Role of Legumes in Improving Soil Fertility and Increasing Crop Productivity in Northeast Thailand

Northeast Thailand constitutes one-third of total area of the whole country and one-third of the total population live in this region. The income of the majority of the people living here is below half of the national average mainly due to low agricultural production and productivity. The low agricultural productivity of the northeast region compared to other regions of Thailand is attributed mainly to erratic rainfall, water shortage during the dry season, undulating terrain and poor and marginal soils. The soils in the region are mostly sandy in texture with low soil moisture holding capacity. The soils are also very low in organic matter and low in general fertility

A QTL study on late leaf spot and rust revealed one major QTL for molecular breeding for rust resistance in groundnut (Arachis hypogaea L.)

Late leaf spot (LLS) and rust are two major foliar diseases of groundnut (Arachis hypogaea L.) that often occur together leading to 50–70% yield loss in the crop. A total of 268 recombinant inbred lines of a mapping population TAG 24 × GPBD 4 segregating for LLS and rust were used to undertake quantitative trait locus (QTL) analysis. Phenotyping of the population was carried out under artificial disease epiphytotics. Positive correlations between different stages, high to very high heritability and independent nature of inheritance between both the diseases were observed. Parental genotypes were screened with 1,089 simple sequence repeat (SSR) markers, of which 67 (6.15%) were found polymorphic. Segregation data obtained for these markers facilitated development of partial linkage map (14 linkage groups) with 56 SSR loci. Composite interval mapping (CIM) undertaken on genotyping and phenotyping data yielded 11 QTLs for LLS (explaining 1.70–6.50% phenotypic variation) in three environments and 12 QTLs for rust (explaining 1.70–55.20% phenotypic variation). Interestingly a major QTL associated with rust (QTLrust01), contributing 6.90–55.20% variation, was identified by both CIM and single marker analysis (SMA). A candidate SSR marker (IPAHM 103) linked with this QTL was validated using a wide range of resistant/susceptible breeding lines as well as progeny lines of another mapping population (TG 26 × GPBD 4). Therefore, this marker should be useful for introgressing the major QTL for rust in desired lines/varieties of groundnut through marker-assisted backcrossing

Changes in root xylem anatomy of peanut genotypes with different drought resistance levels under early-season drought

During the 2014 and 2015 seasons, peanut root anatomy studies were conducted under well-watered and under drought conditions using three peanut genotypes which are known to differ in their physiological responses to early- and mid-season drought (ICGV 98,305, ICGV 98,324 and Tifton-8). Cross sections of the newly formed roots revealed that the average vessel diameter and total vessel area in the first-order roots were significantly reduced under drought in ICGV 98,305 and ICGV 98,324, yet not in Tifton-8, which had the smallest vessel diameters and total area in both well-watered and drought treatments. The xylem vessel structure in newly formed roots of ICGV 98,324 was very responsive to changes in soil moisture content. This adaptive capacity of ICGV 98,324 to change xylem structure as soil moisture conditions change may provide plant breeders an important trait which will lead to better water-use efficiencies in both moist and drought conditions

Association of root, specific leaf area and SPAD chlorophyll meter reading to water use efficiency of peanut under different available soil water

Drought is the major abiotic constraint affecting peanut productivity and quality worldwide. There is a pressing need to improve the water use efficiency (WUE) of rain-fed peanut production. Breeding varieties with higher water use efficiency is seen as providing part of the solution. The objectives of this work were to (i) evaluate genetic variation in WUE, harvest index, root dry weight, specific leaf area (SLA) and SPAD chlorophyll meter reading (SCMR) among peanut genotypes in response to different available soil water levels and (ii) assess the relevance of root dry weight, SLA and SCMR to WUE in peanut under receding soil moisture levels. Two greenhouse experiments were conducted in the dry and rainy seasons in 2002/2003. The 11 peanut genotypes (ICGV 98300, ICGV 98303, ICGV 98305, ICGV 98308, ICGV 98324, ICGV 98330, ICGV 98348, ICGV 98353, Tainan 9, KK 60-3 and Tifton-8) and three soil moisture levels [field capacity (FC), 2/3 available soil water (AW) and 1/3 AW] were laid out in a factorial randomized complete block design (RCBD) with six replications. At 37, 67, and 97 day after sowing (DAS), data were recorded for SLA and SCMR. Root dry weight, harvest index (HI) and WUE were recorded at harvest. Drought reduced WUE, root dry weight and HI. Across both seasons, Tifton-8 and ICGV 98300 had high WUE and also had large root systems under drought conditions. ICGV 98324 and Tifton-8 had low SLA and high SCMR under stressed and non-stressed condition. Under drought conditions, ICGV 98324 had high HI and Tifton-8 had low HI. Root dry weight had a greater contribution to WUE under well-watered and mild drought (2/3 AW). Under severe drought (1/3 AW), SLA showed a more important contribution to WUE than the other traits. Traits that were associated to high WUE under drought conditions were different among different peanut genotypes. ICGV 98300 maintained high root dry weight under 2/3 AW and ICGV 98324 maintained low SLA and high SCMR under 1/3 AW. Tifton-8 had both large root systems and low SLA associated with high WUE.Arachis hypogaea L Breeding Drought resistance Irrigation deficit SCMR SLA Water use efficiency

Association between aflatoxin contamination and drought tolerance traits in peanut

The current study investigates the association between drought tolerance traits and aflatoxin contamination in peanut grown under long-term drought. Two field experiments were conducted at Khon Kaen University, Thailand using a split-split plot design with three drought stress levels as main plots, 11 genotypes as sub-plots, and two soil inoculations of Aspergillus flavus treatments as sub-sub-plots. The effects of temperature, soil moisture and A. flavus population on kernel colonization and aflatoxin contamination, and drought tolerance traits viz. specific leaf area (SLA) and root length density (RLD) were measured. The results demonstrated that elevated soil temperatures and reduced soil moisture, favored aflatoxin production. Drought in combination with higher levels of A. flavus inoculum load in the soil resulted in an increase in the fungal populations in the soil which in turn resulted in increased kernel colonization and subsequent aflatoxin contamination. A combination of SLA and RLD, and kernel colonization had a significant influence on aflatoxin contamination under drought conditions in both seasons (r = 0.73** and 0.76**). The results revealed that drought tolerance traits (SLA and RLD) could be contributing to resistance to aflatoxin contamination suggesting that a combination of SLA, RLD and kernel colonization could be used as selection criteria in selecting parents for aflatoxin resistance