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Vegetable Production

Commercial vegetable production in Maui County includes world famous sweet onions from Kula, cabbage, lettuce, tomatoes, beans, celery, cucumbers, corn, watermelons, and taro. In addition, many other vegetables and melons are grown on small acreages. The value of this sector is over $9 million dollars, grown on over 1,100 acres.

CTAHR's research and extension personnel work with growers to implement programs that address needs and opportunities.

Taro Genetic Improvement Program

A program to improve commercial taros through breeding by increasing resistance to pests such as taro leaf blight (TLB) and aphids, increasing plant vigor and yield, and developing new and exciting varieties for the restaurant and landscape trade. In this program, Hawaiian taro cultivars are being used to incorporate different corm colors, low acridity, soft rot tolerance, early maturation, and brilliant colors. The genetic make up of the Hawaiian taros are very similar, thereby limiting their usefulness in breeding.

We have introduced taro varieties from the center of diversity for use in our breeding program to broaden the genetic base, increase pest resistance and increase yield of the commercial Hawaiian taros. Introduced taro cultivars from Micronesia, Palau, Indonesia, Papua New Guinea, Thailand and Nepal are being used to increase resistance to taro leaf blight. Two to 3 different sources of resistance are being incorporated into improved taros to increase the durability of resistance. Tolerance to aphids is being incorporated into commercial taros using cultivars from Micronesia that reduce the longevity of aphids or reduce the number of offspring and cultivars from Indonesia and Micronesia that reduce longevity and offspring.

Two successful breeding strategies are being employed to generate elite taro hybrids with commercial potential. In Strategy 1, genetic crosses are made between a Hawaiian taro variety and TLB resistant wild type taros introduced from Thailand and Papua New Guinea that are characterized by long stolons, many suckers, and small white fleshed corms. Hybrid plants generated are selected for desirable plant characteristics and used to make an additional (modified) backcross to produce commercial type taros. This process requires at least three years of breeding. In strategy 2, crosses are made between a Hawaiian taro and a TLB resistant introduced taro from Palau and Micronesia similar to the cultivated parent with large corms, few suckers and no or short stolons. Commercial types can be selected in the first year from hybrids generated from these crosses.

Fourteen elite hybrids have been selected using strategy 1 with 2 sources of and fourteen elite hybrids have been selected using strategy 2 with 4 sources of resistance. These elite hybrids are currently being evaluated on on-farm tests and a few are being advanced tested. After four years of on-farm evaluations, two of the elite hybrids were selected in 2004 by several Hanalei growers for commercial production. The two hybrids are more disease tolerant and yield about 30 percent more than the industry standard and are comparable in taste and color.

Future goals for the breeding program are to combine two to three sources of TLB resistance by making crosses between elite hybrids and to generate aphid tolerant hybrids with TLB resistant hybrids.

Publications, Fact Sheets and General Information

Tomato Spotted Wilt Virus Disease Management Program

Major research emphasis focused on the development of management strategies for tomato spotted wilt virus (TSWV) disease. Basic information generated on the biology of TSWV, insect vector, their reservoirs and TSWV-vector interrelationship are being used to further the understanding of the disease complex. Strategies are being implemented and adapted to minimize the disease in Hawaii, other USA locations and countries affected by the problem. These strategies include the use of methods for the detection and diagnosis of the virus, use of resistant genotypes identified for development of commercial resistant plant cultivars, and the utilization of cultural and chemical management methods to reduce disease losses. A collaborative effort with Petoseed Company resulted in the development of a TSWV resistant commercial tomato that is being grown in Hawaii and other locations.

Genetic backcross programs have been initiated to introgress the resistance genes into cultivated tomato and lettuce for development of commercial cultivars suitable for production in Hawaii and other regions such as Florida where we are collaborating with a pathologist and plant breeder. Molecular techniques are being employed to develop DNA markers linked to these genes for resistance to be used to select offspring simply be scoring their DNAs.

This is the emphasis of current research direction. This research uses molecular technology to accelerate breeding for disease resistance using DNA markers linked to resistance genes. Specifically, molecular markers linked to 3 disease resistance genes (root knot nematode, tomato spotted wilt tospovirus, tomato mosaic virus) are currently being used to accelerate breeding for multiple disease resistant commercial tomato breeding lines by assisting in the selection of plants containing the genes of interest. Several elite tomato lines of red beefsteak, yellow beefsteak, red plum, and red grape types of tomatoes have been developed through this technology and are being released to the farming community.

Publications, Fact Sheets and General Information

Links to Disease and Insect Identification and Control for Vegetables and Ornamentals