Variation of seed zinc in a local upland rice germplasm from Thailand

Abstract

This study examined variation in seed zinc (Zn) in a local upland rice germplasm that may affect adaptation in a system of slash-and-burn. Individual seed Zn in farmers' seed lots of local upland rice varieties from a slash-and-burn system was evaluated by staining with dithizone (DTZ). Concentration of Zn in the farmers' seed lots and their single-seed descent genotypes grown at Chiang Mai University was determined by chemical analysis. The DTZ staining of individual seeds in most of the farmers' seed lots covered the intensity of standards that ranged from 19 mg Zn/kg (RD21) to 31 (Nam Roo) mg Zn/kg. Zinc content by chemical analysis was closely correlated with the weighted-average staining for each seed lot. Almost all of the single-seed descent genotypes had higher seed Zn than RD21; two-thirds were higher than Nam Roo. The variation within seed lots detected by DTZ staining was confirmed by seed Zn in the single-seed descent genotypes. Evolutionary adaptation to soil with limited Zn, exacerbated by alkalinity of the ash from slash-and-burn, is made possible by variation in seed Zn among individuals growing together in the same field, and benefits the eaters with Zn-enriched seed.

Characterization of On-farm Rice Germplasm in an Area of the Crop’s Center of Diversity

“…Designation as upland or wetland varieties is purely agronomic, and is not always differentiated by the physiological mechanism for adaptation to aerobic or anoxic soil conditions (e.g., see Colmer, 2003). Nevertheless, adaptation to the water and nutritional conditions of aerobic soil is more likely to be found among the local rice germplasm from the highlands than from the lowlands, as has been demonstrated with adaptation to soil acidity (Laenoi et al, 2015), and seed Zn enrichment, a condition that favors good germination and early establishment in the zinc-deficient, ash-covered soil of the slash-and-burn system (Jaksomsak et al, 2015).…”

“…Detailed studies of the highland rice germplasm from individual villages and sets of varieties have revealed rich genetic diversity in the variation of simple sequence repeats (SSRs) of the DNA (e.g. Pusadee et al, 2009;Pusadee et al, 2014), as well as in useful traits, from resistance to pests (Oupkaew et al, 2011) and disease (Naruebal, 2009), to adaptation to acidic soil (Laenoi et al, 2015), to endosperm density of iron (Pintasen et al, 2007) and zinc (Jaksomsak et al, 2015).…”

The impact of foliar applied zinc fertilizer on zinc and phytate accumulation in dorsal and ventral grain sections of four thai rice varieties with different grain zinc

“…Genotypic variation for Zn in unpolished rice has been found among different rice germplasm, with reports of 14 to 58 mg kg -1 in rice germplasm at IRRI (Welch and Graham, 2004) and 17 to 50 mg kg -1 from local upland rice germplasm from Thailand (Jaksomsak et al 2015). Even though, some genotypes have been considered as high in grain Zn concentration, they often still do not meet the target of at least 28 mg kg -1 in polished rice (Bouis et al 2011) and this is because there is a loss of Zn during the polishing process.…”

The Rice Value Chain: a Case Study of Thai Rice

“…Several adaptive traits have been definitely verified that allow the rice crop to grow and yield reasonably well in these niches, including tolerance to locality-specific biotic stresses of insect pests (Oupkaew et al, 2011), disease (Naruebal, 2009), the physical constraints of soil acidity (Phattarakul, 2008), and flooding of various depths and durations (Sommut, 2003). Those who grow rice for their own consumption directly benefit from the local varieties that are especially rich in the micronutrients iron and zinc (see Prom-u-thai & Rerkasem, 2004;Saenchai et al, 2012;Jaksomsak et al, 2015;Jamjod et al, 2017).…”