation crosses for both AFLP and SSR. Cluster analysis was in agreement with the original assignment for heterotic groups. Inbred line 16, derived from BR-106, was assigned to the BR-105 set, in agreement with single cross yield performance from intra- and interpopulation crosses. However, the same pattern was not observed for SSR where another two lines from BR-106 were also assigned to the BR-105 set. Correlation coefficients of genetic distances (GD) with F-1 grain yield and heterosis were high for BR-106 x BR-106 crosses (0.91** and 0.82** for AFLP and SSR, respectively), moderate for BR-105 x BR-105 crosses (0.52* for AFLP and SSR) and low for BR-105 x BR-106 crosses (0.29 and 0.16 for AFLP and SSR, respectively). The lower correlation at interpopulation level was due to the smaller range of GD caused probably by a previous selection for combining ability. General results showed that the AFLP molecular marker is efficient in assigning maize lines to heterotic groups and that AFLP-based GD is suitable for predicting the maize single cross performance for intrapopulation crosses of broad-based populations. The efficiency of SSR in assigning lines to heterotic groups and for predicting single cross performance was smaller than AFLP.1301879

Partial diallel analysis of agronomic characters in rice (Oryza sativa L.)

Rice (Oryza sativa L.) breeding seeking to combine high productivity and cold tolerance for the temperate Latin America region is an important challenge. We estimated some useful parameters which can be used to investigate the genetic control of agronomic characters in crosses combining cold tolerance and productivity. A partial diallel design was used in crosses between six tropical indica rice cold susceptible genotypes (group 1) and seven japonica or indica/japonica cold tolerant rice genotypes (group 2). Parents and crosses were evaluated for agronomic characters under field conditions in two different experiments in 2005. The results showed significant mid-parent heterosis for all characters (plant height, tiller number, days to 50% flowering, panicle length, grains per panicle, sterility, and one-hundred grain weight). The predominant direction of dominance effects was negative for days to 50% flowering, and positive for all the other characters. General combining ability (GCA) and specific combining ability (SCA) were significant for all characters, although the GCA effects of the two groups were more important than the SCA effects

Partial diallel analysis of agronomic characters in rice (Oryza sativa L.)

Rice (Oryza sativa L.) breeding seeking to combine high productivity and cold tolerance for the temperate Latin America region is an important challenge. We estimated some useful parameters which can be used to investigate the genetic control of agronomic characters in crosses combining cold tolerance and productivity. A partial diallel design was used in crosses between six tropical indica rice cold susceptible genotypes (group 1) and seven japonica or indica/japonica cold tolerant rice genotypes (group 2). Parents and crosses were evaluated for agronomic characters under field conditions in two different experiments in 2005. The results showed significant mid-parent heterosis for all characters (plant height, tiller number, days to 50% flowering, panicle length, grains per panicle, sterility, and one-hundred grain weight). The predominant direction of dominance effects was negative for days to 50% flowering, and positive for all the other characters. General combining ability (GCA) and specific combining ability (SCA) were significant for all characters, although the GCA effects of the two groups were more important than the SCA effects