Mechanical Properties of Bell Pepper Fruits, as Related to the Development of its Harvesting Robot

Adequate knowledge of the mechanical properties of fruits is required for the optimization of fruits harvesting robots. This study was carried out to evaluate some physical and mechanical properties of bell pepper fruits, which will be useful for the design and utilization of bell pepper fruits harvesting robots. Some mechanical properties (failure force, failure energy and compressibility) of matured bell pepper fruits were evaluated at three different dimension sizes and two fruit orientations, according to the American Society of Agricultural and Biological Engineers (ASABE) approved procedure. Results obtained from this study revealed that the fruit size and orientation had significant (p ≤ 0.05) effect on the mechanical properties of the bell pepper fruits. The failure force and failure energy of the fruit increased significantly (p ≤ 0.05) as the fruit locule number increases from 3 to 4. Relatively, the results revealed that the failure force and failure energy of the fruit increased significantly (p ≤ 0.05) as the fruit size increased from small to large size. As portrayed by this study results, the failure force and failure energy of the fruit when loaded in the natural position was higher than values obtained, when the fruit was compressed at the vertical position; irrespective of the fruit size. This revealed that the fruit at the natural position absorbed higher compressive force (pressure) and compressive energy, regardless of the fruit locule number. Results obtained from this study will present useful information for the design, programming and optimization of bell pepper harvesting and handling robots.

ENOregulates tomato fruit size through the floral meristem development network

A dramatic evolution of fruit size has accompanied the domestication and improvement of fruit-bearing crop species. In tomato (Solanum lycopersicum), naturally occurring cis-regulatory mutations in the genes of the CLAVATA-WUSCHEL signaling pathway have led to a significant increase in fruit size generating enlarged meristems that lead to flowers with extra organs and bigger fruits. In this work, by combining mapping-by-sequencing and CRISPR/Cas9 genome editing methods, we isolatedEXCESSIVE NUMBER OF FLORAL ORGANS(ENO), an AP2/ERF transcription factor which regulates floral meristem activity. Thus, theENOgene mutation gives rise to plants that yield larger multilocular fruits due to an increased size of the floral meristem. Genetic analyses indicate thatenoexhibits synergistic effects with mutations at theLOCULE NUMBER(encodingSlWUS) andFASCIATED(encodingSlCLV3) loci, two central players in the evolution of fruit size in the domestication of cultivated tomatoes. Our findings reveal that anenomutation causes a substantial expansion ofSlWUSexpression domains in a flower-specific manner. In vitro binding results show that ENO is able to interact with the GGC-box cis-regulatory element within theSlWUSpromoter region, suggesting that ENO directly regulatesSlWUSexpression domains to maintain floral stem-cell homeostasis. Furthermore, the study of natural allelic variation of theENOlocus proved that a cis-regulatory mutation in the promoter ofENOhad been targeted by positive selection during the domestication process, setting up the background for significant increases in fruit locule number and fruit size in modern tomatoes.

Phenotypic Divergence In Tomato Germplasm

Phenotypic divergence was quantified by multivariate analysis among the 70 genotypes collected from different agro-climatic regions and was available in the gene bank of Energypac Agro Ltd., Gazipur, Bangladesh. Based on the phenotypic value of 11 characters, 70 genotypes were grouped into five clusters. The genotypes of tomato were distributed in different clusters suggesting that no association was found between geographical and phenotypic diversity. Cluster II consisted of maximum twenty three genotypes (32.86%) followed by cluster III of sixteen genotypes (22.85%). Cluster IV and Cluster V comprised of thirteen (18.57%) and ten genotypes (14.29%), respectively. Cluster I consisted of eight genotypes (11.43%). The highest intra-cluster divergence (0.061) for cluster I was invariably smaller than the lowest inter-cluster divergence between cluster IV and cluster V (2.83), thus authenticating the clustering pattern formed in this study. The intra-cluster divergence ranged from 0.007 to 0.061, whereas the inter-cluster divergence ranged from 2.83 to 8.34 between clusters IV and V and clusters III and V, respectively. The four characters that played the greatest role in differentiation were locule number per fruit, pericarp thickness, fruits per plant and days to 50% flowering. Twenty homozygous parents (15 female and five male) were selected from five clusters using range test among genotypes within cluster. From cluster I parents TM409, TM386 and TM528 and from cluster III parents TM403 and TM349 were selected as male. Parents TM356, TM361, TM368, TM371, TM377, TM384, TM422 and TM423 from cluster II; parents TM388, TM390, TM392 and TM410 from cluster IV and parents TM382, TM419 and TM360 from cluster V were selected as female. SAARC J. Agri., 17(2): 185-195 (2019)

Low Overnight Temperature-Induced Gibberellin Accumulation Increases Locule Number in Tomato

The number of locules in tomato affects fruit size, shape, and the incidence of malformation. Low temperature increases locule number and the incidences of malformation in tomato plants. In this study, three flower bud developmental stages (pre-flower bud differentiation, sepal and petal primordium formation, and carpel primordium formation) under different night temperatures (10, 15, and 20 °C) were used to analyze the reason behind locule number change using an RNA sequencing (RNA-seq) approach, Quantitative real-time PCR (qRT-PCR), and ultra-performance liquid chromatography–tandem mass spectrometry (UPLC-MS). The results showed that the “plant hormone signal transduction”, “starch and sucrose metabolism”, and “diterpenoid biosynthesis” categories were remarkably activated during flower bud differentiation. Transcripts of gibberellin (GA)-related genes and endogenous levels of GAs were analyzed, and it was discovered that SlGA2ox genes were significantly downregulated and bioactive GA1 and GA4 accumulated at lower overnight temperature. Exogenous application of bioactive GA1, GA4, and PAC (paclobutrazol) showed that GA1 and GA4 increased the locule number, while PAC decreased the locule number. Taken together, our results suggest that lower overnight temperature reduced the expression of SlGA2ox genes, leading to GA1 and GA4 accumulation, thereby increasing locule number in tomato.

Decreased number of locules and pericarp cell layers underlie smaller and ovoid fruit in tomato smaller fruit (sf) mutant

Fruit size and shape are the primary criteria for domestication and improvement of tomato. The varying sizes and shapes of tomato fruit further signify their importance as agronomic traits. Here, we characterized a tomato mutant, smaller fruit (sf), which bears relatively small and ovoid fruits compared with the large and flat fruits of the wild-type (WT). Phenotypic measurements and histological analyses revealed that fruit diameter but not fruit length of the sf mutant decreased compared with that of the WT. This phenotypic change was attributed to significant decreases in locule number and pericarp cell layers in a transverse direction, which resulted in the transition of fruit shape from flat in the WT to ovoid in sf. Comparison of the transcriptomes of ovaries of sf with the WT using RNA-Seq identified 2596 differentially expressed genes, in which 1737 genes significantly were up-regulated and 859 genes were dramatically down-regulated in the sf ovary. Further analyses confirmed that some genes, such as CRCa, CNRs, CYCs, WUS, SUNs, OFRs, CDKs, participate in regulation of fruit size and shape of sf mutant. Thus, our study adds a new genetic resource regarding fruit size and shape of tomato, and provides a valuable basis for understanding molecular regulation of small and ovoid fruit of the sf mutant.

Evaluation of Tomato (Solanum lycopersicum L.) Genotypes for Horticultural Characteristics on the Upland in Southern Sierra Leone

Notwithstanding the importance of tomato in human diet, the average yield of the crop in Africa hardily exceeds 7.5 tha-1. There is continuous unavailability of high yielding cultivars that are adapted to diverse environment and suitable for different purposes. Consequently, evaluation of introduced tomato genotypes for desired horticultural characteristics to identify superior genotypes for additional improvement in yield and yield related traits is indispensible. Hence eight tomato (Solanum lycopersicum L.) genotypes including parental were field planted in a randomized complete block design with three replications at the Department of Horticulture Nursery Unit, School of Natural resources Management, Njala University, Njala Campus, Moyamba District, Southern Sierra Leone to evaluate them for good horticultural traits. Data collected include plant height at 50% and 100% flowering, stem girth at 50% and 100% flowering, days to first, 50% and 100% flowering, days to maturity, number of fruits set per plant, number of fruits harvested per plant, average fruit weights, fruit length, fruit diameter, fruit flesh thickness, locule number, marketable and nonmarketable fruits per plant. Results from the study indicated that all genotypes studied are adaptable to the Sierra Leone climatic conditions. P1 (097) recorded the highest number of fruits set per plant, number of fruits harvested per plant and tallest and largest plant height and stem girth at 100% flowering. BC2F2 had the highest locule number while R3P9 had the heaviest fruit weight. P2 (213) had the thickest fruit flesh thickness and longest duration to fruit maturity respectively while P1 (097), BC1F2 and R3P9 had the same number of shortest days to maturity. Regarding fruit length and diameter, R3P8 and R6P6 had the longest and widest. With respects to marketable and nonmarketable fruit per plant, P1 (097) recorded the highest correspondingly.