**7. Screening of** *Solanum* **rootstocks against root-knot nematodes**

Traditionally, field and pot screening have been used to identify plant cultivars that are resistant to root-knot-nematodes as screening of rootstocks against root-knot nematodes is essential for every grafting program, because this informs the selection of the right rootstock for grafting. In a field experiment to evaluate the performance of grafted eggplant cultivars on wild *Solanum* rootstocks against root-knot nematodes, results revealed that the wild *Solanum* rootstocks *S. torvum*, *S. sisymbriifolium,* and *S. khasianum* were resistant to root-knot nematode when inoculated with 1000 nematode juveniles [42]. The non-grafted plants generally flowered before the grafted plants, a situation which is attributed to the cut back of the leaves of the scion to reduce transpiration which slowed down the rate of growth. Thirty-three tomato genotypes screened for root-knot nematode resistance under five inoculum levels (100, 500, 1000, 1500, and 2000) showed increasing inoculum level with corresponding increase in gall score and fresh root weight [43]. Among the 33 tomato genotypes tested, Mongal F1 T-11 had the lowest mean gall score of 3.25 and "Beef Master" had a value of 3.75 with reproductive factors of 0.71 and 0.53, respectively. Tomato cultivars that are resistant to root-knot nematodes have a reproductive factor less than one, which implies that the plant is able to suppress the reproduction cycle of the organism once it gains entry into the roots [44]. In a grafting study by Agyeman [19], significant differences were not observed among total soluble solids (TSS), pH, and titrable acidity (TA) for the tomato variety "Pectomech" grafted onto *S. aethiopicum* and *S. macrocarpon* after infection to 500 and 1000 nematodes per pot (**Table 3**).

In a pot culture experiment conducted by Dhivya et al*.* [45], 10 *Solanum* plant genotypes (*S. torvum*, *S. incanum*, *S. xanthocarpum, S. aethiopicum*, *S. sisymbrifolium*, *S. viarum*, *S. violaceum,* 


market players along the vegetable value chain their standard for quality. The quality of

Vegetable farmers and traders prefer tomato cultivars which exhibit firmness and can withstand mechanical damage, whilst in transit to various market centers [38]. The term fruit quality, which can be defined based on the visual and sensory properties such as color and sweetness, has been found to be controlled by certain inherent genes in some plant cultivars; some of these

Conflicting reports on the influence of grafting on fruit quality in vegetables exist. Positive and negative influences of grafting have been documented [40]. In their review of the impact of grafting on fruit quality in vegetables, Rouphael et al. [40] attributed these conflicting results to the differences in environments, production methods, scion/rootstock combinations, and

In an experiment conducted by Matsuzoe et al*.* [41], where tomatoes (Momotaro) were grafted on three *Solanum* species (*S. torvum, S. toxicarum* and *S. sisymbriifolium*), there were, however, no significant differences in the quality of grafted and ungrafted tomatoes in relation to the

Traditionally, field and pot screening have been used to identify plant cultivars that are resistant to root-knot-nematodes as screening of rootstocks against root-knot nematodes is essential for every grafting program, because this informs the selection of the right rootstock for grafting. In a field experiment to evaluate the performance of grafted eggplant cultivars on wild *Solanum* rootstocks against root-knot nematodes, results revealed that the wild *Solanum* rootstocks *S. torvum*, *S. sisymbriifolium,* and *S. khasianum* were resistant to root-knot nematode when inoculated with 1000 nematode juveniles [42]. The non-grafted plants generally flowered before the grafted plants, a situation which is attributed to the cut back of the leaves of the scion to reduce transpiration which slowed down the rate of growth. Thirty-three tomato genotypes screened for root-knot nematode resistance under five inoculum levels (100, 500, 1000, 1500, and 2000) showed increasing inoculum level with corresponding increase in gall score and fresh root weight [43]. Among the 33 tomato genotypes tested, Mongal F1 T-11 had the lowest mean gall score of 3.25 and "Beef Master" had a value of 3.75 with reproductive factors of 0.71 and 0.53, respectively. Tomato cultivars that are resistant to root-knot nematodes have a reproductive factor less than one, which implies that the plant is able to suppress the reproduction cycle of the organism once it gains entry into the roots [44]. In a grafting study by Agyeman [19], significant differences were not observed among total soluble solids (TSS), pH, and titrable acidity (TA) for the tomato variety "Pectomech" grafted onto *S. aethiopicum*

genes or genetic traits can be bred into new genotypes from other wild species [39].

**7. Screening of** *Solanum* **rootstocks against root-knot nematodes**

and *S. macrocarpon* after infection to 500 and 1000 nematodes per pot (**Table 3**).

In a pot culture experiment conducted by Dhivya et al*.* [45], 10 *Solanum* plant genotypes (*S. torvum*, *S. incanum*, *S. xanthocarpum, S. aethiopicum*, *S. sisymbrifolium*, *S. viarum*, *S. violaceum,* 

tomato is based on soluble solids, acidity, sugars, pH, and shelf life [37].

harvest dates.

amount of sugars and their organic acid contents.

10 Recent Advances in Tomato Breeding and Production

P/SA = Pectomech grafted onto *Solanum aethiopicum*; P/SM = Pectomech grafted onto *Solanum macrocarpon*; TSS = Total soluble solids; TA = Titrable acidity; LSD = Least significant difference; ns = no significant difference. Agyeman [19].

**Table 3.** Comparison of grafted rootstocks and inoculum level interaction on TSS, TSS/TA, pH, and TA.

*Physalis peruviana,* and TNAU Tomato Hybrid CO-3 and US-618) consisting of eight wild species and two F1 cultivars were evaluated for their resistance to root-knot nematode over a 60-day period, and the results showed that *S. sisymbrifolium* rootstock had the highest shoot fresh weight and dry weight of 103.87 and 10.44 g, respectively.

The rootstocks, *S. sisymbrifolium, Physalis peruviana*, and *S. torvum* recorded the least nematode population of 39, 40 and 43 per 200 cc of soil and a reproductive factor of 0.71, 0.74, and 0.84, respectively. *Solanum sisymbrifolium*, *P. peruviana,* and *S. torvum* were resistant to root-knot nematode (*Meloidogyne incognita*), and *S. incanum* and *S. aethiopicum* were found to be moderately resistant to *Meloidogyne incognita*.
