An experiment was conducted to evaluate hybrid genotypes of tomato for fruit yield and fruit quality in Horticulture Research Division, NARC, Khumaltar, Lalitpur, Nepal during March to August, 2014 in open field condition. Eleven hybrid genotypes developed from the crosses between HRA and HRD lines, selected as good performer under late blight condition and ‘Srijana’as a local check were taken for the evaluation. Design of experiment was single factorial RCBD with three replications. Observation on traits related to plant morphology, maturity and yield component were recorded to develop, evaluate, identify and recommend high yielding hybrids of tomato. The fruit yield per hectare ranged from 80.83 t/ha (HRA 14 × HRD 7) to 45.89 ton/ha (HRA 15 × HRD 6). Fruit yields of the genotypes HRA 14 × HRD 7, HRA 13 × HRD 7, HRA 20 × HRD 1, HRA 20 × HRD 2, HRA 20 × HRD 6 and HRA 16 × HRD 1 had 80.83 ton/ha, 78.50 ton/ha, 73.75 ton/ha, 70.44 ton/ha, 68.72 ton/ha, 64.64 ton/ha were higher than the yield of ‘Srijana’ (62.33 ton/ha). Based on overall performance, genotypes HRA 14 × HRD 7, HRA 13 × HRD 7, HRA 20 × HRD 1 and HRA 20 × HRD 6 were observed as good performer than Srijana (Check) and selected as high yielder with good fruit quality.
Heterosis plays an important role in switchgrass (Panicum virgatum L.) breeding. To identify superior clones for hybrid development through seasonal single cut, 10 crosses derived from ‘Alamo’ × ‘Kanlow’ and parents were evaluated. The experiment was planted in 2018 using a randomized complete block design with two replications at two locations in Tennessee: the East Tennessee Research and Education Center (ETREC), Knoxville, and the Plateau Research and Education Center (PREC), Crossville. The crosses and their parents were evaluated for biomass yield, plant height, and clonal mass in the fall of 2019 and 2020. The crosses were significantly different in biomass yield within and across locations (P ≤ .05). Average biomass yield of the crosses ranged from 7.1 to 8.7 Mg ha−1 at ETREC and from 10.0 to 11.8 Mg ha−1 at PREC. The crosses demonstrated an average of 46% mid‐parent heterosis (MPH) and 24% high‐parent heterosis (HPH) for biomass yield across the two locations. The MPH and HPH were 3 and −1.3% for plant height and 12 and 1% for clonal mass, respectively. Moderate to strong positive association was found between clonal mass scores and biomass yield at individual locations across years and across locations and years (r = 0.37–0.79, P ≤ .05). The association between biomass yield and plant height was inconsistent (r = −0.24 to 0.67, P ≤ .05). The findings of biomass yield heterosis in these crosses suggested the potential of hybrid cultivars for biomass yield improvement in lowland switchgrass.
Switchgrass can be used as an alternative source for bioenergy production. Many breeding programs focus on the genetic improvement of switchgrass for increasing biomass yield. Quantitative trait loci (QTL) mapping can help to discover marker-trait associations and accelerate the breeding process through marker-assisted selection. To identify significant QTL, this study mapped seven hybrid populations and one combined of two hybrid populations (30 to 96 F1s) derived from Alamo and Kanlow genotypes. The populations were evaluated for biomass yield, plant height, and crown size in a simulated-sward plot with two replications at two locations in Tennessee from 2019 to 2021. The populations showed significant genetic variation for the evaluated traits and exhibited transgressive segregation. The 17,251 single nucleotide polymorphisms (SNPs) generated through genotyping-by-sequencing (GBS) were used to construct a linkage map using a fast algorithm for multiple outbred families. The linkage map spanned 1,941 cM with an average interval of 0.11 cM between SNPs. The QTL analysis was performed on evaluated traits for each and across environments (year and location) that identified five QTL for biomass yield (Logarithm of the odds, LOD 3.12 to 4.34), four QTL for plant height (LOD 3.01 to 5.64), and seven QTL for crown size (LOD 3.0 to 4.46) (P ≤ 0.05). The major QTL for biomass yield, plant height, and crown size resided on chromosomes 8N, 6N, and 8 K explained phenotypic variations of 5.6, 5.1, and 6.6%, respectively. SNPs linked to QTL could be incorporated into marker-assisted breeding to maximize the selection gain in switchgrass breeding.
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