Genotypes MACS1188 (1953 kg/ha) and MACS1184 (1853 kg/ha) were identified as tolerant genotypes.
RODENT CONTROL
Bamboo flowering in Meghalaya
Quarterly survey conducted in all the districts of Meghalaya showed sporadic to mass bamboo flowering in Garo Hills and West Khasi Hills. Some isolated instances of a slight upsurge in rodent population and a slight increase in damage to rice crops was observed only in East Garo Hills.
A total of seven rodent species viz., Bandicota bengalensis, Niviventtor niviventor, Rattus rattus, Rattus nitidus, Mus musculus, Rattus sikkimensis and Cannomys badius were identified from bamboo flowering areas in Meghalaya. However B. bengalensis was the predominant species.
Damage assessment and evaluation of rodenticides Rodent damage to rice, maize and groundnut crop was observed to the tune of 7.25%, 9.45% and 10.25%, respectively. However, damage was negligible in different vegetable crops viz., broccoli, cabbage and cauliflower. The Bandicota bengalensis was recorded the predominant species. Bromadiolone (0.005%) and zinc phosphide (2%) were used for the rodent control by burrow and field placement methods. Zinc phosphide proved effective by reducing rodent activities between 70.51 – 78.00% by burrow placement method whereas bromadiolone reduced the active burrows upto 35%. Use of zinc phosphide followed by bromadiolone to control the residual rodent population proved effective in reducing the rodent population upto 87%. Consumption of rodenticide increased with bamboo bait stations for poison bait placement which resulted increase in the control efficiency.
while least number of seed/fruit (10.75 Nos.) was recorded in tissue cultured plant. However, juice content (42.45%) and acidity (1.74%) were found maximum under C. reshni rootstock. The ascorbic acid content (32.14 mg/100 ml) was found highest in C.
latipes followed by tissue cultured plant (31.98 mg/
100 ml) and lowest in nucellar seedling (30.12 mg/
100 ml).
Performance of nucellar, budded and grafted plants of Khasi mandarin
Three years old Khasi mandarin plants (rootstocks Citrus volkamariana, C. jambhiri, C. latipes, Rangpur lime, Dancy Tanzelo and C. grandis) were evaluated for growth performance. The maximum plant height was recorded on Rangpur lime rootstock (216 cm) followed by C. jambhiri (207.5 cm) and Citrus volkamarian (204.16 cm) and minimum in both Dancy Tanzelo and nucellar seedling (150 cm). Rootstock and scion diameter was maximum in C. volkamariana (76.35 mm, 48.59 mm) and C. latipes (55.19 mm, 47.59 mm) rootstock, respectively and minimum in Dancy Tanzelo (29.79 & 21.64 mm) rootstock while canopy spread was maximum in C. jambhiri (120.87 cm) rootstock.
Khasi mandarin budded on C. jambhiri, rangpur lime and grafted on C. jambhiri, rangpur lime, C.
grandis, C. latipes of two years old were evaluated for growth performance. The grafted plants showed the vigorous growth as compared to budded plants.
Maximum plant height (180.33 & 139.16 cm), scion diameter (47.67 & 25.15 mm) and canopy spread (84.16x83.33 & 72.5x59.16 cm) were recorded under grafted and budded plant of Khasi mandarin on rangpur lime and C. jambhiri rootstock, respectively.
Intercropping with Khasi mandarin
Six crops viz.,, French bean, cow pea (Kashi Kanchan), groundnut (ICGS-76), soybean (JS 335), rice bean (RCRB-1-6) and urd bean (T-9) were grown during kharif season in five years old Khasi mandarin orchard. The result showed that the maximum yield was recorded in cow pea (36.55 q/ha) followed by groundnut (29.8 q/ha), French bean (24.44 q/ha), rice bean (5.59 q/ha), soybean (5.5 q/ha) and urd bean (3.65 q/ha).
Effect of mulching on plant growth, weed population and soil moisture status
An experiment on mulching viz.,, black polythene, pine tree leaves, farm grass, leaves of rice bean,
Flemingia macrophylla, Crotolaria tetragona and Tephrosia candida along with control (without mulch) was conducted on six years old Khasi mandarin. The leaves and grass were applied @ 2 kg/m2 twice in a year i.e. Jul and Nov. Maximum plant height (2.60 m) and canopy spread (97.5 cm) was recorded in Crotolaria tetragona mulch. Stem diameter (6.26 cm) and no. of branch/plant (31 Nos.) were highest in Khasi mandarin mulched with Tephrosia candida leaves and rice bean mulch, respectively. Flowering was noticed in all the treatments. Minimum weed density was recorded in black polythene mulch (0.133 kg/m2) followed by pine leaves (0.28 kg/m2) and maximum in control (0.70 kg/m2). Whereas, the maximum moisture content was noticed in black polythene mulch (37.85%) followed by Flemingia macrophylla (26.94%), Tephrosia candida (23.91%) and minimum in control (17.22%) during Jan.
INSECT PESTS
Seasonal incidence studies of citrus trunk borer (Anoplophora versteegi) on Khasi mandarin
The adult beetles were first noticed on 19th April with an initial population of 0.01 beetles/plant and reached the highest population of 1.6 beetle/plant on 8th May. Thereafter, beetle population declined till the end of July and no beetle population was further observed.
Monitoring of fruit flies
The fruit flies were found as major insect pests of fruits. The fruit fly species, Bactrocera dorsalis was recorded on plum (Prunus domestica), guava (Psidium guajava), peach (Prunus persica), black berry (Prunus nepalensis) and Soh phie (Myrica esculenta) whereas, fruit fly species, B. zonata was recorded only on peach causing severe damage to the fruits.
DISEASES
Citrus scab (Elsinoe fawcettii)
In vitro efficacy of native bio-agents and botanicals Bio-control agents: Seven native Trichoderma spp. were isolated and two T. harzianum isolates (PB2
& PB4) tested against eight E. fawcettii isolates.
Both isolates (PB2 & PB4) were found effective in inhibiting the growth of mycelium of E. fawcettii within 50 hours of incubation. However, the more inhibition was achieved with PB4 isolate (Figs 2&3).
a) Effect of Tricure (Azadirachtin 0.03%): Two field application doses viz, full dose (5ml/ L)
and half dose (2.5 ml/L) were evaluated in-vitro for efficacy against E. fawcettii isolates. It was recorded that half dose of Tricure was effective against B1 and H1 isolates, whereas full dose was effective against all the isolates (Fig.4).
b) Field efficacy of fungicides, bio-control agents and botanicals against citrus scab:
Field efficacy trial for management of citrus scab using seven treatments (Table1) was conducted.
The spraying was done at 15 days interval.
Among the treatments, commercial formulation
Nisarga (Trichoderma viride) @ 5 g/L was found effective followed by Bavistin (Carbendazim)
@ 2 g/ L in the first year trial.
Table 1 Field efficacy of fungicides, bio-control agents and botanicals against citrus scab
Treatments PDI
Nisarga (T. viride) @ 5 g/L 15.60 Tricure(Azadirachtin 0.03%) @ 5 ml/L 26.40 Lantana seed extract @ 200g/L 28.00 Bhoomika (T. viride) @ 5 g/L 23.53 Bavistin (Carbendazim) @ 2 g/L 19.60
Kavach @ 2.5 g/L 26.00
Control 40.40
CD (P=0.05) 2.28
Citrus foot/root rot and gummosis (Phytophthora spp.)
a. Survey for collection of isolates and isolation of pathogen (s)
Survey was conducted in citrus orchards of Government and progressive farmers of Meghalaya, Tinsukia district of Assam and Lohit district of Arunachal Pradesh. Infected root, wood and soil samples were collected from root/crown rot and gummosis affected plants. Pathogen (Phytophthora spp.) was isolated on Corn meal agar medium amended with antibiotics/fungicides and purified in V8 Juice Agar.
b. Morphological identification of Phytophthora spp.
A protocol for sporangial formationof Phytophthora spp was standardized. Hyphal swelling and bulging was recorded with distorted shape of sporangia. Different shapes (papillate, non papillate, spherical, pyriform, ovoid, obovoid.) and size of
sporangia were observed. Additionally, chlamydospore formation was also recorded. The Phytophthora species were morphologically identified with Waterhouse key and Stamp’s Key for Phytophthora identification.
Fig 2 In-vitro efficacy of Trichoderma isolates against Elsinoe isolates
Fig 3 Dual culture of Trichoderma isolate (PB-4) against Elsinoe isolate (C1)
Fig 4 In-vitro efficacy of Tricure against Elsinoe
isolates Fig 5 Distorted sporangia of
P. citropthora, causing foot/
root rot of citrus
c. Molecular identification of Phytophthora spp.
Ten isolates from Assam and Arunachal Pradesh were confirmed as P. parasitica using species specific ITS1 and ITS4 primers (Fig 6).
d) Isolation and bio-efficacy of native bio-control agents for Phytophthora spp.
Fungal bio-agents were isolated from healthy citrus rhizosphere soil samples collected from Meghalaya, Assam and Arunachal Pradesh. Based on the morphological characters seven species of Trichoderma were identified as T. viride, T. virens, T.
harzianum, T. pseudokoningii, T. crassum, T.
longibrachiatum and T. reesei. These species were tested against four representative Phytophthora isolates using dual culture technique, effect of volatile compounds and non-volatile compounds.
(i) In dual culture test, T. harzianum and T.
longibrachiatum were found effective against all four isolates of Phytophthora spp (Fig 7).
(ii) In volatile compound effect experiments, four ways experiments (inoculation of bio-agent and pathogen on ‘0’ day, bio-agents 1, 2 and 3 days ahead to pathogen) were conducted. In
all experiments, T. crassum followed by T.
longibrachiatum was found superior over other species against all four isolates of Phytophthora spp (Fig 8).
(iii) In non-volatile compound effect experiment with 10, 20 and 30% culture filtrate, T. crassum followed by T. harzianum were found superior against all four Phytophthora spp. of citrus (Fig 9).
Fig 9 Effect of non-volatile compounds of Trichoderma spp. on four isolates of Phytophthora spp
GUAVA
Seed protein polymorphism in guava genotypes The sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) was carried out to determine the protein profiles/banding patterns of 11 guava genotypes viz., RCG-1, RCG-2, RCG-3, Allahabad Safeda, L-49, Lalit, Sangam, RCG-11, RCGH-1, RCGH-4 and RCGH-7. The electrophoregram (banding patterns) of seed protein presented in Fig 10 showed distinct polymorphism and led to the detection of 23 polypeptide bands.
Fig 6 Molecular identification of Phytophthora spp. by ITS primers
Fig 7Dual culture of Trichoderma spp. and four isolates of Phytophthora spp.
Fig 8Effect of volatile compounds of Trichoderma spp.
on four isolates of Phytophthora spp.