Part I. R& D Status - pcaarrd - Department of Science and Technology

R&D Status
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4 ............................................................................................................. R&D Status and Directions

Papaya Industry Situation
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World Supply and Demand
From 1992 to 2003, the world’s papaya
production averaged 5.49 million tons (M t)
(Fig. 2). Brazil was the consistent top producer
(25%), followed by Nigeria (13%), Mexico (13%),
and India (12%). The Philippines, averaging 1%,
ranked 14 th .
According to the Food and Agriculture
Organization (FAO), there was an upward trend in
both the export and import trading of fresh papaya
in the global market.
From 1996 to 2002, export trade and world
imports posted an annual growth rate of 13%
and 10%, respectively. Moreover, the world’s
annual export trade was 159,056 t valued at
US$ 102.56 M. Mexico (38%) and Malaysia
(27%) cornered the export trade. The Philippines,
10 th among world’s fresh fruit exporter, supplied
1.3% only. For annual imports, the United States
accounted for 45% followed by Singapore (16%)
and Hong Kong (12%). World importation,
however, increased from 115,473 t in 1996 to
197,124 t in 2002.
The Philippine Papaya Industry
The Philippine Papaya Varieties
Papaya, grown almost throughout the country,
serves as a backyard and a plantation crop, and as
a component of the multiple cropping systems,
usually with coconut, coffee, and pineapple.
Congo
4%
Indonesia
8%
Others
14%
Philippines
1%
Brazil
25%
Venezuela
2%
India
12%
Thailand
2%
Mexico
13%
China
3%
Nigeria
13%
Peru
3%
Total production = 5.49 M t
Fig. 2. Average production (t) of world’s top papaya producers, 1992–2003 (FAO).
Papaya.............................................................................................................................................................. 5

The Philippine papaya has several varieties.
These are ‘Solo,’ ‘Cavite Special,’ ‘Legaspi
Special,’ ‘Morado,’ and the ‘Sinta’ hybrid.
The Solo papaya, a hermaphrodite, is so-called
because one fruit (about 0.45 kg) is enough for
one individual’s consumption. It has four different
types, namely: ‘Kapoho,’ ‘Waimanalo,’ and the redfleshed
‘Sunrise’ and ‘Sunset.’ It produces highquality
fruits with excellent flavor, which is suited
for the export market (PCARRD 1984).
In fact, the Philippines’ export variety for fresh
papaya is based mainly on Solo papaya, which is
grown in large farms owned by multinational
companies.
Predominantly grown in Cavite and in the
neighboring provinces, the Cavite Special papaya
is relatively dwarf and a hermaphrodite (PCARRD
1984). It flowers 6–8 months after planting. Its ripe
fruits, with yellow-orange flesh (usually more than
3 kg), can be harvested in about 10–12 months
after planting.
Like Cavite Special, Legaspi Special has large
fruits with thick red flesh. It weighs more than
3 kg. Also, it is predominantly grown in the Bicol
region, especially in Albay.
Papaya-growing companies put the red-fleshed
Morado, like Cavite Special, in cans along with
other tropical fruits.
In 1995, the University of the Philippines Los
Baños-Institute of Plant Breeding (UPLB-IPB)
released the Sinta hybrid.
This semi-dwarf hybrid moderately tolerates
papaya ringspot virus (PRSV); matures in
8–9 months; and produces medium-sized fruits
(1.2–2.0 kg) with sweet, yellow, thick, and firm
flesh. With a 2 m x 3 m planting distance and good
management practices, Sinta papaya could yield
40–60 t of fruits (17–0 fruits/tree) within 15 months
from transplanting. Moreover, the recommended
harvesting for Sinta papaya should be done in one
fruiting cycle only, particularly in high disease
pressure areas; and, at least three cycles in isolated
areas or those with less disease pressure.
Unfortunately, all the varieties are susceptible
to papaya ringspot (PRS), which is caused by
PRSV.
PRS Outbreak in the Philippines
Until the early ‘80s, growers in Southern
Tagalog found a good business in papaya because
of its year-round production and good income.
Growers then could harvest up to
39 fruits per tree. In three years, they could harvest
as much as 62,400 fruits in a hectare with
1,600 trees (PCARRD 1984).
In 1984, the PRS disease outbreak wreaked
havoc on the thriving papaya industries in Southern
Tagalog and in the Bicol region. In fact, growing
papaya with severe infection became unprofitable
(Sumalde 1995).
PRS affects all stages of plant growth, i.e., from
seedling to maturity stage. Green concentric
ringspots appear on the fruit surface. Other
symptoms include yellowing, mosaic, and deformed
leaves; oily streaks on the stem and petioles; stunted
growth; and sterile fruits.
In 1992, PRS occurred only in Luzon. In 1996,
it reached the Ilocos, Cordillera, Central Luzon,
Southern Tagalog, Bicol, and Central Visayas
(Negros Oriental) regions (Villegas 1996). The
disease severely infected the areas near Silang,
Cavite where the disease originated in 1982 (Bato
and Ceballo 1992). In 2003, it reached Leyte and
Panay (Magdalita 2003) and was observed in
South Cotabato and some parts of General Santos
City, Davao del Sur, and Davao del Norte
(Herradura 2003).
Statistics has shown the damaging effect of the
disease. For instance, Southern Tagalog’s
production drastically declined to about 10,274 t in
1987 from 36,310 t in 1981 (Bureau of Agricultural
Statistics [BAS]). In 2001, its production reached
25,475 t indicating a minor turnaround.
Since the disease outbreak, efforts have been
focused in coming up with management strategies.
Included in these strategies is a quarantine regulation
issued by the DA-Bureau of Plant Industry
(DA-BPI). The regulation prohibits transporting
fruits and planting materials from Luzon to avoid
spreading the disease and protect the commercial
papaya industries in Mindanao. Efforts have gained
some headway as national production output
generally increased in the ‘90s.
6 ............................................................................................................. R&D Status and Directions

After the PRS Outbreak
From a pre-PRS period of 95,550 t in 1982,
production output went down to 88,388 t in 1987;
but reached the 100,000 t level in 1994. For
the next five years, national production was almost
at a plateau before it markedly increased to as much
as 120,000 t in 2000 (Fig. 3).
The area devoted to papaya production also
steadily increased from 1996 to 2000 and slightly
leveled off in 2000. Papaya, among the leading fruit
crops grown in the country, ranked sixth in terms of
area planted and fifth in terms of volume produced
in 2000 (Table 1).
From 1997 to 2001, Southern Tagalog had the
largest papaya hectarage (1,304–1,463 ha),
followed by Southern Mindanao (815–879 ha) and
Western Visayas (712–779 ha). The area planted
in most regions did not vary so much through the
years, except in Central Mindanao where there was
an abrupt increase from 460 ha in 1998 to 855 ha
in 2001. The Autonomous Region in Muslim
9,000
8,000
7,000
6,000
140,000
120,000
100,000
Area (ha)
5,000
4,000
80,000
60,000
Volume (t)
3,000
2,000
1,000
-
Area (ha)
Volume (t)
1982 1984 1987 1994 1995 1996 1997 1998 1999 2000 2001
Year
40,000
20,000
-
Fig. 3. Area (ha) and volume (t) of papaya production in the Philippines, 1982–2001 (BAS).
Table 1. Area (ha) and production (t) of ten important fruit crops in the Philippines, 2000 (BAS).
Commodity Area (ha) Production (t)
Banana 382,491 4,929,570
Mango 133,815 848,328
Pineapple 42,968 1,559,563
Citrus (calamansi and pummelo) 24,066 227,169
Jackfruit 11,999 51,163
Papaya 8,440 121,304
Durian 7,010 25,764
Avocado 5,124 38,086
Sugar apple 3,041 5,340
Mangosteen 1,354 4,692
Papaya.............................................................................................................................................................. 7

Mindanao (ARMM) (91–97 ha) had the least
area planted to papaya.
Supply and Demand
In terms of volume of production, Southern
Mindanao (24,321 t) produced the highest average
volume (Fig. 4), followed by Southern Tagalog
(20,671 t), and Northern Mindanao (17,088 t).
From 1996 to 2000, the top producers were
Laguna, Cavite, Camarines Sur, and Quezon
in Luzon; Cebu in Visayas; and Misamis Oriental,
North and South Cotabato, Davao City, and Davao
del Norte in Mindanao (Table 2). From 1994 to
2001, the growth rate for volume of papaya
(3.57%) was almost similar to the papaya hectarage
(3.51%) (Table 3).
In terms of papaya utilization, in an average
volume of 109,730 t (1992–2001), about 92% was
consumed locally as food; 2%, exported; and
6%, used as feed/wasted (Fig. 5).
From 1992 to 2001, papaya supply in the
Philippines increased (Table 4). In 2001, the
country’s supply was more than enough to meet
local demand. Even so, there were regions where
supply could not cope with the demand. These were
Cordillera Administrative Region (CAR), Central
Luzon, ARMM, Caraga, Central Mindanao, and
all the Visayas regions. The National Capital Region
had practically zero production. The per capita
consumption ranged from 1.33 to 1.51 kg/year for
an average of 1.42 kg/year for 10 years.
Export
The Philippines exported fresh (1,119 t) and
dried papaya (240 t) at an average of 1,359 t
annually from 1996 to 2000 (Table 5). The value
for dried papaya exports, however, declined from
1996 to 1999 and slightly increased in 2000.
Total exports, likewise, declined from 1996
to 1998 but bounced back in 1999 and in 2000
(Fig. 6). Fresh papaya exports accounted for 82%
of total exports, while dried papaya accounted
for 18%.
The same erratic trend was observed in
terms of value of papaya exports, particularly for
fresh papaya which ranged from US$85,280 to
US$3.3 M (Fig. 7).
From 1996 to 2000, Japan (66%) and Hong
Kong (29%) imported 95% of the total volume of
Philippine fresh papaya.
Table 2. Top ten papaya-producing provinces in the Philippines, 1996-2000. a
Volume (t)
Province 1996 1997 1998 1999 2000 Ave.
Philippines 113,992 110,113 107,094 112,862 121,303 115,530
1 Misamis Oriental 19,137 13,552 13,837 15,122 20,762 17,119
2 South Cotabato 12,768 13,215 12,629 11,554 10,631 12,065
3 Laguna 6,100 6,984 7,267 7,210 9,076 7,245
4 North Cotabato 3,468 4,045 3,399 5,288 5,475 4,567
5 Quezon 4,463 2,940 3,024 3,182 4,500 4,286
6 Cavite 2,779 3,757 3,841 4,274 4,595 3,841
7 Davao City 4,932 3,965 3,285 3,358 3,634 3,841
8 Camarines Sur 3,221 2,915 4,327 4,221 3,683 3,690
9 Cebu 4,005 3,260 2,820 3,105 4,094 3,554
10 Davao del Norte 5,195 4,989 4,322 1,878 2,053 3,440
Average 5,296
a There are 79 papaya-producing provinces in the country.
8 ............................................................................................................. R&D Status and Directions

30000
1997 1998 1999 2000 2001
25000
Volume produced (t)
20000
15000
10000
5000
0
CAR
Ilocos Region
Cagayan Valley
Central Luzon
Southern Tagalog
Bicol
Western Visayas
Central Visayas
Eastern Visayas
Western Mindanao
Northern Mindanao
Southern Mindanao
Central Mindanao
CARAGA
ARMM
Region
Fig. 4. Volume (t) of papaya produced by region, 1997–2001, Philippines (BAS).
Table 3. Growth rate of area (ha) for and volume (t) of papaya production in the Philippines,
1994–2001 (BAS).
Area
Volume
Year ha Change (%) t Change (%)
1994 7,052 104,250
1995 7,161 1.55 108,409 3.99
1996 7,375 2.99 113,974 5.13
1997 7,490 1.56 110,112 -3.39
1998 7,589 1.32 107,096 -2.74
1999 7,913 4.27 112,862 5.38
2000 8,440 6.66 121,304 7.48
2001 8,416 -0.28 127,787 5.34
Six-year growth rate from 1995 to 2001:
1995 7,161 108,409
2001 8,416 17.53 Total 127,787 17.87 Total
3.51 Average 3.57 Average
Papaya.............................................................................................................................................................. 9

Food
(export)
2%
Feed/waste
6%
Food (local)
92%
Fig. 5. Utilization of papaya in the Philippines, 1992–2001 (BAS).
Table 4. Supply and utilization accounts in papaya in the Philippines, 1992–2001.
Utilization
Supply
(production, Exports Feed and Net Food Disposable
Year t) (t) Waste (t) Total kg/yr g/day
1992 93,968 1,268 5,562 87,138 1.36 3.72
1993 97,537 2,084 5,727 89,726 1.37 3.76
1994 104,250 3,426 6,049 94,775 1.38 3.78
1995 108,409 2,313 6,366 99,730 1.46 4.00
1996 113,974 1,400 6,754 105,820 1.51 4.14
1997 110,112 407 6,582 103,123 1.44 3.95
1998 107,096 3,307 6,227 97,562 1.33 3.65
1999 112,862 1,203 6,700 104,959 1.40 3.85
2000 121,304 2,524 7,127 111,653 1.46 4.00
2001 127,787 4,163 7,417 116,207 1.49 4.09
Average 109,729 2,209 6,451 101,069 1.42 3.89
10 ............................................................................................................. R&D Status and Directions

Table 5. Volume (t) and value (‘000 US$ free on board [FOB]) of Philippine papaya exports (all
products), 1996–2000.
Volume (t)
Ave.
Growth %
Product 1996 1997 1998 1999 2000 Average Rate (%) Share
Fresh papaya 1,400 407 60 1,203 2,524 1,119 465 82
Dried papaya 288 287 170 182 274 240 4 18
3,000
Dried papaya
2,500
Fresh papaya
TOTAL
Volume (t)
2,000
1,500
1,000
500
-
1996 1997 1998 1999 2000
Year
Fig. 6. Volume (t) of Philippine papaya exports (all products), 1996–2000 (National Statistics
Office [NSO]).
4,000
3,500
Dried papaya
Value (‘000 US$ FOB)
3,000
2,500
2,000
1,500
1,000
Fresh papaya
TOTAL
500
-
1996 1997 1998 1999 2000
Year
Fig. 7. Value (‘000 US$ FOB) of Philippine papaya exports (all products), 1996–2000 (BAS).
Papaya.............................................................................................................................................................. 11

New Zealand was relatively a new export
market, albeit small compared with Japan, but
ranked 3 rd (1.9% share) among buyers of Philippine
fresh papaya. Exporting fresh papaya to New
Zealand was made possible in 2000 after
establishing the quarantine protocol agreement
similar to what had been done with Japan and
South Korea.
Making up the fourth and fifth top importers of
Philippine fresh papaya were Saudi Arabia (1.2%
share) and United Arab Emirates (0.8% share).
Singapore, China, South Korea, United States, and
the Canary Islands comprised the sixth up to the
tenth top importing countries.
In terms of value, Japan accounted for 90%
share while Hong Kong had about 8% share. New
Zealand, however, accounted for 0.9% share.
On the other hand, Australia imported most of
the Philippine dried papaya and obtained 73%
share, followed by the United States with 20%
share. Both countries also cornered 87% share of
the value of Philippine dried papaya exports. The
other top importers of dried papaya were Canada,
Germany, and Japan.
Key Industry Players
Generally, the Philippine papaya industry’s key
players can be classified as papaya growers,
contract growers, input suppliers, consumers, and
exporters.
Papaya growers can be differentiated based on
the size of their farms. Typical papaya growers,
about 79% of all papaya growers, have less than
3 ha. The other growers have 3–10 ha (18.4%)
and more than 10 ha (2.5%) (NSO 1991). Large
papaya growers such as T’Boli Agro-Industrial
Development, Inc. (TADI), Del Monte Philippines,
and Dole Philippines, Inc., operate in Mindanao.
On the other hand, small-scale growers usually
produce their own seeds or buy planting materials
from local nurseries. The Philippine papaya
production, except for the export variety Solo, is
widely dispersed and mostly run on a backyard
scale.
Some companies enter into contract-growing
arrangements with selected individual producers
using their preferred cultivars. For instance, Del
Monte Philippines has contract-growing
arrangements with papaya farmers in Misamis
Oriental and Bukidnon. They also produce their
own seed stocks and supply contract growers with
planting materials. In some cases, they supply all
the required inputs while producers complement
with land, labor, and management.
According to the DA’s SAP for Papaya 2002,
Metro Manila obtains the Cavite Special and the
Morado papayas from Cavite and Oriental
Mindoro, and the Solo papaya from Davao and
South Cotabato. Also, growers from Davao and
South Cotabato supply the Solo papaya to other
local supermarkets and export markets.
When exporting to Japan, South Korea, and
New Zealand markets, companies follow
established quarantine protocol for fresh papaya,
which requires a phytosanitary certificate and a
vapor heat treatment (VHT).
In the Philippines, one of the VHT plants is
located in Panabo, Davao del Norte. It is being
operated by Dole Philippines, Inc. to facilitate fresh
papaya and mango exports. For other markets such
as Hong Kong and the Middle East, exporters
accomplish phytosanitary certificate only.
Some companies also export fresh and dried
papaya. They put fresh papaya in can as fruit
cocktails. TADI and Orient Foods, Inc. produce
dried papaya.
Strengths, Weaknesses, Opportunities,
and Threats (SWOT) Analysis
The members of the National Papaya R&D
Committee 2004 prepared the SWOT analysis on
the Philippine papaya industry.
The SWOT analysis was based on the
available data/information in the DA’s SAP for
Papaya 2002, Department of Science and
Technology-United Nations Development Program
(DOST-UNDP) Gain Export (GAINEX) report,
and discussions with experts and other industry
stakeholders. Results are shown in Table 6.
12 ............................................................................................................. R&D Status and Directions

Table 6. SWOT analysis on the Philippine papaya industry.
Strengths Weaknesses
• Available varieties and hybrids • Susceptible to pests
• Suitable agroclimatic conditions • Poor technology adoption
• Year-round production • Susceptible to typhoon
• Versatile crop • Inadequate production and postproduction
• Varied uses technology
• Highly nutritious • Lack of certified seeds
• High domestic and export demand • High cost of pesticides
• Lack of irrigation systems in some growing areas
Opportunities Threats
• Growing domestic and export markets • Frequent typhoon occurrence in some growing
• Expanding product lines (processed, areas
nutraceuticals, papain) • Competition with other fruits
• Biotechnology tools available • Pest problems
• Proximity to export markets • Importer’s preference
• Sanitary and phytosanitary trade barriers
Papaya.............................................................................................................................................................. 13

Technological Milestones
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○
R&D Investments
The Philippine government invested almost
P32 M for papaya R&D from 1990 to 2003
(Table 7). This amount was only one fifth of the
investments made in mango (P171 M) and more
than half in banana (P53 M) or in ornamental
horticulture (more than P58 M from 1990 to 2000).
These commodities, including papaya, have
been accorded high priority by DOST under its
Science and Technology Agenda for National
Development (STAND) and by DA through its High
Value Commercial Crops (HVCC) Program.
Projects and Studies on Papaya
With the government’s investment for papaya R&D,
43 studies were conducted from 1990 to 2003.
The studies focused on varietal improvement (14),
crop production and management (11),
crop protection (10), biotechnology (5), postharvest
handling (2), and socioeconomics and marketing
(1) (Table 8). Biotechnology studies, however, got
the bulk of the budget (74%) followed by studies
on varietal improvement (14%).
Biotechnology projects on papaya came in
1997 as part of the DOST-approved biotechnology
Table 7. R&D investment in papaya, mango, and banana in the Philippines, 1990–2003 (PCARRD). a
Budget (P)
Year Papaya Mango Banana
1990 1,251,535 1,267,080 2,408,819
1991 646,860 733,632 2,720,652
1992 267,143 490,974 3,223,068
1993 305,400 516,854 1,155,633
1994 279,923 808,323 948,520
1995 54,620 1,810,000 4,152,432
1996 833,257 24,294,978 725,285
1997 583,239 26,697,469 1,385,025
1998 6,935,687 16,852,386 6,358,381
1999 6,088,604 24,625,654 12,605,363
2000 7,523,477 22,353,352 9,965,250
2001 5,735,122 35,252,081 5,437,691
2002 438,147 9,501,840 770,000
2003 709,308 6,239,466 1,658,804
Total 31,652,322 171,444,089 53,514,923
a PCARRD’s Research and Development Management Information System (RDMIS).
14 ............................................................................................................. R&D Status and Directions

Table 8. Studies on papaya by discipline and budget in the Philippines, 1990–2003. a
No. of
Budget
Discipline Studies Percent (P) Percent
1. Biotechnology 5 12 23,329,722 74
2. Varietal improvement 14 32 4,363,460 14
3. Crop protection 10 23 1,836,920 6
4. Crop production and management 11 26 1,558,885 5
5. Postharvest handling 2 5 548,335 2
6. Socioeconomics and marketing 1 2 15,000 0.05
Total 43 100 31,652,322 100.00
a PCARRD’s RDMIS.
program. From 1998 to 2003, there were five
approved biotechnology studies on papaya with
funding from DOST, PCARRD, and the Australian
Center for International Agricultural Research
(ACIAR). The support amounted to P23 M.
IPB researchers solely implemented the studies to
produce papaya with resistance to PRSV and
papaya with delayed ripening characteristics.
Varietal improvement studies on papaya mainly
revolved around collection, evaluation, purification,
and hybridization. About 82% of the R&D
investment on varietal improvement went to papaya
breeding at IPB. The papaya breeding project
started in 1981 even when PRS was still unheard
of (Villegas 1996). During the first phase (1981–
1990), this UPLB-funded project lost a lot of
breeding lines developed because of PRS. Hence,
the project objectives had to be refocused to include
PRSV resistance/tolerance.
PCARRD and UPLB funded the second phase
from 1990 to 1995. It came up with a PRSVtolerant
Sinta papaya, which is considered as an
R&D milestone. DOST supported the third phase
(1996–2002). This involved further breeding work
that identified four promising PRSV-tolerant F 1
hybrids and adopted micropropagation as an
alternative method to produce planting materials.
Together with this breeding project were other
projects or studies related to PRS. Almost 6% of
the R&D investments were put to crop protection
(vector control, virus eradication, and management
strategies), while 5% went to crop production and
management. In fact, DOST funded the PCARRDpackaged
papaya rehabilitation and development
program in Southern Tagalog and in the Bicol region
where PRS had taken its toll on papaya plantations.
Among the R&D efforts, postharvest handling
(2%) and socioeconomics and marketing (0.05%)
researches got the least budget from the total
investments. PCARRD funded basic research
on reducing fruit injury of the Solo papaya that is
subjected to VHT.
Technological Breakthroughs
and Information Generated
The National Agriculture R&D Network
(NARRDN) has reported 13 research findings
on papaya from 1990 to 2003 (Table 9). These
were published in the PCARRD’s R&D Highlights
and in the PCARRD-based Horticulture Information
Network (HORTINET) Web site (http://
www.hortinet.pcarrd.dost.gov.ph).
The research findings have generated
information and technologies that give significant
development or new knowledge, offer bright
prospect for business, possess significant social and
economic implications that need to be disseminated
and validated under the actual farming situations.
Papaya.............................................................................................................................................................. 15

Table 9. Papaya research findings in the Philippines, 1990–2003. a
Title TM b ACP c ID d TV e
1. Papaya genetic transformation for ringspot virus
resistance (2002)
X
2. Germplasm collection and hybridization of papaya
(2002) X
3. Papaya varieties tolerant to ringspot virus with
good horticultural traits (1999)
X
4. Isolation/detection of virus-like particles in banana,
papaya, and citrus (1997)
X
5. Papaya rehabilitation and development project in
Southern Tagalog and Bicol Region (1997)
6. Modified atmosphere (MA) storage for banana,
papaya, and pineapple (1996)
X
7. Papaya rehabilitation and development project in
Southern Tagalog/Bicol (1996)
X
8. Hybrid papaya (1995) X X
9. Control of PRSV vectors (1993) X
10. Occurrence and severity of papaya ringspot
disease and its vectors
X
11. Reduction of fruit injury in Solo papaya (1992) X
12. Control of papaya spider mites (1992) X
13. Six promising strains of papaya (1990) X
a PCARRD
b Technology milestones.
c
Action/Commercialization programs.
d Information for dissemination.
e Technology for verification.
Sinta Hybrid
Among the findings, notable is the development
of Sinta hybrid at IPB (Villegas et al.
1994). The institute took 14 years (1981–1995) to
develop the hybrid (Villegas 1995).
The demand for growing Sinta papaya has
been increasing because of the growers’ desire to
rehabilitate papaya plantings affected by the disease
(Villegas 1996b). Sinta papaya, coupled with
available disease management strategies, is the only
variety that can be profitably grown in PRSVinfected
areas. Because of anticipated demand for
Sinta, a micropropagation technique using nodal
cuttings was also developed to complement seed
production (Villegas et al. 2000).
Based on a serological test, tissue culturederived
Sinta papaya was proven to be virus-free.
This means that the materials can be safely
transported to other areas without bringing the
dreaded virus. Field performance of the materials
also showed reduced juvenile period without offtypes.
Four Promising F 1
Hybrids
Another interesting development was the four
promising F 1
hybrids that have high qualities and
tolerance to PRSV (Villegas 2002). These hybrids
are the two medium-sized, yellow-fleshed hybrids
and the medium-sized, red- and yellow-fleshed Solo
hybrids. These, however, await further field
evaluation before being released as new varieties.
16 ............................................................................................................. R&D Status and Directions

Interspecific Hybridization
for PRSV Resistance
IPB researchers also studied the transfer of
PRSV-resistant genes from wild Carica species
(C. cauliflora, C. pubescens, C. quercifolia, and
C. stipulata). They employed embryo rescue to
produce the base population. Through manual
pollination, the first backcross generation was
produced containing the PRSV-resistant genes from
C. quercifolia (Siar 2003).
Corollary to this, Mendoza-Garces (2002)
identified morphological, cytological, biochemical,
and molecular markers to characterize and confirm
the hybridity of C. papaya x C. quercifolia F 1
hybrid.
Based on cytological and morphological
analyses between C. papaya and C. quercifolia
genomes, partial homeology indicates the transfer
of useful PRSV-resistant genes from the wild species
(C. quercifolia) to cultivated papaya germplasm as
a result of hybridization.
Molecular Markers for Genetic
Diversity Analysis
In view of the genetic diversity of germplasm
collections on papaya, the papaya collections were
also characterized by using optimized simple
sequence repeats (SSR) protocol. Six SSR primers
(CPY1, CPY2, ACC1, ACC3, BGAL1, and
BGAL2), developed at UPLB IPB, were used to
characterize genetic diversity among 54 papaya
accessions (Garcia 2002). A partial genetic diversity
profile of Philippine papayas was produced with 3
primer pairs and 54 papaya accessions.
Genetic Transformation in Papaya
Researchers from IPB have been successful in
inducing somatic embryogenesis in papaya, which
is needed for genetic engineering (Villegas 1996).
On the development of PRSV-resistant papaya
from the somatic embryos and growing multishoots,
transgenic lines were produced and maintained for
screenhouse screening against PRSV (Magdalita
2003). These transgenic lines contain the coat
protein (cp) gene of Philippine PRSV isolate, which
was transferred into papaya genome either through
the modified transformation system via particle
bombardment or Agrobacterium-mediated
transformation.
Of the gene transfer technique, the project
adopting the Agrobacterium-mediated
transformation technique is more advanced in
producing R 2
transgenic lines; while the project
adopting the particle bombardment technique has
only produced R 1
transgenic lines.
While developing papaya with delayed ripening
characteristics, R 2
transgenic lines were produced
and maintained for greenhouse evaluation
(Mendoza 2003). The transgenic lines contain the
ACC synthase gene (from Davao Solo), which
was transferred to the Solo papaya by using a
gene gun technique. Another technique, using
Agrobacterium-mediated transformation, was also
initiated by transferring ACC oxidase gene (local
gene) to papaya genome (Magdalita 2003). The
project adopting the gene gun technique produced
R 2
generations for greenhouse evaluation, while
the project on Agrobacterium-mediated
transformation technique is in the laboratory stage
still regenerating transgenic plants.
Management Strategies Against PRSV
and Spider Mites
Researches on crop protection mostly dealt with
basic studies on rational PRSVmanagement
strategies and on controlling spider mites.
PRSV is a tiny entity which has flexous
filamentous particles. An isolate of it produces
mosaic, mottle, and ringspots in papaya.
Aphids are the PRSV vectors. Initially, there
were five that were identified (Bato et. al. 1993).
These are Aphis craccivora Koch (cowpea aphid,
black bean aphid, or indigo aphid; A. gossypii
Glover; Rhopalosiphum maidis Fitch (corn aphid);
Myzus persicae Sulzer (green peach aphid and
green tobacco aphid); and Lipaphis erysimi
Kaltenbach (false cabbage aphid). In 1995, five
more aphids were identified as PRSV vectors.
These are A. glycines (soybean aphid), A. malvae
(cotton aphid), Micromyzus formosanus Tak.
(onion aphid), Macrosiphum solanifolii Ashm.
(potato aphid), and A. medicaginis Koch (Sumalde
Papaya.............................................................................................................................................................. 17

et al. 1995). These aphids acquire and transmit
virus very quickly through sap feeding. It is still
unknown, however, whether the virus is
transmissible via the seed, but it may be seedborne
(Bajet 1996).
Bato et al. (1993) identified nine natural
enemies of aphids. These are coccinelid beetle,
syphid fly, chalcids, braconids, chrysopids,
staphylinids, mirids, hemerobiid, and
Entomophtora sp. (a fungus).
Scientists use serological assays, mechanical
transmission, electron microscopy, or a mix of the
three to detect PRSV-infected papaya. Using
serological assays, scientists confirmed that the
Philippine PRSV is identical to the viruses in
Thailand, Australia, Hawaii, and Taiwan (Bajet
1996).The PRSV strain was successfully isolated
in zucchini squash (Cucurbita pepo cv. Blackjack)
(Bajet 1997; 1996). Along with okra, corn,
mungbean, eggplant, cucumber, jelly melon,
pumpkin, squash, centrosema, ‘gabi,’ ‘upo,’
‘patola,’ ‘melon-melonan,’ and ‘balatong-aso,’
zucchini squash serves as an alternate host of the
vectors and the virus (Sumalde 1995). The isolate
produced the typical symptoms in both the squash
and papaya.
Similarly, the molecular variability of PRSV can
be known through cloning and deoxyribonucleic acid
(DNA) sequencing (Aquino and Valencia 2001).
Based on the entire cp gene sequences, isolates
from Bulacan, Cavite, Quezon, Isabela, and
Marinduque were identified at 97–98% sequence
homology. Scientists need to further verify isolates
variability and dendogram development based on
genetic coefficient to confirm the virus’ genetic
variability.
Planting PRSV-tolerant variety like the Sinta
papaya is one of the recommended practices to
manage PRS (Villegas 1996 a and b; Sumalde et al
1995; Bato et al. 1993). The Sinta papaya could
only serve as a stopgap measure in the absence of
resistant varieties. It must be combined with other
disease management strategies such as:
• Roguing or proper disposing of infected
plants;
• Controlling the vector by eliminating
alternate hosts;
• Intercropping with taller crops or by
spraying insecticides;
• Isolating plants;
• Subjecting plants into quarantine;
• Conducting proper cultural management
practices such as weeding, fertilization, and
irrigation during dry season; and
• Treating papaya as an annual crop rather
than as a perennial crop.
These disease management strategies were
being employed in the papaya rehabilitation and
development project in Southern Tagalog and in
the Bicol region (Sumalde et al. 1997; 1995). The
project also involved information, education, and
communication (IEC) campaigns through
consultative meetings, training-seminars,
and trimedia to enhance awareness of papaya
growers on PRSV and to strengthen linkages among
concerned stakeholders. The IEC materials of this
project were supplemented with other publications
from other researchers in the NARRDN.
In Davao, Pableo et. al. of BPI-Davao National
Crops Research and Development Center (BPI-
DNCRDC) suggested practical steps to control
spider mites. These include inspection, judicious
spraying with formetana, and removal of
nonfunctional leaves.
Modified Atmosphere (MA) Storage
and VHT of Solo Papaya
Postharvest Training and Resarch Center
(PHTRC) researchers’ findings on the postharvest
handling of papaya focused mostly on the Solo
variety. Serrano (1996) optimized the application
of MA storage of the Solo papaya to delay ripening
during commercial shipment trials from Misamis
Oriental to Laguna. On the other hand, Lizada
et al. (1991) determined the effect of VHT on the
ripening characteristics, fruit injury, and disease
incidence on the Solo papaya.
18 ............................................................................................................. R&D Status and Directions

Institutional Capability
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The institutions involved in papaya researches are
UPLB, Cavite State University , University of
Southern Mindanao, Leyte State University
(formerly Visayas State College of Agriculture),
Bicol University College of Agriculture and Forestry,
Don Mariano Marcos Memorial State University,
BPI, and BPI-DNCRDC, and DA regional stations.
These agencies implement basic (especially
UPLB) and applied (particularly BPI, DA, and other
agricultural universities) research projects.
The lack of institutional linkages on papaya
R&D and weak technology transfer are among the
major concerns.
Papaya.............................................................................................................................................................. 19

R&D Gaps
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There are several R&D on papaya
that have been conducted and have produced
significant findings. Even so, there are still concerns
that need to be addressed. Some are the following:
• PRSV-susceptible Solo papaya. The
Solo papaya, which is currently the
country’s export variety, is susceptible to
PRSV. Also, some export markets do not
prefer its yellow flesh. Hence, a need to
develop a red-fleshed Solo papaya that has
high tolerance to PRSV and has delayed
ripening characteristics.
• Lack of inbred varieties with desirable
attributes of Sinta. Sinta papaya is
acceptable for local consumers because of
its medium-sized and good quality fruits. It
has moderate tolerance to PRSV. Its being
a hybrid, however, requires that a grower
should always buy seeds to continue planting
papaya. Hence, a need to acquire useful
germplasm and develop inbred varieties like
that of Solo papaya and with the desirable
attributes of Sinta papaya. With these,
growers can select their desired seeds, plant
more than one seed or seedling per hill, and
later on select the best plants for papaya
production.
• Lack of effective control measures for
insect pests. Other than the five aphid
species that transmit PRSV, there are other
important insect pests that attack papaya.
Their biology, ecology, and epidemiology
should be systematically understood, so
that effective control measures could be
implemented.
• Weak management strategies for PRS
and bacterial crown rot. The two major
diseases of papaya are PRS and bacterial
crown rot.
For PRS, there are two ways to reduce
infection to manageable level:
a) Develop tolerant/resistant varieties/
hybrids through conventional breeding
or through biotechnology interventions;
and
b) Develop cropping systems that will
control the aphids.
Bacterial crown rot, however, is also
becoming a major threat to papaya industry.
Therefore, there is a need to conduct basic
management studies of this disease,
including host-plant resistance and effective
pest management strategies.
• Lack of fertilizer and water management
program. Papaya is a fast-growing
plant with a shallow root system that
supports a shoot system that continuously
produces huge leaves, numerous flowers,
and large fruits.
There is, therefore, a need to
continuously monitor the nutritional status
and water requirements of the plants for
maximum production. Basic studies should
also be conducted to establish critical
nutrient levels as a guide to a sound and
efficient fertilization and water management
program.
The R&D directions for papaya present a
total systems approach in addressing these
R&D gaps. Also, Appendix 1 summarizes the
state of the art for papaya, which includes the
major research, development, and extension
(RDE) programs to address papaya R&D
concerns.
20 ............................................................................................................. R&D Status and Directions