Heritability of Flower Number and Fruit Set under Heat Stress in Tomato

Abstract

<jats:p>The growing volatility of the climate, and its potential impact on crop production, has prompted several physiologic and genetic analyses under high-temperature conditions. Tomato is grown in warm temperate, subtropical, and tropical regions of the world, where daytime and nighttime temperatures regularly exceed the optimum temperatures for tomato growth during the summer, exerting stress on tomato production. Recent trends indicate more frequent extreme summer temperatures, which may grow even greater in the future, impacting crop growth. The objective of the current study was to estimate the heritability of flower and fruit set ability of tomato populations under heat stress conditions so that improvement for these traits can be planned. We developed two tomato populations using contrasting parents from the North Carolina State University (NCSU) tomato breeding program and the World Vegetable Center (formerly Asian Vegetable Research and Development Center). The F<jats:sub>2</jats:sub> and F<jats:sub>2</jats:sub>-derived F<jats:sub>3</jats:sub> families (F<jats:sub>2:3</jats:sub> populations) were grown at the Piedmont Research Station (PRS), Salisbury, NC, where summer growing temperatures are warmer than optimum for tomato production. Heritability estimates of the number of flowers per cluster, the number of fruit per cluster, and fruit set (measured as a percentage) were determined in two populations of tomato—NC10137 (NC714 × CLN-2413A) and NC10418 [230 HS-1(99) × NC 1CS]—by regression analysis using the offspring-on-parents method. Broad-sense heritability across the traits was high (47.2%–100%), whereas narrow-sense heritability was very low (1.4%–22.5%). There was a positive correlation between the number of flowers and the number of fruit per cluster (<jats:italic>r</jats:italic> = 0.50, <jats:italic>P</jats:italic> &lt; 0.05), which was in close agreement with previous findings. These findings will be useful in investigating the genetic control of heat stress tolerance in tomato and in facilitating crop improvement in the future.</jats:p>

Genomic and Phenotypic Diversity of Cultivated and Wild Tomatoes with Varying Levels of Heat Tolerance

“…Moderate to high broad-sense heritabilities found for number of inflorescences per plant, number of flowers per inflorescence, number of fruits per plant, fruit weight, and fruit setting percentage implied that the lines had a consistent response to heat stress across the environments (greenhouse and outdoor). Broad-sense heritability for the number of flowers per inflorescence was consistent with previously reported values (0.712–0.86) [ 63 ]. Similarly, the high broad-sense heritability recorded for fruit weight was consistent with the reported value under permissive temperature conditions (0.97) [ 64 ].…”

Application of stress susceptibility index and multivariate analysis of tomato (Solanum lycopersicum L.) to identify thermo-tolerant genotypes

“…Six genotypes exhibited staticity in the number of fruits per cluster, EC-165700, EC-620389, EC-620395, EC-620401, Akshaya and Anagha. Tomato is perceived with propensity towards bud drop (Tolessa nd Heuvelink 2018), under developed fruit and flower drop (Panthee et al 2018) and small parthenocarpic fruits with low flower number and fruit set (Adams et al 2001) at elevated temperature contributing to shrinking in the number of fruits per cluster. Genotypes exhibiting vegetative heat tolerance, recovers better towards the end of the summer (when the temperature cools), and exhibits upper canopy fruiting (Panthee et al 2018) maintaining fruit number per cluster.…”

“…Tomato is perceived with propensity towards bud drop (Tolessa nd Heuvelink 2018), under developed fruit and flower drop (Panthee et al 2018) and small parthenocarpic fruits with low flower number and fruit set (Adams et al 2001) at elevated temperature contributing to shrinking in the number of fruits per cluster. Genotypes exhibiting vegetative heat tolerance, recovers better towards the end of the summer (when the temperature cools), and exhibits upper canopy fruiting (Panthee et al 2018) maintaining fruit number per cluster. Variability in the number of fruits per cluster and trimming in the number of fruits per cluster in the summer were previously been reported (Alsamir et al 2018;Panthee et al 2018;Gonzalo et al 2020).…”

“…Genotypes exhibiting vegetative heat tolerance, recovers better towards the end of the summer (when the temperature cools), and exhibits upper canopy fruiting (Panthee et al 2018) maintaining fruit number per cluster. Variability in the number of fruits per cluster and trimming in the number of fruits per cluster in the summer were previously been reported (Alsamir et al 2018;Panthee et al 2018;Gonzalo et al 2020).…”

“…Heat stress correlated fruit number trimming, primarily linked with reduced fruit set and pollen viability, (Sato et al 2002;Zhou et al 2017;Driedonks et al 2018), was consistent in this work as well. Heat tolerant genotypes exhibit increased chlorophyll content, higher number of stomata and bigger stomatal pore size (Sato et al 2002), thereby maintaining substrate carbon conversion about 25% irrespective of temperature (Panthee et al 2018). These seasonal and varietal interplay in number of fruits per cluster has been reported by Rajashekar et al 2006;Alam et al 2010;Ashrafuzzman et al 2010;Hossain et al 2014.…”