The Relationship Between the Stay‐Green Trait and Grain Yield in Elite Sorghum Hybrids Grown in a Range of Environments

Abstract

The stay-green drought adaptation mechanism has been widely promoted as a way of improving grain yield and lodging resistance in sorghum [Sorghum bicolor (L.) Moench] and as a result has been the subject of many physiological and genetic studies. The relevance of these studies to elite sorghum hybrids is not clear given that they sample a limited number of environments and were conducted using inbred lines or relatively small numbers of experimental F^ hybrids. In this study we Investigated the relationship between stay-green and yield using data from breeding trials that sampled 1668 unique hybrid combinations and 23 environments whose mean yields varied from 2.3 to 10.5 t ha"^ The strength and direction of the association between stay-green and grain yield varied with both environment and genetic background (male tester). The majority of associations were positive, particularly in environments with yields below 6 t ha"^ As trial mean yield increased above 6 t ha"^ there was a trend toward an increased number of negative associations; however, the number and magnitude of the positive associations were larger. Given that post-flowering drought is very commonly experienced by sorghum crops world wide and average yields are 1.2 and 2.5 t ha"^ for the world and Australia, respectively, our results indicate that selection for staygreen in elite sorghum hybrids may be broadly beneficial for increasing yield in a wide range of environments.

Changes in Whole-Plant Metabolism During Grain-Filling Stage in Sorghum Bicolor L. (Moench) Grown Under Elevated Co2 and Drought

“…The reduction in leaf senescence under elevated [CO 2 ] (data not shown) indicates that this treatment alleviates some of the drought effects. In sorghum, drought stress during and after flowering stages (as applied in our experiment) can cause premature leaf senescence (Rosenow and Clark, 1995), and it is well known that the retention of green leaves during the grain-filling stage generally results in higher grain yield (Valdez et al, 2011;Jordan et al, 2012). In our experimental design, the greater amount of green leaves under elevated [CO 2 ] did not have an impact on yield (Table I) but rather can be related to the observed changes in grain quality, as will be discussed further.…”

PHENOTYPIC AND GENOTYPIC VARIANCE AND HERITABILITY OF STAY GREEN CHARACTER AMONG 22 ELITE SORGHUM (Sorghum bicolor (L.) Moench) GENOTYPES

“…Genotypic and phenotypic variance and estimation of heritability of some characters 321 cence is one of effective strategies to increase yields of cereal crop in water-stress condition. There were association between stay green and grain yield that was affected by environment and genetic background of plant (Jordan et al, 2012). Five sweet sorghums showed good TLA and not significantly different with superior grain sorghum genotypes Unpad 1.1 or Unpad 1.3 (Table 3).…”

Bigger is not always better: Reducing leaf area helps stay-green sorghum use soil water more slowly

“…It should also be noted that these experiments were conducted under non-limiting water conditions, and leaf area growth driven by higher temperature is likely restricted by water availability in rain-fed sorghum growing areas. Finally, the stay-green trait has been associated with increased grain yield over a large range of environments (mild to severe postanthesis drought) that are also typically affected by high temperatures (Jordan et al, 2012).…”

“…Stay-green (Stg) is a trait that has been associated with delayed leaf senescence, increased harvest index and improved grain yields of sorghum crops when water is limited towards the end of the growing season (Borrell et al, 2000a,b;Jordan et al, 2012). For this reason, it has been an important trait in the Australian sorghum breeding programme.…”