Estimation of Genetic Parameters of Cayenne Peppers (Capsicum Annuum L.) from IPB University for Its Resistance Against Begomoviruses in Aceh

Pest attack is one of the important causes of a significant loss in pepper crop. Insect Silverleaf whitefly is a virus vector for Begomovirus, a virus causing chilli leaf curl disease (Parining & Dewi, 2018; Yadav, et al., 2020). Yellow leaf curl disease has attacked pepper plants in Indonesia reached up to 4537.8 ha in 2016 and has increased to 4591.9 ha in 2017 and 4986.4 ha in 2018 (Kementerian Pertanian, 2019). The research of Koeda, et. al. (2016) found that 500-3000 pepper plants planted by farmers, 4 out of 5 plantations have been attacked by this virus 100%. The application of resistant varieties is still the most effective way to reduce plant diseases caused by Begomovirus. Varieties Anies and Seloka are some resistant varieties produced from hybridization between IPB C120 x IPB C5 and IPB C2 x IPB C5. Ganefianti (2010) has assessed several pepper genotypes against Begomovirus. Variety IPB C5 was one of them. This variety was tested and was very susceptible to Begomovirus attack with a disease intensity 40%. Variety IPB C12 was found to be resistant against Begomovirus. This potential genotype can be used as resistant varieties assembly. Resistant varieties were obtained through plant breeding techniques. The study of cayenne pepper resistance against Begomovirus should include the assays of its genetic diversity, determination of heritability value and evaluation of its resistance to Begomovirus. The objective of this research was to determine cayenne pepper genotypes and varieties which resistant to Begomovirus attack.


INTRODUCTION
Pest attack is one of the important causes of a significant loss in pepper crop. Insect Silverleaf whitefly is a virus vector for Begomovirus, a virus causing chilli leaf curl disease (Parining & Dewi, 2018;Yadav, et al., 2020). Yellow leaf curl disease has attacked pepper plants in Indonesia reached up to 4537.8 ha in 2016 and has increased to 4591.9 ha in 2017 and 4986.4 ha in 2018 (Kementerian Pertanian, 2019). The research of Koeda, et. al. (2016) found that 500-3000 pepper plants planted by farmers, 4 out of 5 plantations have been attacked by this virus 100%.
The application of resistant varieties is still the most effective way to reduce plant diseases caused by Begomovirus. Varieties Anies and Seloka are some resistant varieties produced from hybridization between IPB C120 x IPB C5 and IPB C2 x IPB C5. Ganefianti (2010) has assessed several pepper genotypes against Begomovirus. Variety IPB C5 was one of them. This variety was tested and was very susceptible to Begomovirus attack with a disease intensity 40%.
Variety IPB C12 was found to be resistant against Begomovirus. This potential genotype can be used as resistant varieties assembly.
Resistant varieties were obtained through plant breeding techniques. The study of cayenne pepper resistance against Begomovirus should include the assays of its genetic diversity, determination of heritability value and evaluation of its resistance to Begomovirus. The objective of this research was to determine cayenne pepper genotypes and varieties which resistant to Begomovirus attack.

Research Methods
This research employed Randomized Block Design (RBD) Non-Factorial with three replications, where each replication was consist of seven genotypes assessed and three comparing varieties. There were 30 experimental units with 20 plants for each experiment resulted in 600 experimental plants in total. The sampled plants are also used for disease attack observation.

Seed Sowing
The pepper seeds were sowed in a 50-hole-tray. The media (compost+husk charcoal) were placed evenly. Insecticide Agrimec was used to control pest and disease attack, applied with a concentration of 0.5 ml/L. AB mix was applied to fertilize the plants with a concentration 5 ml/L.
One month before planting, the field needed to be tilled through plowing to loose the soil. The beds were made in size 5 m x 1 m. The manure, 10 kg per bed, was applied two weeks before replanting. The distance between the experimental plots was 0.5 m, and the spacing was 50 cm x 50 cm. The beds then were covered with black and silver mulch plastic films that were applied in the afternoon to be stretched (Wijayanto, 2018). The mulch films should be stretched and tighten, and bamboo stakes were applied at each end of the beds, and each end of mulch was inserted into the stakes to keep the mulch films tightened.

Seed Replanting
Seed replanting was done five weeks after sowing, where these seeds reached ± 10 cm in height and already have 5-7 leaves. The replanting activity was done in the evening (5-6 pm) to avoid sunlight exposure. One seed for one hole, each plot was planted with 20 plants. The stakes and raffia were installed three days after planting. The installation of stakes (1.5 m at each hole) was important to avoid this replanting cayenne from being struck with the mulch films due to the gust of wind.
Fruit harvesting was done by picking the fruits and its stalks when it was 75% -100% ripe. This harvesting activity is done once a week for four weeks.

Variables Observed 2.3.1. Incubation Period
Begomovirus incubation period in sampled plants was observed daily after the plants were infected, manifested by thickening of midrib and yellowing of leaf lamina.

Scoring/Symptom Type
This variable was observed using the leaf symptom score explained by Ganefianti (2008)  Yellowing lamina, mosaic on leaves 2 Curl and yellow leaves 3 Yellowing, upward and downward leaf curling 4 Yellowing, upward and downward leaf curling 5 Yellowing, upward and downward leaf curling and dwarf

Disease Intensity
The disease intensity was calculated in the interval 15 days based on the symptoms described in Table 1. Plant resistance was categorized by Ganefianti (2010) in Table  2. The disease Intensity was recorded. This variable was recorded using the formula:

Disease Intensity (%) =
Where: ni = number of diseased plants on the ith grade zi = numerical value of its category N = total number of plants evaluated Z = the highest numerical value

Plant Resistance Against Begomovirus
Several symptoms were shown by plants infected by Begomovirus, such as midrib thickening and midrib thickening. The midrib was a yellow mosaic on leaves, yellowing on some parts of leaf lamina, yellowing followed by downward leaf curling, smaller leaves and yellowing followed by upward and downward leaf curling dwarf. Also, there was a symptom where the leaves were smaller, yellowing, and upward leaf curling, as described in Figure 1. The increase of viral infection was linear with the increase of plant age and vector population. The increase of the whitefly population has escalated the chance of infection by the virus. Different virus species attributed the difference of symptom shown by the infected plants. Upward leaf curling and mosaic are found in pepper plants and found in other plants such as tomato, which is infected by TYLCV (Tomato Yellow Leaf Curl Virus), and bean, which is infected by BCMV (Bean Common Mosaic Virus). Different soil fertility levels, climate, plant age, and plant genotype have also contributed to these different symptoms (Hannum, et al., 2019).  Table 6 described that the incubation period and disease intensity varied. The longest incubation period by Begomovirus was found in genotype F6 Gada (48.51 DAP), and this was significantly different compared to other genotypes and varieties. Genotype F5074035-2-4-2 has experienced the highest disease intensity (30.94%). This result was insignificant compared to genotype F5074136-2-3-2 and variety Selekta, but it was significantly different compared to genotypes F6 Gada, Seloka 4-10-2-2, F5136074-1-4-3, F5074035-2-1-2, F5074077-1-1-3, and varieties F1 Gada and Anies. The lowest disease intensity was possessed by genotype F6 Gada (12.08%).
A plant from genotype F5074035-2-4-2 demonstrated the shortest period of incubation (15 DAP) with symptoms of curling and yellowing leaves and dwarfism. This dwarfism disabled plants from producing flowers resulted in the inability to produce fruits. When Begomovirus attacks susceptible plants in their early development, the plants will experience dwarfism. When this infection happens in later development, the infection will not have a significant effect to yield. However, the vegetative phase's attack will significantly decrease the yield (Ganefianti, et al., 2017).

Study of Resistance Genes
The diversity observed in character influences by two factors, genetic and environment. If there is a high genetic variance with low fenotypic variance in a population, its filial will have similar characteristics genetically. This broad variance of genetics is substantial in the selection process, enables us to select the best genotype (Allard, 1960). The measurement of genotypic variance, phenotypic variance, error variance, genotypic coefficient of variability, phenotypic coefficient of variability and heritability from variables disease incidence, rating scale/scoring, disease intensity and incubation period were presented in Table 7.  (Zen & Bahar, 1996).  Heritability is an estimation of genetic variance towards phenotypic variance. If a plant possesses high heritability, its phenotypic character has been influenced mostly by genetic factors. Previous research conducted by Ganefianti, et al. (2015a) informed that variable scoring/ symptom had high broad-sense heritability. It is indicated that this variable has been controlled by the genetic factor, not an environmental factor.
In this study of pepper resistance against Begomovirus, we exploit the genotypes tested to have the lowest symptoms. Ganefianti (2015b) stated that variable scoring/symptom and disease intensity had been managed by three genetic components: additive, dominance, and gene interaction. Strong influence from dominance and gene interaction has enabled us to select resistant genotypes (to Begomovirus) by estimating disease intensity and symptom scoring system.